Spectrally-resolved white-light interferometry as a profilometry tool

Phase-shifting interferometry and white-light interferometry are reliable techniques for surface analysis in which the optical path difference has to be changed by some transducer to evaluate the phase. We present here a different procedure in which optical path modulation is completely avoided. This technique is based on the spectral analysis of white-light interferograms. By means of a spectroscopic device, a non-visible interferogram is split into its monochromatic components and absolute, unambiguous values of the phase are obtained along the spectral axis. Only one interferogram is required to obtain the profile of one-dimensional surfaces with nanometric resolution.     

Five different fluxional processes in polyfluorophenyl palladium(II) complexes with 2,4,6-tris(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine. The driving effect of the solvent

The polydentate N-donor ligand 2,4,6-tris(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine (Me(2)-TpzT) has been used to synthesize the new palladium derivatives Pd(R)(2)(Me(2)-TpzT), R = C(6)F(5), 1; R = m-C(6)ClF(4), 2. In the case of complex 2, four different atropisomers have been detected at low temperature. The new complexes exhibit a rich dynamic behavior, including three metallotropic processes (metal-hurdling, 1,4-metallotropic shifts, and an intermolecular process) and two processes involving restricted rotation of aromatic rings (the polyfluorophenyl groups and the uncoordinated pyrazole group adjacent to the metal fragment). The fluxional behavior has been studied by (1)H and (19)F NMR spectroscopy using variable temperature NMR studies and (1)H,(1)H and (19)F,(19)F EXSY experiments. The study of solutions of 2 in 1,1',2,2'-tetrachloroethane-d(2) gave the following order for the free energy of activation: pyrazole rotation < 1,4-metallotropic shift < intermolecular exchange < polyfluorophenyl rotation. The process of metal hurdling was not found in this solvent. However, in acetone-d(6) such a process was detected and was found to be of lower energy than the 1,4-metallotropic shift. In dilute acetone-d(6) or 1,1',2,2'-tetrachloroethane-d(2 )()solutions, the intermolecular process was not observed. Conclusions concerning the different mechanisms have been deduced from the data obtained.     

How to turn the catalytic asymmetric hydroboration reaction of vinylarenes into a recyclable process

Optically pure rhodium(I) complexes [Rh(cod)(Lbond;L)]X (cod=cyclooctadiene; L-L= (R)-2,2'-bis(diphenylphosphino)1-1'-binaphthyl ((R)-BINAP), (S,S)-2,4-bis(diphenylphosphino)pentane ((S,S)-BDPP), 2-diphenylphosphino-1-(1'-isoquinolyl)naphthalene ((S)-QUINAP); X=BF(4), PF(6), SO(3)CF(3), BPh(4)) were immobilised onto smectite clays such as montmorillonite K-10 (MK-10) and bentonite (Na(+)-M). (19)F, (31)P and (11)B NMR experiments recorded in CDCl(3) during the impregnation process provided evidence that montmorillonite K-10 may immobilise ionic metal complexes throughout the cationic and anionic counterparts. However, when bentonite was used as the solid, only the cationic metal complex was immobilised through cationic exchange while the counteranion remained in solution. When we used these preformed catalytic systems in the hydroboration of prochiral vinylarenes, we obtained high activities and enantiomeric excess with (S)-1-(2-diphenylphosphino-1-naphthyl)isoquinoline-modified rhodium complexes. These activities and selectivities are competitive with the homogeneous counterparts. The significant features of this method are the simple separation and good retention of the active metal in the solid, which allows efficient recycling even on exposure to air.     

Folding Wheels and Fans

 If two non-adjacent vertices of a connected graph that have a common neighbor are identified and the resulting multiple edges are reduced to simple edges, then we obtain another graph of order one less than that of the original graph. This process can be repeated until the resulting graph is complete. We say that we have folded the graph onto complete graph. This process of folding a connected graph G onto a complete graph induces in a very natural way a partition of the vertex-set of G. We denote by F(G) the set of all complete graphs onto which G can be folded. We show here that if p and q are the largest and smallest orders, respectively, of the complete graph in F(W _n ) or F(F _n ), then K _s is in F(W _n ) or F(F _n ) for each s, q≤s≤p. Lastly, we shall also determine the exact values of p and q. Received: October, 2001 Final version received: June 26, 2002     

Low frequency magnetic noise in epitaxial antiferromagnetically coupled Fe/Cr multilayers

For antiferromagnetically coupled epitaxial [Fe/Cr(001)]₁₀ multilayers we detected a strong enhancement of the magnetism-related electrical noise in the vicinity of the orientation transition between the easy and hard axes. Our measurements are performed at different temperatures and we also identified the noise caused by depinning of domain walls (DWs). We are able to detect and follow in real time the motion of rather extended (of the order of 100 μm) DWs by comparing the magnetic noise in the presence and absence of a DC transport current, respectively. The presence of large and small (<1 μm) DWs is confirmed by magnetic force microscopy images obtained at room temperature.     

