Microstructures of negative and positive azeotropes.

Azeotropes famously impose fundamental restrictions on distillation processes, yet their special thermodynamic properties make them highly desirable for a diverse range of industrial and technological applications. Using neutron diffraction, we investigate the structures of two prototypical azeotropes, the negative acetone-chloroform and the positive benzene-methanol azeotrope. C-HO hydrogen bonding is the dominating interaction in the negative azeotrope but C-ClO halogen bonding contributes as well. Hydrogen-bonded chains of methanol molecules, which are on average longer than in pure methanol, are the defining structural feature of the positive azeotrope illustrating the fundamentally different local mixing in the two kinds of azeotropes. The emerging trend for both azeotropes is that the more volatile components experience the more pronounced structural changes in their local environments as the azeotropes form. The mixing of the acetone-chloroform azeotrope is essentially random above 20 Å, where the running Kirkwood-Buff integrals of our structural model converge closely to the ones expected from thermodynamic data. The benzene-methanol azeotrope on the other hand displays extended methanol-rich regions and consequently the running Kirkwood-Buff integrals oscillate up to at least 60 Å. Our study provides the first experimental insights into the microstructures of azeotropes and a direct link with their thermodynamic properties. Ultimately, this will provide a route for creating tailored molecular environments in azeotropes to improve and fine-tune their performances.

Molecular Reorientation Dynamics Govern the Glass Transitions of the Amorphous Ices.

The glass transitions of low-density amorphous ice (LDA) and high-density amorphous ice (HDA) are the topic of controversial discussions. Understanding their exact nature may be the key to explaining the anomalies of liquid water but has also got implications in the general context of polyamorphism, the occurrence of multiple amorphous forms of the same material. We first show that the glass transition of hydrogen-disordered ice VI is associated with the kinetic unfreezing of molecular reorientation dynamics by measuring the calorimetric responses of the corresponding H2O, H2(18)O, and D2O materials in combination with X-ray diffraction. Well-relaxed LDA and HDA show identical isotopic-response patterns in calorimetry as ice VI, and we conclude that the glass transitions of the amorphous ices are also governed by molecular reorientation processes. This "reorientation scenario" seems to resolve the previously conflicting viewpoints and is consistent with the fragile-to-strong transition from water to the amorphous ices.

Evolution of Hydrogen Dynamics in Amorphous Ice with Density.

The single-particle dynamics of hydrogen atoms in several of the amorphous ices are reported using a combination of deep inelastic neutron scattering (DINS) and inelastic neutron scattering (INS). The mean kinetic energies of the hydrogen nuclei are found to increase with increasing density, indicating the weakening of hydrogen bonds as well as a trend toward steeper and more harmonic hydrogen vibrational potential energy surfaces. DINS shows much more pronounced changes in the O-H stretching component of the mean kinetic energy going from low- to high-density amorphous ices than indicated by INS and Raman spectroscopy. This highlights the power of the DINS technique to retrieve accurate ground-state kinetic energies beyond the harmonic approximation. In a novel approach, we use information from DINS and INS to determine the anharmonicity constants of the O-H stretching modes. Furthermore, our experimental kinetic energies will serve as important benchmark values for path-integral Monte Carlo simulations.

Polar stacking of molecules in liquid chloroform.

Using neutron diffraction and the isotopic substitution technique we have investigated the local structure of liquid chloroform. A strong tendency for polar stacking of molecules with collinear alignment of dipole moments is found. We speculate that these polar stacks contribute to the performance of chloroform as a solvent.

Does facilitating pollinator learning impede deceptive orchid attractiveness? A multi-approach test of avoidance learning.

