bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of linear polarization in the Hα line in solar flares
Authors: Kotrč P.
Published: May 2003

Large solar telescopes built at places with a quite excellent seeing, equipped with a sophisticated optics and control system are too expensive and unique to be used currently in hunting of sudden and short‐lasting activity events, e.g. flares and eruptive prominences. For a systematic observation of selected kinds of active phenomena it is still necessary to use smaller or medium‐sized telescopes equipped with a special setup of devices. Detection of linear polarization in the Hα line emitted in a flare seems to be just a right task and delicate matter for such a systematic observation. This kind of polarization is supposed to be generated by particle beams accelerated in thke corona and directed towards denser chromospheric layers where the particle beams deposit their kinetic energy. As the accelerated particle beams possess a preferred direction of velocity they can produce a linearly polarized light. However, the occurrence of the accelerated particle beams and the related linear polarization in the Hα line may have a tendency to appear: 1) at the early beginning of a flare 2) in pulses lasting just a few seconds or even less. To measure the linear polarization in flares regularly we have built an additional branch in the Ondřejov multichannel flare spectrograph. In this paper we describe the optical system, the detectors, the method used for data recording and reduction and we also briefly discuss the first results.
Speckle spectro‐polarimetry of magnetic structures
Authors: Janssen K. , Kneer F.
Published: May 2003

Two‐dimensional spectrograms were obtained with the Vacuum Tower Telescope, Tenerife, in order to study small‐scale structures and faculae on the Sun. Using the speckle reconstruction method, we obtain high‐resolution images and wavelength scans. Magnetic fields can be studied from Stokes V profiles, and velocity maps are gained by the Doppler shift of the center of gravity of Stokes I. Here some results about small‐scale structures and their magnetic fields are shown.
Study of polar faculae by means of spectro‐polarimetric observations and radiative transfer calculations
Authors: Okunev O. , Kneer F.
Published: May 2003

Polar faculae are of special interest for solar physics because of their close relationship to the global magnetic field of the Sun and to solar activity, and because of the recently found kilogauss magnetic fields, which are very unusual for the structures outside active regions at high latitudes of the Sun. The idea is that polar faculae can be represented by bundles of unresolved small‐scale magnetic flux tubes, which are characterized by sizes of about 100 km and strong magnetic fields. High resolution spectro‐polarimetric observations of the considered structures were performed and complemented by the radiation transfer calculations with oblique rays passing through an inhomogeneous magnetic medium. The recent results of observations and numerical calculations are presented.
Solar activity I: aspects of magnetic activity
Authors: Briand C.
Published: May 2003

It is now accepted that the solar activity has direct impact on the Earth climate, but is also responsible for the geomagnetic storms. It is thus fundamental to understand the mechanisms responsible for this activity.

We present here first some aspects of the solar activity at the different atmospheric layers of the sun: active region at photospheric levels, filaments (prominences) and flares at chromospheric level and CME's at coronal level. A quick sum‐up of the principal characteristics of each is given as well as the key questions still under investigation. In the second part, two principal parameters are presented to describe these features: helicity and topology. Finally, we sum‐up the observational challenges for new solar telescopes.
Solar activity II: Sunspots and pores
Authors: Sobotka M.
Published: May 2003

Sunspots and pores appear as a consequence of interactions between strong magnetic fields and moving plasma. A wide variety of small‐scale features, presumably of convective origin, are observed in photospheric layers of sunspots and pores: Umbral dots, light bridges, penumbral filaments, and penumbral grains. Each type of features has specific morphological, photometric, spectral, and kinematic characteristics. Spots and pores modify velocity fields in adjacent photosphere and sub‐photospheric layers. Recent high‐resolution spectral, broad‐band, and helioseismic observations of the structure, dynamics, and magnetic fields of sunspots and pores, together with theoretical interpretations, are discussed in this review.
Material flow in sunspots
Authors: Schmidt W.
Published: May 2003

Observations nowadays reveal more and more details about the small‐scale structure of the penumbra and umbra. Recent measurements of the motions in the penumbra indicate that (i) the Evershed flow is confined to a thin photospheric layer and (ii) the material rises from and sinks to subphotospheric layers within the penumbra. This flow pattern solves the question of the mass budget of the Evershed flow in a natural way. The nature of umbral dots and their role for the spot's energy budget remains unclear, since they are obviously unresolved even in the best existing measurements.
Structure of a simple sunspot from the inversion of IR spectral data
Authors: Mathew S.K. , Solanki S.K. , Lagg A. , Collados M. , Berdyugina S.V. , Frutiger C. , Krupp N. , Woch J.
Published: May 2003

Analysis of spectral data of two neighboring infrared lines, Fe I 15648.5 Å (g = 3) and FeI 15652.9 Å (geff = 1.53) are carried out for a simple sunspot when it was near the solar disk center (μ = 0.92), to understand the basic structure of sunspot magnetic field. Inversions of Stokes profiles are carried out to derive different atmospheric parameters both as a function of location within the sunspot and height in the atmosphere. As a result of the inversion we have obtained maps of magnetic field strength, temperature, line‐of‐sight velocity, field inclination and azimuth for different optical depth layers between log(τ5) = 0 and log(τ5) = –2.0. In this paper we present few results from our inversion for a layer averaged between log(τ5) from 0.0 to –0.5.
The Zeeman effect: applications to solar physics
Authors: Landi Degl'Innocenti E.
Published: May 2003

This contribution is intended to give a brief review of some of the results concerning the Zeeman effect which have been recently published in the literature or which appear to be particularly relevant at the light of recent technological improvements in observations. The arguments emphasized are the Zeeman effect in molecular lines, the asymmetries observed in Stokes profiles from sunspots, and the interpretation of spectropolarimetric observations in the infrared.
Studying magneto‐convection by numerical simulation
Authors: Vögler A. , Schüssler M.
Published: May 2003

