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This paper presents new evidence on foreign plants and their effects on a host industry. I test the predictions of a Melitz-type model using a panel of domestic and foreign plants in the Chilean manufacturing sector. Foreign ownership is a strong predictor of plant productivity and size advantages. Moreover, productivity gains for a domestic incumbent are positively associated with foreign plants' presence in the same industry and region. I also find a positive correlation between foreign entry and exit of less productive domestic plants, but inconclusive evidence on the effects on productivity of new domestic plants.

The free energy profile and the (classical) kinetics of chemical reactions in (soft) condensed phase are modeled theoretically by means of molecular dynamics simulations, the Perturbed Matrix Method (PMM) and the quasi Gaussian entropy (QGE) theory. In this paper we describe the theoretical framework and apply the model to the intramolecular proton transfer reaction of aqueous malonaldehyde. Although in the present application we disregard the quantum effects for the proton dynamics along the reaction coordinate (i.e., tunneling), the classical-like view of the proton transition over the reaction free energy surface seems to properly describe the kinetic process and shows that water acts lowering the reaction free energy barrier. Moreover, a weak temperature dependence of the free energy surface is obtained, implying small entropy variations in the transition. Interestingly the activation entropy, as provided by the QGE model, is negative in the whole temperature range considered, thus indicating an entropy reduction at the transition structure. Finally, by comparing our results with theoretical and experimental literature data, we critically address the actual role of tunneling in this reaction and discuss the emerging kinetic scheme. Copyright (c) 2006 John Wiley & Sons, Ltd.

Ths study reports different mechanisms (i.e., microvascular spasm and discrete microinfarction) that may underlie different pattern of slow-reflow after elective coronary stenting on the basis of the different tissue level of perfusion achieved, assessed by blush grade and MRI. Catheter Cardiovasc Interv 2004;61:222–226. © 2004 Wiley-Liss, Inc.

Background: This study correlates biomarkers of atopy (serum total and specific IgE) and inflammation (serum eosinophil cationic protein) with bronchial hyperreactivity assessed after the complete end of pollination, in a group of farmers suffering from grass-allergic asthma. Methods: A total of 28 asthmatic farmers, with allergy to grass pollen, reporting persistent asthma symptoms after grass pollination, were enrolled. An accurate allergologic screening excluded other sensitizations. Analysis of total and grass-specific IgE and eosinophil cationic protein was carried out before (March) and during (May) the following spring. After the complete end of pollination, bronchial hyperreactivity was assessed. Results: Symptoms (cough, wheezing) persisted during the autumn for a mean period of 41 days (range 13-69). Total IgE was moderately high and grass-specific IgE ranged from 9.25 to 41.12 kU/l without significant differences before and during spring. On the contrary, serum ECP levels significantly increased during the pollination period. PD 20 methacholine evaluated after the end of grass pollination was negatively significantly correlated with levels of total IgE (r = -0.73; P < 0.01) and the increase (from March to May) of serum ECP (r = -0.75; P < 0.01). However, PD 20 methacholine did not correlate with grass-specific IgE and serum ECP absolute values of both March and May. A positive correlation was found between number of postseasonal days with symptoms and both spring increase of serum ECP (r = 0.75; P = 0.04) and levels of total IgE (r = 0.76; P < 0.01). The number of postseasonal days with symptoms inversely correlated with postseason PD 20 methacholine (r = -0.76; P < 0.01). Conclusions: The study demonstrates that in grass-sensitized farmers with asthmatic symptoms persisting for several weeks after grass pollination has ceased, the degree of airways hyperreactivity and the duration of postseasonal symptoms are directly related to the spring increase of ECP levels, as well as to the level of total IgE in serum. This allows us to identify two candidate biomarkers for the risk of developing prolonged asthma symptoms, and for the effective monitoring of anti-inflammatory treatment and allergen-specific immunotherapy.

The equilibrium structure of borazine, B3N3H6, has been optimized at the HF-SCF level using the 6-31G, 6-31G∗, 6-31 + G∗, 6-31 + + G∗∗, 6-311G∗∗, DZP and TZP basis sets and at the secondorder Moeller-Plesset perturbation theory, with all orbitals active, with the 6-31G∗ basis set (MP2/ 6-31G∗). The D3h symmetry conformation is established to be, at all the adopted levels of theory, the global minimum of the molecule. The planar structure has been studied employing several basis sets and the effects of basis set extension and of polarization d-functions on the molecular geometry are discussed. The bond distances and the ring angles of borazine determined at the MP2/6-31G∗ level are, (BN) 1.430 A, (BH) 1.197 A, (NH) 1.012 A, (BNB) 122.9° and (NBN) 117.1°. HF-SCF and MP2/6-31G∗ vibrational frequencies have been calculated in the harmonic approximation and the vibrational spectrum of borazine is reassigned accordingly.