It has often been proposed that nectarless deceptive orchid species exploit naïve pollinators in search of food before they learn to avoid their flowers, and that intraspecific floral trait polymorphism, often noted in this plant group, could prolong the time needed for learning, thus increasing orchid reproductive success. We tested the importance of avoidance learning in a European deceptive orchid, Anacamptis morio, which has been reported to have a highly variable fragrance bouquet among individuals. We used an indirect approach, i.e. we facilitated pollinators' ability to learn to avoid A. morio by adding anisaldehyde to selected inflorescences, a scent compound that is easily perceived by the natural pollinators and produced in large quantities by the closely related, nectar producing Anacamptis coriophora, a species that shares pollinator species with A. morio. In a series of three experiments (in artificial arrays, in natural populations and in bumblebee behavioural observations), we consistently found no difference either of reproductive success of or visitation rates to scent-added versus control inflorescences. We also found that the decrease of reproductive success over time in artificial populations of this deceptive species was not as important as expected. Together, these data suggest that pollinators do not fully learn to avoid deceptive inflorescences, and that pollinator avoidance behaviour alone may explain the lower reproductive success usually found in deceptive orchids. We discuss the possible explanations for this pattern in deceptive orchids, particularly in relation to pollinator cognition and learning abilities. Lastly, in light of our results, the potential for higher average reproductive success in deceptive orchids with high phenotypic variability driven by avoidance learning thus appears to be challenged.

Floral scent in food-deceptive orchids: species specificity and sources of variability.

One third of all orchid species are deceptive and do not reward their pollinators. Such deceptive orchids are often characterised by unusually high variation in floral signals such as colour and scent. In this study, we investigated the scent composition of two Mediterranean food-deceptive orchids Orchis mascula, Orchis pauciflora, and their hybrid, O. x colemanii. Scent was collected IN SITU by headspace sorption and was subsequently analysed with gas chromatography and gas chromatography-mass spectrometry. We compared variation of odour compounds within and between populations as well as species. We identified 35 floral scent compounds, mainly monoterpenes, which were shared by both species. Both quantitative and qualitative variability within and among populations was high. Many individuals within species could be classified to different "odour-types". In spite of high qualitative and quantitative intra- and inter-population variability, the species were clearly differentiated in their scent bouquets, whereas most hybrid individuals emitted an intermediate scent.

[Coronary fistula in adults. Review with reference to personal experience]. / Koronarfisteln beim Erwachsenen. Ubersichtsarbeit unter Einbezug eigener Erfahrungen.

A consecutive series of 5384 coronary arteriograms was retrospectively investigated for the presence of coronary artery fistulas. 15 fistulas were found in 14 patients, corresponding to a prevalence of 0.26%. All the fistulas were small and hemodynamically insignificant. There were no fistula-associated complications. Most of the fistulas were discovered as incidental findings during an otherwise indicated coronary angiography (8 patients). In the 6 patients without other cardiac pathology, the investigation was performed because of a systolo-diastolic murmur in 2 cases, myocardial ischemia caused by a "coronary-steal phenomenon" in 2 cases, and chest pain in 2 cases. With the exception of a fistula between two coronary arteries and a postoperative fistula, all of them originated from the proximal part of the coronary arteries (9 from the right, 6 from the left). Most of the fistulas drained into the main pulmonary artery (73%).

Coronary stenting without anticoagulation.

Stents are useful bail-out devices in coronary angioplasty. They are also used electively for situations associated with poor angioplasty results (e.g., restenotic lesions, venous grafts) and may reduce restenosis rates. However, the significant incidence of stent thrombosis necessitated aggressive anticoagulation with associated hemorrhagic complications. This remains a major limitation of stenting. We present our experience of stenting with half (disarticulated) Palmaz-Schatz coronary stents in eight consecutive patients, managed with aspirin alone. No patient experienced acute or subacute stent thrombosis.

Use of half (disarticulated) Palmaz-Schatz stents for thrombus-containing coronary lesions.

Coronary stenoses associated with thrombus can lead to poor angioplasty results and increased procedural complications. Stenting in the presence of thrombus is associated with an increased risk of stent thrombosis. We report eight patients in whom half a Palmaz-Schatz stent was implanted for inadequate angioplasty results owing to thrombus. Stenting resulted in improved angioplasty results; no stent thrombosis occurred.