Following a brief overview of the two main approaches to investigate the interaction between magnetic fields and convective flows near the solar surface layers by numerical simulation, namely idealized model problems and ‘realistic’ large‐eddy simulations, we present first results obtained with a newly developed MHD code. The first example concerns the realistic simulation of the magnetic field dynamics in a solar plage region while the second example demonstrates small‐scale dynamo action in idealized compressible convection.
Invasive echocardiography: The use of catheter imaging by the interventional cardiologist
Authors: Rhodes John F. , Lane Geoffrey K. , Tuzcu E. Murat , Latson Larry A.
Published: May 2003

Ultrasound imaging is frequently used for diagnostic purposes or guidance during procedures in the pediatric and congenital cardiac catheterization laboratory. As new imaging modalities emerged, many interventional cardiologists rather than noninvasive specialists are now performing the ultrasound imaging as part of the catheterization. The focus of this discussion will be to detail the technique and application of echocardiography by the interventional cardiologist. Cathet Cardiovasc Intervent 2003;59:277–290. © 2003 Wiley‐Liss, Inc.
Nonhealing wound resulting from a foreign‐body reaction to a radial arterial sheath
Authors: Subramanian Rajesh , White Christopher J. , Sternbergh W. Charles , Ferguson Daniel L. , Gilchrist Ian C.
Published: May 2003

Several patients developed sterile inflammation at their radial arterial access site. Pathologic examination of biopsy material from one patient demonstrated a foreign‐body reaction to material most likely from the gel‐coated arterial access sheath. Surgical excision of the inflamed tissue resulted in healing. Cathet Cardiovasc Intervent 2003;59:205–206. © 2003 Wiley‐Liss, Inc.
Is adjunctive balloon postdilatation necessary after coronary stent deployment? Final results from the POSTIT trial
Authors: Brodie Bruce R. , Cooper Christopher , Jones Michael , Fitzgerald Peter , Cummins Frank
Published: May 2003

Early‐generation balloon‐expandable stents required postdilatation with noncompliant balloons at high pressure to optimize stent deployment. The need for adjunctive balloon postdilatation with modern stent delivery systems is unknown. Patients undergoing elective stenting were randomized to Boston Scientific NIR, Guidant Tri‐Star/Tetra, and Medtronic AVE S670 stents. The primary endpoint was optimum stent deployment defined as a minimal stent diameter (MSD) ≥ 90% of the average reference lumen diameter assessed by intravascular ultrasound (IVUS) performed immediately following stent deployment. If, by operator assessment, the primary endpoint was not achieved with the stent delivery system, adjunctive postdilatation with noncompliant balloons was performed. Of 256 patients with IVUS studies adequate for core laboratory analysis, only 29% achieved optimum stent deployment with the stent delivery system. None of the baseline clinical or angiographic variables predicted optimum stent deployment. Of the procedural variables, the type of stent and nominal stent size were not predictors, but higher deployment pressures were associated with a higher frequency of optimum stent deployment (< 12 atm 14% vs. ≥ 12 atm 36%; P = 0.007). The inability to achieve optimum stent deployment was not due to undersizing the stent delivery balloon, but rather to an inability of the stent delivery balloon to expand fully the stent to nominal size. In patients who underwent postdilatation, the frequency of achieving optimum stent deployment increased from 21% to 42%, minimal stent area increased from 6.6 ± 2.2 to 7.8 ± 2.3 mm2, and MSD increased from 2.6 ± 0.5 to 2.8 ± 0.4 mm. These data stress the continued need for adjunctive balloon postdilatation with modern stent delivery systems. Cathet Cardiovasc Intervent 2003;59:184–192. © 2003 Wiley‐Liss, Inc.
Correlates of failure following treatment with Sr‐90 beta irradiation for in‐stent restenosis
Authors: Almeda Francis Q. , Chua David Y. , Nathan Sandeep , Kim Susie , Meyer Peter M. , Nguyen Cam , Chu James C.H. , Kavinsky Clifford J. , Snell R. Jeffrey , Schaer Gary L.
Published: May 2003

We sought to determine the correlates of failure following intracoronary radiation therapy (IRT) with Sr‐90 using the Novoste Beta‐Cath system for the treatment of in‐stent restenosis (ISR) in a broad range of patients. IRT has been shown to be more efficacious compared to placebo for the treatment of ISR in large randomized trials. However, even in patients treated with IRT, major adverse cardiac events occur in approximately 20% of cases on follow‐up. This trial sought to elucidate the correlates of failure following successful IRT for ISR. To determine the correlates of IRT failure, we retrospectively compared the demographics, lesion characteristics, and clinical outcomes of 102 consecutive patients with ISR treated with Sr‐90 from September 1998 to July 2001. IRT failure was defined as death, myocardial infarction (MI), or target vessel revascularization (TVR) due to repeat ISR on follow‐up. A comparison of the clinical and angiographic profile of IRT failures (n = 16) vs. IRT successes (n = 86) revealed that a history of smoking (75% vs. 40%; P = 0.012), current use of calcium channel blockers (84% vs. 45%; P = 0.013), ostial location of target lesion (44% vs. 16%; P = 0.020), and mean posttreatment minimal luminal diameter (MLD; 1.64 ± 0.19 vs. 2.21 ± 0.29 mm; P < 0.001), respectively, were correlated with failure using univariate analysis. After multivariate regression analysis, the correlates of failure that remained significant were treatment of an ostial lesion (OR = 31.2; 95% CI = 2.6–382.7; P = 0.007) and final posttreatment MLD (P < 0.001). Ostial location of target lesion and smaller posttreatment MLD are correlated with subsequent death, MI, and TVR following therapy with Sr‐90 for ISR. Cathet Cardiovasc Intervent 2003;59:176–183. © 2003 Wiley‐Liss, Inc.
Vessel caliber and restenosis: A prospective clinical and angiographic study of NIR stent deployment in small and large coronary arteries in the same patient
Authors: Ruygrok Peter N. , Webster Mark W. , Ardill Justin J. , Chan Charles C. , Mak Koon H. , Meredith Ian T. , Stewart James T. , Ormiston John A. , Price Sue
Published: May 2003

