b-colouring outerplanar graphs with large girth

A b-colouring of a graph is a colouring of its vertices such that every colour class contains a vertex that has a neighbour in all other classes. The b-chromatic number of a graph is the largest integer $k$ such that the graph has a $b$-colouring with $k$ colours. We show here how to compute in polynomial time the $b$-chromatic number of an outerplanar graph of girth at least $8$. This generalizes the seminal result of Irving and Manlove on trees.     

Efficient γ-amino-proline-derived cell penetrating peptide-superparamagnetic iron oxide nanoparticle conjugates via aniline-catalyzed oxime chemistry as bimodal imaging nanoagents

Aniline-catalyzed oxime chemistry was employed to conjugate a γ-amino-proline-derived cell penetrating peptide to superparamagnetic iron oxide nanoparticles (SPIONs). Internalization of the novel nanoconjugate into HeLa cells was found to be remarkably higher compared to the analogous TAT-SPION conjugate.     

Designing organometallic compounds for catalysis and therapy

Bioorganometallic chemistry is a rapidly developing area of research. In recent years organometallic compounds have provided a rich platform for the design of effective catalysts, e.g. for olefin metathesis and transfer hydrogenation. Electronic and steric effects are used to control both the thermodynamics and kinetics of ligand substitution and redox reactions of metal ions, especially Ru(II). Can similar features be incorporated into the design of targeted organometallic drugs? Such complexes offer potential for novel mechanisms of drug action through incorporation of outer-sphere recognition of targets and controlled activation features based on ligand substitution as well as metal- and ligand-based redox processes. We focus here on η(6)-arene, η(5)-cyclopentadienyl sandwich and half-sandwich complexes of Fe(II), Ru(II), Os(II) and Ir(III) with promising activity towards cancer, malaria, and other conditions.     

A new selective fluorogenic probe for trivalent cations

A new selective chromo-fluorogenic probe for Fe(3+), Cr(3+) and Al(3+) is reported. Detection limits are in the μM range and the fluorogenic sensing ability could be observed by the naked eye when illuminated with UV-light. No response is observed with divalent cations.     

Encapsulation of atmospheric CO(2) by a self-assembled decanuclear cadmium complex via unfamiliar perchlorato and carbonato bridges

A decanuclear Cd complex has been found as a carbonate-containing capsule. The structure strongly resembles a ten-blade waterwheel with a central carbonate ligand surrounded by two superimposed Cd(5)O(5) crowns with a pentagonal antiprism-like disposition. The capsule is doubly capped by two pentadentate perchlorate anions.     

Antimicrobial and antioxidant activities of essential oils of Satureja thymbra growing wild in Libya

The composition of essential oil isolated from Satureja thymbra, growing wild in Libya, was analyzed by GC and GC-MS. The essential oil was characterized by γ-terpinene (39.23%), thymol (25.16%), p-cymene (7.17%) and carvacrol (4.18%) as the major constituents. Antioxidant activity was analyzed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. It possessed strong antioxidant activity (IC50 = 0.0967 mg/mL). The essential oil was also screened for its antimicrobial activity against eight bacterial and eight fungal species, showing excellent antimicrobial activity against the microorganisms used, in particular against the fungi. The oil of S. thymbra showed bacteriostatic activity at 0.001-0.1 mg/mL and was bactericidal at 0.002-0.2 mg/mL; fungistatic effects at 0.001-0.025 mg/mL and fungicidal effects at 0.001-0.1 mg/mL. The main constituents thymol, carvacrol and γ-terpinene also showed strong antimicrobial activity. The commercial fungicide bifonazole showed much lower antifungal activity than the tested oil.     

Cytotoxic Podophyllotoxin Type-Lignans from the Steam Bark of <em>Bursera fagaroides </em>var. <em>fagaroides</em>

The hydroalcoholic extract of the steam bark of B. fagaroides var. fagaroides displayed potent cytotoxic activity against four cancer cell lines, namely KB (ED₅₀ = 9.6 × 10^-2 μg/mL), PC-3 (ED₅₀ = 2.5 × 10^-1 μg/mL), MCF-7 (ED₅₀ = 6.6 μg/mL), and HF-6 (ED₅₀ = 7.1 × 10^-3 μg/mL). This extract also showed anti-tumour activity when assayed on mice inoculated with L5178Y lymphoma cells. Bioactivity-directed isolation of this extract, afforded seven podophyllotoxin-type lignans identified as podophyllotoxin (1), β-peltatin-A-methylether (2), 5'-desmethoxy-β-peltatin-A-methylether (3), desmethoxy-yatein (4), desoxypodophyllotoxin (5), burseranin (6), and acetyl podophyllotoxin (7) by 1D and 2DNMR and FAB-MS analyses, and comparison with reported values. All the isolated compounds showed potent cytotoxic activity in the cell lines tested, especially compound 3, which exhibited greater activity than camptothecin and podophyllotoxin against PC-3 (ED₅₀ = 1.0 × 10^-5 μg/mL), and KB (ED₅₀ = 1.0 × 10^-5 μg/mL). This is the first report of the isolation of podophyllotoxin and its acetate in a Bursera species.     

Improved signal-to-noise ratio in laboratory-based phase contrast tomography

In conventional X-ray microtomography (μCT), the three-dimensional (3D) distribution of the attenuation coefficient of X-rays is measured and reconstructed in a 3D volume. As spatial resolution increases, the refraction of X-rays becomes a significant phenomenon in the imaging process. Although this so-called phase contrast was initially a cumbersome feature in lab-based μCT, special phase retrieval algorithms were developed to exploit these effects. Clear advantages in terms of visualization and analysis can be seen when phase retrieval algorithms are applied, including an increased signal-to-noise ratio. In this work, this is demonstrated both on simulated and measured data.     

Disordered carbon nanofibers/LiCoPO<Subscript>4</Subscript> composites as cathode materials for lithium ion batteries

LiCoPO₄-coated disordered carbon nanofibers (CNFs/LiCoPO₄) were obtained by a sol–gel method, using triethyl phosphite or triethyl phosphate as the phosphorous source. The crystal structure of the products was analyzed by X-ray powder diffraction, while morphology was studied using scanning electron microscopy, transmission electron microscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy. Optimal synthesis conditions for the CNFs/LiCoPO₄ in light of the best electrochemical performance are discussed. The best discharge capacity 105 mAh/g (or ca. 63% of the theoretical capacity) shows the material with 40% CNFs/LiCoPO₄ and addition coating by carbon black. This composition has a best purity of active materials and point coverage of CNFs. The X-ray photoelectron C1s spectra of the CNFs surface without and with sputter erosion show enhancement of C–O bonds at the fiber surface, which does not influence significantly electrochemical behavior of the composite materials.     

A new phenanthrene-based bis-oxime chemosensor for Fe(III) and Cr(III) discrimination

The synthesis of two new 2,7-disubstituted phenanthrene-based bis oximes is described. The ability of these two compound for complexing heavy metal cations have been studied and complexation constants and complex stoichiometry for Cr³⁺ and Fe³⁺ complex have been determined. The fluorescent properties of ligand 2 make this compound able to act as a sensor able to discriminate between Cr³⁺ and Fe³⁺. Detection limits for these two cations have been evaluated.