Mid-term follow-up after maze IV procedures for concomitant atrial fibrillation.

BACKGROUND: We performed a retrospective analysis of the maze IV procedures performed in our surgical department for concomitant atrial fibrillation. METHODS: Preoperative, in-hospital and postoperative follow-up data were collected from 46 consecutive patients who underwent the maze IV operation between April 2006 and December 2010. All electrocardiograms and Holters were reviewed. RESULTS: One patient died in-hospital. During a mean follow-up of 25 +/- 16.3 months seven patients died: two related to a hemorrhagic stroke, one due to right ventricular failure, the remainder deaths were not cardiac related. The success rate, defined as no recurrence of AF or atrial flutter with a blanking period of 6 months postoperatively, was 73.7%. Plots of probability of freedom of atrial fibrillation over time are drawn and reach a stable level after one year. CONCLUSIONS: The mid term results of the maze IV procedures for concomitant atrial fibrillation are very good. The results are stable for the remainder of follow-up.

Study of the single-crystal X-ray diffuse scattering in paracetamol polymorphs.

Single-crystal diffuse X-ray scattering from paracetamol polymorphs is successfully calculated with Monte Carlo (MC) models that are used to simulate the crystals. In order to obtain the correct model appropriate force constants are required that describe the interatomic potentials used in the MC algorithm. Coefficients for an empirical 'Buckingham'-type formula are used to determine these force constants. These coefficients are subsequently refined using the least-squares method and are found to converge on similar values for both polymorphic forms. An investigation of the correlation space generated from each model provides what would be expected given that strong displacive correlations exist between the molecules comprising the densely hydrogen-bonded layers. More disordered motions between these layers are present in the model for form (II) as opposed to form (I). An investigation into the peculiarities of librational disorder was also conducted, however, correlation values turn out to be so small that any structural information concerning librational correlation is inconclusive. The purpose of this experiment was to identify if the diffuse scattering features could provide further insight into understanding the physical reasoning behind the metastability of form (II). The form (II) → (I) phase transition is also not currently well understood and usually phase transitional information can be obtained from pronounced diffuse scattering features. Since the diffuse scattering is modelled adequately using harmonic potentials it is our conjecture that the 'diffuse' is essentially thermal in origin and does not afford any extra information about the form (II) → (I) phase transition.

Local order in layered NiPS3 and Ni0.7Mg0.3PS3.

The family of two-dimensional magnetic materials M(II)PS(3) where M = Mn, Fe, Ni, Mg, Zn, etc shows a wide range of fascinating magnetic behaviour. It also shows potentially useful chemical properties including intercalation of nonlinear optical molecules and lithium ions. These properties are due to a crystal structure in which the ab planes are well-ordered in the plane but poorly correlated along c. Here, the short-range ordering is modelled in NiPS(3) and Ni(1 - x)Mg(x)PS(3) (x = 0.3). X-ray diffuse scattering from NiPS(3) shows pronounced streaking along c, indicative of stacking faulting in these layered compounds. Electron diffraction from Ni(1 - x)Mg(x)PS(3) (x = 0.3) shows substantial diffuse scattering due to short-range order within the ab plane, and this can be modelled by allowing the metal species to cluster. The possibility of clustering has implications for interpretation of the magnetic behaviour of the family, including the glassiness observed in Fe(1 - x)Mn(x)PS(3).

Diffuse scattering study of aspirin forms (I) and (II).