Retrospective analyses of patient cohorts undergoing stent deployment have shown that small vessel diameter and long lesion length are two angiographic predictors of increased restenosis. We determined the effects of these factors in patients with lesions treated in both small‐ and large‐diameter coronary arteries. This multicenter prospective quantitative angiographic study evaluated patients with de novo coronary disease undergoing intervention who had at least two lesions ≤ 16 mm length, one in a vessel ≤ 2.75 mm diameter (9 or 16 mm length seven‐cell NIR stent) and the other in a vessel ≥ 3.0 mm diameter (9 or 16 mm nine‐cell NIR stent). Of 94 patients enrolled, 76% were male, mean age was 62 years (range, 40–85), 41% were hypertensive, 18% had diabetes, 15% were current smokers, and 64% had hypercholesterolemia. Additional lesions were treated in 23% of patients. The procedural success rate was 99%. Six months postprocedure, there were no deaths or late stent occlusions. One patient suffered a Q‐wave myocardial infarction, one a non–Q‐wave infarction, eight underwent percutaneous reintervention, two coronary artery bypass graft surgery operations, and five stenting of other nonstudy lesions. The mean reference diameter for the small vessel was 2.35 mm and the large vessel 3.22 mm. Six‐month angiography was performed in 87 patients (92% of those eligible). The overall restenosis rate was 24% in the small vessel (9 mm length stent, 17%; 16 mm length stent, 30%) and 15% in the large vessel (9 mm length stent, 3%; 16 mm length stent, 22%), respectively. Multivessel stenting including treatment of lesions in small‐caliber vessels can be performed with a good clinical and angiographic outcome. When the patient, operator, technique, and stent type are the same, vessel caliber and stent length both appear to influence the restenosis rate. Cathet Cardiovasc Intervent 2003;59:165–171. © 2003 Wiley‐Liss, Inc.
Unusual vertebral artery origins: Examples and related pathology
Authors: Koenigsberg Robert A. , Pereira Lorianne , Nair Bronwyn , McCormick Daniel , Schwartzman Robert
Published: May 2003

Anomalies of the vertebral arteries are uncommon, but important to recognize in the diagnosis and catheter based evaluation and treatment of patients suffering cerebrovascular disease. This article illustrates our experience with such anomalies. These include the vertebral artery arising as the fourth and most distal branch of the aortic arch, as a right subclavian artery branch arising distal to the right thyrocervical trunk, as a right common carotid artery branch in a patient with an aberrant right subclavian artery, and a case of left vertebral artery proximal duplication, with both aortic and left subclavian vertebral arteries present in the same patient; the latter join to form a single distal cervical vertebral artery. Cathet Cardiovasc Intervent 2003;59:244–250. © 2003 Wiley‐Liss, Inc.
One‐step treatment of patent ductus arteriosus and pulmonary artery stenosis by cardiac catheterization
Authors: Santoro Giuseppe , Bigazzi Maurizio Cappelli , Palladino Maria Teresa , Carrozza Marianna , Russo Maria Giovanna , Calabrò Raffaele
Published: May 2003

Coexistence of pulmonary artery (PA) stenosis and patent ductus arteriosus (PDA) may lead to overestimating the relative importance of these malformations. This article reports on a patient with a trivial PDA and severe PA stenosis erroneously diagnosed as moderate PDA. He was successfully submitted to simultaneous PA stenting and PDA embolization. Cathet Cardiovasc Intervent 2003;59:271–275. © 2003 Wiley‐Liss, Inc.
Transcatheter closure of recurrent postmyocardial infarction ventricular septal defects utilizing the Amplatzer postinfarction VSD device: A case series
Authors: Goldstein Jeffrey A. , Casserly Ivan P. , Balzer David T. , Lee Richard , Lasala John M.
Published: May 2003

The initial therapy for postmyocardial infarction ventricular septal defects is surgical repair of the defect. Unfortunately, a significant number of patients develop recurrent ventricular septal defects (VSDs) following operative repair. Transcatheter closure offers an alternative to reoperation in these critically ill patients. We present a series of four patients in whom recurrent ventricular septal defects were closed using an Amplatzer VSD device. Cathet Cardiovasc Intervent 2003;59:238–243. © 2003 Wiley‐Liss, Inc.
Sterile inflammation associated with transradial catheterization and hydrophilic sheaths
Authors: Kozak Mark , Adams David R. , Ioffreda Michael D. , Nickolaus Michelle J. , Seery Thomas J. , Chambers Charles E. , Ettinger Steven M. , McNulty Patrick H. , Gilchrist Ian C.
Published: May 2003

In 1999, we noted the development of inflammation and/or abscesses at the site of radial access in a group of patients. Over a 3‐year period, we noted this inflammation in 33 patients out of 2,038 (1.6%) who had catheterization via the radial approach. The radial abscesses occurred in 30 patients out of 1,063 (2.8%) in whom we could confirm the use of a hydrophilic‐coated sheath, but in no patient for whom we can document that an uncoated sheath was used. No infectious agent could be implicated, and the time course for the development of the abscess, typically 2 to 3 weeks, seemed long for a bacterial infection. Later patients had biopsies, and granulomatous reactions were seen in most. Additionally, a few of the biopsies showed an amorphous extravascular substance consistent with the catheter coating. All patients had good long‐term outcomes. Cathet Cardiovasc Intervent 2003;59:207–213. © 2003 Wiley‐Liss, Inc.
Compassionate use of the amplatzer ASD closure device for residual postinfarction ventricular septal rupture following surgical repair
Authors: Lowe Harry C. , Jang Ik‐Kyung , Yoerger Danita M. , MacGillivray Thomas E. , de Moor Michael , Palacios Igor F.
Published: May 2003

We report successful transcatheter closure of a post‐MI ventricular septal rupture acutely following unsuccessful surgical repair. Catheter closure was accomplished by the use of a 26‐mm Amplatzer atrial septal occluder. Initial attempts to close the defect with the use of 28‐mm and 33‐mm CARDIOSEAL were unsuccessful. Closure technique, immediate and long‐term follow‐up outcomes are reported. Cathet Cardiovasc Intervent 2003;59:230–233. © 2003 Wiley‐Liss, Inc.
Percutaneous interventions in radial artery grafts: Clinical and angiographic outcomes
Authors: Sharma Arvind K. , Ajani Andrew E. , Garg Nidhi , GebreEyesus Afework , Varghese Jerry , Pinnow Ellen , Waksman Ron , Pichard Augusto D. , Lindsay Joseph
Published: May 2003

