Incomplete Relaxation Research Articles

Epitaxy of nonpolar AlN on 4H-SiC (1-100) substrates

AlN has been grown on 4H-SiC (1-100) substrates by rf-plasma molecular beam epitaxy. The epilayers assume a metastable 4H structure to match the in-plane stacking arrangement of the substrate. Initial two-dimensional nucleation of 4H-AlN is revealed by reflection high-energy electron diffraction. The epitaxial quality is evidenced by narrow x-ray diffraction ω-scan linewidths less than 70 arcsec for both symmetric and asymmetric reflections. The AlN growth surface exhibits a smooth and anisotropic morphology similar to that of GaN (1-100). Large residual stress is present in the epilayers, consistent with incomplete relaxation of misfit strain during growth.

Achalasia-like syndrome in systemic sclerosis

Two methods of quantifying oesophageal emptying for liquids have been used to assess the dysphagia of patients with systemic sclerosis: the oesophageal infusion scintiscan and the timed Gastrografin swallow. Upper gastrointestinal endoscopy and oesophageal manometry were also performed. Thirteen patients with oesophageal symptoms were studied. Eight had dysphagia, and all of these had endoscopies with no evidence of oesophagitis or stricture. Four of these eight subjects had gross delay of oesophageal emptying for fluids, and manometry showed absence of oesophageal peristalsis and incomplete relaxation of the lower oesophageal sphincter. This abnormality is similar to achalasia. Two of these four patients have benefited from pneumatic dilatation with improvement in their severe dysphagia. We believe that pneumatic dilatation should be considered in patients with systemic sclerosis and severe dysphagia where reflux oesophagitis is not apparent.

Caffeine administration results in greater tension development in previously fatigued canine muscle in situ

In isolated single skeletal myocytes undergoing long-term fatiguing contractions, caffeine (CAF) can result in nearly immediate restoration of generated tension to near-prefatigue levels by increasing Ca2+ release via activation of sarcoplasmic reticulum release channels. This study tested whether arterial CAF infusion (>5 mm) would cause a similar rapid restoration of tetanic isometric tension during contractions to fatigue in perfused canine hindlimb muscle in situ. Tetanic contractions were elicited by electrical stimulation (200 ms trains, 50 Hz, 1 contraction s(-1)), and biopsies were taken from the muscle at rest and during contractions: (1) following the onset of fatigue (tension approximately 60% of initial value); and (2) following CAF administration. Resting muscle ATP, PCr and lactate contents were 25.2 +/- 0.4, 76.9 +/- 3.3 and 14.4 +/- 3.3 mmol (kg dry weight)(-1), respectively. At fatigue, generated tetanic tension was 61.1 +/- 6.9% of initial contractions. There was a small but statistically significant recovery of tetanic tension (64.9 +/- 6.6% of initial value) with CAF infusion, after which the muscle showed incomplete relaxation. At fatigue, muscle ATP and PCr contents had fallen significantly (P < 0.05) to 18.1 +/- 1.1 and 18.9 +/- 2.1 mmol (kg dry weight)(-1), respectively, and lactate content had increased significantly to 27.7 +/- 5.4 mmol (kg dry weight)(-1). Following CAF, skeletal muscle ATP and PCr contents were significantly lower than corresponding fatigue values (15.0 +/- 1.3 and 10.9 +/- 2.2 mmol (kg dry weight)(-1), respectively), while lactate was unchanged (22.2 +/- 3.9 mmol (kg dry weight)(-1)). These results demonstrate that caffeine can result in a small, but statistically significant, recovery of isometric tension in fatigued canine hindlimb muscle in situ, although not nearly to the same degree as seen in isolated single muscle fibres. This suggests that, in this in situ isolated whole muscle model, alteration of Ca2+ metabolism is probably only one cause of fatigue.

