Block-spiral magnetism: An exotic type of frustrated order.

Competing interactions in quantum materials induce exotic states of matter such as frustrated magnets, an extensive field of research from both the theoretical and experimental perspectives. Here, we show that competing energy scales present in the low-dimensional orbital-selective Mott phase (OSMP) induce an exotic magnetic order, never reported before. Earlier neutron-scattering experiments on iron-based 123 ladder materials, where OSMP is relevant, already confirmed our previous theoretical prediction of block magnetism (magnetic order of the form [Formula: see text]). Now we argue that another phase can be stabilized in multiorbital Hubbard models, the block-spiral state. In this state, the magnetic islands form a spiral propagating through the chain but with the blocks maintaining their identity, namely rigidly rotating. The block-spiral state is stabilized without any apparent frustration, the common avenue to generate spiral arrangements in multiferroics. By examining the behavior of the electronic degrees of freedom, parity-breaking quasiparticles are revealed. Finally, a simple phenomenological model that accurately captures the macroscopic spin spiral arrangement is also introduced, and fingerprints for the neutron-scattering experimental detection are provided.

Novel Magnetic Block States in Low-Dimensional Iron-Based Superconductors.

Inelastic neutron scattering recently confirmed the theoretical prediction of a ↑↑↓↓-magnetic state along the legs of quasi-one-dimensional iron-based ladders in the orbital-selective Mott phase (OSMP). We show here that electron doping of the OSMP induces a whole class of novel block states with a variety of periodicities beyond the previously reported π/2 pattern. We discuss the magnetic phase diagram of the OSMP regime that could be tested by neutrons once appropriate quasi-1D quantum materials with the appropriate dopings are identified.

Functional Improvement After Outpatient Cardiac Rehabilitation in Acute Coronary Syndrome Patients is Not Related to Improvement in Left Ventricular Ejection Fraction.

INTRODUCTION: Cardiac rehabilitation (CR) improves the functional capacity and the prognosis of patients with coronary artery disease. AIM: Our study was aimed at assessing the relationship between functional improvement (evaluated with 6-min Walk Test-6MWT) and the improvement in left ventricular ejection fraction (LVEF) after CR. METHODS: We collected data from 249 patients (age 66.79 ± 11.06 years; males 81.52%) with a recent history of Acute Coronary Syndrome that performed CR. The functional improvement after CR was expressed as the Δ between distance covered at the final versus the initial 6-min Walking Test (6-MWT), while LVEF was calculated with transthoracic echocardiogram at the beginning and at the end of the CR. RESULTS: Patients were divided accordingly to their pre-rehab LVEF (≥ 55% vs < 55%). With superimposable age and baseline 6MWT distance covered (434.58 vs 405.12 m, p = 0.08), the latter group presented higher Δ meter values at 6MWT (167.93 vs 193.97 m, p = 0.018). However, no statistically significant positive correlation between Δ meters and Δ LVEF was found. Moreover, linear regression analyses found that nor baseline LVEF nor Δ LVEF were significant determinants of Δ meters when considering the whole group, with age, basal 6MWT and peak CK-MB as additional covariates in the model. CONCLUSION: Although it could be expected that an increase in LVEF is related to the functional improvement after CR, no significant correlation was found in our population.

Electronic self-organization in the single-layer manganite Pr1-xCa1+xMnO4.

We use neutron scattering to investigate the doping evolution of the magnetic correlations in the single-layer manganite Pr1-xCa1+xMnO4, away from the x=0.5 composition where the CE-type commensurate antiferromagnetic (AF) structure is stable. We find that short-range incommensurate spin correlations develop as the system is electron doped (x<0.5), which coexist with the CE-type AF order. This suggests that electron doping in this system induces an inhomogeneous electronic self-organization, where commensurate AF patches with x=0.5 are separated by electron-rich domain walls with short-range magnetic correlations. This behavior is strikingly different than for the perovskite Pr1-xCaxMnO3, where the long-range CE-type commensurate AF structure is stable over a wide range of electron or hole doping around x=0.5.

Safety of recreational scuba diving in type 1 diabetic patients: the Deep Monitoring programme.