In the modern era, radial artery graft is being used with increasing frequency to replace saphenous vein as a conduit for coronary artery bypass surgery. Several reports have shown encouraging early results of radial grafts compared to saphenous grafts. Despite these advantages, radial artery graft failure requiring revascularization does occur. We report on the clinical, angiographic, and technical characteristics and the follow‐up results of 22 patients who underwent percutaneous intervention of radial grafts. Cathet Cardiovasc Intervent 2003;59:172–175. © 2003 Wiley‐Liss, Inc.
Endovascular brachytherapy for treatment of bilateral renal artery in‐stent restenosis
Authors: Chrysant George S. , Goldstein Jeffrey A. , Casserly Ivan P. , Rogers Jason H. , Kurz Howard I. , Thorstad Wade L. , Singh Jasvindar , Lasala John M.
Published: May 2003

Percutaneous transluminal angioplasty of renal artery stenosis is an attractive alternative to surgical therapy. However, even with endovascular stenting, the overall rate of restenosis is 21%. While brachytherapy for coronary in‐stent restenosis has proven efficacy, its use for renal artery in‐stent restenosis has not been formally evaluated. We report a case of bilateral in‐stent renal artery restenosis treated with endovascular brachytherapy. Cathet Cardiovasc Intervent 2003;59:251–254. © 2003 Wiley‐Liss, Inc.
First case reports of controlled blunt microdissection for percutaneous transluminal angioplasty of chronic total occlusions in peripheral arteries
Authors: Mossop Peter , Cincotta Marion , Whitbourn Robert
Published: May 2003

Percutaneous transluminal angioplasty (PTA) can fail to revascularize peripheral arteries when a chronic total occlusion (CTO) cannot be crossed by guidewires. This article describes application of a new controlled blunt microdissection (CMD) catheter designed to cross CTOs. Two men presenting with severe claudication had iliac CTOs that resisted crossing with guidewires. Using standard techniques, the CMD catheter was advanced to the CTO. Following attempts to cross the CTO with guidewires, the jaw of the CMD distal assembly was actuated, advancing through the CTO as plaque was blunt‐dissected. After angioplasty and stenting, restored distal flow was restored. Ischemic symptoms had not recurred at 1‐ and 28‐month follow‐up. The concept of blunt intraluminal microdissection has been applied to convert failing to successful PTA of peripheral arteries. CTOs that had resisted guidewire crossing were successfully crossed using the CMD catheter, allowing treatment by angioplasty and stenting. Cathet Cardiovasc Intervent 2003;59:255–258. © 2003 Wiley‐Liss, Inc.
The dilemma of success: Percutaneous coronary interventions in patients ≥ 75 years of age—successful but associated with higher vascular complications and cardiac mortality
Authors: Assali Abid R. , Moustapha Ali , Sdringola Stefano , Salloum Joseph , Awadalla Hany , Saikia Sangeeta , Ghani Mohammad , Hale Susan , Schroth G. , Rosales Oscar , Anderson H. Vernon , Smalling Richard W.
Published: May 2003

Elderly patients are increasingly referred to percutaneous coronary interventions (PCIs). Recent reports suggest complications rates are declining in the elderly. We sought to determine whether procedural and in‐hospital outcomes are different in patients aged ≥ 75 years undergoing nonemergent PCI as compared to patients age < 75 years. The outcome of 266 consecutive patients age ≥ 75 years undergoing nonemergent PCI was compared to that of 1,681 consecutive patients age < 75 years. Compared with younger patients, greater proportions of elderly patients were women and had a history of hypertension, peripheral vascular disease, and cerebral vascular events. Elderly patients had more extensive coronary involvement. Procedural success was similar in both groups (94%). The in‐hospital cardiac death rate was significantly higher in the elderly patients (2.3% vs. 0.7%; P = 0.03). Aged patients also had a significantly higher incidence of vascular and bleeding complications. Blood transfusion was required more often in the elderly group (4.5% vs. 2.6%; P = 0.07). The hospitalization length was significantly higher in the elderly group (4.1 ± 6.0 vs. 2.5 ± 4.3 day; P = 0.0004). By multivariate logistic regression (adjusted for baseline clinical and angiographic variables), age ≥ 75 years was found to be an independent predictor of in‐hospital cardiac death (odds ratio = 3.9; 95% CI = 1.3–11.5; P = 0.015). Although PCI is technically successful in patients aged ≥ 75 years; it is associated with more acute cardiac and vascular complications and higher in‐hospital cardiac mortality. Cathet Cardiovasc Intervent 2003;59:195–199. © 2003 Wiley‐Liss, Inc.
Experimental and Theoretical Multiple Kinetic Isotope Effects for an SN2 Reaction. An Attempt to Determine Transition‐State Structure and the Ability of Theoretical Methods to Predict Experimental Kinetic Isotope Effects
Authors: Fang Yao‐ren , Gao Ying , Ryberg Per , Eriksson Jonas , Kołodziejska‐Huben Magdalena , Dybała‐Defratyka Agnieszka , Madhavan S. , Danielsson Rolf , Paneth Piotr , Matsson Olle , Westaway Kenneth Charles
Published: May 2003

The secondary α‐deuterium, the secondary β‐deuterium, the chlorine leaving‐group, the nucleophile secondary nitrogen, the nucleophile 12C/13C carbon, and the 11C/14C α‐carbon kinetic isotope effects (KIEs) and activation parameters have been measured for the SN2 reaction between tetrabutylammonium cyanide and ethyl chloride in DMSO at 30 °C. Then, thirty‐nine readily available different theoretical methods, both including and excluding solvent, were used to calculate the structure of the transition state, the activation energy, and the kinetic isotope effects for the reaction. A comparison of the experimental and theoretical results by using semiempirical, ab initio, and density functional theory methods has shown that the density functional methods are most successful in calculating the experimental isotope effects. With two exceptions, including solvent in the calculation does not improve the fit with the experimental KIEs. Finally, none of the transition states and force constants obtained from the theoretical methods was able to predict all six of the KIEs found by experiment. Moreover, none of the calculated transition structures, which are all early and loose, agree with the late (product‐like) transition‐state structure suggested by interpreting the experimental KIEs.
Role of the Coordination of the Azido Bridge in the Magnetic Coupling of Copper(II) Binuclear Complexes
Authors: Cabrero Jesús , de Graaf Coen , Bordas Esther , Caballol Rosa , Malrieu Jean‐Paul
Published: May 2003