Analytical studies of Spodopteralittoralis sex pheromone components by electroantennography and coupled gas chromatography-electroantennographic detection

In this paper we present analytical studies of the sex pheromone components of the Egyptian armyworm Spodoptera littoralis (Lepidoptera, Noctuidae) by electroantennography (EAG) and coupled gas chromatography-electroantennographic detection (GC-EAD). EAG responses in three different preparations, using an insect's head, an excised antenna and a live insect, have been recorded. EAG depolarizations of live insects were significantly higher than those elicited by the insect's head or the excised antenna. The responses were dose-dependent. Live insects also allowed regular pheromone stimulations for 40 min with only 38% decrease of the EAG initial depolarization. The synthetic pheromone blend elicited the highest EAG activity (2.0+/-0.3 mV), followed by the major compound (Z,E)-9,11-tetradecadienyl acetate (I) (1.54+/-0.1mV), and the minor components (Z)-9-tetradecenyl acetate (II), (E)-11-tetradecenyl acetate (III), tetradecyl acetate (IV) and (Z)-11-tetradecenyl acetate (V) (1.21-1.32 mV range). (Z,E)-9,12-tetradecadienyl acetate (VI), although not present in the pheromone blend of our strain, also showed an EAG activity (1.32+/-0.09 mV) similar to that of the monoenic components. GC-EAD responses confirmed the composition of the sex pheromone blend, the major response being elicited by the main component I followed by the other minor compounds II-V. The new dienic compound found in the female pheromone gland, (E,E)-10,12-tetradecadienyl acetate (VII), was not electrophysiologically active. Regarding sensitivity, the minimum amount detectable to elicit an antennal response in our GC-EAD system was 15 pg of the major component. In our system, which was built with cheap and easily available materials, no cooling of the effluent at the outlet of the chromatographic column is required.     

Absolute structures of zaluzanines A and B

2D NMR,¹H and¹³C as well as single crystal X-ray studies were performed in order to establish the correct configuration of all assymetrical centers in the zaluzanines A and B. This work enabled us to correct the previously proposed absolute configuration at the C-5 and C-6 centers, obtained by chemical correlations. Crystals of zaluzanin B (1c) are orthorhombic witha=6.8176(6),b=12.870(2), andc=18.507(5) Å, space groupP2₁2₁2₁ and the crystals of the carbodibromo derivative of zaluzanin A diacetate (4) are also orthorhombic witha=14.6123(5),b=15.1218(4), andc=19.9384(4) Å, space groupP2₁2₁2.     

4‐Styrylquinolines from cyclocondensation reactions between (2‐aminophenyl)chalcones and 1,3‐diketones: crystal structures and regiochemistry

Structures are reported for two matched sets of substituted 4‐styrylquinolines which were prepared by the formation of the heterocyclic ring in cyclocondensation reactions between 1‐(2‐aminophenyl)‐3‐arylprop‐2‐en‐1‐ones with 1,3‐dicarbonyl compounds. (E)‐3‐Acetyl‐4‐[2‐(4‐methoxyphenyl)ethenyl]‐2‐methylquinoline, C₂₁H₁₉NO₂, (I), (E)‐3‐acetyl‐4‐[2‐(4‐bromophenyl)ethenyl]‐2‐methylquinoline, C₂₀H₁₆BrNO, (II), and (E)‐3‐acetyl‐2‐methyl‐4‐{2‐[4‐(trifluoromethyl)phenyl]ethenyl}quinoline, C₂₁H₁₆F₃NO, (III), are isomorphous and in each structure the molecules are linked by a single C—H…O hydrogen bond to form C(6) chains. In (I), but not in (II) or (III), this is augmented by a C—H…π(arene) hydrogen bond to form a chain of rings; hence, (I)–(III) are not strictly isostructural. By contrast with (I)–(III), no two of ethyl (E)‐4‐[2‐(4‐methoxyphenyl)ethenyl]‐2‐methylquinoline‐3‐carboxylate, C₂₂H₂₁NO₃, (IV), ethyl (E)‐4‐[2‐(4‐bromophenyl)ethenyl]‐2‐methylquinoline‐3‐carboxylate, C₂₁H₁₈BrNO₂, (V), and ethyl (E)‐2‐methyl‐4‐{2‐[4‐(trifluoromethyl)phenyl]ethenyl}quinoline‐3‐carboxylate, C₂₂H₁₈F₃NO₂, (VI), are isomorphous. The molecules of (IV) are linked by a single C—H…O hydrogen bond to form C(13) chains, but cyclic centrosymmetric dimers are formed in both (V) and (VI). The dimer in (V) contains a C—H…π(pyridyl) hydrogen bond, while that in (VI) contains two independent C—H…O hydrogen bonds. Comparisons are made with some related structures, and both the regiochemistry and the mechanism of the heterocyclic ring formation are discussed.     

Optimization of stir bar sorptive extraction applied to the determination of pesticides in vinegars

Stir bar sorptive extraction (SBSE) has been evaluated for analysing pesticides in vinegar. The extraction analytical conditions have been optimised using a two-level factorial design expanded further to a central composite design. After optimization, the proposed analytical conditions are: sample volume 40 mL, sampling time 150 min, and stirring speed 1000 rpm. On the basis of the results, it was decided not to add NaCl. The SBSE procedure developed shows detection limits and linear ranges adequate for analysing this type of compound, giving recoveries close to 100%. The repeatability and reproducibility values obtained were lower than 18 and 23%, respectively. The method was applied to a variety of commercial vinegars. SBSE is a very simple, solvent-free, and fast technique with high sensitivities.     

Telemetry-based estimate of orientation accuracy for the Tat’yana-2 satellite

Some results of processing the data registered by the Moscow University satellite named Tat’yana-2 are discussed. An estimate for the course angle in the process of the satellite orientation with respect to the Earth is obtained. The predicted angular motion of the satellite and the telemetry data are compared. An improved algorithm for the orientation with respect to the Earth is proposed for small satellites to enhance the orientation accuracy when the course angle is arbitrary. A possibility of using the micro vibratory gyroscopes to control the orientation of small satellites is estimated.