We present a deterministic model for on-line social networks based on transitivity and local knowledge in social interactions. In the Iterated Local Transitivity (ILT) model, at each time-step and for every existing node x, a new node appears which joins to the closed neighbour set of x. The ILT model provably satisfies a number of both local and global properties that were observed in real-wor...

A detailed understanding of the sources, transformations and fates of organic species in the environment is crucial because of the central roles that they play in human health, biogeochemical cycles and the Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at ...

A series of potent antimicrobial agents have been prepared. These derivatives are cephalosporins carrying a pyridine ring substituted with a heterocycle in the C-3 position. Some of them showed excellent activity not only against Gram-negative organisms including Pseudomonas aeruginosa but also against Gram-positive ones. In view of their biological and physico-chemical properties, 7 beta-[2-(2...

DNA (deoxyribonucleic acid) is the genetic material common to all of Earth's organisms. Our biological understanding of DNA is extensive and well-exploited. In recent years, chemists have begun to develop DNA for nonbiological applications in catalysis, encoding, and stereochemical control. This Review summarizes key advances in these three exciting research areas, each of which takes advantage...

The structure of a new antibiotic designated lydicamycin was elucidated as shown in Fig. 1 by NMR spectral analysis including a variety of 2D techniques. Lydicamycin possesses a novel skeleton containing tetramic acid and amidinopyrrolidine moieties.

In many crop producing areas of the world there are reports of yield decline and loss of productive potential in soils. Little is known about the long term effects of sugarcane monocropping on changes in physical, chemical and biological properties of soils. The aim of this study was to quantify the physical and chemical condition of soils under sugarcane production in northern Kwazulu-Natal, a...

The concept of hormesis, as an adaptive response of biological systems to moderate environmental challenges, has raised considerable nano-toxicological interests in view of the rapid pace of production and application of even more innovative nanomaterials and the expected increasing likelihood of environmental and human exposure to low-dose concentrations. Therefore, the aim of this review is t...

Morphological control of nanocrystals has become increasingly important, as many of their physical and chemical properties are highly shape dependent. Nanocrystal shape control for both single- and multiple-material systems, however, remains empirical and challenging. New methods need to be explored for the rational synthetic design of heterostructures with controlled morphology. Overgrowth of ...

Characterisation of engineered nanomaterials (NMs) is of outmost importance for the assessment of the potential risks arising from their extensive use. NMs display indeed a large variety of physico-chemical properties that drastically affect their interaction with biological systems. Among them, hydrophobicity is an important property that is nevertheless only slightly covered by the current ph...

Peptide-bond isosteres can enable a deep interrogation of the structure and function of a peptide or protein by amplifying or attenuating particular chemical properties. In this Minireview, the electronic, structural, and conformational attributes of four such isosteres-thioamides, esters, alkenes, and fluoroalkenes-are examined in detail. In particular, the ability of these isosteres to partak...