It is well‐known that the azido bridge gives rise antiferromagnetic (AF) or ferromagnetic (F) coupling depending on its coordination mode, namely end‐to‐end or end‐on, respectively. The aim of the present work is to analyse the factors contributing to this different magnetic behaviour. The difference dedicated configuration interaction (DDCI) method is applied to several binuclear CuII azido‐bridged models with both types of coordination. In end‐on complexes, the direct exchange and the spin polarisation contributions are found to be responsible for the ferromagnetic coupling. In end‐to‐end complexes, both the direct exchange and the spin polarisation are small and the leading term is the antiferromagnetic dynamical polarisation contribution. The most relevant physical effects are included in the DDCI calculations so that good quantitative agreement is reached for the coupling constant as well as the spin densities.
One‐Step Preparation, Structural Assignment, and Xray Study of 2,2‐Di‐n‐butyl‐ and 2,2‐Diphenyl‐6‐aza‐1,3‐dioxa‐2‐stannabenzocyclononen‐4‐ones Derived from Amino Acids
Authors: Beltrán Hiram I. , Zamudio‐Rivera Luis S. , Mancilla Teresa , Santillan Rosa , Farfán Norberto
Published: May 2003

Twenty‐four 2,2‐di‐n‐butyl‐ and 2,2‐diphenyl‐6‐aza‐1,3‐dioxa‐2‐stannabenzocyclononen‐4‐ones, each having a transannular N→Sn bond, have been prepared by one‐step reactions of α‐amino acids (1 a–l), salicylaldehyde (2), and either di‐n‐butyltin(IV) oxide (3) or diphenyltin(IV) oxide (4). The new methodology constitutes an easy, highly efficient one‐step synthesis of diorganotin(IV) derivatives, such as 5 a–l and 6 a–l, from iminic tridentate ligands without isolation of the Schiff bases. The structures of all the compounds have been established by a combination of 1H, 13C, 15N, and 119Sn NMR spectroscopy, IR spectroscopy, mass spectrometry, and elemental analysis. In all cases, the 119Sn chemical shifts, as well as the 1J(119Sn,13C) coupling constants, are indicative of pentacoordinated tin atoms in solution. The structures of compounds 5 a, d, f, 6 a, b, b‐racemic, c, d, f, g, and l have been established by single‐crystal Xray diffraction analyses. The tin atoms in 5 d, f, 6 a, b, b‐racemic, c, d, g, and l each have a distorted trigonal‐bipyramidal (TBP) geometry, with the oxygen atoms from the phenol and carboxylate moieties occupying the axial positions, and the imine nitrogen and phenyl or n‐butyl substituents occupying the equatorial positions. Compounds 5 a and 6 f show distorted octahedral (DOC) geometries due to intermolecular coordination of the carbonyl oxygen to the tin atom, in a trans disposition to the N→Sn bond, leading to trimeric 5 a and a polymeric structure for compound 6 f. Additionally, measurement of the one‐bond coupling constants 1J(119Sn,13C) in diphenyltin(IV) complexes (6 a–l) and their correlation with the CSn‐C bond angles has allowed the derivation of an equation that can be applied to assess the geometry around the tin atom for other diphenyltin(IV) compounds in solution.
Multimeric Cyclic RGD Peptides as Potential Tools for Tumor Targeting: Solid‐Phase Peptide Synthesis and Chemoselective Oxime Ligation
Authors: Thumshirn Georgette , Hersel Ulrich , Goodman Simon L. , Kessler Horst
Published: May 2003

The αvβ3 integrin receptor plays an important role in human metastasis and tumor‐induced angiogenesis. Targeting this receptor may provide information about the receptor status of the tumor and enable specific therapeutic planning. Solid‐phase peptide synthesis of multimeric cyclo(‐RGDfE‐)‐peptides is described, which offer the possibility of enhanced integrin targeting due to polyvalency effects. These peptides contain an aminooxy group for versatile chemoselective oxime ligation. Conjugation with para‐trimethylstannylbenzaldehyde results in a precursor for radioiododestannylation, which would allow them to be used as potential tools for targeting and imaging αvβ3‐expressing tumor cells. The conjugates were obtained in good yield without the need of a protection strategy and under mild conditions.
Synthesis and Characterization of Ion‐Exchangeable Titanate Nanotubes
Authors: Sun Xiaoming , Li Yadong
Published: May 2003

Titanate nanotubes were synthesized under hydrothermal conditions. The optimized synthesis (100–180 °C, longer than 48 h), thermal and hydrothermal stability, ion exchangeability and consequent magnetic and optical properties of the titanate nanotubes were systematically studied in this paper. First, nanotubes with monodisperse pore‐size distribution were prepared. The formation mechanism of the titanate nanotubes was also studied. Second, the thermal and hydrothermal stability were characterized with Xray diffraction (XRD), high‐resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR), and Raman spectroscopy. Results showed that sodium ions played a significant role in the stability of the frameworks. Third, the selective ion exchangeability was demonstrated with a series of ions. The ion substitution also enlarged the BET surface area of the titanate nanotubes to 240 m2 g−1. Combination of these two features implied that these nanotubes might be functionalized by substitution of different transitional‐metal ions and consequently used for selective catalysis. Magnetism, photoluminescence, and UV/Vis spectra of the substituted titanate nanotubes revealed that the magnetic and optical properties of the nanotubes were modifiable.
Definitive Ab Initio Studies of Model SN2 Reactions CH3X+F− (X=F, Cl, CN, OH, SH, NH2, PH2)
Authors: Gonzales Jason M. , Pak Chaeho , Cox R. Sidney , Allen Wesley D. , Schaefer III Henry F. , Császár Attila G. , Tarczay György
Published: May 2003