Full three-dimensional diffuse scattering data have been recorded for both polymorphic forms [(I) and (II)] of aspirin and these data have been analysed using Monte Carlo computer modelling. The observed scattering in form (I) is well reproduced by a simple harmonic model of thermally induced displacements. The data for form (II) show, in addition to thermal diffuse scattering (TDS) similar to that in form (I), diffuse streaks originating from stacking fault-like defects as well as other effects that can be attributed to strain induced by these defects. The present study has provided strong evidence that the aspirin form (II) structure is a true polymorph with a structure quite distinct from that of form (I). The diffuse scattering evidence presented shows that crystals of form (II) are essentially composed of large single domains of the form (II) lattice with a relatively small volume fraction of intrinsic planar defects or faults comprising misoriented bilayers of molecular dimers. There is evidence of some local aggregation of these defect bilayers to form small included regions of the form (I) structure. Evidence is also presented that shows that the strain effects arise from the mismatch of molecular packing between the defect region and the surrounding form (II) lattice. This occurs at the edges of the planar defects in the b direction only.

Single-crystal diffuse scattering studies on polymorphs of molecular crystals. I. The room-temperature polymorphs of the drug benzocaine.

The drug benzocaine (ethyl 4-aminobenzoate), commonly used as a local anaesthetic, is a bimorphic solid at room temperature. Form (I) is monoclinic P2(1)/c, while the metastable form (II) is orthorhombic P2(1)2(1)2(1). Three-dimensional diffuse X-ray scattering data have been collected for the two forms on the 11-ID-B beamline at the Advanced Photon Source (APS). Both forms show strong and highly structured diffuse scattering. The data have been interpreted and analysed using Monte Carlo (MC) modelling on the basis that the scattering is purely thermal in origin and indicates the presence of highly correlated molecular motions. In both forms (I) and (II) broad diffuse streaks are observed in the 0kl section which indicate strong longitudinal displacement correlations between molecules in the 031 directions, extending over distances of up to 50 A. Streaks extending between Bragg peaks in the hk0 section normal to [100] correspond to correlated motions of chains of molecules extending along a that are linked by N-H...O=C hydrogen bonds and which occur together as coplanar ribbon pairs. The main difference between the two forms is in the dynamical behaviour of the ribbon pairs and in particular how they are able to slide relative to each other. While for form (I) a model involving harmonic springs is able to describe the motion satisfactorily, as simple excursions away from the average structure, there is evidence in form (II) of anharmonic effects that are precursors of a phase transition to a new low-temperature phase, form (III), that was subsequently found.

The crystal and magnetic structures of LaCa(2)Fe(3)O(8) and NdCa(2)Fe(3)O(8).

The crystal and magnetic structures of LaCa(2)Fe(3)O(8) and NdCa(2)Fe(3)O(8) have been established using a combination of x-ray, neutron and electron diffraction. It was already considered likely that LaCa(2)Fe(3)O(8) and NdCa(2)Fe(3)O(8) were made up of stacked perovskite-like layers of FeO(6) octahedra, with every third layer being replaced by a layer of tetrahedrally coordinated Fe, rather like a variation on the Brownmillerite (Ca(2)Fe(2)O(5)) structure type. We have gone further and determined a likely space group for this Grenier phase and determined the magnetic structure of the compounds at room temperature. The space group is found to be P 2(1)ma (b axis as the long axis), and the crystal structure has been refined, subject to the stacking faulting along the long axis that is apparent in electron diffraction patterns. The magnetic structure of LaCa(2)Fe(3)O(8) is shown to consist of antiferromagnetically ordered Fe(3+) ions on a collinear G-type antiferromagnetic structure, with the magnetic moments most likely (anti)parallel with the c axis, and of magnitude 3.4 ± 0.2µ(B) (3.6 ± 0.2µ(B) for NdCa(2)Fe(3)O(8)). The result is reasonable given the magnetic structures of the end members of the La(1-x)Ca(x)FeO(3) series, LaFeO(3) (x = 0) and Ca(2)Fe(2)O(5) (x = 1).

Neutron diffuse scattering in deuterated para-terphenyl, C(18)D(14).