A comparison of signal instability in 2D and 3D EPI resting-state fMRI

Spatiotemporally structured noise, such as physiological noise, is a potential source of artifacts in functional magnetic resonance imaging (fMRI) and is the main limiting factor for the detection of small blood oxygen level-dependent (BOLD) signal variations. fMRI was employed to detect low-frequency BOLD signal fluctuations, which are thought to be related to spontaneous neuronal activity in the resting human brain. The sensitivity to noise, that is, signal variations of non-BOLD origin, was investigated for two- (2D) and three-dimensional (3D) imaging techniques. Incomplete relaxation between subsequent scans increases the level of temporally and spatially correlated signal variations originating from physiological and/or systemic noise. Although inflow effects are suspected to be reduced in 3D echo-planar imaging (EPI) compared with multi-slice 2D EPI, the noise level was higher in the 3D technique. The noise level in 3D fMRI experiments was significantly increased by instabilities of the transverse steady-state magnetization as the repetition time was of the order of T(2). By implementing radiofrequency spoiling, temporal signal fluctuations and erroneous inter-regional correlation in connectivity maps were diminished to a level present in data sets acquired with 2D EPI.

New developments in flavivirus vaccines with special attention to yellow fever

Here we review recent epidemiological trends in flavivirus diseases, findings related to existing vaccines, and new directions in flavivirus vaccine research. We emphasize the need for stepped-up efforts to stop further spread and intensification of these infections worldwide. Although the incidence and geographic distribution of flavivirus diseases have increased in recent years, human vaccines are available only for yellow fever, Japanese encephalitis, tick-borne encephalitis and Kyasanur forest disease. Factors contributing to resurgence include insufficient supplies of available vaccines, incomplete vaccination coverage and relaxation in vector control. Research has been underway for 60 years to develop effective vaccines against dengue, and recent progress is encouraging. The development of vaccines against West Nile, virus recently introduced to North America, has been initiated. In addition, there is considerable interest in improving existing vaccines with respect to increasing safety (e.g. eliminating the newly recognized syndrome of yellow fever vaccine-associated viscerotropic adverse disease), and to reducing the cost and number of doses required for effective immunization. Traditional approaches to flavivirus vaccines are still employed, while recent advancements in biotechnology produced new approaches to vaccine design, such as recombinant live virus, subunit and DNA vaccines. Live chimeric vaccines against dengue, Japanese encephalitis and West Nile based on yellow fever 17D virus (ChimeriVax) are in phase I/II trials, with encouraging results. Other chimeric dengue, tick-borne encephalitis and West Nile virus candidates were developed based on attenuated dengue backbones. To further reduce the impact of flavivirus diseases, vaccination policies and vector control programs in affected countries require revision.

KTP Laser assisted microendoscopic cricopharyngeal myotomy and web excision for dysphagia management

Cricopharyngeal dysfunction is defined as the delayed or incomplete relaxation of the cricopharyngeal muscle during swallowing. This may cause dysphagia and aspiration, affecting the quality of life. For this condition, injection of botulinum toxin into the cricopharyngeus, dilatation of cricopharynx with bougies and external cricopharyngeal myotomy have been the treatment of choice with varying results. We present in this paper the treatment of this clinical condition by KTP 532 laser a recent advance in the field of Otolaryngology and Head and Neck Surgery. Very few series have been reported in literature so far regarding the use of laser for cricopharyngeal myotomy. This is perhaps the first series of eight cases of KTP laser assisted microendoscopic cricopharyngeal myotomy and web excision reporting the benefit of this treatment by an Indian author in an Indian Journal. KTP laser assisted cricopharyngeal myotomy avoids an external scar; aids precise incision at the cricopharynx by direct visualization, brings optimum results in deglutition and reduces postoperative morbidity and complications. The short hospital stay reduces the overall cost. The use of KTP 532 laser in the treatment of selected cases with cricopharyngeal dysfunction is therefore safe and effective.

