Emission from a slab of resonant two-level atoms induced by a delta-pulse excitation

Using eigenmode analysis I calculate in the linear regime the emission characteristics from a slab of two-level resonant atoms excited by a delta-pulse propagating normal to the surface of the slab. I show that the qualitative features of the emitted spectra in the forward and backward directions to be different from each other; I also find the effects of the total linewidth of the resonance line and of the deviation in the spatial periodicity of the initial atomic polarization from k ₀, where k ₀ = ω₀/c and ω₀ is the two level resonant frequency, on the spectra. The dominant spatial mode of the system is identified as the key parameter for determining the forward emission spectral width.     

A Class of Non-associated Materials: n-Monotone Materials—Hooke’s Law of Elasticity Revisited

Generalized Standard Materials are governed by maximal cyclically monotone operators and modeled by convex potentials. Géry de Saxcé’s Implicit Standard Materials are modeled by biconvex bipotentials. We analyze the intermediate class of n-monotone materials governed by maximal n-monotone operators and modeled by Fitzpatrick’s functions. Revisiting the model of elastic materials initiated by Robert Hooke, and insisting on the linearity, coaxiality and monotonicity properties of the constitutive law, we illustrate that Fitzpatrick’s representation of n-monotone operators coming from convex analysis provides a constructive method to discover the best bipotential modeling a n-monotone material. Giving up the symmetry of the linear constitutive laws, we find out that n-monotonicity is a relevant criterion for the materials characterization and classification.     

Theoretical conformational analysis of opiate peptides Leu-Enkephalin (H-Tyr-Gly-Gly-Phe-Leu-OH) and its two thioamide analogs (H-Tyr-Glyψ[CSNH]Gly-Phe-Leu-OH) and (H-Tyr-Gly-Glyψ[CSNH]Phe-Leu-OH)

In order to find informations on the native structure of the Leu-Enkephalin opiate peptide, the parent peptide and its two thioamide analogs (Thio-Gly2)Leu-Enkephalin and (Thio-Gly3)Leu-Enkephalin were studied by the theoretical method PEPSEA. This comparative conformational analysis showed that the active conformation is a β turn structure centered on Gly3 and Phe4. Moreover, this study showed also that the more active analog (Thio-Gly2)Leu-Enk has a lower tendency to adopt this structure. Consequently, its high activity can only be explained by its long lifetime due to its resistance to enzymatic hydrolysis, following the substitution of the amide linkage by the thioamide one. The weakly active analog (Thio-Gly3)Leu-Enk does not adopt this structure and prefers instead a β turn structure centered on Gly2 and Gly3. This study also confirmed the importance of the distances between the Tyr and Phe residues at positions 1 and 4, and that of the terminal Tyrosine N-H group which must be free of any intramolecular hydrogen bond in order to be available in the molecular recognition process.     

The detection and location estimation of disasters using Twitter and the identification of Non-Governmental Organisations using crowdsourcing

This paper provides the humanitarian community with an automated tool that can detect a disaster using tweets posted on Twitter, alongside a portal to identify local and regional Non-Governmental Organisations (NGOs) that are best-positioned to provide support to people adversely affected by a disaster. The proposed disaster detection tool uses a linear Support Vector Classifier (SVC) to detect man-made and natural disasters, and a density-based spatial clustering of applications with noise (DBSCAN) algorithm to accurately estimate a disaster’s geographic location. This paper provides two original contributions. The first is combining the automated disaster detection tool with the prototype portal for NGO identification. This unique combination could help reduce the time taken to raise awareness of the disaster detected, improve the coordination of aid, increase the amount of aid delivered as a percentage of initial donations and improve aid effectiveness. The second contribution is a general framework that categorises the different approaches that can be adopted for disaster detection. Furthermore, this paper uses responses obtained from an on-the-ground survey with NGOs in the disaster-hit region of Uttar Pradesh, India, to provide actionable insights into how the portal can be developed further.

     

The metal-to-ligand charge-transfer luminescences of ruthenium(II)-polypyridine-tetraam(m)ine complexes. Support for the interconvertibility of optical and thermal (kinetic) Franck-Condon parameters

This is the first report of the metal-to-ligand charge-transfer (MLCT) emission spectra of the bis-ethylenediamine- and tetraammine-bipyridineruthenium(II) complexes. The emission maxima occur at 800 and 840 nm, respectively, at 77 K in DMSO/H(2)O glasses. The MLCT excited states of these complexes have short lifetimes (less than 50 ns), and as a consequence, the emission intensities are very small. The energies of the emission maxima are very close to those expected on the basis of the difference in reduction potentials of the metal and ligand (DeltaE(1/2)) and the values of the reorganizational free energies (chi(r)) of the vertical transitions estimated from the electron-transfer self-exchange reactions of the complexes (hnu(max)(em) congruent with FDeltaE(1/2) - chi(r), where F is Faraday's constant). The low energy of the emissions is in large part a consequence of the substantial contributions of the reorganizational free energies.     

