Molecular conformation of the racemic indan derivative (±)-1-trans-3-(3,4-dichlorophenyl)-2,3-dihydro-1H-indene-1-carboxamide

This paper presents the structural characterization of the indan derivative (±)-1-trans-3-(3,4-dichlorophenyl)-2,3-dihydro-1H-indene-1-carboxamide, which was unambiguously determined by X-ray diffraction (XRD) to be a racemate (R/S: 50/50) crystallizing in an achiral crystal structure (P2₁/c, a = 9.3180(1) Å, b = 7.9070(2) Å, c = 19.7550(4) Å, β = 103.250(1)°, V = 1416.75(5) Å³ and Z = 4). The diastereomers are related by the inversion symmetry and linked by H bond forming a dimer. The crystal packing is stabilized by hydrogen bonds, including the classical one responsible for the formation of centrosymmetric dimers, and non-classical ones involving C–H···O and C–H···π-aryl interactions. The intra and intermolecular geometry of the title compound is compared to the (±)-1-trans-3-(3,4-dichlorophenyl)-2,3-dihydro-1H-indene-1-carboxylic acid one, which also present an achiral crystal structure from racemates (R/S: 50/50). The two indan derivatives crystallize in a very similar unit cell.     

Fluoropolymer piezoelectrets with tubular channels: resonance behavior controlled by channel geometry

Ferro- or piezoelectrets are dielectric materials with two elastically very different macroscopic phases and electrically charged interfaces between them. One of the newer piezoelectret variants is a system of two fluoroethylenepropylene (FEP) films that are first laminated around a polytetrafluoroethylene (PTFE) template. Then, by removing the PTFE template, a two-layer FEP structure with open tubular channels is obtained. After electrical charging, the channels form easily deformable macroscopic electric dipoles whose changes under mechanical or electrical stress lead to significant direct or inverse piezoelectricity, respectively. Here, different PTFE templates are employed to generate channel geometries that vary in height or width. It is shown that the control of the channel geometry allows a direct adjustment of the resonance frequencies in the tubular-channel piezoelectrets. By combining several different channel widths in a single ferroelectret, it is possible to obtain multiple resonance peaks that may lead to a rather flat frequency-response region of the transducer material. A phenomenological relation between the resonance frequency and the geometrical parameters of a tubular channel is also presented. This relation may help to design piezoelectrets with a specific frequency response.     

Combining local and nonlocal terms in a nonlinear elliptic problem

In this paper, we study the existence, uniqueness, multiplicity, and stability of positive solution of a nonlinear elliptic problem that combines local and nonlocal terms, taking the form of an integral in the space. The proofs are mainly based on fixed point theorems, bifurcation techniques, sub‐supersolutions, and continuation arguments. Copyright © 2012 John Wiley & Sons, Ltd.     

Morpho-physiological analysis of the insect fat body: A review

The insect fat body is the main organ of the intermediate metabolism of insects. The majority of proteins of the haemolymph is synthesized in this tissue, which also presents the functions of lipids, carbohydrates and proteins storage. This tissue is also responsible for the synthesis of vitellogenins, proteins with an important role in the reproduction of the insects, being incorporated into the oocytes during vitellogenesis. The fat body consists of thin layers or strings, generally one or two cells thick, or small nodules suspended in the hemocele through connective tissues and trachea. Within a species, the structure of this tissue is more or less constant, but can have considerable differences between insects of different orders. In this way, this article makes a review about the main morpho-physiological features of the fat body cells of the insects, as well as a phylogenetic study of the fat body between basal and derived species of the Attini tribe ants.     

Laser-induced alteration of contaminated papers

Cleaning of paper objects represents one of the most complex cases of laser ablation, since low volumes of dispersed material phases are evaporated while a sensitive and fragile fibrous organic matrix has to be preserved. Conventional chemical and mechanical cleaning methods suffer from the common phenomenon that the foreign matter is diluted into the substrate rather than removed. The application of a laser beam allows highly localized and optically specific interaction. However, the occurrence of extreme temperatures and light intensities may cause irreversible alteration of the paper matrix. Further, incomplete removal and/or chemical conversion of contaminations may result in insufficient cleaning or affect the ageing behaviour. Laser treatments were performed by Q-switched Nd:YAG lasers at three wavelengths (355 nm, 532 nm, and 1064 nm). Papers contaminated with inks and adhesive-tape remnants served as model samples. Multispectral imaging and colorimetric results served to quantify and systematize the results. PACS 81.05.Lg; 81.65.Cf; 81.70.Fy     

Reverse saturable absorption in chlorophyll A solutions

The dynamic nonlinear absorption of a chloroform solution of chlorophyll A was investigated using the Z-scan technique with picosecond pulses at 532 nm. The nonlinear absorption exhibits a reverse saturation, indicating a strong intersystem crossing (singlet–triplet) process. The time evolution of the optical nonlinearity, modeled by means of a five-level energy diagram, allows the determination of excited-state cross sections and the lifetime of the intersystem crossing based on its absorption characteristics and efficient formation of triplet states. Chlorophyll A was found to be a good candidate for a sensitizer in photodynamic therapy. Received: 14 February 2002 / Published online: 2 May 2002     

Basic-functionalized recyclable ionic liquid catalyst: A solvent-free approach for Michael addition of 1,3-dicarbonyl compounds to nitroalkenes under ultrasound irradiation

A task-specific ionic liquid (TSIL) has been introduced as a recyclable catalyst in Michael addition. A series of nitroalkenes and various C-based nucleophiles were reacted in the presence of 30 mol% of recyclable basic-functionalized ionic liquid. Good to excellent yields were obtained in 30 min under ultrasound irradiation.     

Type,cotype and twisted sums induced by complex interpolation

This paper deals with extensions or twisted sums of Banach spaces that come induced by complex interpolation and the relation between the type and cotype of the spaces in the interpolation scale and the nontriviality and singularity of the induced extension. The results are presented in the context of interpolation of families of Banach spaces, and are applied to the study of submodules of Schatten classes. We also obtain nontrivial extensions of spaces without the CAP which also fail the CAP.     

Silicene-terminated surface of calcium and strontium disilicides: properties and comparison with bulk structures by computational methods

The bulk and surface structures of calcium and strontium disilicides are investigated by computational methods using density functional theory. The investigated structures are R6, R3 and P1-CaSi₂ and P1-SrSi₂. The investigated properties are the cleavage energy at the silicene sheet, buckling of the bulk and surface silicene layers, charge transfer from calcium to silicon, band structure of bulk and surface-terminated structures and adsorption energies on H atoms and H₂ molecules on the silicene-terminated surface of the R3 phase. The cleavage energy at the silicene surface is low in all cases. Structures P1-CaSi₂ and R3-CaSi₂ contain silicene sheets with different coordination to Ca, while R6-CaSi₂ contains both types of the sheets. It is shown that the properties of the two types of silicene-like sheets in R6-CaSi₂ are similar to those of the corresponding sheets in P1-CaSi₂ and R3-CaSi₂, and the thermodynamically stable R6 phase is a good candidate for experimental investigation of silicene-terminated surface in calcium disilicide.