The equations of a holomorphic subspace in a complex Finsler space

In [Mu1] we underlined the motifs of holomorphic subspaces in a complex Finsler space: induced nonlinear connection, coupling connections, and the induced tangent and normal connections. In the present paper we investigate the equations of Gauss, H-and A-Codazzi, and Ricci equations of a holomorphic subspace. We deduce the link between the holomorphic curvatures of the Chern-Finsler connection and its induced tangent connection. Conditions for totally geodesic holomorphic subspaces are obtained. Communicated by János Szenthe     

New ferrocene-containing structures: Poly(silyl ester)s

Two new polymeric structures containing ferrocene units along the chains, namely poly(silyl ester)s, have been synthesized and characterized: a geminal poly(silyl ester) (g-PSE) and one having a disiloxane spacer between the silyl ester groups (s-PSE). The condensation polymerization of AA/BB monomer systems in solution was used in both cases as preparation method involving a silicon-containing diol, (diphenylsilane diol or 1,3-bis(hydroxy)-tetramethyldisiloxane), and 1,1′-di(chlorocarbonyl)ferrocene. The polymers were investigated by differential pulse voltammetry in order to evaluate the redox behavior. Due to the presence of the silyl ester groups in the chain, these polymers are hydrolytically degradable.     

Accurate intermolecular ground state potential of the Ar-N2 van der Waals complex

After carrying out a systematic basis set convergence study, we evaluate several ground state potential energy surfaces of the Ar-N(2) van der Waals complex at the coupled cluster singles and doubles model including connected triples corrections. We use the aug-cc-pVXZ (X=5,Q,D) and the daug-cc-pVQZ basis sets augmented with a set of 3s3p2d1f1g (denoted 33211) and 3s3p2d2f1g (denoted 33221) midbond functions, respectively. aug-cc-pVTZ-33211 results were available in the literature. The aug-cc-pV5Z-33211 (daug-cc-pVQZ-33221) surface is characterized by a T-shaped minimum at R(e)=3.709 (3.701) A and of 99.01 (102.50) cm(-1), and a linear saddle point at 4.260 (4.257) A and D(e)=75.28 (79.73) cm(-1). These results are compared with the values provided by the semiempirical potentials available, and those of previous theoretical studies. The basis set convergence of the intermolecular potentials is also analyzed. From the potentials the rovibronic spectroscopic properties are determined. We study the basis set convergence of the rotational frequencies. The binding parameters that characterized the aug-cc-pVTZ-33211 surface are reasonable, but the surface is not good enough to evaluate the microwave spectra. The aug-cc-pVQZ-33211 basis set results considerably improve the triple zeta and are close to the aug-cc-pV5Z-33211. Considering the small differences between the quadruple and the quintuple zeta surfaces, the latter results can be expected to be close to convergence. At this level the differences with respect to the accurate experimental frequencies are in the order of 0.7%. In the case of the daug-cc-pVXZ-33211,33221 (X=5,Q,T,D) series, the convergence of the interaction energies with respect to basis set improvement is not so smooth. The errors in the frequencies obtained with the daug-cc-pVQZ-33221 basis set with respect to experiment are in the order of 0.4%.     

Glow discharge mass spectrometry

Over the past twenty years or so, glow discharge mass spectrometry (GDMS) has become the industry standard for the analysis of trace elements in metals and semiconductors. A review of its history is followed by a picture of the present situation and a look to where the future may lie. Applications are summarised, including the ability of GDMS to offer depth-resolved data and non-conductor analysis, and the well-documented quantitative nature of the results is reviewed. The effects resulting from the physical properties of the analyte material are discussed at length. Finally, recent work such as fast flow sources and pulsed glow discharges is reviewed.     

Accurate intermolecular ground state potential of the Ne-N2 van der Waals complex

Ab initio ground state potential energy surfaces are obtained from interaction energies calculated with the coupled cluster singles and doubles model including connected triples corrections [CCSD(T)] and the aug-cc-pVXZ (X=5,Q,T,D) basis sets augmented with two different sets of midbond functions (denoted 33221 and 33211). The aug-cc-pV5Z-33221 surface is characterized by a T-shaped 49.5 cm(-1) minimum at Re=3.38 Angstroms and a linear saddle point at 3.95 Angstroms with De=36.6 cm(-1). These results agree well with the values provided by the accurate semiempirical potentials available. The rovibronic spectroscopic properties are determined and compared to the available experimental data and previous theoretical results. We study the basis set convergence of the intermolecular potentials and the rotational frequencies. The aug-cc-pVTZ basis sets provide reasonable binding parameters, but seem not to be converged enough for the evaluation of the microwave spectra. The aug-cc-pVQZ basis sets considerably improve the triple zeta results. The differences between the results obtained with the aug-cc-pVTZ-33221 basis set surface and those with the aug-cc-pVQZ-33221 are smaller than those of the corresponding bases with the set of 33211 midbond functions. The aug-cc-pVQZ surfaces are close to the aug-cc-pV5Z, that are expected to be close to convergence. With our best surfaces the errors in the frequencies with respect to the accurate experimental results go down to 0.6%.     