Functional Consequences of Sarcomeric Protein Abnormalities in Failing Myocardium

Sarcomeric protein abnormalities have been recognized for many years in heart failure due to dilated cardiomyopathy (DCM). In contrast, virtually nothing is known about myofilament abnormalities in heart failure occurring in association with diastolic dysfunction. With the exception of sarcomeric protein mutations that cause DCM, the most important mechanism of myofilament dysfunction in DCM is probably altered post-translational modification, in particular the phosphorylation state of troponins I and T and possibly myosin light chain. Other modifications, including oxidation and glycation, may also play a role. Myosin heavy chain isoform switching occurs in human heart failure, but its functional significance is uncertain. Myofilament abnormalities contribute significantly to myocardial dysfunction in DCM, although their relative importance compared with abnormal calcium handling is debated. One consistent functional abnormality in DCM is increased myofilament calcium sensitivity of tension generation, which contributes to slowed or incomplete relaxation. More recently, decreases in the optimal frequency of myofilament work and power generation have been recognized. These changes may contribute to depression of the force-frequency relation in DCM. Altered mechanoenergetics constitute one of the most important manifestations of myofilament dysfunction in heart failure. DCM and hemodynamic overload are associated with more economical and efficient energy utilization by the contractile machinery, which may be protective of the myocardium. This change is strongly associated with depressed myofibrillar ATPase activity. We speculate that the effectiveness of mechanical therapies such as resynchronization may at least in part be related to improved mechanical function without loss of this mechanoenergetic advantage.

Impaired Bolus Transit Across the Esophagogastric Junction in Postfundoplication Dysphagia

This study assessed the effect of fundoplication on liquid and solid bolus transit across the esophagogastric junction (EGJ) in relation to EGJ dynamics and dysphagia. Twelve patients with gastro-esophageal reflux disease (GERD) were studied before and after fundoplication. Concurrent high-resolution EGJ manometry and fluoroscopy were performed whilst swallowing liquid barium and a solid bolus. The EGJ transit time, EGJ opening duration, transit efficacy, and EGJ relaxation were measured. During the test symptoms of dysphagia were scored using a visual analog scale. The minimal opening aperture at fluoroscopy was located at the manometric EGJ in all subjects. Fundoplication markedly reduced the EGJ opening diameter from 1.0 +/- 0.1 to 0.6 +/- 0.1 cm (p < 0.01) and rendered deglutative EGJ relaxation incomplete. After fundoplication, a higher intrabolus pressure was found (p < 0.05) associated with a reduced axial bolus length (p < 0.001). EGJ transit time increased from 6.9 +/- 0.9 to 9.8 +/- 1.0 s for liquids (p < 0.01) and from 2.8 +/- 0.5 to 5.8 +/- 0.8 s (p < 0.01) for solids after fundoplication. No relation between EGJ transit and dysphagia scores was observed before fundoplication. In contrast, EGJ transit time significantly correlated with dysphagia scores both during liquid (r = 0.84; p < 0.01) and solid (r = 0.69; p < 0.05) bolus transit following fundoplication. Fundoplication patients exhibit a restricted hiatal opening and an incomplete deglutative EGJ relaxation. To facilitate EGJ transit despite these altered EGJ dynamics a higher intrabolus pressure is created by augmented bolus compression. Fundoplication increases EGJ transit time, the degree of which is associated with postoperative dysphagia.

Coarse-grained distributions and superstatistics

We show an interesting connection between non-standard (non-Boltzmannian) distribution functions arising in the theory of violent relaxation for collisionless stellar systems [D. Lynden-Bell, Mon. Not. R. Astron. Soc. 136 (1967) 101.] and the notion of superstatistics recently introduced by [Beck and Cohen Physica A 322 (2003) 267]. The common link between these two theories is the emergence of coarse-grained distributions arising out of fine-grained distributions. The coarse-grained distribution functions are written as a superposition of Boltzmann factors weighted by a non-universal function. Even more general distributions can arise in case of incomplete violent relaxation (non-ergodicity). They are stable stationary solutions of the Vlasov equation. We also discuss analogies and differences between the statistical equilibrium state of a multi-components self-gravitating system and the metaequilibrium (or quasi-equilibrium) states of a collisionless stellar system. Finally, we stress the important distinction between entropies, generalized entropies, relative entropies and H -functions. We discuss applications of these ideas in two-dimensional turbulence and for other systems with long-range interactions.

