Exact Null Controllability of a Stage and Age-Structured Population Dynamics System

This paper is concerned with the exact null controllability of an age-dependent life cycle dynamics with nonlocal transition processes arising as boundary conditions. We investigate the controllability for the pest by acting on eggs in a small age interval. The main method is based on the derivation of estimations for the adjoint variables related to an optimal control problem. A fixed point theorem is then used to draw conclusions.     

Evaluation of N‐hydroxymethylphthalimide in alkaline medium: Novel entry to the tricyclic [1,3]oxazepine core via an intramolecular π and O‐cationic cyclization

Fused isoindolo[1,3]benzo(or thieno)oxazepines 8a,b and one of their positional isomers aromatic tricyclic N,O‐acetals 13b are reported to occur efficiently in a three‐step sequence from N‐hydroxy‐methylphthalimide (6) . The key step of this methodology is the intramolecular arylation of an endocyclic and/or exocyclic N‐acyliminium cation. The mechanism leading to these species, in particular to a tricyclic lactam 13b , is discussed.     

Diastereoselective access to chiral non‐racemic [1,3]oxazolo‐[2,3‐a]isoindol‐5‐one ring systems viaO‐cationic cyclization

Dedicated to Professor Jean Morel for his retirement The title compounds 4 have been prepared from suitable β‐amino‐ alcohol 2 and phthalic anhydride ( 5 ) in a three‐step sequence in moderate to good yields (58‐94%). The key step of this methodology is based on an intramolecular O‐cationic cyclization involving N‐acyliminium species. The high levels of the observed chemoselectivity during the intermolecular or intramolecular cyclization were also discussed.     

Covalently bonded infinite zigzag chain structure in a novel Zn(II) complex of 2,5-dihydroxy-1,6-benzenedicarboxylic acid

Reaction of the disodium salt of 2,5-dihydroxy-1,6-benzenedicarboxylic acid (DHBDC) and zinc sulfate in aqueous solution at room temperature yields complex [Zn(H₂O)₂(DHBDC)]_n. The coordination tetrahedron around Zn center exhibits a highly irregular geometry, two carboxylato oxygen atom and two water–ligand oxygen atoms occupying the coordination sites. Structural analyses of this complex reveal that the individual zero-dimensional units (0D) are covalently linked through their metal ends, forming infinite 1D zigzag chains. These chains, in turn, are engaged in 2D hydrogen bonding, resulting in a 3D supramolecular architecture.     

Comparison of various extraction methods for identification and determination of volatile metabolites from the brown alga Dictyopteris membranacea

Three different methods: hydrodistillation (HD), focused microwave-assisted hydrodistillation (FMAHD) and supercritical fluid extraction (SFE) have been applied, for the first time together, for the extraction of volatile metabolites of the brown alga Dictyopteris membranacea. The oils obtained were analyzed by GC-MS (identification and determination of metabolites) and the results were compared. The main chemical classes of compounds identified were C11 hydrocarbons for HD method, sesquiterpenes for FMAHD method and sulphur compounds for SFE method.     

Site-specific incorporation of glycosylated serine and tyrosine derivatives into proteins

Glycosylation of proteins can have a dramatic effect on their physical, chemical, and biological properties. Analogues of dihydrofolate reductase and firefly luciferase containing glycosylated amino acids at single, predetermined sites have been elaborated. Misacylated suppressor tRNAs activated with glycosylated serine and tyrosine derivatives were used for suppression of the nonsense codons in a cell-free protein biosynthesizing system, thereby permitting the preparation of the desired glycosylated proteins. In this fashion, it was possible to obtain proteins containing both mono- and diglycosylated amino acids, including glycosylated serine and tyrosine moieties. For the modified firefly luciferases, the effect of these substitutions on the wavelength of the light emitted by firefly luciferase was investigated. The maximum wavelength for mutants containing peracetylated glycosylated serine derivatives at position 284 showed a red shift in the emission spectra. For mutants containing glycosylated tyrosines, the red shift was observed only when the carbohydrate moiety was fully deacetylated.     