Synthesis of the monomeric antioxidant

The thermal decomposition oftrans-3,5-di-tert-butyl-4-hydroxy-cinnamic acid (BHC) in the solid state, in aqueous solution and in solutions in organic solvents was studied in order to develop a preparative method for the synthesis of the monomeric antioxidant 3,5-di-tertbutyl-4-hydroxystyrene (BHS). Thermal methods of analysis showed that, during the solidstate decomposition of BHC, its decarboxylation was accompanied by desalkylation and polymerization of the styrenic decomposition products. BHC decarboxylation is aqueous solution was also accompanied by polymerization. A kinetic study of BHC decomposition in organic solvents by 1 H-NMR spectrometry revealed that only the decomposition of BHC in aprotic dipolar solvents such as dimethylsulphoxide and dimethylformamide, at temperatures lower than 150°C, could be used as a preparative method for the synthesis of BHS. The decarboxylation of BHC took place by zero-order kinetics through a mechanism involving the ionization of BHC in the aprotic dipolar solvent. The reaction rate increased drastically with increasing solvent polarity and in the presence of trace amounts of BHC sodium salt. Both monomeric antioxidants, i.e. BHS and BHC, may be used to obtain polymer-bound antioxidants, e.g. by melt-grafting onto polyethylene.

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Zusammenfassung Für die Ausarbeitung eines Verfahrens zur Herstellung des monomeren Antioxidans 3,5-Di-terc-butyl-4-hydroxystyrol (BHS) wurde die thermische Zersetzung vontrans-3,5-Di-terc-butyl-4-hydroxyzimtsäure (BHC) im festen Zustand, in wäßriger Lösung und in Lösungen mit organischen Lösungsmitteln untersucht. Thermoanalytische Verfahren zeigten, daß bei der Feststoffzersetzung von BHC ihre Decarboxylierung durch Desalkylierung und durch Polymerisierung der Styrol-Zersetzungsprodukte begleitet wird. Auch die BHC-Decarboxylierung in wäßriger Lösung wurde durch Polymerisierung begleitet. Mittels 1H-NMR Spektroskopie angefertigte kinetische Studien der Zersetzung von BHC in organischen Lösungsmitteln zeigten, daß die Zersetzung von BHC nur in aprotischen dipolaren Lösungsmitteln, wie z.B. in Dimethylsulfoxid und Dimethylformamid und nur bei Temperaturen unterhalb von 150C als präparatives Verfahren zur Synthese von BHS geeignet ist. Die Decarboxylierung von BHC verlief nach einer Reaktionsordnung 0-ter Ordnung, am Mechanismus ist die Ionisierung von BHC im aprotischen dipolaren Lösungsmittel beteiligt. Die Reaktionsgeschwindigkeit wird mit steigender Lösungsmittelpolarität und in Gegenwart von Spuren von BHC-Natriumsalz drastisch angehoben. Beide monomeren Antioxidationsmittel, d.h. BHS und BHC, können verwendet werden, um Polymerbindungs-Antioxidationsmittel herzustellen, z.B. durch Schmelz-Auf-polymerisieren auf Polyethylen.

     

Recent Reviews. 56

Reviews are listed in order of appearance in the sources indicated. In multidisciplinary review journals, only those reviews which fall within the scope of this Journal are included. Sources are listed alphabetically in three categories: regularly issued review journals and series volumes, contributed volumes, and other monographs. Titles are numbered serially, and these numbers are used for reference in the index. Major English-language sources of critical reviews are covered. Encyclopedic treatises, annual surveys such as Specialist Periodical Reports, and compilations of symposia proceedings are omitted. This installment of Recent Reviews covers principally the latter part of the 1999 literature. Previous installment: J. Org. Chem. 2000, 65(1), 267-74.     

Engineering Multifunctional Gold Decorated Dendritic Mesoporous Silica/Tantalum Oxide Nanoparticles for Intraperitoneal Tumor‐Specific Delivery

Nonspecific high‐energy radiation for treatment of metastatic ovarian cancer is limited by damage to healthy organs, which can be mitigated by the use of radiosensitizers and image‐guided radiotherapy. Gold (Au) and tantalum oxide (TaO_x) nanoparticles (NPs), by virtue of their high atomic numbers, find utility in the design of bimetallic NP systems capable of high‐contrast computed tomography (CT) imaging as well as a potential radiosensitizing effect. These two radio‐dense metals are integrated into dendritic mesoporous silica NPs (dMSNs) with radial porous channels for high surface‐area loading of therapeutic agents. This approach results in stable, monodispersed dMSNs with a uniform distribution of Au on the surface and TaO_x in the core that exhibits CT attenuation up to seven times greater than iodine or monometallic dMSNs without either TaO_x or Au. Tumor targeting is assessed in a metastatic ovarian cancer mouse model. Ex vivo micro‐CT imaging of collected tumors shows that these NPs not only accumulate at tumor sites but also penetrate inside tumor tissues. This study demonstrates that after intraperitoneal administration, rationally designed bimetallic NPs can simultaneously serve as targeted contrast agents for imaging tumors and to enhance radiation therapy in metastatic ovarian cancer.     

Ternary Copolymerization: Azeotropy and Pseudoazeotropy

An analysis of experimental data for ternary copolymerizations has been performed by an optimizing calculation method, resulting in the estimation of the r _ij copolymerization constants. The azeotrope calculation results have been compared to those based on the r _ij constants found for binary copolymerization. For each set of r _ij constants, the possibility of the ternary azeotropy was studied. The formation of quasihomogeneous ternary copolymers was studied subsequent to the determination of the ternary pseudoazeotropy domains occurring at the intersection of the partial pseudoazeotropy domains.