Mechanistic Insights into the Reversible Formation of Iodosylarene–Iron Porphyrin Complexes in the Reactions of Oxoiron(IV) Porphyrin π‐Cation Radicals and Iodoarenes: Equilibrium,Epoxidizing Intermediate,and Oxygen Exchange

We have shown previously that iodosylbenzene–iron(III ) porphyrin intermediates ( 2 ) are generated in the reactions of oxoiron(IV ) porphyrin π‐cation radicals ( 1 ) and iodobenzene (PhI), that 1 and 2 are at equilibrium in the presence of PhI, and that the epoxidation of olefins by 2 affords high yields of epoxide products. In the present work, we report detailed mechanistic studies on the nature of the equilibrium between 1 and 2 in the presence of iodoarenes (ArI), the determination of reactive species responsible for olefin epoxidation when two intermediates (i.e., 1 and 2 ) are present in a reaction solution, and the fast oxygen exchange between 1 and H₂¹⁸O in the presence of ArI. In the first part, we have provided strong evidence that 1 and 2 are indeed at equilibrium and that the equilibrium is controlled by factors such as the electronic nature of iron porphyrins, the electron richness of ArI, and the concentration of ArI. Secondly, we have demonstrated that 1 is the sole active oxidant in olefin epoxidation when 1 and 2 are present concurrently in a reaction solution. Finally, we have shown that the presence of ArI in a reaction solution containing 1 and H₂¹⁸O facilitates the oxygen exchange between the oxo group of 1 and H₂¹⁸O and that the oxygen exchange is markedly influenced by factors such as ArI incubation time, the amounts of ArI and H₂¹⁸O used, and the electronic nature of ArI. The latter results are rationalized by the formation of an undetectable amount of 2 from the reaction of 1 and ArI through equilibrium that leads to a fast oxygen exchange between 2 and H₂¹⁸O.     

New HPLC-chiral stationary phases for enantiomeric resolution of sulfoxides and selenoxides

Summary Enantiomers of several sulfoxides and some selenoxides can be easily separated by using a new chiral stationary phase (CSP-DACH-DNB) containing the 3,5-dinitrobenzoyl derivative of R,R-(-)1,2-diamino-cyclohexane as selector, covalently bonded to the siliceous matrix. The easy operative conditions and the high enantioselectivity values (α) allow a direct transfer of the analytical separations to a semi-preparative and preparative scale.     

Estimating Sampling Errors in REA Survey: A Model Approach for the Synthetic Presentation of Results for Main Variables Involved in Economic Analysis

A new sample business survey for agriculture, the REA survey, and a project of integration with the FADN network (RICA in Italy) have significantly changed the production of statistical information nowadays available with reference to the agricultural sector. On the basis of this relevant information, new economic analyses are being developed on farms’ performance, agricultural households’ income and the Common Agricultural Policy (CAP). In this paper the authors estimate the relationship between the levels of variables of interest and their sampling errors using models in order to improve the accessibility of the information on estimates accuracy to the final users (agricultural analysts, policy makers). The paper is the result of a joint research of the three authors. Sections 1–3 and 6 by Pizzoli, Sects. 4 and 5 by Rondinelli, Sect. 7 by Filiberti, conclusions joint to the three authors.     

Analysis of reflectance and modulation spectroscopic lineshapes in optoelectronic device structures

We discuss the spectral lineshapes of reflectance and modulated reflectance (MR) measurements on optoelectronic device structures such as epi-layers, quantum wells (QWs), vertical-cavity surface emitting-lasers (VCSELs) and resonant-cavity light-emitting diodes (RCLEDs). We consider the various methods for the extraction of built-in electric fields and band-gap energies from Franz-Keldysh oscillations (FKO), using the example of a tensilely strained InGaAs QW system, whose InGaAsP barriers yield strong FKO. We describe how critical point transition energies can be easily obtained by eye from Kramers-Kronig (KK) transforms of low field or QW modulation spectra, using the example of the modulated transmittance spectra of dilute-nitrogen InGaAsN p-i-n structures. We also discuss how the ordinary reflectivity spectrum, usually acquired at the same time as the MR signal, may also be exploited to extract layer thicknesses and compositions, and information about the active QW absorption spectrum in VCSEL and RCLED structures.     