On the interpretations of Tsallis functional in connection with Vlasov–Poisson and related systems: Dynamics vs thermodynamics

We discuss different interpretations of Tsallis functional in astrophysics. In principle, for t → + ∞ , a self-gravitating system should reach a statistical equilibrium state described by the Boltzmann distribution. However, this tendency is hampered by the escape of stars and the gravothermal catastrophe. Furthermore, the relaxation time increases almost linearly with the number of particles N so that most stellar systems are in a collisionless regime described by the Vlasov equation. This equation admits an infinite number of stationary solutions. The system can be trapped in one of them as a result of phase mixing and incomplete violent relaxation and remains frozen in this quasi-stationary state for a very long time until collisional effects finally come into play. Tsallis distribution functions form a particular class of stationary solutions of the Vlasov equation named stellar polytropes. We interpret Tsallis functional as a particular H-function in the sense of Tremaine, Hénon and Lynden-Bell [Mon. Not. R. astr. Soc. 219 (1986) 285]. Furthermore, we show that the criterion of nonlinear dynamical stability for spherical stellar systems described by the Vlasov–Poisson system resembles a criterion of thermodynamical stability in the microcanonical ensemble and that the criterion of nonlinear dynamical stability for barotropic stars described by the Euler–Poisson system resembles a criterion of thermodynamical stability in the canonical ensemble. Accordingly, a thermodynamical analogy can be developed to investigate the nonlinear dynamical stability of barotropic stars and spherical galaxies but the notions of entropy, free energy and temperature are essentially effective. This analogy provides an interpretation of the nonlinear Antonov first law in terms of ensemble inequivalence. Similar ideas apply to other systems with long-range interactions such as two-dimensional vortices and the HMF model. We propose a general scenario to understand the emergence of coherent structures in long-range systems and discuss the dynamical/thermodynamical “duality” of their description. We stress that the thermodynamical analogy that we develop is only valid for systems whose distribution function depends only on energy. We discuss two other, independent, interpretations of Tsallis functional in astrophysics, in relation with generalized kinetic equations and quasi-equilibrium states of collisional stellar systems.

Arterial stiffness-a predictor of myocardial stiffness in early hypertension

Arterial stiffness an independent predictor of cardiovascular and all cause mortality in hypertensive patients. Left ventricular diastolic dysfunction(LVDD) i.e.,incomplete relaxation of the ventricle during early diastolic filling, is quite pravelent in hypertension. We hypothesized that hypertensive subjects with stiffer arteries will also have higher left ventricular stiffness. We studied 60 subjects with untreated essential hypertension mean age 48±2, 30 female. Brachial BP and heart rate(HR) measured with an automated BP monitor (Omron). Aortic pressure waveform derived by applanation tonometry (SphygmoCor) aortic systolic and diastolic BP and mean BP, augmentation index (AIx%), a measure of aortic wave reflection, and pulse pressure (PP) amplification(brachial PP-aortic PP) derived. Aortic stiffness measured by carotid-femoral pulse wave velocity (PWV) with Complior. Diastolic function was assesed by conventional Doppler and Tissue Doppler imaging (TDI).Peak early (E) and late(A) of transmitral and mitral annular velocities and E/A ratio measured. Statistical analysis was performed with JMP version 5,results are expressed as Mean±SEM, p<0.05 considered significant. 30 patients had LVDD with higher PWV (10.8±0.3 vs 9.6±0.2,p<0.01) and AIx(30±2 vs 22±2,p<0.01) than those with normal diastolic function. E/A inversely correlated with AIx (r=-0.30,p±0.01), HR corrected AIx (R=-0.45, p<50.0001), age (r=-0.46, p±0.001), MBP (r=-0.33, p<0.05), aortic systolic BP(r=-0.28, p<0.05) and PWV(r=-0.33,p<0.01) and positively with PP amplification(r=0.26, p<0.001). The relationship between AIx and E/A was significant when corrected for age and MBP, the model explaining 42% of the variance in E/A. In the subset of patients with diastolic dysfunction (n=30), there was a higher correlation between E/A and AIx(r=-0.56,p<0.001), HR corrected AIx(r=-0.66,p<0.0001) and PP amplification (r=0.47, p<0.001), significant when corrected for age and MBP,the model explained 52% of the variance in E/A. Functional myocardial and vascular abnormalities are very common in early hypertension and stiffness changes in the left ventricle parallel those in the arteries. Therefore a stiff vasculature may predict the development of LVDD and if identified early, these changes may be prevented.

