Active infrared thermography applied to the investigation of art and historic artefacts

Infrared thermography (IRT) is a non-destructive technique that has recently been extensively applied to the investigation of cultural heritage. It provides information on the surface and subsurface structure of the artefacts by the analysis of the heat diffusion process within the sample. IRT has been successfully applied to the study of historic large structures and buildings most of the time by means of the so-called passive approach, where only the naturally occurring temperature changes in the sample are analysed. On the other hand, IRT has also been applied to the study of other art and historic artefact by applying the so-called active method where the thermal stimulation of the sample is required. In this article, an overview of the applications of active thermography to the investigation of art and historic artefacts will be presented and discussed.     

Mid-infrared (MIR) metabolic fingerprinting of amniotic fluid: A possible avenue for early diagnosis of prenatal disorders?

This work describes a mid-infrared (MIR) metabolic profiling study of 2^nd trimester amniotic fluid in relation to selected prenatal disorders, with results focusing on fetal malformations (FM), preterm delivery (PTD) and premature rupture of membranes (PROM), the latter two conditions occurring later in pregnancy. Partial least squares-discriminant analysis (PLS-DA) models were obtained for FM and pre-PTD subject groups, supported by Monte Carlo Cross Validation (MCCV), and identified specific MIR profile changes. For pre-PROM subjects, minor changes were noted. MIR interpretation was assisted by intra- (MIR/MIR) and inter- (MIR/NMR) domain statistical correlation analysis, the results unveiling possible biomarker MIR signatures for FM and pre-PTD subjects. Biofluid MIR metabolic profiling holds enticing possibilities as a low cost, easy to use, rapid method and the results presented have shown its sensitivity to clinically diagnosed conditions such as FM, and to the pre-clinical stages of PTD. Specific improvement needs are discussed, namely regarding sample numbers and experimental reproducibility.     

Conductivity drop and crystallites redistribution in gold film

Electrical conductivity of Au film deposited on Si(100), Si(111) and BK7 glass substrates, ranging from 20 nm to 1000 nm, was measured. Conductivity drop and a decrease of averaged crystallite size are observed around film thickness of 200 nm. Investigation of the conductivity drop led to the discovery that a redistribution of crystallites of {111} and {220} occurs in the conductivity drop region. By analyzing the relationship of distribution of crystallites, averaged crystallite size and conductivity ratios and together with the atomic force microscope pictures, leads to the conclusion that the thermal conductivity drop region is caused by the presence of many small crystallites. These small crystallites are responsible for yielding a lower averaged crystallite size and causing a higher grain boundary scattering. PACS 73.50; 68.47.De; 68.55.Jk     

Biocomputing security system: concatenated enzyme-based logic gates operating as a biomolecular keypad lock

A biomolecular security system mimicking a keypad lock device was developed using enzyme-based concatenated AND logic gates resulting in the implication logic network.     

Finite-length models of carbon nanotubes based on Clar sextet theory

Finite-length models of metallic and semiconducting carbon nanotubes (CNTs) based on Clar sextet theory of aromatic systems are proposed. For metallic CNTs, the electronic properties of finite-length models converge monotonically to the values expected for quasi-monodimensional metallic systems. For semiconducting CNTs, the use of finite-length models as proposed in this work leads to a fast convergence of the electronic properties to the values expected for the corresponding infinite-length nanotube.     

Redox-switchable chromophores based on metal (Ni, Pd, Pt) mixed-ligand dithiolene complexes showing molecular second-order nonlinear-optical activity

The synthesis and full characterization of the redox-active nickel triad mixed-ligand dithiolene complexes based on Bz(2)pipdt = 1,4-dibenzylpiperazine-3,2-dithione and dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate ligands are reported. These complexes show a reversibly bleacheable solvatochromic peak and a remarkably high negative molecular first hyperpolarizability, whose values depend on the metal being highest for the platinum(II) compound.     

Mixed-ligand Pt(II) dithione-dithiolato complexes: influence of the dicyanobenzodithiolato ligand on the second-order NLO properties

The mixed-ligand dithiolene complex [Pt(Bz(2)pipdt)(dcbdt)] (1) bearing the two ligands Bz(2)pipdt = 1,4-dibenzyl-piperazine-3,2-dithione and dcbdt = dicyanobenzodithiolato, has been synthesized, characterized and studied to evaluate its second-order optical nonlinearity. The dithione/dithiolato character of the two ligands gives rise to an asymmetric distribution of the charge in the molecule. This is reflected by structural data showing that in the C(2)S(2)PtS(2)C(2) dithiolene core the four sulfur atoms define a square-planar coordination environment of the metal where the Pt-S bond distances involving the two ligands are similar, while the C-S bond distances in the C(2)S(2) units exhibit a significant difference in Bz(2)pipdt (dithione) and dcbdt (dithiolato). 1 shows a moderately strong absorption peak in the visible region, which can be related to a HOMO-LUMO transition, where the dcbdt ligand (dithiolato) contributes mostly to the HOMO, and the Bz(2)pipdt one (dithione) mostly to the LUMO. Thus this transition has ligand-to-ligand charge transfer (CT) character with some contribution of the metal and undergoes negative solvatochromism and molecular quadratic optical nonlinearity (μβ(0) = -1296 × 10(-48) esu), which was determined by the EFISH (electric-field-induced second-harmonic generation) technique and compared with the values of similar complexes on varying the dithiolato ligand (mnt = maleonitriledithiolato, dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato). Theoretical calculations help to elucidate the role of the dithiolato ligands in affecting the molecular quadratic optical nonlinearity of these complexes.     

Global compactness for a class of quasi-linear elliptic problems

We prove a global compactness result for Palais-Smale sequences associated with a class of quasi-linear elliptic equations on exterior domains.     

Square-planar mixed ligand nickel dithiolenes as second-order non-linear chromophores: synthesis and characterisation of [Ni(Me<Subscript>2</Subscript>pipdt)(dddt)]

Abstract  The novel [Ni(Me₂pipdt)(dddt)] complex based on the Me₂pipdt (1,4-dimethylpiperazine-3,2-dithione) and dddt (5,6-dihydro-1,4-dithine-2,3-dithiolate) ligands has been synthesised and characterised. Structural data, vibrational marker, solvatochromic behaviour of the typical absorption in the near infrared region, and approximate theoretical calculations suggest that an unbalanced electron distribution at the dithiolene core occurs in the ground and excited states. In particular, the dddt ligand gives a prevailing contribution to the HOMO, and Me₂pipdt to the LUMO. The charge-transfer character of the HOMO–LUMO transition makes this complex a potential second-order non-linear optic chromophore. Graphical Abstract