Neutron diffuse scattering is used to explore the short-range order (SRO) in deuterated para-terphenyl, C(18)D(14). The crystal shows SRO because the central of the three phenyl groups of each molecule can twist positively or negatively and these twists are correlated over the local scale. The presence of incipient Bragg peaks at [Formula: see text] at 200 K shows that these flips are negatively correlated along the a direction (nearest neighbour correlation coefficient of ∼-0.3) and b direction (nearest neighbour correlation coefficient of ∼-0.87) and appear essentially uncorrelated along c. Diffuse peak anisotropy indicates that the range of the correlations along b is found to be ∼3 times that along a. These correlations persist, although weaker, at room temperature. A Monte Carlo simulation was used to impose a correlation structure on the population of central ring twists that was deduced from Bragg scattering. By then allowing displacive relaxation of the structure, the observed diffuse scattering was well reproduced. Modelling the displacive motions of molecules showed that the positions of nearest ab-plane neighbour molecules are strongly positively correlated, particularly for motions approximately parallel to a, while the displacive correlations are weaker between molecules stacked along c. The apparent contradiction that the displacements are most strongly correlated along a while the occupancies are most strongly correlated along b is explained in terms of the connectivity of molecular interactions.

The interpretation and analysis of diffuse scattering using Monte Carlo simulation methods.

Studies of diffuse scattering had a prominent place in the first issue of Acta Crystallographica 60 years ago at a time when conventional crystallography (determination of the average structure from Bragg peaks) was in its infancy. Since that time, conventional crystallography has developed enormously while diffuse-scattering analysis has seemingly lagged well behind. The paper highlights some of the extra difficulties involved in the measurement, interpretation and analysis of diffuse scattering and plots the progress that has been made. With the advent of the latest X-ray and neutron sources, area detectors and the ever-increasing power of computers, most disorder problems are now tractable. Two recent contrasting examples are described which highlight what can be achieved by current methods.

A room-temperature X-ray diffuse scattering study of form (II) of the trimorphic molecular system p-(N-methylbenzylidene)-p-methylaniline.

Three-dimensional X-ray diffuse scattering data have been collected at room temperature for form (II) of the trimorphic molecular system p-(N-methylbenzylidene)-p-methylaniline. Although this polymorph has been reported to have a perfectly normal ordered average structure, strong and highly structured diffuse scattering was observed, indicating that substantial thermal disorder is present. A diffuse scattering analysis has been carried out using Monte Carlo simulation techniques. Narrow streaks of intensity extending between Bragg peaks in the h0l section were found to arise from planes of diffuse scattering in three dimensions. These are caused by highly correlated molecular displacements along chains of end-to-end disposed molecules running in the a-c direction, corresponding to methyl-methyl intermolecular interactions. A second significant feature--rods of diffuse scattering running in the b* direction--indicates that molecular layers normal to b have a tendency to undergo lateral displacements with little correlation between layers. Finally, the internal flexibility of the molecule is required for a best fit. Changes in the two dihedral angles are found to be strongly correlated and show large excursions (> +/- 20 degrees) from the average values. All of these features suggest possible mechanisms for the way in which form (II) might transform to other polymorphs.

Simultaneous fitting of X-ray and neutron diffuse scattering data.

Conventional crystallographic refinement uses the Bragg-peak intensities and gives the single-site average crystal structure. Information about short-range order and local order is contained in the diffuse scattering that is distributed throughout reciprocal space. Models of the short-range order in materials can now be automatically refined. The complementarity of X-ray and neutron diffraction data, and the value of simultaneously refining a structural model against both types of data, has long been known. This paper presents the first refinement of a short-range-order model against comprehensive X-ray and neutron diffuse scattering data simultaneously. The sample is the organic molecular crystal benzil, C(14)H(10)O(2) (for neutron work H is replaced by D). The technique gives new insights into local order in crystalline materials, including the dynamic correlation structure indicative of the dynamics of molecules in the crystalline state, and successfully overcomes limitations of using only the X-ray data set.

The molecular conformation of Ibuprofen, C13H18O2, through X-ray diffuse scattering.