The molecular structure and benzene ring distortions of ethynylbenzene have been investigated by gas-phase electron diffraction and ab initio MO calculations at the HF/6-31G* and 6-3G** levels. Least-squares refinement of a model withC 2v, symmetry, with constraints from the MO calculations, yielded the following important bond distances and angles:r g(C i -C o )=1.407±0.003 A,r g(C o -C m )=1.397±0.003 A,r g(C m -C p )=1.400±0.003 A,r g(Cr i -CCH)=1.436 ±0.004 A,r g(C=C)=1.205±0.005 A, ∠C o -C i -C o =119.8±0.4°. The deformation of the benzene ring of ethynylbenzene given by the MO calculations, including

Structures, vibrational spectra and methyl rotational barriers of diacetamide, CH 3 CONHCOCH 3 , and of hydrogen-bonded dimers have been determined by ab initio methods. The HF/4–31G * geometry of the isolated molecule reveals a planar configuration of the amide groups and a tendency of the CH 3 group to eclipse the CO bond; MP2/6–31G * //HF/4–31G * calculations indicate the E, Z configuration of diacetamide as the most stable isomer. The structural changes induced by dimerization of E,Z -diacetamide have been determined at the HF/6–31G level for two CO⋯HN hydrogen-bonding models and are more remarkable for the cyclic than for the open structure dimer. Hydrogen bonding effects on the vibrational spectrum of diacetamide have been investigated by comparing monomer and dimer IR spectra. The Fourier transform infrared (FT-IR) spectra of diacetamide and of the N-deuterated species, CH 3 CONDCOCH 3 , measured in Ar and N 2 low-temperature matrices, have been assigned on the basis of HF/4–31G * calculations. The vibrational spectrum of the monomer has been compared with the IR spectra of concentrated matrices, where CH 3 CONHCOCH 3 undergoes appreciable self association by CO⋯HN hydrogen bonds to form structurally disordered dimers, and with the IR crystal spectra, where the strongest association gives rise to well defined cyclic dimers.

This paper reports the results of Hartree-Fock self-consistent field calculations on the stable equilibrium structures (D2h and C3v,) of the halide dimers Be2F4 and Mg2F4, on those of the mixed dimer molecules BeMgF4 (C2v and C3v) and LiNaF2C2v, and on the ion-pairs Li2BeF4 (D3ddm and C2v), LiBCl4 and LiAlCl4 (C2v and C3v).

The effects of electron correlation on the molecular structure and stability of tropone and tropolone molecules have been studied by MP2/6-31G* calculations. Geometry optimizations have been carried out for tropone, cis -tropolone and the non-hydrogen bonded orthogonal and trans rotamers of tropolone. The tropone seven-membered ring exhibits an appreciable triene-like character which is slightly smoothed upon OH substitution. The asymmetry of the hydrogen bonding of tropolone, emerging from previous HF/6-31G* studies, is reduced by inclusion of electron correlation, and the proton tunnelling barrier height drastically lowers from 70 kJ mol −1 (HF/6-31G*) to 25 kJ mol −1 (MP2/6-31G*). The structural changes induced by OH torsion, supported by additional MP2/6-31G* geometry optimizations of the analogous systems 1,4-pentadiene-3-one and 2-hydroxy-1,4-pentadiene-3-one indicate that intramolecular CO⋯HO hydrogen bonding is favoured by π-delocalization through the cyclic carbon skeleton. SCF calculations on the centrosymmetrical tropolone dimer indicate that self-association enhances π-delocalization in the troponoid ring and causes vibrational frequency shifts which satisfactorily agree with the changes observed in the FT-IR matrix spectra of isolated tropolone molecules and of solid samples.

Geometries of guanidine and eight of its N-imino derivatives (CH3, SiH3, OH, CN, F, Cl, CHO, and NO2) were calculated using ab initio molecular orbital techniques. MP2, MP4, and CISD geometries indicate that the guanidine molecule is pyramidal at amino groups and π-conjugation through the amidine skeleton is modest. MP2 structures of the eight N-imino guanidines reveal that substituting the hydrogen atom of the imino nitrogen by a functional group leads to a concerted variation of the CN bond distances. Topological electron density analyses indicate that the structural changes calculated upon N-imino substitution are largely due to changes of conjugation onto the amidine π-skeleton. Intermolecular hydrogen bonding involving the imino and amino groups is also found to affect the amidine geometry. Special attention has been paid in the work of 2-cyanoguanidine. The centrosymmetric dimer and a more extended hydrogen-bonded complex have been proposed as simulation of the crystal environment and the respective...