Transient failure of opening of the lower oesophageal sphincter on upright oesophagrams: radiographic and clinical findings

The purpose of our study was to determine the frequency, radiographic features, and clinical importance of transient failure of opening of the lower oesophageal sphincter (LOS) on upright double-contrast views of the oesophagus. A computerized search of radiology records identified 16 patients who had transient failure of opening of the LOS on upright views from biphasic oesophagrams or upper gastrointestinal tract examinations using high-density barium but normal opening of the LOS on prone views using low-density barium. The radiographic findings were reviewed and correlated with the clinical and manometric findings. In all cases, barium studies revealed tapered, beaklike narrowing of the distal oesophagus on upright double-contrast views, with a normal-appearing distal oesophagus, normal opening of the LOS, and intact peristalsis on prone single-contrast views. Only seven patients (44%) had dysphagia. Five of these patients had clinical follow-up, and the dysphagia improved or resolved without specific treatment for LOS dysfunction in four. The remaining patient had persistent dysphagia, but this individual had polymyositis as the likely cause for his dysphagia. Manometry revealed incomplete relaxation of the LOS in two patients and normal relaxation in one. Our experience suggests that failure of opening of the LOS may be observed as a transient finding of little clinical importance on upright double-contrast views of the oesophagus using high-density barium, with normal opening of the LOS on prone single-contrast views using low-density barium. It is important to be aware of this finding, so that it is not mistaken for achalasia or other abnormalities of the distal oesophagus.

Achalasia with Complete Relaxation of Lower Esophageal Sphincter: Radiographic-Manometric Correlation

To evaluate retrospectively the presence of complete relaxation of the lower esophageal sphincter (LES) at manometry in patients with achalasia depicted on barium esophagograms. The institutional review board approved this retrospective study and did not require informed consent. A search of radiology and manometry records identified 21 patients (12 men, nine women; mean age, 52.4 years) with achalasia depicted on barium esophagograms who had undergone manometric examinations and met the inclusion criteria. Radiologic reports and images were reviewed for presence or absence of primary peristalsis, impaired LES opening, esophageal dilatation, delayed emptying of barium, and nonperistaltic contractions. Manometry reports were reviewed for presence or absence of peristalsis or simultaneous esophageal contractions. Resting and residual LES pressures were recorded to determine whether LES relaxation was complete or incomplete. Medical records were reviewed to determine clinical presentation and follow-up (treatment and patient course), and radiographic files were reviewed to determine radiographic findings at follow-up examinations. Clinical characteristics (eg, age, dysphagia, and weight loss) were correlated with LES relaxation at manometry. Data were analyzed statistically with Fisher exact and Wilcoxon rank sum testing. All 21 patients with radiographic findings of achalasia had aperistalsis at manometry. Fourteen patients (67%) had incomplete LES relaxation at manometry during swallowing, and seven (33%) had complete LES relaxation. There were no significant differences between patients with complete LES relaxation and those with incomplete LES relaxation in mean age (P = .59), duration of dysphagia (P = .18), or weight loss (P > .99). Clinical follow-up findings were available for six patients with complete LES relaxation at manometry and 10 with incomplete relaxation. Symptoms resolved after treatment in all six patients with complete LES relaxation. Six (60%) of 10 patients with incomplete LES relaxation had resolution of symptoms after treatment, and four (40%) had substantial improvement. These data suggest that in patients with typical radiographic findings of achalasia, the barium study can be used to guide treatment without a need for manometry. If radiographic findings are equivocal, however, manometry may be required for a more certain diagnosis.