A study of the three-dimensional distribution of the X-ray diffuse scattering from the pharmaceutical Ibuprofen (2-(4-isobutylphenyl)propionic acid, C(13)H(18)O(2)) has been undertaken. The most important aspects of the molecular flexibility have been isolated, as have key correlations between variables within a single molecule. Hence, aspects of the conformational space of the molecule within a crystalline environment have been outlined. For example the correlations between torsional twists on different bonds in the molecule (corresponding to the torsional angles on atoms C3, O1 and C11) have been established. Even though the atoms are on opposite sides of the phenyl group, there is a strong negative correlation between the torsional angle on C3 and that on C11. This shows that the ability to predict the conformation a fragment of a molecule will adopt based on the conformations of the fragment found in other molecules may be limited, as aspects of molecular geometry far from the fragment itself will have impact on its conformation. Between molecules, the positional coordinate components which coincide with the direction of propagation of strong intermolecular contacts, particularly the -COOH-HOOC- dimerising interactions, are positively correlated. On the other hand, motions perpendicular to such directions, and rotations about the torsional angles, do not propagate strongly from molecule to molecule.

Interpretation of diffuse scattering in the high-Tc superconductor HgBa2CuO4+δ.

Published diffuse X-ray scattering from the high-Tc superconductor HgBa2CuO4+δ has been reexamined with a view to developing a model that more satisfactorily accounts for the observed patterns. The present work agrees with the previous conclusion that the doping oxygen atoms form long and isolated interstitial chains that run in both tetragonal directions. However, a distinctly different model is proposed for the accompanying displacement patterns of the atoms surrounding these linear defects. In this new model it is proposed that it is the correlated shifts of the Ba atoms along the length of the defect chains that are the primary source of the observed scattering, and that the variations of intensity in the generated diffuse streaks of scattering originate from lateral shifts of both Hg and Ba atoms away from defects. The new model yields diffraction patterns that are in much more convincing agreement with the observations than the original model.

Tetraplegia after a tracheal resection procedure.

We describe a 27-year-old patient who was admitted to our hospital for a tracheal stenosis caused by an adenocystic carcinoma. A tracheal resection procedure was performed and the head was fixed to the anterior chest wall by two sutures. Postoperatively he became tetraplegic, from which he completely recovered after the sutures were removed. We think that the decreased blood flow in the arterial spinal artery with flexion of the neck in combination with hypotension was the direct cause of this major complication.

Long-term survival after bronchial sleeve resection: univariate and multivariate analyses.

BACKGROUND: Long-term results after bronchial sleeve resection remain controversial, especially in relation to nodal involvement. In a previous report, there were no 10-year survivors among patients with N1 or N2 disease. METHODS: From 1960 to 1989, 145 patients underwent bronchial sleeve resection for a bronchogenic tumor. Follow-up was updated until the end of 1994, so the minimum follow-up was 5 years for surviving patients. A univariate analysis and a multivariate analysis were performed. RESULTS: For the whole group, 5-year, 10-year, and 15-year survival rates were 46%, 33%, and 22%, respectively. The median survival time was 53 months. Five-year and 10-year survival rates for the 71 patients with no disease were 62% and 51%, respectively; for the 58 patients with N1 disease, 31% and 10%; and for the 16 patients with N2 disease, 5-year and 7-year survival rates were 31% and 13%. There was a highly significant difference in survival between patients with no and N1 or N2 disease but not between those with N1 and N2 disease. Multivariate analysis showed only nodal stage and patient age to be significant factors in relation to survival. CONCLUSIONS: Long-term results after bronchial sleeve resection are influenced chiefly by nodal stage. A significantly lower survival is found in patients with N1 and N2 disease, and most of these patients die of distant metastases.

Diffuse X-ray scattering from benzil, C(14)H(10)O(2): analysis via automatic refinement of a Monte Carlo model.

