Orbital currents in extended Hubbard models of high-Tc_c cuprates

Motivated by the recent report of broken time-reversal symmetry and zero momentum magnetic scattering in underdoped cuprates, we investigate under which circumstances orbital currents circulating inside a unit cell might be stabilized in extended Hubbard models that explicitly include oxygen orbitals. Using Gutzwiller projected variational wave functions that treat on an equal footing all instabilities, we show that orbital currents indeed develop on finite clusters, and that they are stabilized in the thermodynamic limit if additional interactions, e.g. strong hybridization with apical oxygens, are included in the model.Comment: 4 page

Topologically protected edge states in small Rydberg systems

We propose a simple setup of Rydberg atoms in a honeycomb lattice which gives rise to topologically protected edge states. The proposal is based on the combination of dipolar exchange interaction, which couples the internal angular momentum and the orbital degree of freedom of a Rydberg excitation, and a static magnetic field breaking time reversal symmetry. We demonstrate that for realistic experimental parameters, signatures of topologically protected edge states are present in small systems with as few as 10 atoms. Our analysis paves the way for the experimental realization of Rydberg systems characterized by a topological invariant, providing a promising setup for future application in quantum information.Comment: 6 pages, 6 figure

Prophylactic anti-coagulation in cancer palliative care: a prospective randomised study

Goals: The objective of this study was to determine utility of prophylactic anti-coagulation in cancer patients hospitalised for palliative care in a specialised centre. Materials and methods: Prospective 1:1 open randomised study was designed. Twenty patients aged 55 to 88years with advanced cancer and an estimated life expectancy of less than 6months were assigned to either receive treatment with 2,850/3,800U (70kg) of daily subcutaneous nadroparin or no treatment. Suspicion of venous thrombo-embolism (deep vein thrombosis and pulmonary embolism) was confirmed by echo-Doppler examination of the lower limbs and/or by spiral computed tomography scan of the lungs. Bleeding episodes were recorded. Platelet count was measured on days 7 and 14. Survival time from study entry was determined. Main results: One venous thrombo-embolism and one major bleeding occurred in the group receiving nadroparin, whereas two minor bleedings occurred in the control group. At 3months, nine of ten participants had died in the control group vs five of ten in the group receiving nadroparin (P = 0.141). Five participants could be discharged home (P = 0.141). Conclusions: Decision to administer prophylactic nadroparin in hospitalised cancer patients under palliative care remains a challenge. Better mobility score at admission and the likelihood to be discharged home may be useful for practical purposes. The observation of a potential influence of prophylactic nadroparin on survival deserves further studie

Massive pulmonary embolism: surgical embolectomy versus thrombolytic therapy—should surgical indications be revisited?†

OBJECTIVES The treatment of massive pulmonary embolism (PE) is a matter of debate. We present our institutional experience of patients suffering from massive PE with the aim of comparing the early results, the outcome and quality of life (QoL) between patients primarily assigned to either pulmonary surgical embolectomy (SE) or thrombolytic therapy (TL). A subgroup of patients (TS) with failed responses to TL requiring SE was separately analysed. METHODS All consecutive patients (January 2001-December 2007) with computed tomography (CT)-scan-confirmed massive bilateral central or paracentral PE were reviewed. All clinical data were retrieved from our patients' registry and completed by the evaluation of the CT-scan-derived right ventricle/left ventricle ratio (RV/LV ratio). Follow-up focused on clinical outcome and QoL was obtained. RESULTS Eighty patients were analysed including 28 SE (35%) and 52 TL (65%), of whom 11 (21%) required TS. Demographics and preoperative characteristics were similar between SE and TL. Analysis of the RV/LV ratio revealed a ratio of 1.66 for SEand 1.44 for TL. The early mortality rate was not significantly different between the two groups (SE: 3.6% versus TL: 13.5%), whereas early mortality was 27% in those patients treated initially with thrombolysis and subsequently requiring SE (TS-group). Severe bleeding complications were lower in the SE-group (3.6% versus 26.5% P=0.013). Intracerebral bleeding rates and neurological events were not statistically different. After a mean follow-up of 63±21 months, the mortality rate was 17.9% in the SE-group and 23.1% in the TL-group. CONCLUSIONS SE is an excellent treatment option in massive PE with comparable early mortality rates and significantly less bleeding complications than TL. Patients having surgery after inefficient thrombolysis have the worst early outcome. The RV/LV CT-scan ratio might serve as a predictor to differentiate patients, who could profit from direct surgical intervention than thrombolytic treatment attempts. Further studies are required to confirm these result