A novel microfluidic flow-injection analysis device with fluorescence detection for cation sensing. Application to potassium

A microfabricated device has been developed for fluorimetric detection of potassium ions without previous separation. It is based on use of a fluorescent molecular sensor, calix–bodipy, specially designed to be sensitive to and selective for the target ion. The device is essentially made of a Y-shape microchannel moulded in PDMS fixed on a glass substrate. A passive mixer is used for mixing the reactant and the analyte. The optical detection arrangement uses two optical fibres, one for excitation by a light-emitting diode, the other for collection of the fluorescence. This system enabled the flow-injection analysis of the concentration of potassium ions in aqueous solutions with a detection limit of 0.5 mmol L⁻¹ and without interference with sodium ions. A calibration plot was constructed using potassium standard solutions in the range 0–16 mmol L⁻¹, and was used for the determination of the potassium content of a pharmaceutical pill. Figure Photography of the microfluidic channel showing the ridges in the PDMS substrate at the top of the channel     

Electronic properties of 3,3'-dimethyl-5,5'-bis(1,2,4-triazine): towards design of supramolecular arrangements of N-heterocyclic Cu(I) complexes

A new efficient and safe synthesis of 3,3'-dimethyl-5,5'-bis-(1,2,4-triazine) is presented. The electron-density distribution and electrostatic properties (charge, electrostatic potential) of this molecule were analyzed. These properties were derived from a high-resolution single-crystal X-ray diffraction experiment at 100 K and compared to the results obtained from ab initio DFT quantum-mechanical calculations. Comparisons of its electrostatic potential features and integrated atomic charges (quantum theory of atoms in molecules, QTAIM) have been made with those of related molecules such as bipyrimidine ligands. Two methods were used to derive integrated charges: one is based on the conventional analytical procedure and the second uses a steepest-ascent numerical algorithm. Excellent agreement was obtained between these two methods. Charges and electrostatic potential were used as predictive indices of metal chelation and discussed in the light of complexation abilities of the title compound and related molecules. The crystal structure of a Cu(I) complex of 3,3'-dimethyl-5,5'-bis(1,2,4-triazine) is reported here. In the solid state, this complex forms a three-dimensional multibranch network with open channels in which counterions and solvent molecules are located. This architecture involves both cis and trans isomers of the title compound.     

Long argan fruit drying time is detrimental for argan oil quality

Argan oil is extracted from the kernels of argan fruits that have been sun-dried for either a few days or up to several weeks. The influence of the fruit drying time on the quantity, quality, and preservation of solvent-extracted argan oil was compared with press-extracted argan oil. Quantitatively, the time necessary for efficient fruit peeling and the amount of extracted oil were determined with regard to the fruit drying time (0 to 28 days). Argan oil quality was studied using, as markers, moisture content, specific extinction, acid index, peroxide index, fatty acid composition, and Rancimat oxidative stability. Oil from fresh fruit presents a high moisture content, high acidity and peroxide values, and short shelf life. Ten to fourteen days of sun-drying is optimum to obtain high quality argan oil.     

Thermal degradation of a reactive flame retardant based on cyclotriphosphazene and its blend with DGEBA epoxy resin

Hexaglycidyl cyclotriphosphazene (HGCP) was synthesized, and characterized by FTIR, ³¹P, ¹H, and ¹³C-NMR. This compound was used as a reactive flame retardant to blend with commercial epoxy resin DGEBA (Diglycidyl ether of bisphenol A). Its effect on the DGEBA decomposition pathways was characterized by studying both gas and solid phases produced during thermogravimetric analysis (TGA). The gases evolved during TGA in air were studied by means of thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR), while the solid residues were analysed by FTIR and scanning electron microscopy (SEM). The results showed that HGCP presents a good dispersion in DGEBA, and the blend thermoset with 4,4′-methylene-dianiline (MDA) curing agent leads to a significant improvement of the thermal stability at elevated temperature with higher char yields compared with pure DGEBA thermoset with the same curing agent. Improvement has also been observed in the fire behaviour of blend sample.