A recently developed method for fitting a Monte Carlo computer-simulation model to observed single-crystal diffuse X-ray scattering has been used to study the diffuse scattering in benzil, diphenylethanedione, C(6)H(5)-CO-CO-C(6)H(5). A model involving 13 parameters consisting of 11 intermolecular force constants, a single intramolecular torsional force constant and a local Debye-Waller factor was refined to give an agreement factor, R = [summation operator omega(Delta I)(2)/summation operator omega I(obs)(2)](1/2), of 14.5% for 101,324 data points. The model was purely thermal in nature. The analysis has shown that the diffuse lines, which feature so prominently in the observed diffraction patterns, are due to strong longitudinal displacement correlations. These are transmitted from molecule to molecule via a network of contacts involving hydrogen bonding of an O atom on one molecule and the para H atom of the phenyl ring of a neighbouring molecule. The analysis also allowed the determination of a torsional force constant for rotations about the single bonds in the molecule. This is the first diffuse scattering study in which measurement of such internal molecular torsion forces has been attempted.

Diffuse scattering and partial disorder in complex structures.

The study of single-crystal diffuse scattering (SCDS) goes back almost to the beginnings of X-ray crystallography. Because SCDS arises from two-body correlations, it contains information about local (short-range) ordering in the sample, information which is often crucial in the attempt to relate structure to function. This review discusses the state of the field, including detectors and data collection and the modelling of SCDS using Monte Carlo and ab initio techniques. High-quality, three-dimensional volumes of SCDS data can now be collected at synchrotron light sources, allowing ever more detailed and quantitative analyses to be undertaken, and opening the way to approaches such as three-dimensional pair distribution function studies (3D-PDF) and automated refinement of a disorder model, powerful techniques that require large volumes of low-noise data.

Revealing how interactions lead to ordering in para-terphenyl.

How does the ordering in a crystal arise from the interactions present? Crystal structure determination shows what the crystal structure is, but in solving directly for atomic coordinates leaves questions as to why (or how) aspects of the structure arise. The answers to such questions are crucial in the study of what drives structural phase transitions or in crystal structure prediction. In this work, modeling of the neutron diffuse scattering from deuterated para-terphenyl, C18D14, shows directly how the observed short-range order arises out of intramolecular and intermolecular interactions. This approach provides real-space descriptions of cooperative molecular motions and correlations, and explains the two-dimensional critical behavior observed in other experiments. In doing so, it is found that intramolecular and intermolecular interactions, and the molecules themselves, can be thought of as acting as nanoscale mechanical linkages.

X-ray diffuse scattering from HMTA: analysis via a Monte Carlo model.

Hexamethylenetetramine (HMT, C(6)H(12)N(4), also referred to as urotropin) and azelaic acid [A, HOOC-(CH(2))(7)-COOH] form a co-crystal or adduct (HMTA, also referred to as urotropin azelate) which exhibits several structural phases as a function of temperature. At room temperature, the structure is orthorhombic, but shows substantial disorder. Here, this disorder is explored by analyzing the diffuse scattering from single crystals of HMTA via Monte Carlo simulation. The disorder is in part occupational, with two orientations of azelaic acid occurring, and in part thermally induced, which is to say dynamic. The occupational disorder can be thought of as a combination of limited-range in-plane (bc plane) negative correlations combined with effectively zero correlation between planes (along a), rather like stacking faults. Size effect, the cross-correlation between molecular orientation and displacement from average position, is required to reproduce the observed diffuse scattering.

High-energy diffuse scattering on the 1-ID beamline at the advanced photon source.

This paper reports on experiments in which high-energy (65.35 keV) X-rays were used to record the detailed diffuse diffraction patterns of a number of ceramic materials. The methodology has enabled a greater q-range to be explored (up to sintheta/lambda approximately 0.97) than is possible with laboratory-based experiments, with better q-space resolution and increased sensitivity, thus allowing previously unseen detail in diffraction patterns to be recorded. In all, 11 sections of data have been collected for Ca-CSZ, eight for Y-CSZ and six for wüstite.