Asymmetric speed modulation of a rotary blood pump affects ventricular unloading

OBJECTIVES Rotary blood pumps (RBPs) running at a constant speed are routinely used for the mechanical support of the heart in various clinical applications, from short-term use in heart-lung machines to long-term support of a failing heart. Their operating range is delineated by suction and regurgitation events, leaving limited control on the cardiac workload. This study investigates whether different ratios of systolic/diastolic support are advantageous over a constant-speed operation. METHODS In order to effectively control the load on the heart, this study aimed at developing a pulsatile control algorithm for rotary pumps to investigate the impact of pump speed modulation during systole and diastole on the left ventricle unloading. The CentriMagTM RBP with a modified controller was implanted in four sheep via a left thoracotomy and cannulated from the ventricular apex to the descending aorta. To modulate the pump speed synchronized with the heartbeat, custom-made real-time software detected the QRS complex of the electrocardiogram and controlled the pump speed during systole and diastole. Four different speed modulations with the same average speed but different systolic and diastolic speeds were compared with the baseline and the constant speed support. Left ventricular (LV) pressure and volume, coronary flow and pump flow were analysed to examine the influence of the pump speed modulation. RESULTS Pulsatile setting reduces the cardiac workload to 64% of the baseline and 72% of the constant speed value. Maximum unloading is obtained with the highest speed during diastole and high-pulse amplitude. End-diastolic volume in the pulsatile modes varied from 85 to 94% of the baseline and 96 to 107% of the constant speed value. Consequently, the mechanical load on the heart can be adjusted to provide assuagement, which may lead to myocardial recovery. The higher pump speed during systole results in an increase in the pulse pressure up to 140% compared with the constant speed. CONCLUSIONS The present study is an initial step to more accurate speed modulation of RBPs to optimize the cardiac load control. To develop future control algorithms, the concept of high speed during diastole having a maximal unloading effect on the LV and high speed during systole increasing the pulse pressure is worth considerin

Persistent sensitivity disorders at the radial artery and saphenous vein graft harvest sites: a neglected side effect of coronary artery bypass grafting procedures

Objective: The use of radial artery conduits in coronary artery bypass grafting (CABG) surgery is associated with improved long-term patency and patient survival rates as compared with saphenous vein conduits. Despite increasing popularity, relative incidence of local harvest-site complications and subjective perception of adverse long-term sequelae remain poorly described. Methods: To allow for direct comparison, we investigated a consecutive series of patients in whom both the radial artery and the saphenous vein had been harvested for isolated CABG during a 36-month period. Patients were identified from a prospective database that collects baseline clinical information. The patients' own perceptions were assessed by a standardized direct telephone survey regarding any persistent functional impairment from their arm and leg operation sites. Results: Out of 1756 CABG patients during the study period, 168 (10%) were eligible (78% men, median age: 60.1 ± 9.6 years, range: 29.6-82.4 years). Of these, 123 (73%) could be contacted and interviewed at a median follow-up time of 2.5 ± 0.9 years. Surgical wound complications at harvest sites (arms and legs) had occurred in 3% and 12%, respectively, and persistent symptoms (arms and legs) were self-reported as follows: chronic pain (5% and 8%), numbness (32% and 34%) and paresthesia/dysesthesia (14% and 7%). Overall, 39% of the patients reported persistent discomfort at the arm and 39% at the leg. Both sites were simultaneously affected in 21% (P = n.s., paired testing). Logistic regression modeling showed that patients with adverse long-term sequelae were younger (P < 0.005), had a higher body mass index (P < 0.05) and a lower EuroSCORE (P < 0.001) at the time of operation (EuroSCORE, European System for Cardiac Operative Risk Evaluation). Perioperative wound complications, however, did not predict persistence of symptoms. Conclusions: Persistent harvest-site discomfort occurs with astonishing frequency after CABG surgery and affects arms and legs equally. Although usually considered a minor complication, long-term limitation to quality of life may be substantial, particularly in younger and relatively healthy patients. Thus, harvest-site discomfort clearly belongs to the list of possible post-CABG complications of which patients need to be awar

Thermodynamics of a Heavy Ion-Irradiated Superconductor: the Zero-Field Transition

Specific heat measurements show that the introduction of amorphous columnar defects considerably affects the transition from the normal to the superconducting state in zero magnetic field. Experimental results are compared to numerical simulations of the 3D XY model for both the pure system and the system containing random columnar disorder. The numerics reproduce the salient features of experiment, showing in particular that the specific heat peak changes from cusp-like to smoothly rounded when columnar defects are added. By considering the specific heat critical exponent alpha, we argue that such behavior is consistent with recent numerical work [Vestergren et al., PRB 70, 054508 (2004)] showing that the introduction of columnar defects changes the universality class of the transition.Comment: 4 pages, 2 figure

A geographical tool for personal exposure assessment

The European policy in urban atmospheric pollution aims at reducing its impact on human health. This problem of public health is closely related to exposure of citizens during the day. Its estimation through persons activities defines the space-time budget. Sooner or later the local authorities in charge of air quality will provide to the population about their collective or individual exposure. We have developed here a tool that supplies this information. It is based on a multi-source approach. It exploits a Geographic Information System (GIS) gathering information such as individuals mobility, the topographic database, and concentrations of pollutants. Maps and dynamic representations of individual exposure are obtained. They display indoor (home, place of work) and outdoor exposure