[Myocardial infarct in patients with normal coronary arteries]. / Der Myokardinfarkt beim Patienten mit normalen Koronararterien.

Between November 1992 and April 1993, 864 coronary angiographies were performed at our institution. In 14 patients (1.6%), no significant coronary disease (> 50% stenosis) was found despite documented myocardial infarction. Of these, 2 patients (0.2%), aged 46 and 33 years, had perfectly smooth coronary arteries at angiography. The most commonly postulated mechanism of myocardial infarction in such patients is coronary spasm with superimposed thrombosis. The same risk factors as those operative in atherosclerotic coronary artery disease are thought to play a role in this setting. The prognosis is good. In one of the patients with < 50% stenosis of coronary vessels, a history of cocaine abuse could be elicited as the possible causal factor of acute myocardial infarction. Cocaine-induced coronary spasm can lead to arrhythmias, myocardial infarction or accelerated coronary atherosclerosis even in patients with normal coronary arteries. Myocarditis must be considered in the differential diagnosis of acute myocardial infarction in young patients with chest pain, typical electrocardiographic and enzymatic changes but without risk factors.

Left main coronary angioplasty in a 10-year-old boy with homozygous familial hypercholesterolemia.

Homozygous familial hypercholesterolemia is a rare cause of premature coronary artery disease. A young boy with this disorder who underwent successful coronary angioplasty for left main stem stenosis is presented.

[Heart sounds--a mathematical transformation of blood pressure? On the origin of heart sounds]. / Der Herzschall--eine mathematische Transformation des Blutdrucks? Uber den Ursprung der Herztöne.

Two main theories exist concerning the origin of the heart sounds. The first proposes that rapid pressure fluctuations cause the cardiac valve leaflets to vibrate and produce the sound. The second theory suggests that sudden pressure perturbations cause the entire cardiohemic mass to vibrate as a whole. In 35 patients (26 men and 9 women, aged 18 to 73) with various heart diseases microtransducer catheters (Millar) were used to simultaneously record aortic pressures and aortic internal phonocardiograms in order to determine if they had a common mode of origin and propagation. The propagation velocities of the first heart sound and the foot of the aortic pressure pulse were found to be similar, 5.24 +/- 0.61 m/s and 5.97 +/- 1.87 m/s respectively (+/- SE). It was possible to derive facsimiles of the aortic internal phonocardiogram by double differentiation of the corresponding aortic pressure pulse and conversely to derive the pressure pulse by double integration of the phonocardiogram. These data support the concept that the low-frequency pressure variations produced by the entire cardiohemic mass, which predominate in the aortic pressure pulse waveforms, are generated and propagated in the same manner as the high-frequency pressure variations, which are the first and second heart sounds.

[Peripheral arterial complications of various catheter angiography methods]. / Periphere Arterienkomplikationen katheterangiographischer Methoden.

Between 1980 and 1988 12,251 arterial punctures for cardiac catheterization (CC), percutaneous transluminal angioplasty (PTA), or pure diagnostic intraarterial angiography (IAA) have been performed in our clinics. 54 (0.44%), 39 (0.63%, CC), 12 (0.67%, PTA), 3 (0.07%, IAA) patients suffered from a complication at the site of the arterial puncture necessitating surgical correction. Adults developed false aneurysms or large hematomas whereas children tended to show thrombotic arterial occlusions. Generally the surgical procedures of these complications proved to be quite simple (over two thirds) but some, especially in children, turned out to be more difficult. 3 arterial spasms in children and 1 prolonged wound healing in the groin, all without long-term sequelae and 1 severe graft infection necessitating ligation of the common femoral artery with severe ischemic signs for several months were the only complications of our corrective surgical procedures. We therefore plead for these iatrogenic complications of arterial puncture for an early correction performed by a surgeon with at least some experience in vascular surgery.