Two cases of massive mitral regurgitation due to mitral valve disruption following percutaneous balloon valvuloplasty are reported. This severe complication occurred in two elderly women with recurrent mitral stenosis after previous surgical commissurotomy. Due to their unstable hemodynamic and clinical condition, both patients underwent emergency valve replacement. At surgery, the commissures appeared fused and heavily calcified; the chordae tendineae thickened, shortened, and fused; and the leaflets presented a large tear with sheared edges. Because the technical aspects of both procedures were unremarkable, the anatomic features of the mitral valve seemed to affect the occurrence of severe mitral regurgitation. Percutaneous balloon valvuloplasty should be therefore applied carefully to patients with prior surgical valvotomy, in whom the structural alterations of the mitral apparatus may predispose to severe valvular damage.

HF-SCF calculations are reported for the ions PO2− and ClO2− and for the charge-transfer complexes LiPO2 and LiClO2. Ab initio calculations indicate that the association between PO2− and ClO2− with the lithium atom depends on the position of the metal with respect to the anionic group and may occur in either bidentate or monodentate fashion. C2v and Cs symmetry structures were found to be stationary points on the total energy surfaces; the C2v bidentate form is the most stable equilibrium structure. Monodentate isomers of Cs and C2v symmetry were also characterized. Vibrational frequencies of the anions and of the C2v bidentate forms were computed.

Molecular orbital calculations are reported for different structures of the molecule Li 2 CO 3 . The calculations were carried out at the RHF-SCF level employing contracted Gaussian basis sets 3-21G and 3-21G*. Configurations of C 2v and C 3v symmetry were examined and were found to be stationary points. The bidentate structure is the stable equilibrium form of Li 2 CO 3 while the monodentate one is a saddle point for lithium atom migration around the group CO 2− 3 . The non-planar C 3v structure is the highest energy point on the hypersurface explored. Harmonic frequencies of vibration were computed for CO 2− 3 and bidentate C 2v symmetry Li 2 CO 3 .

Introduction: The aim of this study was to compare the outcome of anatomical pulmonary vein (PV) radiofrequency (RF) ablation with that of an integrated approach (anatomical with electrophysiological confirmation of PV disconnection). Methods: Sixty consecutive patients affected by drug-refractory paroxysmal (39), persistent (13), and permanent (8) atrial fibrillation (AF) were assigned to an anatomical (group A: 30 patients; 25 male, 5 female, mean age: 55 ± 7 years) or integrated approach (group B: 30 patients; 26 male, 4 female, mean age: 52 ± 9 years). In all cases, RF ablation was performed by means of the Carto system in order to anatomically create circumferential lines around PVs. In group B, the persistence of PV potentials was then assessed with a multipolar circular catheter. If PV potentials persisted, RF pulses targeting the electrophysiological breakthroughs were delivered to disconnect PVs. Results: Total procedure duration, fluoroscopy time, and RF delivery time were similar in both groups: 227 ± 43, 50 ± 23, and 43 ± 16 minutes (group A); 232 ± 32, 55 ± 15, and 42 ± 10 minutes (group B), respectively (ns). One asymptomatic PV stenosis and one pericardial effusion occurred in group A and B, respectively. After 15.4 ± 7.4 months, 17 (57%) group A patients and 25 (83%) group B patients were in stable sinus rhythm (P = 0.02) (RR 1.78; 95% CI: 1.7–2.9). Conclusions: PV ablation by means of an integrated anatomical and electrophysiological approach seems more effective than a purely anatomical RF ablation approach. Electrophysiological confirmation of PV disconnection could be a useful marker of successful RF treatment of AF.

Polarizable ion calculations have been performed to determine the stable configurations of mixed metal halide microclusters and the respective molecular geometries. The results were achieved by the use of accurate model parameters obtained from the fitting of experimental molecular constants. Mixed dimers, trimers and tetramers are considered in this study. Matrix isolation spectroscopy measurements have been performed to provide an experimental characterization of the mixed molecules Li 2 FCl and LiNaFCl.

Lead dihalides and mixed lead and tin dihalides were the object of an ab-initio SCF study developed on the grounds of non-empirical pseudopotential calculations. Optimized molecular geometries and calculated vibrational frequencies are reported for the following molecules: PbF2, PbCl2, PbBr2, PbI2, PbClBr, PbClI, PbBrI, SnClBr, SnClI and SnBrI. The calculated molecular constants are compared with the available experimental geometries and vibrational spectroscopy data. The agreement between calculated and experimental data is found to be quite satisfactory, suggesting that a high level of accuracy is obtained from the use of the pseudopotential method.