Lower Esophageal Sphincter (LES) Hypertension Influences Intraesophageal (ILP) and Upper Esophageal Sphincter (UES) Pressures in Achalasic Patients

Introduction: The diagnosis of achalasia is realized by manometry when absent and/or incomplete LES relaxation and aperistalsis in the distal two-thirds of the esophageal body was observed. Secondary findings are represented by elevated ILP and UES hypertension. Aim of this study was to evaluate the correlation between these two findings and elevated LES resting pressure. Methods: One-hundred-thirty-one patients referred to our Institution from January 1994 to November 2004 with symptoms suggestive for esophageal achalasia were retrospectively evaluated. All the patients previously undergone Upper GI endoscopy, and Rx Barium swallow, and manometry confirmed the diagnosis. The patients were subdivided into two groups: Group A: LES resting pressure whithin our normal range (9-32 mmHg); Group B: LES resting pressure >32 mmHg. Stata 6 for Windows (Stata Corporation, Texas, US) was used for all statistical analyses. Univariate analyses for discontinuous variables were done with use of Student's t test; categorical variables were compared by use of χ2-tests and P < 0.05 was considered to be statistically significant. Results: All patients (mean age 45.7 years; range 11-83; 64 males, 67 females) complained dysphagia. One-hundred-eleven (84.7%) reported undigested food regurgitation, 104 (79.4%) retrosternal pain, 49 (37%) weight loss, and 37 (28.2%) cough. Endoscopy showed fluid retention in 69 patients (52.7%), and esophagitis was observed in 39 (29.8%). Rx Barium swallow revealed esophageal dilation in 112 patients (85.5%). Hypertensive LES was identified in 105 patients (80.1%), incomplete and/or absent LES relaxation was found in all cases, ILP was elevated in 53 patients (40.45%), and hypertensive UES was described in 31 (23.6%). In 14 patients (10.7%) esophageal manometry showed “vigorous” variant of achalasia. In Group A, LES resting pressure was 28.6±2.6 mmHg (Mean±SD), ILP was 0.48±3.3 mmHg (Mean±SD), and UES resting pressure was 67.5±37.7 (Mean±SD). In Group B, LES resting pressure was 45.7±12.8 mmHg (Mean±SD), ILP was 7.7±7.6 mmHg (Mean±SD), and UES resting pressure was 86.7±46.2 (Mean±SD). Univariate analysis showed that in Group B ILP and hypertensive UES were significantly higher (p<0.0005, and p=0.03, respectively) when compared with group A. Conclusions: Elevated ILP and hypertension of UES are important features of manometric assessment in achalasia, and they are more frequent in patients with elevated LES resting pressure.

A family of models of partially relaxed stellar systems

N-body simulations of collisionless collapse have offered important clues for the construction of realistic stellar dynamical models of elliptical galaxies. Understanding this idealized and relatively simple process, by which stellar systems can reach partially relaxed equilibrium configurations (characterized by isotropic central regions and radially anisotropic envelopes), is a prerequisite to more ambitious attempts at constructing physically justified models of elliptical galaxies in which the problem of galaxy formation is set in the generally accepted cosmological context of hierarchical clustering. In a previous paper we have discussed the dynamical properties of a family of models of partially relaxed stellar systems (the models), designed to incorporate the qualitative properties of the products of collisionless collapse at small and at large radii. Here we revisit the problem of incomplete violent relaxation, by making a direct comparison between the detailed properties of such family of models and those of the products of collisionless collapse found in N-body simulations that we have run for the purpose. Surprisingly, the models thus identified are able to match the simulated density distributions over nine orders of magnitude and also to provide an excellent fit to the anisotropy profiles and a good representation of the overall structure in phase space. The end-products of the simulations and the best-fitting models turn out to be characterized by a level of pressure anisotropy close to the threshold for the onset of the radial-orbit instability. The conservation of Q, a third quantity that is argued to be approximately conserved in addition to total energy and total number of particles as a basis for the construction of the family, is discussed and tested numerically.