AIM: To verify whether, with thorough practical and theoretical training, well-controlled, non-complicated diabetic patients can safely go diving underwater with no additional medical or metabolic risks. METHODS: Twelve diabetic patients participated in the study after undergoing training focused on their diabetic status. Two dives per day were scheduled during two five-day stays on the island of Ventotene (Italy). Capillary blood glucose (BG) was checked at 60, 30 and 10 minutes before diving, and corrective measures adopted if necessary, based on BG absolute levels and dynamics. A device for continuous subcutaneous glucose monitoring (CGM), expressly modified for the purpose, was worn during dives. RESULTS: Data were gathered from 90 dives; mean BG at 60, 30 and 10 minutes before diving was 205.8+/-69.6 mg/dL, 200.0+/-66.4 mg/dL and 200.5+/-61.0mg/dL, respectively. In 56 of the 90 dives, supplementary carbohydrates or insulin were necessary, but only one dive was interrupted on account of hypoglycaemic symptoms. Mean post-dive BG was 158.9+/-80.8 mg/dL. CGM recordings showed that glucose levels gradually decreased during the dives (nadir: -19.9%). CONCLUSION: Experienced, well-controlled, complication-free young diabetic patients can safely go scuba diving, provided that they apply a rigorous protocol based on serial pre-dive BG measurements. The specific variables of underwater diving do not appear to involve significant additional risks of hypoglycaemia.

A new 2D-based method for myocardial velocity strain and strain rate quantification in a normal adult and paediatric population: assessment of reference values.

BACKGROUND: Recent advances in technology have provided the opportunity for off-line analysis of digital video-clips of two-dimensional (2-D) echocardiographic images. Commercially available software that follows the motion of cardiac structures during cardiac cycle computes both regional and global velocity, strain, and strain rate (SR). The present study aims to evaluate the clinical applicability of the software based on the tracking algorithm feature (studied for cardiology purposes) and to derive the reference values for longitudinal and circumferential strain and SR of the left ventricle in a normal population of children and young adults. METHODS: 45 healthy volunteers (30 adults: 19 male, 11 female, mean age 37 +/- 6 years; 15 children: 8 male, 7 female, mean age 8 +/- 2 years) underwent transthoracic echocardiographic examination; 2D cine-loops recordings of apical 4-four 4-chamber (4C) and 2-chamber (2C) views and short axis views were stored for off-line analysis. Computer analyses were performed using specific software relying on the algorithm of optical flow analysis, specifically designed to track the endocardial border, installed on a Windows based computer workstation. Inter and intra-observer variability was assessed. RESULTS: The feasibility of measurements obtained with tissue tracking system was higher in apical view (100% for systolic events; 64% for diastolic events) than in short axis view (70% for systolic events; 52% for diastolic events). Longitudinal systolic velocity decreased from base to apex in all subjects (5.22 +/- 1.01 vs. 1.20 +/- 0.88; p < 0.0001). Longitudinal strain and SR significantly increased from base to apex in all subjects (-12.95 +/- 6.79 vs. -14.87 +/- 6.78; p = 0.002; -0.72 +/- 0.39 vs. -0.94 +/- 0.48, p = 0.0001, respectively). Similarly, circumferential strain and SR increased from base to apex (-21.32 +/- 5.15 vs. -27.02 +/- 5.88, p = 0.002; -1.51 +/- 0.37 vs. -1.95 +/- 0.57, p = 0.003, respectively). Values of global systolic SR, both longitudinal and circumferential, were significantly higher in children than in adults (-1.3 +/- 0.2, vs. -1.11 +/- 0.2, p = 0.006; -1.9 +/- 0.6 vs. -1.6 +/- 0.5, p = 0.0265, respectively). No significant differences in longitudinal and circumferential systolic velocities were identified for any segment when comparing adults with children. CONCLUSION: This 2D based tissue tracking system used for computation is reliable and applicable in adults and children particularly for systolic events. Measured with this technology, we have established reference values for myocardial velocity, Strain and SR for both young adults and children.

Charge transfer in heterostructures of strongly correlated materials.

In this work, recent theoretical investigations by the authors in the area of oxide multilayers are briefly reviewed. The calculations were carried out using model Hamiltonians and a variety of non-perturbative techniques. Moreover, new results are also included here. They correspond to the generation of a metallic state by mixing insulators in a multilayer geometry, using the Hubbard and double-exchange models. For the latter, the resulting metallic state is also ferromagnetic. This illustrates how electron or hole doping via transfer of charge in multilayers can lead to the study of phase diagrams of transition metal oxides in the clean limit. Currently, these phase diagrams are much affected by the disordering standard chemical doping procedure, which introduces quenched disorder in the material.

Spin dynamics of the block orbital-selective Mott phase.

