The role of new eudesmane-type sesquiterpenoid and known eudesmane derivatives from the red alga Laurencia obtusa as potential antifungal–antitumour agents

A new eudesmane sesquiterpenoid, eudesma-4(15),7-diene-5,11-diol (1) along with the known trinor-sesquiterene, teuhetenone (2), and a seco-eudesmane sesquiterpene, chabrolidione B (3), have been isolated from the Red Sea red alga Laurencia obtusa. The chemical structures were elucidated on the basis of extensive spectroscopic analysis. The antifungal and cytotoxic activities of the isolated metabolites were tested against several fungi, yeast and human mammary carcinoma cell line (MCF-7). Compounds 1 and 3 showed a much better activity [minimum inhibitory concentration (MIC): 2.9 μM] than that of amphotericin B (MIC: 4.6 μM). Interestingly, compound 2, the least active antifungal compound, retained the high anticancer activity against MCF-7 (22 μM) in comparison with cisplatin (59 μM), which was determined by employing lactate dehydrogenase assay. Compounds 1–3 are recorded here for the first time from algal flora. The chemotaxonomic importance of the isolated metabolites was discussed.     

Spectral Response of a Stochastic Oscillator under Impacts

An approximate analytical procedure is presented to estimate theresponse spectrum of an oscillator with elastic impacts under a Gaussian whitenoise excitation. The proposed approach is based on a perturbation analysis ofthe problem and on the use of the stochastic averaging principle. The basicidea is to replace the initial system by a more regular system obtained byapproximating the nonlinear restoring force by a Chebychev polynomial, and thento construct for this regular system two approximations: one for the flowand one for the stationary distribution of the response amplitude. Ananalytical approximation of the response spectrum can then be derived fromthese results. Predictions from this analytical approximation are compared with corresponding digital simulation estimates and with the ones obtained from theconventional equivalent linearization method.     

Impact of molecular conformation on barriers to internal methyl rotation: the rotational spectrum of m-methylbenzaldehyde

The ground state spectrum of m-methylbenzaldehyde (m-MBA) was measured with a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. The methyl rotor on m-MBA introduces an internal rotation barrier, which leads to splitting of the torsional energy level degeneracy into A and E states. Ab initio calculations predict a low torsional barrier for both the O-cis and O-trans conformers, resulting in a large doublet splitting up to several gigahertz in the frequency spectrum. The rotational constants, distortion terms, and V(3) values for both species have been determined from the ground state rotational spectrum using the BELGI-C(s) fitting program. There are significant differences in the torsional potential for the O-cis and O-trans m-MBA conformers. Molecular orbitals and resonance structures for each conformer are analyzed to understand the difference in torsional barrier height as well as the irregular shape of the O-trans torsional potential.     

Coupled ab initio potential energy surfaces for the two lowest 2A′ electronic states of the C2H molecule

Realistic two-valued potential energy surfaces for the reaction C(³P) + CH(X²Π) → C₂ + H have been constructed from a set of high level ab initio data describing the first two ²A′ electronic states of the C₂H system. These states have linear equilibrium configurations, known as the X ²Σ⁺ and A²Π states, and are coupled by a conical intersection. They lead to the formation of C₂(X¹Σ⁺ _g) and C₂(a³Π_u) considering an adiabatic dissociation process. The ab initio calculations are of the multireference configuration interaction variety and were carried out using a polarized triple-zeta basis set. Using the ab initio adiabatic energies and the matrix elements of the dipole moment, a 2 × 2 diabatic representation of the electronic Hamiltonian was built. Each element of this Hamiltonian matrix was expressed within the double many-body expansion (DMBE) scheme which is based, in this case, on the extended Hartree-Fock approximate correlation energy model (EHFACE). The analytical adiabatic potential energy surfaces are then obtained as the eigenvalues of this matrix, and display correctly the Σ/Π conical intersection. Moreover, the non-adiabatic couplings given by our analytical model are compared with the ab initio ones, and good qualitative agreement is observed.     

Quark gluon scattering at higher orders in QCD

The infrared evolution equation which sums up leading logarithmic terms is solved for the partonic reactionqgqX in the elastic case i.e.M _X0. The results of the exactO( _s ³ ) calculation are reproduced.     

Die Herstellung von Reinstsiliciumscheiben: Mehr Chemie als man glaubt

Monocrystalline semiconductor wafers made of silicon represent the base material for microelectronic devices. The transfer of the precursor material quartz into a 300 mm wafer deposited with an epitaxial layer requires a multitude of process steps, part of which are determined by chemical reactions. This article has introduced into the manufacturing of semiconductor silicon and the processes etching, polishing, cleaning and epitaxy. This technology branch, though, is distinguished by extreme requirements regarding surface perfection and cleanliness, which may be expressed in atomic layers (surface roughness of the wafers) and ppt (contamination of chemicals)     

Fluorescence as probe for transport and lateral order in vapor grown Langmuir-Blodgett(LB) multilayer-type single crystals of anthracene chromophores with fatty acid tails

Fluorescence spectra of anthracene moieties with fatty acid tails attached at the 2-position are reported for Langmuir-Blodgett(LB)-type multilayer configurations obtained as single crystals in the gas phase. These systems are considered the best ordered experimental model systems for chromophores with fatty acid tails arranged in the LB multilayer configuration. Closest agreement of the fluorescence spectrum with that of the unsubstituted anthracene crystal is found for the 4-(2-anthryl)-1-butanoic acid (2A4) crystal. Packing of the anthracene moieties is very similar in both crystals. Low-temperature spectra (10 K) reveal strong broadening of the peaks due to spatial disorder in the 2A4 crystal. 7-(2-Anthryl)-1-heptanoic acid (2A7) crystals and even more so actual 2A7 LB multilayers have less structured fluorescence spectra that extend further to lower energies. Picosecond time resolved fluorescence decay curves show exciton transport and trapping in low energy traps. Compressed ground state pairs with excimer-type spatial configurations are excited directly in the red (476 nm) to emit structureless excimer-type fluorescence.     

Evaluation of a new maintenance concept for the preservation of highways

Asphalt roads gradually deteriorate over time and need mendingto remain in a good state. Inspections are performed to obtaininformation about the current state of the road; when the levelof damage reaches the established standards, the road is repairedthrough a maintenance action that is considered most cost-effective.Because of economies of scale, it is to a certain extent economicalto limit the number of maintenance services by integrating neighbouringsegments into a homogeneous section which is completely repaired.In this report we consider the question of whether it is economicallyjustified to adopt a maintenance concept in which the road isoccasionally regenerated from junction to junction with a distanceof several kilometers. The big advantage of junction-to-junctionmaintenance is that it can be done within special road barrierconstructions which reduce the road capacity only slightly,so that the road can be maintained 24 hours a day.