[Education of heart surgery patients--did it reach the goal?]. / Information des herzoperierten Patienten--Ziel erreicht?

To find out how well informed they were about their disease and operation, 104 patients who had undergone aortocoronary bypass surgery (group A) or heart valve replacement (group B) were asked to complete a questionnaire on discharge from the operating hospital and, after patient briefing during in-hospital rehabilitation, again 3 months after the operation. The level of anxiety and presence of depression were also assessed. We found the following percentages of wrongly or inadequately answered questions (the figures in brackets are from the second questionnaire 3 months after the operation): all questions 40 (27), anticoagulation 26 (15), prophylaxis of endocarditis 54 (29), risk factors 21 (21), nutrition 56 (38), exercise 47 (32), anatomy/physiology 35 (21), postoperative course 40 (24). The learning effect was significant (p less than 0.005) for all but the risk factor questions. There were no significant differences between men and women or between group A and group B. With a proportion of 14% (13%) anxiety was a common problem which had subsided by the end of rehabilitation. With percentiles of 3% (5%), depression was rare.

Comparison of computed tomographic lung density with haemodynamic data of the pulmonary circulation.

Computed tomographic (CT) lung density measurements were prospectively correlated with pulmonary haemodynamic data in 33 patients with chronic heart disease. Cardiac catheterisation and five specific computed tomographic scans (three at nearly total lung capacity, one at functional residual capacity, and one at residual volume) were performed. There was a significant correlation between anterior lung density and mean pulmonary artery pressure (r = 0.86), pulmonary vascular resistance (r = 0.80), and pulmonary artery wedge pressure (r = 0.65). Lung density, as measured by CT, thus provides a valuable estimate of pulmonary arterial pressure and pulmonary vascular resistance, but is affected by other pathological conditions, such as emphysema and congestional or post-inflammatory fibrosis.

[A new model for the quantitative analysis of left ventricular regional function]. / Ein neues Modell für die quantitative Analyse der regionalen Funktion des linken Ventrikels.

A computer-assisted model for quantitative analysis of left ventricular segmental wall motion is presented. In contrast to standard rectangular and radial chord methods, no coordinate and reference system is used. Normal wall motion of 5 ventricular segments in the RAO projection was evaluated in 20 patients with normal ventriculograms. Segmental wall motion abnormalities after myocardial infarction were then analyzed by the computer-assisted method in 60 patients and the results compared with the visual assessment of an experienced cardiologist as standard reference. 96% of all segments with normal motion, 95% of all hypokinetic segments and 100% of all dyskinetic segments were correctly identified by computer analysis. Akinesia, however, was detected only in 25% of all cases and misinterpreted chiefly as hypokinesia. Further refinement of the software should improve detection of akinesia and classification of hypokinesia.

[Treatment of stable angina pectoris: when to operate?]. / Behandlung der stabilen Angina pectoris: wann chirurgisch?

The decision whether to treat the patient with stable angina medically or surgically is influenced by factors which determine the natural course of coronary artery disease: severity of coronary narrowing, presence or absence of collaterals, area of myocardium at risk, left ventricular function, presence of ventricular arrhythmias, risk factors. In the present study diagnostic criteria are discussed which may enable the physician to identify the coronary patient who is especially at risk for myocardial infarction or sudden death. Our knowledge of the natural course of ischemic heart disease and the medical and surgical possibilities has identified two groups of patients who profit from coronary bypass surgery: (1) patients with angina pectoris refractory to medical therapy, and (2) patients with left main disease or triple vessel disease, particularly if left ventricular function is also mildly to moderately affected. Patients with one- or two-vessel disease should undergo surgery only if proximal coronary narrowing jeopardizes a large myocardial area. The possibilities and limitations of percutaneous transluminal coronary angioplasty as an alternative to coronary bypass surgery are briefly discussed.