Transience and Persistence in the Depositional Record of Continental Margins

Continental shelves and coastal plains are large persistent depositional landforms, which are stationary (nonmigrating) at their proximal ends and characterized by relatively steady long-term growth. In detail, however, their surface form and stratigraphic record is built of transient freely migrating landscape elements. We derive the timescales of crossover from transient to persistent topographic forms using empirical scaling relations for mean sediment accumulation as a function of averaging time, based upon tens of thousands of empirical measurements. A stochastic (noisy) diffusion model with drift predicts all the gross features of the empirical data. It satisfies first-order goals of describing both the surface morphology and stratigraphic completeness of depositional systems. The model crossover from noise-dominated to drift-dominated behavior corresponds to the empirical crossover from transport-dominated (autogenic) transient behavior to accommodation-dominated (subsidence) persistent behavior, which begins at timescales of 102–103 years and is complete by scales of 104–105 years. Because the same long-term scaling behavior emerges for off-shelf environments, it is not entirely explicable by steady subsidence. Fluctuations in sediment supply and routing probably have significant influence. At short-term (transient) scales, the exponents of the scaling relations vary with environment, particularly the prevalence of channeled sediment transport. At very small scales, modeling sediment transport as a diffusive process is inappropriate. Our results indicate that some of the timescales of interest for climate interpretation may fall within the transitional interval where neither accommodation nor transport processes are negligible and deconvolution is most challenging

Targeted delivery of platinum-based anticancer complexes

The most widely used anticancer drugs are platinum-based. Their efficacy might be improved by carriers which can transport large numbers of Pt centres, shield the drug from premature activation, and/or deliver Pt specifically to cancer cells using vectors which recognise specific targets. We describe recent progress using functionalized carbon nanotubes (CNTs) and nanorods, hollow Prussian blue (HPB), magnetic iron oxide and gold nanoparticles, liposomes, nanogels and polymers, as well as active targeting by conjugation to biodegradable proteins and peptides (e.g. EGF, heparin, herceptin, somatostatin and TAT). Spatially targeted activation of PtIV prodrugs using light is also a promising approach. Interestingly, use of these new delivery and targeting systems for platinum drugs can lead to species with unusual reactivity which can kill cancer cells by new mechanisms

Dual action photosensitive platinum(II) anticancer prodrugs with photoreleasable azide ligands

The synthesis, characterisation and properties of novel photosensitive Pt(II) complexes [Pt(terpyridine)(N3)]CF3SO3 (1b∙CF3SO3) and [Pt(N^C^N)(N3)] (2b) containing photoreleasable azide ligands with potential as dual photochemotherapeutic and photodynamic therapeutic agents are reported. Their X-ray crystal structures show distorted square-planar Pt(II) coordination geometry with π-stacking between adjacent planar Pt units. These complexes intercalate into DNA with similar binding ability as their chlorido analogues and generate singlet oxygen upon irradiation with blue light (420 nm). Photoactivation of azido complexes leads to the release of the azide ligands and the formation of new platinum species. These properties appear to be favourable for potential dual-action photoactive prodrugs

Influence of substrate miscut angle on surface morphology and luminescence properties of AlGaN

The influence of substrate miscut on Al0.5Ga0.5 N layers was investigated using cathodoluminescence (CL) hyperspectral imaging and secondary electron imaging in an environmental scanning electron microscope. The samples were also characterized using atomic force microscopy and high resolution X-ray diffraction. It was found that small changes in substrate miscut have a strong influence on the morphology and luminescence properties of the AlGaN layers. Two different types are resolved. For low miscut angle, a crack-free morphology consisting of randomly sized domains is observed, between which there are notable shifts in the AlGaN near band edge emission energy. For high miscut angle, a morphology with step bunches and compositional inhomogeneities along the step bunches, evidenced by an additional CL peak along the step bunches, are observed

Axial functionalisation of photoactive diazido platinum(iv) anticancer complexes

Mono-axial functionalised octahedral diazido Pt(IV) complexes trans,trans,trans-[Pt(py)2(N3)2(OR1)(OR2)] (OR1 = OH and OR2 = anticancer agent coumarin-3 carboxylate (cou, 2a), pyruvate dehydrogenase kinase (PDK) inhibitors 4-phenylbutyrate (PhB, 2b) or dichloroacetate (DCA, 2c)), and their di-axial functionalised analogues with OR1 = DCA and OR2 = cou (3a), PhB (3b), or DCA (3c) have been synthesised and characterised, including the X-ray crystal structures of complexes 2a, 3a, 3b and 3c. These complexes exhibit dark stability and have the potential to generate cytotoxic Pt(II) species and free radicals selectively in cancer cells when irradiated. Mono-functionalised complexes 2a–2c showed higher aqueous solubility and more negative reduction potentials. Mono- and di-functionalised complexes displayed higher photocytotoxicity with blue light (1 h, 465 nm, 4.8 mW cm−2) than the parent dihydroxido complex 1 (OR1 = OR2 = OH) in A2780 human ovarian (IC50 0.9–2.9 μM for 2a–2c; 0.11–0.39 μM for 3a–3c) and A549 human lung cancer cells (5.4–7.8 μM for 2a–2c; 1.2–2.6 μM for 3a–3c) with satisfactory dark stability. Notably, no apparent dark cytotoxicity was observed in healthy lung MRC-5 fibroblasts for all complexes (IC50 > 20 μM). Significantly higher platinum cellular accumulation and photo-generated ROS levels were observed for the di-functionalised complexes compared with their mono-functionalised analogues when cancer cells were treated under the same concentrations

Reactions of the Antiarthritic Drug Aurothiomalate With Phenylmercury(II) Compounds: NMR Studies

Clinical formulations of the antiarthritic drug aurothiomalate sometimes contain phenylmercury(ll) compounds as antimicrobial preservative agents and, in the presence of para-chloromercuri-benzoate, aurothiomalate is a potent inhibitor of collagenase. By 1H NMR spectroscopy, para-hydroxymercuribenzoate and para-hydroxymercuriphenylsulphonate were shown to react with aurothiomalate by complexing only with the terminal thiomalate of aurothiomalate oligomers, thereby converting them to ring complexes. The reaction was also detected by UV spectroscopy. The arylmercury complexes produced no change in the bulk of the thiomalate residues of aurothiomalate indicating considerable stability of the polymeric structure of aurothiomalate in which each gold is bound to two thiolate residues. The potent inhibition of the mercurial induced collagenase activity may be due either to aurothiomalate or to a complex formed between the terminal thiomalate residues with the arylmercurial. The arylmercury complexes may be unsuitable as antimicrobials in solutions of aurothiomalate because of complexation with the terminal thiomalate residues