The energetics of the stationary points of the gas‐phase reactions CH3X+F−→CH3F+X− (X=F, Cl, CN, OH, SH, NH2 and PH2) have been definitively computed using focal point analyses. These analyses entailed extrapolation to the one‐particle limit for the Hartree–Fock and MP2 energies using basis sets of up to aug‐cc‐pV5Z quality, inclusion of higher‐order electron correlation [CCSD and CCSD(T)] with basis sets of aug‐cc‐pVTZ quality, and addition of auxiliary terms for core correlation and scalar relativistic effects. The final net activation barriers for the forward reactions are: E$\rm{_{F,F}^{\,b}}$=−0.8, E$\rm{_{F,Cl}^{\,b}}$=−12.2, E$\rm{_{F,CN}^{\,b}}$=+13.6, E$\rm{_{F,OH}^{\,b}}$=+16.1, E$\rm{_{F,SH}^{\,b}}$=+2.8, E$\rm{_{F,NH_{2}}^{\,b}}$=+32.8, and E$\rm{_{F,PH_{2}}^{\,b}}$=+19.7 kcal mol−1. For the reverse reactions E$\rm{_{F,F}^{\,b}}$=−0.8, E$\rm{_{Cl,F}^{\,b}}$=+18.3, E$\rm{_{CN,F}^{\,b}}$=+12.2, E$\rm{_{OH,F}^{\,b}}$=−1.8, E$\rm{_{SH,F}^{\,b}}$=+13.2, E$\rm{_{NH_{2},F}^{\,b}}$=−1.5, and E$\rm{_{PH_{2},F}^{\,b}}$=+9.6 kcal mol−1. The change in energetics between the CCSD(T)/aug‐cc‐pVTZ reference prediction and the final extrapolated focal point value is generally 0.5–1.0 kcal mol−1. The inclusion of a tight d function in the basis sets for second‐row atoms, that is, utilizing the aug‐cc‐pV(X+d)Z series, appears to change the relative energies by only 0.2 kcal mol−1. Additionally, several decomposition schemes have been utilized to partition the ion–molecule complexation energies, namely the Morokuma–Kitaura (MK), reduced variational space (RVS), and symmetry adapted perturbation theory (SAPT) techniques. The reactant complexes fall into two groups, mostly electrostatic complexes (FCH3⋅F− and ClCH3⋅F−), and those with substantial covalent character (NCCH3⋅F−, CH3OH⋅F−, CH3SH⋅F−, CH3NH2⋅F− and CH3PH2⋅F−). All of the product complexes are of the form FCH3⋅X− and are primarily electrostatic.
A New Strategy for the Design of Water‐Soluble Synthetic Receptors: Specific Recognition of DNA Intercalators and Diamines.
Authors: Wada Kenji , Mizutani Tadashi , Matsuoka Hideki , Kitagawa Susumu
Published: May 2003

Water‐soluble zinc bisporphyrin receptors 1 and 2 having two Lewis acidic sites (zinc) in the hydrophobic environment consisting of alkyl chains and a bisporphyrin framework, and covered with hydrophilic exterior (twelve or eighteen carboxyl groups) were prepared. The receptors show high affinity for diamines and DNA intercalators in water where the binding constants Ka are of the order of 107 and 108 M−1, respectively. Diamines and DNA intercalators are bound to the receptor through different mechanisms. Diamines are bound through hydrophobic interactions and zinc–nitrogen interactions, while DNA intercalators are bound through hydrophobic interactions and charge‐transfer interactions. Flexible alkyl chains can make van der Waals contact with guests and create a hydrophobic environment around the bound guest by an induced‐fit‐type mechanism. For the binding of DNA intercalators, the following features are noteworthy: 1) Binding constants are similar between the zinc porphyrins and zinc‐free porphyrins; 2) the binding constant is larger for the guest having the lower LUMO; this indicates the important contribution of charge‐transfer interactions to binding; 3) the hydrophobic and cationic nature of DNA intercalators is substantially important, and 4) higher ionic strength reduced the binding affinities; this shows a moderate contribution of electrostatic interactions. The conformational instability of the receptors also contributes to the tight binding: hydrophobic and electrostatic interactions cannot both be favorable at the same time in the guest‐free receptor. Enthalpy–entropy compensation observed for the binding of diamines and DNA intercalators is characterized by a relatively small slope (α=0.74) and a large intercept (β=7.75 kcal mol−1) in the ΔH ° versus TΔS ° plot; this shows that a conformational change of receptors and a significant desolvation occur upon binding. The receptor can competitively bind to propidium iodide to deprive DNA of the intercalated propidium iodide. These features of water‐soluble receptors consisting of a rigid framework and flexible side chains with a large solvent‐accessible area are in contrast to highly preorganized rigid receptors, and they can provide useful guidelines for rational design of induced‐fit artificial receptors in water.
Self‐Assembled Monolayers of Novel Surface‐Bound Dendrons: Peripheral Structure Determines Surface Organization
Authors: Dong Bin , Huo Fengwei , Zhang Lu , Yang Xunyu , Wang Zhiqiang , Zhang Xi , Gong Shaoyun , Li Jinghong
Published: May 2003

The synthetic and functional versatility of dendrimers and their well‐defined shapes make them attractive molecules for surface modification. We synthesized six structurally very similar surface‐bound dendrons and used them as building blocks for the preparation of self‐assembled monolayers (SAMs) on a gold surface. We studied the effects of the surface‐bound dendron's main structure, peripheral substituents, and the coadsorption process on its self‐assembling behavior. Using scanning tunneling microscopy (STM), we observed nanostripes for SAMs of the surface‐bound dendron consisting of symmetrical benzene rings. When we changed the symmetrical dendron's structure slightly, by increasing or decreasing the numbers of benzene rings at one wedge, we found no ordered structures were formed by the asymmetrical dendrons. We also introduced two kinds of substituents, heptane chains and oligo(ethylene oxide) chains, to the symmetrical dendron's periphery. Heptane chains appear to enhance the interaction between symmetrical backbones, leading to the formation of stripes, while oligo(ethylene oxide) chains appear to weaken the interaction between symmetrical backbones, resulting in a homogeneous structure. Dendrons with both heptane and oligo(ethylene oxide) chains exhibit nanophase separation in a confined state, leading to the formation of a honeycomb structure. Electrochemical studies provide additional evidence for understanding the resulting surface organizations: surface‐bound dendrons with symmetrical structures form denser monolayers than their asymmetrical analogues; SAMs comprising peripherally substituted dendrons exhibit blocking effects proportionate to their hydrophilic fraction.
Organic Reactions and Nanoparticle Preparation in CO2‐Induced Water/P104/p‐Xylene Microemulsions
Authors: Zhang Rui , Liu Jun , He Jun , Han Buxing , Wu Weize , Jiang Tao , Liu Zhimin , Du Jimin
Published: May 2003