Studies on calcium‐containing poly(urethane ether)s

The calcium salt of mono(hydroxyethoxyethyl)phthalate [Ca(HEEP)₂] was synthesized by the reaction of diethylene glycol, phthalic anhydride, and calcium acetate. Calcium‐containing poly(urethane ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI) with a mixture of Ca(HEEP)₂ and poly(ethylene glycol) (PEG₃₀₀ or PEG₄₀₀) with di‐n‐butyltin dilaurate as a catalyst. A series of calcium‐containing PUEs of different compositions were synthesized with Ca(HEEP)₂/PEG₃₀₀ (or PEG₄₀₀)/diisocyanate (HMDI or TDI) molar ratios of 2:2:4, 3:1:4, and 1:3:4 so that the coating properties of the PUEs could be studied. Blank PUEs without calcium‐containing ionic diols were also prepared by the reaction of PEG₃₀₀ or PEG₄₀₀ with HMDI or TDI. The PUEs were well characterized by Fourier transform infrared, ¹H and ¹³C NMR, solid‐state cross‐polarity/magic‐angle‐spinning ¹³C NMR, viscosity, solubility, and X‐ray diffraction studies. The thermal properties of the polymers were also studied with thermogravimetric analysis and differential scanning calorimetry. The PUEs were applied as top coats on acrylic‐coated leather, and their physicomechanical properties were also studied. The coating properties of PUEs, such as the tensile strength, elongation at break, tear strength, water vapor permeability, flexing endurance, cold crack resistance, abrasion resistance, color fastness, and adhesive strength, were better than the standard values. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2865–2878, 2003     

CuPc molecules adsorbed on Au(1 1 0)-(1 × 2): growth morphology and evolution of valence band states

We present the growth morphology, the long-range ordering, and the evolution of the valence band electronic states of ultrathin films of copper phthalocyanine (CuPc) deposited on the Au(1 1 0)-(1 × 2) reconstructed surface, as a function of the organic molecule coverage. The low energy electron diffraction patterns present a (5 × 3) reconstruction from the early adsorption stages. High-resolution UV photoelectron spectroscopy data show the disappearance of the Au surface states related to the (1 × 2) reconstruction, and the presence of new electronic features related to the molecule-substrate interaction and to the CuPc molecular states. The CuPc highest occupied molecular orbital gradually emerges in the valence band, while the interface electronic states are quenched, upon increasing the coverage.     

Periodic solutions of nonlinear impulsive differential inclusions with constraints

In this paper we obtain the existence of periodic solutions for nonlinear ``invariance' problems monitored by impulsive differential inclusions subject to impulse effects.

     

Fermi, Majorana and the Statistical Model of Atoms

We give an account of the appearance and first developments of the statistical model of atoms proposed by Thomas and Fermi, focusing on the main results achieved by Fermi and his group in Rome. Particular attention is addressed to the unknown contribution to this subject by Majorana, anticipating some important results reached later by leading physicists.     

Effects of tributyltin(IV) chloride on the gametes and fertilization of Ascidia malaca (Ascidiacea: Tunicata)

Ascidia malaca gametes before fertilization incubated in 10^?5 or 10^?7 M solutions of tributyltin(IV) chloride, TBTCl, for 3 h appear highly damaged under transmission electron microscopy observation. Also, the fertilization process is affected by the compound: the damaged spermatozoa are present in the vitelline coat and the egg does not cleave. An increase of microbodies, structurally similar to peroxisomes, have been detected in the egg peripheral cytoplasm, probably in relation to their role in alleviating damage to some cellular components. The results have shown that the reproduction of ascidians under unfavourable environmental conditions is prevented. Copyright © 2003 John Wiley & Sons, Ltd.     

Approximate symmetries and conservation laws for Itô and Stratonovich dynamical systems

A new definition for the approximate symmetries of Itô dynamical system is given. Determining systems of approximate symmetries for Itô and Stratonovich dynamical systems have been obtained. It has been shown that approximate conservation laws can be found from the approximate symmetries of stochastic dynamical systems which do not arise from a Hamiltonian. The results have been applied to an example.