Immobilization of oxomolybdenum species in a layered double hydroxide pillared by 2,2'-bipyridine-5,5'-dicarboxylate anions

A Zn,Al layered double hydroxide (LDH) with Zn/Al = 1.45 and containing nitrate anions was prepared by coprecipitation and characterized by powder X-ray diffraction, Zn K-edge extended X-ray absorption fine structure spectroscopy (EXAFS), thermogravimetric analysis, FTIR and FT Raman spectroscopy, and (27)Al MAS NMR spectroscopy. Three Zn...O and four Zn...M (M = Zn, Al) shells could be fitted to the low-temperature (40 K) EXAFS spectrum, in accordance with a model for an ordered cationic sheet. The nitrate anions were easily exchanged by 2,2'-bipyridine-5,5'-dicarboxylate anions, resulting in an increase in the basal spacing from 9 to 18 A. The basal spacing of the pillared derivative indicates that the anions are arranged with their longest dimension nearly perpendicular to the host layers. This material exhibits a high encapsulating ability, as evidenced by its interaction with a dichloromethane solution of the dioxomolybdenum(VI) complex MoO(2)Cl(2)(THF)(2). A material with a metal loading of 11.2 wt % was obtained. Molybdenum K-edge EXAFS analysis could not substantiate the formation of a supported complex of the type MoO(2)Cl(2)(N-N) but instead indicated the formation of unidentate-bridged entities of the type [O(2)Mo-O-MoO(2)] with a metal-metal separation of 3.29 A. The molybdenum-containing LDH was active as a catalyst for the liquid-phase epoxidation of cis-cyclooctene, 1-octene, and trans-2-octene using tert-butyl hydroperoxide as the oxygen source, yielding the corresponding epoxides as the only products. For reactions carried out with no additional solvent (other than n-decane) or in the presence of 1,2-dichloroethane, the solid catalyst could be recycled with no major loss of activity. Other tests confirmed that the systems functioned as true heterogeneous catalysts.     

Experimental results on neutrino-electron scattering

A determination of sin² θ _w based on measurements of elastic scattering of muon-neutrinos and muon-anti-neutrinos on atomic electrons is described. These purely leptonic processes were studied using the CHARM calorimeter exposed to neutrino and antineutrino wide-band beams at the CERN super proton synchrotron. A total of 83±16 neutrino-electron and 112±21 antineutrino-electron events have been detected. From the measurement of the ratio of muon-neutrino and muon-antineutrino cross-sections a value of sin² θ _w =0.211±0.037 was obtained.     

Measurement of neutrino oscillations in realistic underground experiments

Summary We conside the possibility of investigating neutrino oscillations in a realistic environment. We discuss theoretical uncertainties coming from flux calculations, geomagnetic effects and propagation through matter, as well as the capability of identifying the neutrinoinduced events in real apparata.

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Riassunto Si studiano le reali possibilità di esperimenti sotterranei nella ricerca di eventuali oscillazioni di neutrini. Sono discusse le imprecisioni derivanti dal calcolo teorico del flusso aspettato e gli effetti geomagnetici e di propagazione attraverso la materia. Si tiene infine conto della capacità di apparati reali nella identificazione di eventi indotti da neutrini.

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Резюме Мы рассматриваем возможность исследования нейтринных осцилляций в реальных подземных экспериментах. Мы обсуждаем теоретические неопределенности, связанные с вычислениями потока, геомагнитными эффектами и распространением через вещество. Также рассматривается возможность идентификации событий, индуцированных нейтрино, с помощью существующей аппаратуры.

     

Reversible coordinative chain transfer polymerization of styrene by rare earth borohydrides,chlorides/dialkylmagnesium systems

The ability of various rare earth borohydride and chloride complexes/n‐butylethylmagnesium systems to operate styrene chain transfer polymerization in mild conditions has been assessed. Thirteen precatalysts have been considered: the rare earth trisborohydrides Ln(BH₄)₃(THF)_x (x = 3, Ln = Nd (1), La (2), Sm (3), x = 2, Ln = Y (4), Sc (5)), the rare earth chlorides LnCl₃(THF)_x (x = 3, Ln = Nd (6), La (7), Sm (8), Y (9), x = 2, Ln = Sc (10)), the mixed La(BH₄)₂Cl(THF)_2.6 (11) and the half‐lanthanidocenes Cp*Ln(BH₄)₂(THF)₂ (Ln = Nd (12), La (13)). Six systems were found to be active precatalysts for the polymerization of styrene. 1 , 2 , and 11 led to an efficient transmetalation of the growing polystyrene chain with the simultaneous occurrence of βH elimination, whereas 7 , 12 , and 13 led to catalyzed chain growth behavior. It is noteworthy that the catalyzed chain growth obtained with 12 and 13 occurs with significant stereoselectivity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 802–814, 2010     

Standardization of ceruloplasmin measurements is still an issue despite the availability of a common reference material