Nanometer‐sized gold particles are synthesized by the reduction of HAuCl4 with KBH4 in the CO2‐induced microemulsion of (EO)27(PO)61(EO)27 (P104; EO=ethylene oxide, PO=propylene oxide)/p‐xylene/CO2/H2O. The recovery of gold particles from the microemulsion can be easily accomplished by the venting of CO2, while the surfactant remains in the organic phase. The effect of the molar ratio of the reductant to HAuCl4, the concentration of the reactants, and the molar ratio of water to EO segments (W0) in the reverse micelles on the size of the gold particles is studied. The hydrolysis of benzoyl chloride (BzCl) and p‐nitrophenyl chloroformate (NPhCl) has also been carried out in the microemulsion. The results show that the observed rate constants kobs of both substrates increase significantly with W0, and that W0 has a larger influence on the hydrolysis of BzCl. The different extents of the influence of W0 on the two reactions can be ascribed to the different reaction mechanisms and the expected changes in nucleophilicity and polarity of water in the reverse micelles.
η6‐Mesityl,η1‐Imidazolinylidene–Carbene–Ruthenium(II) Complexes: Catalytic Activity of their Allenylidene Derivatives in Alkene Metathesis and Cycloisomerisation Reactions
Authors: Çetinkaya Bekir , Demir Serpil , Özdemir Ismail , Toupet Loïc , Sémeril David , Bruneau Christian , Dixneuf Pierre H.
Published: May 2003

The reaction of electron‐rich carbene‐precursor olefins containing two imidazolinylidene moieties [(2,4,6‐Me3C6H2CH2)NCH2CH2N(R)C]2 (2a: R=CH2CH2OMe, 2 b R=CH2Mes), bearing at least one 2,4,6‐trimethylbenzyl (R=CH2Mes) group on the nitrogen atom, with [RuCl2(arene)]2 (arene=p‐cymene, hexamethylbenzene) selectively leads to two types of complexes. The cleavage of the chloride bridges occurs first to yield the expected (carbene) (arene)ruthenium(II) complex 3. Then a further arene displacement reaction takes place to give the chelated η6‐mesityl,η1‐carbene–ruthenium complexes 4 and 5. An analogous η6‐arene,η1‐carbene complex with a benzimidazole frame 6 was isolated from an in situ reaction between [RuCl2(p‐cymene)]2, the corresponding benzimidazolium salt and cesium carbonate. On heating, the RuCl2(imidazolinylidene) (p‐cymene) complex 8, with p‐methoxybenzyl pendent groups attached to the N atoms, leads to intramolecular p‐cymene displacement and to the chelated η6‐arene,η1‐carbene complex 9. On reaction with AgOTf and the propargylic alcohol HCCCPh2OH, compounds 4–6 were transformed into the corresponding ruthenium allenylidene intermediates (4→10, 5→11, 6→12). The in situ generated intermediates 10–12 were found to be active and selective catalysts for ring‐closing metathesis (RCM) or cycloisomerisation reactions depending on the nature of the 1,6‐dienes. Two complexes [RuCl2{η1‐CN(CH2C6H2Me3‐2,4,6)CH2CH2N‐ (CH2CH2OMe)}(C6Me6)] 3 with a monodentate carbene ligand and [RuCl2{η1‐CN[CH2(η6‐C6H2Me3‐2,4,6)]CH2CH2N‐(CH2C6H2Me3‐2,4,6)}] 5 with a chelating carbene–arene ligand were characterised by Xray crystallography.
meso‐Substituted Aromatic 34π Core‐Modified Octaphyrins: Syntheses, Characterization and Anion Binding Properties
Authors: Anand Venkataramanarao G. , Venkatraman Sundararaman , Rath Harapriya , Chandrashekar Tavarekere K. , Teng Weijie , Ruhlandt‐Senge Karin
Published: May 2003

Modified octaphyrins with 34π electrons have been synthesized and characterized following a simple synthetic methodology. An acid‐catalyzed α,α coupling of tetrapyrranes containing furan, thiophene and selenophene rings resulted in the formation of the respective octaphyrins in relatively good yield. Solution studies by 1H NMR and 2D NMR methods and single crystal Xray structural characterization reveal an almost flat structure with two heterocyclic rings inverted. Specifically, in 14 two selenophene rings (one on each biselenophene unit) are inverted while in 15 two furan rings (one on each bifuran unit) are inverted when the meso substituent are mesityl groups. On changing the mesityl substituent to m‐xylyl group as in 19, the location of ring inversion shifts to pyrrole rings (one on each bipyrrole unit) indicating the dependence of structure on the meso substituents. UV/Vis studies, both in freebase and protonated forms reveal typical porphyrinic character and the aromatic nature of the octaphyrins. The Δδ values evaluated by 1H NMR spectroscopy also support their aromatic nature. The protonated forms of octaphyrins bind TFA anion in a 1:2 ratio. The TFA anions are located one above and below the plane of the octaphyrin macrocycle and they are held by weak electrostatic NH‐O interactions similar to that observed for protonated rubyrins. However, in the present case, there is an additional non‐electrostatic CH‐O interaction involving β‐CH of the inverted heterocyclic ring and the carbonyl oxygen of the TFA. Furthermore, inter molecular interactions between the CH of the meso‐mesityl group and the fluorine of CF3 group of bound TFA leads to the formation of one‐dimensional supramolecular arrays with interplanar distance of 13 Å between two octaphyrins.
The Magnetic Properties of Myoglobin as Studied by NMR Spectroscopy
Authors: Bertini Ivano , Luchinat Claudio , Turano Paola , Battaini Giuseppe , Casella Luigi
Published: May 2003