AGA technical review on the clinical use of esophageal manometry

AGA technical review on the clinical use of esophageal manometry

Statistical mechanics of geophysical turbulence: application to jovian flows and Jupiter’s great red spot

We propose a parameterization of 2D geophysical turbulence in the form of a relaxation equation similar to a generalized Fokker–Planck equation [P.H. Chavanis, Phys. Rev. E 68 (2003) 036108]. This equation conserves circulation and energy and increases a generalized entropy functional determined by a prior vorticity distribution fixed by small-scale forcing [R. Ellis, K. Haven, B. Turkington, Nonlinearity 15 (2002) 239]. We discuss applications of this formalism to jovian atmosphere and Jupiter’s great red spot. We show that, in the limit of small Rossby radius where the interaction becomes short-range, our relaxation equation becomes similar to the Cahn–Hilliard equation describing phase ordering kinetics. This strengthens the analogy between the jet structure of the great red spot and a “domain wall”. Our relaxation equation can also serve as a numerical algorithm to construct arbitrary nonlinearly dynamically stable stationary solutions of the 2D Euler equation. These solutions can represent jets and vortices that emerge in 2D turbulent flows as a result of violent relaxation. Due to incomplete relaxation, the statistical prediction may fail and the system can settle on a stationary solution of the 2D Euler equation which is not the most mixed state. In that case, it can be useful to construct more general nonlinearly dynamically stable stationary solutions of the 2D Euler equation in an attempt to reproduce observed phenomena.

A family of models of partially relaxed stellar systems

Recently we have found that a family of models of partially relaxed, anisotropic stellar systems, inspired earlier by studies of incomplete violent relaxation, exhibits some interesting thermodynamic properties. Here we present a systematic investigation of its dynamical characteristics, in order to establish the basis for a detailed comparison with simulations of collisionless collapse, planned for a separate paper. For a full comparison with the observations of elliptical galaxies, the models should be extended to allow for the presence a sizable dark halo and of significant rotation. In the spherical limit, the family is characterized by two dimensionless parameters, i.e. Ψ, measuring the depth of the galaxy potential, and ν, defining the form of a third global quantity Q, which is argued to be approximately conserved during collisionless collapse (in addition to the total energy and the total number of stars). The family of models is found to have the following properties. The intrinsic density profile beyond the half-mass radius rM is basically universal and independent of Ψ. The projected density profiles are well fitted by the R 1/n law, with n ranging from 2.5 to 8.5, dependent on Ψ, with n close to 4 for concentrated models. All models exhibit radial anisotropy in the pressure tensor, especially in their outer parts, already significant at r ≈ rM .A t fi xed values ofν, models with lower Ψ are more anisotropic; at fixed values of Ψ, models with lower ν are more concentrated and more anisotropic. When the global amount of anisotropy, measured by 2Kr/KT, is large, the models are unstable with respect to the radial-orbit instability; still, a wide region of parameter space (i.e., sufficiently high values of Ψ ,f or ν> 3/8) is covered by models that are dynamically stable; for these, the line profiles (line-of-sight velocity distribution) are Gaussian at the 5% level, with a general trend of positive values of h4 at radii larger than the effective radius Re.

Author reply to Letter to the Editor: ‘Functional heartburn’: symptom for achalasia or hypertensive lower oesophageal sphincter? – Riegler et al.