The purpose of measurement standardization is to achieve closer comparability of results obtained using different commercial systems. Regarding serum protein immunoassays, a reference preparation (BCR-470) was released in 1993 and adopted by manufacturers across the world to value-assign their assay calibrators for routine methods to reduce method-dependent variation. Moving from nephelometric (Beckman Immage 800) to turbidimetric determination (Roche Cobas c 501) of seven serum proteins, we preliminarily checked the comparability of results between the two systems. The study was performed according to the CLSI EP9-A protocol on 30 fresh sera, tested on each system in duplicate, and subdivided on two different days, without recalibration and using manufacturers’ control materials to validate the runs. Both manufacturers’ package inserts provide statements that kit calibrators are traceable to BCR-470. Suggested reference intervals are also the same. Although a fairly good correlation was observed (r = 0.955), the comparison of ceruloplasmin methods produced evidence of highly significant proportional (regression slope, 0.572) and constant bias (intercept, 0.05 g/L). Absolute and percentage mean differences were −0.11 g/L (95% confidence interval (CI) −0.13 to −0.10 g/L) and −39.1% (CI −43.1 to −35.2%), respectively. No other evaluated proteins showed similar problems. Lacking a ceruloplasmin reference method, it is impossible to demonstrate that one of the two assays produces true ceruloplasmin values. The problem is, however, that results coming from the two assays are clearly not comparable. This may be either due to a lack of commutability of the reference material with biological samples in the evaluated assays or to calibration problems by manufacturers in one of the stages of the calibration hierarchy.     

Temporal integration of loudness measured using categorical loudness scaling and matching procedures

Temporal integration of loudness of 1 kHz tones with 5 and 200 ms durations was assessed in four subjects using two loudness measurement procedures: categorical loudness scaling (CLS) and loudness matching. CLS provides a reliable and efficient procedure for collecting data on the temporal integration of loudness and previously reported nonmonotonic behavior observed at mid-sound pressure level levels is replicated with this procedure. Stimuli that are assigned to the same category are effectively matched in loudness, allowing the measurement of temporal integration with CLS without curve-fitting, interpolation, or assumptions concerning the form of the loudness growth function.     

Characterization of polyether‐poly(methyl methacrylate)‐lithium perchlorate blend electrolytes

Solid polymer electrolyte (SPE) systems based on interpenetrating blends of poly(ethylene oxide‐co‐propylene oxide) and poly(methyl methacrylate) host matrices, with lithium perchlorate as guest salt, were prepared. These electrolytes were presented as free‐standing films, and their thermal and electrochemical properties were characterized by conductivity and electrochemical stability measurements. The properties of the interpenetrating blends of poly(ethylene oxide‐co‐propylene oxide) and poly(methyl methacrylate) host matrices as the electrolyte component of a solid‐state electrochromic device are reported and the results obtained suggest that this electrolyte provides an encouraging performance in this application. The most conducting electrolyte composition of this SPE system is the formulation designated as SPE2‐0PC (5.01 × 10^?4 S cm^?1 at about 57°C). The lowest decomposition temperature was registered with the SPE6‐15PC composition (233°C). The average transmittance in the visible region of the spectrum was above 41% for all the samples analyzed. After coloration the device assembled with 71 wt% PC presented an average transmittance of 15.71% and an optical density at 550 nm of 0.61. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of non-associated electrolyte solutions on the behaviour of poly(vinyl alcohol)-based hydrogels

The aim of this paper is to present the behaviour of the poly(vinyl alcohol) hydrogels [PVA-HG] in sodium and potassium chlorides aqueous solutions, due to their interactions. The tested [PVA-HG]-s have been obtained by repeated freezing and thawing cycles. White, heterogeneous hydrogels have been obtained. These hydrogels exhibit a mechanical active behaviour at their contact with electrolytes aqueous solutions, manifested by important changing in mass, volume and density of the hydrogel samples. These modifications could be explained by water elimination from the hydrogels that initially reached the equilibrium of swelling. The kinetic of the water desorption and the reversibility of this process, have been studied and some of the factors that influence this behaviour have been evidenced. The sensitivity of PVA hydrogels to electrolyte nature and concentration could be used in sensors design and also could explain some aspects of electrolytes diffusion through PVA membranes and targeted drugs delivery.     

Exact controllability of a spherical cap: Numerical implementation of HUM

This paper deals with the numerical implementation of the exact boundary controllability of the Reissner model for shallow spherical shells (Ref. 1). The problem is attacked by the Hilbert uniqueness method (HUM, Refs. 2–4), and we propose a semidiscrete method for the numerical approximation of the minimization problem associated to the exact controllability problem. The numerical results compare well with the results obtained by a finite difference and conjugate gradient method in Ref. 5.This work was done when the first two authors were at CNR-IAC, Rome, Italy as Graduate Students.     

Open-cyclic warfarin isomerism: 5-hydroxywarfarin

Addition of a 5-hydroxy substituent to warfarin [3-(1-phenyl-3-oxobutyl)-4-hydroxycoumarin] shifts the solution equilibrium in chloroform to favor the open isomeric form over the two cyclic diastereomeric hemiketals. X-ray diffraction analysis reveals 5-hydroxywarfarin crystallizes as the open isomer in contrast to the more than 20 warfarin and analog structures which occur ascis ortrans hemiketal forms in the solid. The two peri hydroxyl groups in the structure of 3-(1-phenyl-3-oxobutyl)-4,5-dihydroxycoumarin are intramolecularly H-bonded. Methyl kctal derivatives of 5-hydroxywarfarin and a close analog effectively model the minor cyclic hemiketal forms in solution. Structures of bothcis andtrans cyclic methyl ketals of 3-(4-oxopent-2-yl)-4,5-dihydroxy-coumarin have been determined and the aryl hydroxyls H-bond to the dihydropyranyl ring oxygens of the cyclic ketals. Nuclear magnetic resonance studies suggest that these intramolecular H-bonds persist in chloroform solution. Infrared spectroscopy on the series of compounds in KBr pellets is consistent with the crystallographically determined structures and H-bonding schemes.