Deoxymyoglobin has been investigated by NMR spectroscopy to determine the magnetic anisotropy through pseudocontact shifts and the total magnetic susceptibility through Evans measurements. The magnetic anisotropy values were found to be Δχax=−2.03±0.08×10−32 m3 and Δχrh=−1.02±0.09×10−32 m3. The negative value of the axial susceptibility anisotropy originates from the z tensor axis lying in the heme plane, unlike all other heme systems investigated so far. This magnetic axis is almost exactly orthogonal to the axial histidine plane. The other two axes lie essentially in the histidine plane, the closest to the heme normal being tilted by about 36° from it, towards pyrrole A on the side of the proximal histidine. From the comparison with cytochrome c′ it clearly appears that the position of the one axis lying in the heme plane is related to the axial histidine orientation. Irrespective of the directions, the magnetic anisotropy is smaller than that of the analogous reduced cytochrome c′ and of the order of that of low‐spin iron(III). The magnetic anisotropy of the system permits the measurement of residual dipolar couplings, which, together with pseudocontact shifts, prove that the solution structure is very similar to that in the crystalline state. Magnetic measurements, at variance with previous data, demonstrate that there is an orbital contribution to the magnetic moment, μeff=5.5 μB. Finally, from the magnetic anisotropy data, the hyperfine shifts of iron ligands could be separated in pseudocontact and contact components, and hints are provided to understand the spin‐delocalisation mechanism in S=2 systems by keeping in mind the delocalisation patterns in low‐spin S=1/2 and high‐spin S= 5/2 iron(III) systems.
Synthesis and Reactions of Terminal Osmium and Ruthenium Complexed Phosphinidenes [(η6‐Ar)(L)MPMes*]
Authors: Termaten Arjan T. , Nijbacker Tom , Schakel Marius , Lutz Martin , Spek Anthony L. , Lammertsma Koop
Published: May 2003

Novel, very stable ruthenium and osmium containing terminal phosphinidene complexes [(η6‐Ar)(L)MPMes*] (Ar=benzene, p‐cymene; L=PR3, CO, and RNC) have been prepared by dehydrohalogenation of novel [(η6‐Ar)MX2(PH2Mes*)] complexes in the presence of a stabilizing ligand. Xray crystal structures are reported for [(η6‐C6H6)(PPh3)RuPMes*] (9) and [(η6‐pCy)(PPh3)OsPMes*] (4). Dehydrohalogenation in the absence of a stabilizing ligand resulted in the new Pspiroannulated Ru2P2‐ring structure 16. Dehydrohalogenation in the presence of but‐2‐yne gave a novel phosphaallyl complex [(η6‐Ar)Ru(η3‐R2PC(Me)CHMe)] 26, for which an Xray crystal structure is reported. The mechanism by which 16 and 26 are obtained is presumed to involve the intermediate formation of the 16‐electron (η6‐benzene)RuPMes* phosphinidene complex.
Molecular Nitrides Containing Group 4 and 5 Metals: Single and Double Azatitanocubanes
Authors: Abarca Angel , Galakhov Mikhail V. , Gracia José , Martín Avelino , Mena Miguel , Poblet Josep‐M. , Sarasa José P. , Yélamos Carlos
Published: May 2003

Treatment of [{Ti(η5‐C5Me5)(μ‐NH)}3(μ3‐N)] (1) with the imido complexes [Ti(NAr)Cl2(py)3] (Ar=2,4,6‐C6H2Me3) and [Ti(NtBu)Cl2(py)3] in toluene affords the single azatitanocubanes [{Cl2(ArN)Ti}(μ3‐NH)3{Ti3(η5‐C5Me5)3(μ3‐N)}]⋅(C7H8) (2⋅C7H8) and [{Cl2Ti}(μ3‐N)2(μ3‐NH){Ti3(η5‐C5Me5)3(μ3‐N)}] (3), respectively. Similar reactions of complex 1 with the niobium and tantalum imido derivatives [{M(NtBu)(NHtBu)Cl2(NH2tBu)}2] (M=Nb, Ta) in toluene give the single azaheterometallocubanes [{Cl2(tBuN)M}(μ3‐N)(μ3‐NH)2{Ti3(η5‐C5Me5)3(μ3‐N)}] (M=Nb (4), Ta (5)), both complexes react with 2,4,6‐trimethylaniline to yield the analogous species [{Cl2(ArN)M}(μ3‐N)(μ3‐NH)2{Ti3(η5‐C5Me5)3(μ3‐N)}]⋅(C7H8) (Ar=2,4,6‐C6H2Me3, M=Nb (6⋅C7H8), Ta (7⋅C7H8)). Also the azaheterodicubanes [M{(μ3‐N)2(μ3‐NH)}2{Ti3(η5‐C5Me5)3(μ3‐N)}2]⋅2C7H8 [M=Ti (8⋅2C7H8), Zr (9⋅2C7H8)], and [M{(μ3‐N)5(μ3‐NH)}{Ti3(η5‐C5Me5)3(μ3‐N)}2]⋅2 C7H8 (Nb (10⋅2C7H8), Ta (11⋅2C7H8)) were prepared from 1 and the homoleptic dimethylamido complex [M(NMe2)x] (x=4, M=Ti, Zr; x=5, M=Nb, Ta) in toluene at 150 °C. Xray crystal structure determinations were performed for 6 and 10, which revealed a cube‐ and double‐cube‐type core, respectively. For complexes 2 and 4–7 we observed and studied by DNMR a rotation or trigonal‐twist of the organometallic ligands [{Ti(η5‐C5Me5)(μ‐NH)}3(μ3‐N)] (1) and [(μ3‐N)(μ3‐NH)2{Ti3(η5‐C5Me5)3(μ3‐N)}]1−. Density functional theory calculations were carried out on model complexes of 2, 3, and 8 to establish and understand their structures.