Sirs, We greatly appreciate the opportunity to further clarify the methodology of our routine daily activity adopted in our study.1 All patients referred to our open-access gastrointestinal service undergo a detailed interview and both specific and aspecific symptoms of GERD and dyspepsia are scored, dysphagia included. We omitted to report about the latter symptom but it was neither dominant nor co-dominant in any of our patients who finally received a diagnosis of functional heartburn (FH). The score for dysphagia was 0 (none) and 1 (mild; symptom could be ignored and was recalled only after specific inquiring) in 36 and 25 of the 61 FH cases, respectively. Oesophageal manometry is always performed before pH-monitoring in patients referred to our service using an 8-channel, water-perfused manometry catheter. With the stationary pull-through technique the lower oesophageal sphincter (LOS) is identified, and then, at each 0.5 cm station, the basal tone is measured at the end of expiration and the relaxation is assessed with wet swallows; the pressure inversion point is routinely identified. Oesophageal body peristalsis is assessed and pressures measured with at least 10 wet swallows. The upper oesophageal sphincter is finally identified and the catheter removed. By means of oesophageal manometry, we identified 36 new cases of achalasia (incomplete relaxation of the LOS and aperistalsis in the body of the oesophagus), and seven new cases of hypertensive LOS (some preserved peristalsis, mean resting LOS pressure >45 mmHg and/or LOS relaxation incomplete or of inadequate duration) during the study period (from February 1999 to February 2004). Heartburn score was 2 (moderate; symptom could not be ignored and was spontaneously reported, but neither daily activities nor sleep were influenced) and 1, in two and three of the 36 achalasia cases, respectively. Among the seven patients with hypertensive LOS the heartburn score was 1 in one case and 3 (severe; symptom influenced daily activities and/or sleep) in one case. However, achalasia and hypertensive LOS patients neither received a diagnosis of FH nor entered the study. The term FH has been proposed for endoscopy-negative patients with episodic retrosternal burning in the absence of pathological gastro-oesophageal reflux, pathology-based motility disorders or structural explanations.2 In our series, the diagnosis of FH was based on normal endoscopic (apart from hiatal hernia) and pH-metric findings, as well as on an adequate LOS relaxation with wet swallows at oesophageal manometry (pressure <8 mmHg above gastric pressure, the LOS contracting after it is traversed by the peristaltic wave).3 Patients who were not able to undergo an oesophageal manometric evaluation before pH-metric assessment were excluded from the study. Therefore, achalasia and hypertensive LOS were all firmly excluded in our series. We are pleased to reassure Dr Riegler and co-workers that the diagnosis of FH in our study was made with a high level of accuracy.

Role of impaired myocardial relaxation in the production of elevated left ventricular filling pressure

Although present in many patients with heart failure and a normal ejection fraction, the role of isolated impairments in active myocardial relaxation in the genesis of elevated filling pressures is not well characterized. Because of difficulties in determining the effect of prolonged myocardial relaxation in vivo, we used a cardiovascular simulated computer model. The effect of myocardial relaxation, as assessed by tau (exponential time constant of relaxation), on pulmonary vein pressure (PVP) and left ventricular end-diastolic pressure (LVEDP) was investigated over a wide range of tau values (20-100 ms) and heart rate (60-140 beats/min) while keeping end-diastolic volume constant. Cardiac output was recorded over a wide range of tau and heart rate while keeping PVP constant. The effect of systolic intervals was investigated by changing time to end systole at the same heart rate. At a heart rate of 60 beats/min, increases in tau from a baseline to extreme value of 100 ms cause only a minor increase in PVP of 3 mmHg. In contrast, at 120 beats/min, the same increase in tau increases PVP by 23 mmHg. An increase in filling pressures at high heart rates was attributable to incomplete relaxation. The PVP-LVEDP gradient was not constant and increased with increasing tau and heart rate. Prolonged systolic intervals augmented the effects of tau on PVP. Impaired myocardial relaxation is an important determinant of PVP and cardiac output only during rapid heart rate and especially when combined with prolonged systolic intervals. These findings clarify the role of myocardial relaxation in the pathogenesis of elevated filling pressures characteristic of heart failure.