Iron-based superconductors display a variety of magnetic phases originating in the competition between electronic, orbital, and spin degrees of freedom. Previous theoretical investigations of the multi-orbital Hubbard model in one-dimension revealed the existence of an orbital-selective Mott phase (OSMP) with block spin order. Recent inelastic neutron scattering (INS) experiments on the BaFe2Se3 ladder compound confirmed the relevance of the block-OSMP. Moreover, the powder INS spectrum revealed an unexpected structure, containing both low-energy acoustic and high-energy optical modes. Here we present the theoretical prediction for the dynamical spin structure factor within a block-OSMP regime using the density-matrix renormalization-group method. In agreement with experiments, we find two dominant features: low-energy dispersive and high-energy dispersionless modes. We argue that the former represents the spin-wave-like dynamics of the block ferromagnetic islands, while the latter is attributed to a novel type of local on-site spin excitations controlled by the Hund coupling.

Incorrect echocardiographic diagnosis in patients with mechanical prosthetic valve dysfunction: correlation with surgical findings.

PURPOSE: To identify the rate of occurrence and type of incorrect echocardiographic diagnoses in patients with mechanical valve prostheses. PATIENTS AND METHODS: We studied 170 consecutive patients (73 women and 97 men) with a total of 208 prostheses who underwent surgery for mitral (n = 136) or aortic (n = 72) valve dysfunction between January 1991 and December 1997. Preoperative echocardiographic data were compared with surgical findings. Any major discrepancy between the echocardiographic reports and surgery was judged to be unconfirmed when the preoperative echocardiographic diagnosis was not confirmed at surgery, but the prosthesis was found to be dysfunctioning; and was judged to be erroneous when the preoperative echocardiographic diagnosis was not confirmed, and surgical inspection failed to reveal any other prosthetic abnormality. RESULTS: There were 25 (12%) diagnostic errors. Of the 136 mitral prostheses, there were 9 unconfirmed diagnoses of paravalvular regurgitation (6 had a fibrous tissue overgrowth, 1 had a thrombus with fibrous tissue overgrowth, 1 had endocarditis vegetations, and 1 had a ball variance) and 5 erroneous diagnoses. Eleven diagnostic errors were made in the 72 aortic prostheses: there were 9 unconfirmed diagnoses (paravalvular regurgitation was diagnosed as transvalvular in 7, and transvalvular regurgitation as paravalvular in 2 cases), and 2 erroneous diagnoses. CONCLUSIONS: Although echocardiography has gained great credibility among clinicians, special care should be taken when assessing patients in whom prosthetic valve dysfunction is suspected.

Safety, feasibility, and diagnostic accuracy of accelerated high-dose dipyridamole stress echocardiography.

Protocols for dipyridamole stress testing have evolved in the last 16 years in the neverending quest of optimal diagnostic accuracy and user friendliness. Higher dipyridamole dose in a shorter infusion time provides higher sensitivity, but concern over safety is still controversial. An accelerated high-dose (0.84 mg/kg in 6 minutes without atropine) dipyridamole stress test was performed on 1,295 patients in 2 echocardiographic laborotories: Institute of Clinical Physiology of Pisa and Niguarda Hospital of Milan. During testing, there were no deaths and no patients had ventricular fibrillation. Major adverse reactions occurred in 3 cases (1 every 431 studies): 1 myocardial infarction, 1 brief cardiac asystole, and 1 transient ischemic attack. Overall feasibility was 97%. In 66 patients with normal function at rest who were evaluated off therapy, with coronary angiography performed independently of test results, the accelerated high-dose protocol showed a sensitivity of 85% (confidence interval [CI] 73% to 92%) and a specificity of 93% (CI 83% to 97%) for angiographically assessed coronary artery disease (quantitatively assessed diameter reduction > or = 50%). Diagnostic accuracy of the accelerated high dose was 89% (CI 79% to 95%). Thus, accelerated high-dose dipyridamole stress echocardiography was reasonably safe and well tolerated. This protocol is especially appealing for its excellent diagnostic accuracy coupled with the short imaging time and no need for drug cocktails.

Magnetic domains and stripes in a spin-fermion model for cuprates

Monte Carlo simulations applied to a model of interacting fermions and classical spins show the existence of antiferromagnetic spin domains and charge stripes upon hole doping. The stripes have a filling of approximately 1/2 hole per site, and they separate spin domains with a pi phase shift among them. The observed stripes run either along the x or y axes. No particular boundary conditions or external fields are needed to stabilize these structures. When magnetic incommensurate peaks are observed at momentum pi(1,1-delta), charge incommensurate peaks appear at (0,2delta). The charge fluctuations responsible for the stripe formation also induce a pseudogap in the density of states.