Rapid Determination of Simple Polyphenols in Grapes by LC Using a Monolithic Column

The development of a rapid, reliable and reproducible LC method for the determination and quantification of 13 polyphenols (gallic acid, protocatechuic aldehyde, gentisic acid, catechin, vanillinic acid, caffeic acid, vanillin, epicatechin, syringaldehyde, p-coumaric acid, ferulic acid, sinapic acid and resveratrol) in grapes and derived products is reported. The polyphenols were separated in less than 8 min. Employed was an RP-18e (100 mm × 4.6 mm) monolithic type column. A gradient method with the following solvents was utilised for the chromatographic separation: A: 90% water, 2% acetic acid in methanol, and B: 90% methanol, 2% acetic acid in water. Two detectors in series were employed: a UV–Vis detector and a fluorescence excitation/emission detector. Influence of temperature (15–40 °C) and solvent flow rate (2–5 mL min^?1) on the separation were studied, and 25 °C and 2.5 mL min^?1 were found to be the optimum conditions. The relative standard deviations of the resulting peak areas, for both intra- and inter- experiments, were less than 2.4 and 2.6%, respectively. Finally, the developed method has been utilised for the quantification of the polyphenols in real samples.     

Density functional study on the functionalization of BN nanotubes with nitramide

Chemical functionalization of a boron nitride nanotube (BNNT) with nitramide molecule (H₂NNO₂) has been investigated using density functional theory. It was found that the molecule prefers to be adsorbed and dissociated on a diagonal B-N bond of the tube surface so that the -NH₂ and -NO₂ groups are attached on B and N atoms, releasing energy of 0.50 eV. The results show that the functionalized BNNT is more soluble than the pristine one which may render the chemical modification process to be an effective way for purification of the BNNTs. Depending on the cleavage behavior of nitramide on the tube, HOMO/LUMO gap of the system can be either decreased or increased while the chemically modified BNNT is still a semiconductor. Furthermore, the chemical functionalization results in hindered field emission in the tube by raising the potential barrier of the electron emission.     

Cytotoxic effect and electrophysiological study on human MRC-5 fibroblasts of R-irniine, a natural alkylpyrrolidine alkaloid

R-irniine is a natural 2-alkylpyrrolidine alkaloid extracted from Arisarum vulgare Targ., a species belonging to the Araceae family known in Morocco for its toxicity. Cytotoxic and electrophysiological studies of this compound on human MRC-5 fibroblasts were carried out. Cytotoxic potential of R-irniine was detected on MRC-5 fibroblasts at 40 microg/mL. We carried out the electrophysiological study of this compound on MRC-5 cells by using the technique of patch-clamp in "Whole cell" configuration. R-irniine showed no effect on the outward potassium current of the MRC-5 fibroblasts.     

Essential oil from Ocimum basilicum (Omani Basil): a desert crop

The focus of the present study was on the influence of season on yield, chemical composition, antioxidant and antifungal activities of Omani basil (Ocimum basilicum) oil. The present study involved only one of the eight Omani basil varieties. The hydro-distilled essential oil yields were computed to be 0.1%, 0.3% and 0.1% in the winter, spring and summer seasons, respectively. The major components identified were L- linalool (26.5-56.3%), geraniol (12.1-16.5%), 1,8-cineole (2.5-15.1%), p-allylanisole (0.2-13.8%) and DL-limonene (0.2-10.4%). A noteworthy extra component was beta- farnesene, which was exclusively detected in the oil extracted during winter and spring at 6.3% and 5.8%, respectively. The essential oil composition over the different seasons was quite idiosyncratic, in which the principal components of one season were either trivial or totally absent in another. The essential oil extracted in spring exhibited the highest antioxidant activity (except DPPH scavenging ability) in comparison with the oils from other seasons. The basil oil was tested against pathogenic fungi viz. Aspergillus niger, A. fumigatus, Penicillium italicum and Rhizopus stolonifer using a disc diffusion method, and by determination of minimum inhibitory concentration. Surprisingly high antifungal values were found highlighting the potential of Omani basil as a preservative in the food and medical industries.