Giant cluster coexistence in doped manganites and other compounds

Computational studies of models for manganese oxides show the generation of large coexisting metallic and insulating clusters with equal electronic density, in agreement with the recently discovered micrometer-sized inhomogeneities in manganites. The clusters are induced by disorder on exchange and hopping amplitudes near first-order transitions of the nondisordered strongly coupled system. The random-field Ising model illustrates the qualitative aspects of our results. Percolative characteristics are natural in this context. The conclusions are general and apply to a variety of compounds.

Resistivity of Mixed-Phase Manganites.

The resistivity rho(dc) of manganites is studied using a random resistor-network, based on phase separation between metallic and insulating domains. When percolation occurs, both as chemical composition or temperature vary, results in good agreement with experiments are obtained. Similar conclusions are reached using quantum calculations and microscopic considerations. Above the Curie temperature, it is argued that ferromagnetic clusters should exist in Mn oxides. Small magnetic fields induce large rho(dc) changes and a bad-metal state with (disconnected) insulating domains.

Color Doppler echocardiographic assessment of atrial septal defect size: correlation with surgical measurements.

In patients with atrial septal defect (ASD), color flow Doppler echocardiography provides visualization of the transseptal jet, the maximal dimension of which can be assumed to correspond to the maximal dimension of the true orifice. To test whether color flow Doppler echocardiography can provide an alternative method for measurement of ASD size, we studied 63 consecutive patients with echocardiographic evidence of ASD. In 48 patients the maximal dimension of the jet was measured in the parasternal, apical, or subcostal four-chamber view or in the parasternal short-axis view. In the remaining 15 patients transesophageal echocardiography was performed because of transthoracic views were inadequate. The transesophageal studies also measured, from two-dimensional images, the maximal transverse discontinuity in the atrial septum. All patients underwent surgical repair, during which the surgeon directly measured the maximal dimension of ASD. Linear regression equations were performed to compare transthoracic and transesophageal dimensions to those measured at operation. Correlation coefficients were as follows for transthoracic versus surgical measurements: r = 0.745, standard error = 4.35, p less than 0.001. Transesophageal measurements derived from both two-dimensional images and echocardiographic jet width showed similar excellent correlation with surgical measurements (n = 0.91, standard error = 4.33, p less than 0.001; and r = 0.919, standard error = 4.42, p less than 0.001, respectively). We conclude that ASD size derived from color flow Doppler echocardiography shows a good correlation with the anatomic maximal dimension observed at operation. Both transesophageal color flow Doppler echocardiography of jet width and direct surgical measurement of the defect provide an accurate estimation of ASD size.

Transesophageal echocardiography in the evaluation of mediastinal masses.

To assess the diagnostic impact of transesophageal echocardiography in the evaluation of mediastinal masses, 30 patients with mediastinal abnormalities detected by routine chest roentgenogram underwent transthoracic and transesophageal echocardiography. Subsequently, 29 of the patients underwent computed tomography and 16 underwent magnetic resonance imaging. The location and structure of the masses as well as their relationship to the surrounding structures were assessed. Anatomic confirmation and histopathologic diagnosis of the mediastinal masses by surgical resection and biopsy was available for all patients. Transesophageal echocardiography was more accurate than transthoracic echocardiography in detecting mediastinal masses (90% versus 73%), in identifying their structure (100% versus 90%), and in evaluating their relationship to contiguous organs (89% versus 81%). No complication was observed during the examinations. Computed tomography correctly diagnosed the location, structure, and relationships in all patients but one; magnetic resonance imaging correctly evaluated the mediastinal masses in all 16 patients. Our study suggests that transesophageal echocardiography is a valuable and safe complementary method of evaluating mediastinal masses. Moreover, this technique allows the obstruction of vessels and heart cavities, valve regurgitation, and right and left ventricular function to be easily assessed.

Aneurysm of an aberrant right subclavian artery. Report of a surgically treated case.

A 53-year-old man was admitted for treatment of an aberrant right subclavian artery aneurysm that had been diagnosed 5 years earlier and had recently begun to enlarge. The aneurysm, which involved the right subclavian artery from its origin, measured 47 mm in diameter and about 10 cm in length. Because of the lesion's size and friability, a 2-stage operation was performed. In the 1st stage, the right subclavian and right vertebral arteries were revascularized with double bypass grafts via a right cervical approach. In the 2nd stage, the patient was repositioned and a left thoracotomy incision was made. With the aid of left-heart bypass, the aorta was cross-clamped proximal and distal to the lesion, and the aneurysmal orifice was closed with a Dacron patch. The patient was discharged from the hospital on the 17th postoperative day and remains asymptomatic 24 months later. We recommend the 2-stage technique for similar cases because it prevents limb ischemia and reduces the risk of hemorrhagic and embolic complications.

Successful resection of a tuberculous pseudoaneurysm of the descending thoracic aorta: case report and review of the literature.

An aneurysm of the descending thoracic aorta was found in a 55-year-old woman. She had hemoptysis, fever, and weight loss beginning 1 month before hospitalization. A miliary tuberculosis developed after angiography. The patient underwent surgical resection of the aneurysm, which proved to be tuberculous. The aortic wall was reconstructed with a Dacron patch. Antituberculosis pharmacotherapy, started before operation, was discontinued after 16 months of administration. The patient is doing well 19 months after operation. The English literature reports only 7 other cases of surgical treatment of tuberculous aneurysm of the thoracic aorta. According to previous reports, early surgical intervention, combined with preoperative and prolonged postoperative antituberculosis therapy and close postoperative follow-up, is mandatory in this group of patients.

Left ventricular performance in chronic mitral regurgitation: temporal response to valve repair and prognostic value of early postoperative echocardiographic parameters.

BACKGROUND: The temporal response of the left ventricle due to the relief of volume loading after mitral valve repair, and the prognostic value of early changes in left ventricular size and function, are not fully documented. The purpose of this study was to analyze the evolution of left ventricular performance after surgery, and to evaluate how early postoperative echocardiographic parameters compare with late ventricular function. METHODS: We studied 58 patients with chronic degenerative mitral regurgitation using echocardiography, before, and 9 +/- 3 days and 38 +/- 6 months after mitral valve repair. RESULTS: Between the preoperative and early postoperative study, left ventricular end-diastolic and left atrial size, and ejection fraction decreased, whereas left ventricular end-systolic dimension did not change. Between the early and late postoperative study left ventricular end-systolic size decreased significantly, there was a further decrease in left ventricular end-diastolic dimension and a significant increase in ejection fraction; left atrial size did not change. Multivariate analysis showed that preoperative and early postoperative ejection fraction, and the early postoperative reduction in diastolic dimension were the best predictors of late left ventricular function. CONCLUSIONS: In patients with chronic degenerative mitral regurgitation, the greatest reduction in end-diastolic dimension occurs within 2 weeks of the reversal of volume overload; a significant reduction in end-systolic dimension with an increase in ejection fraction occurs later. In our experience, early postoperative echocardiographic measurements of left ventricular size and function can provide important prognostic information.

Neopterin levels are independently associated with cardiac remodeling in patients with chronic heart failure.

OBJECTIVES: Neopterin, a marker of inflammation and monocyte activation, is found increased in patients with heart failure (HF). This study investigates whether neopterin levels correlate with left ventricular (LV) remodeling and brain natriuretic peptide (BNP), a marker of cardiac stress, in chronic HF (CHF) patients with different severity of disease. DESIGN AND METHODS: The relationship between neopterin and LV dimensions, NT-proBNP, and pro-inflammatory cytokines were studied in 98 CHF patients, while nineteen healthy subjects were enrolled as controls. Nineteen (19%) patients were in NYHA class I, 38 (39%) in NYHA class II, 27 (28%) in NYHA class III, and 14 (14%) in NYHA class IV. RESULTS: Neopterin levels were higher in CHF patients than in age- and gender-matched healthy controls, and related with indexed LV end-diastolic volume (LVEDVi). Prospectively CHF patients were separated into tertiles of low, medium and high neopterin levels. Among patients, male gender, LVEDVi, diuretic treatment, NYHA class I, NT-proBNP and IL-8 levels were significant determinants of urine neopterin levels by bivariate analysis. Neopterin levels were associated only to LV remodeling, as assessed by LVEDVi, and IL-8 levels, a crucial monocyte chemoattractant, by multivariate ordinal regression analysis. CONCLUSIONS: The relationship between elevated neopterin levels and LV enlargement in CHF patients suggests a crucial role of monocyte activation in the development of cardiac dysfunction in CHF patients. Assessment of neopterin levels is a potential biomarker to evaluate the progression of LV remodeling in CHF patients.