Nature and origin of the operators entering the master equation of an open quantum system

By exploiting the peculiarities of a recently introduced formalism for describing open quantum systems (the Parametric Representation with Environmental Coherent States) we derive an equation of motion for the reduced density operator of an open quantum system that has the same structure of the celebrated Gorini-Kossakowski-Sudarshan-Lindblad equation, but holds regardless of markovianity being assumed. The operators in our result have explicit expressions in terms of the Hamiltonian describing the interactions with the environment, and can be computed once a specific model is considered. We find that, instead of a single set of Lindblad operators, in the general (non-markovian) case there one set of Lindblad-like operators for each and every point of a symplectic manifold associated to the environment. This intricacy disappears under some assumptions (which are related to markovianity and the classical limit of the environment), under which it is possible to recover the usual master equation formalism. Finally, we find such Lindblad-like operators for two different models of a qubit in a bosonic environment, and show that in the classical limit of the environment their renown master equations are recovered.Comment: 19 pages, 1 figur

On tests of the quantum nature of gravitational interactions in presence of non-linear corrections to quantum mechanics

When two particles interact primarily through gravity and follow the laws of quantum mechanics, the generation of entanglement is considered a hallmark of the quantum nature of the gravitational interaction. However, we demonstrate that entanglement dynamics can also occur in the presence of a weak quantum interaction and non-linear corrections to local quantum mechanics, even if the gravitational interaction is classical or absent at short distances. This highlights the importance of going beyond entanglement detection to conclusively test the quantum character of gravity, and it requires a thorough examination of the strength of other quantum forces and potential non-linear corrections to quantum mechanics in the realm of large masses.Comment: 16 pages, 4 figure

Experience of 10 years in routine trans operative endoscopy and calibration in fundoplication due to gastroesophageal reflux disease

Background: Endoscopy and intraoperative calibration in fundoplication for gastroesophageal reflux disease (GERD), confirm an adequate technique avoiding postoperative failure. Intraoperative changes and morbidity in routine use are unknown.Methods: Retrospective study in a single center, data were taken primarily from electronic archive medical records. A total of 899 who underwent fundoplication surgery with endoscopy and/or routine intraoperative calibration due to GERD met the required criteria between 1 January 2010 and 31 December 2020. The primary objective was to identify the number of calibration and intraoperative endoscopy findings. Also, the morbidity associated with its routine use was analyzed.Results: Over a 10-year study period, the most frequent calibration in the Nissen Fundoplication was 60Fr in 472 cases (61.4 %). The most used calibration in Toupet Fundoplication was 60Fr in 26 cases (21.1%). Endoscopy was performed in 786 patients (71.38%), of which; 3 patients (0.3%) required changes, secondary to fundoplication rotation in 2 patients (0.2%) and redundant gastric fundus in 1 patient (0.1%).Conclusions: Routine intraoperative calibration and endoscopy achieved excellent results in 96.8% of fundoplication’s, ensuring adequate esophageal position and corroborating an adequate intraoperative technique; decreasing the rate of failures and immediate postoperative dysphagia

Neuroendocrine and psychological assessment in a guinness 10 days scuba dive

his study was designed to evaluate physiological and psychological stress parameters in 2 professional trained scuba divers, using a unique Physiopathologic model, offered by the guinness 240 hours scuba dive. Two scuba dive masters have spent 240 hours at 6-8 meters depth (26.4 ft) in Ponza Island water (Italy). Blood samples were collected daily in the underwater bell; samples were carried out of water in waterproof bags. Breath samples were collected, measuring ethylene release. Psychological assessment was performed using the State and Trait Anxiety Inventory and the Zung self-rating depression scale. In the studied subjects, Cortisol and prolactin showed physiological pulsatile secretion. Breath ethylene didn't exceed normal values. At the start of the study, no subjects showed high levels of state anxiety, trait anxiety and current depression. Psychometric scales scores remained steady during the diving period and no subjects showed anxiety and/or depression and/or panic symptoms during the time of observation. The present study shows that, although the long-time diving, well trained professional divers did not develop anxiety and/or depression. No subject discontinued the diving due to occurred psychological disorders or systemic events. The present report shows that the long-term diving permanence is possible, at least in well trained scuba divers

Budget Deficits and Exchange-Rate Crises

This paper investigates currency crises in an optimizing general equilibrium model with overlapping generations. It is shown that a rise in government budget deficits financed by future taxes generates a decumulation of external assets, leading up to a speculative attack and forcing the monetary authorities to abandon the peg.Budget deficits, foreign exchange reserves, currency crises,

30-Day Morbidity and Mortality of Bariatric Surgery During the COVID-19 Pandemic: a Multinational Cohort Study of 7704 Patients from 42 Countries.

BACKGROUND There are data on the safety of cancer surgery and the efficacy of preventive strategies on the prevention of postoperative symptomatic COVID-19 in these patients. But there is little such data for any elective surgery. The main objectives of this study were to examine the safety of bariatric surgery (BS) during the coronavirus disease 2019 (COVID-19) pandemic and to determine the efficacy of perioperative COVID-19 protective strategies on postoperative symptomatic COVID-19 rates. METHODS We conducted an international cohort study to determine all-cause and COVID-19-specific 30-day morbidity and mortality of BS performed between 01/05/2020 and 31/10/2020. RESULTS Four hundred ninety-nine surgeons from 185 centres in 42 countries provided data on 7704 patients. Elective primary BS (n = 7084) was associated with a 30-day morbidity of 6.76% (n = 479) and a 30-day mortality of 0.14% (n = 10). Emergency BS, revisional BS, insulin-treated type 2 diabetes, and untreated obstructive sleep apnoea were associated with increased complications on multivariable analysis. Forty-three patients developed symptomatic COVID-19 postoperatively, with a higher risk in non-whites. Preoperative self-isolation, preoperative testing for SARS-CoV-2, and surgery in institutions not concurrently treating COVID-19 patients did not reduce the incidence of postoperative COVID-19. Postoperative symptomatic COVID-19 was more likely if the surgery was performed during a COVID-19 peak in that country. CONCLUSIONS BS can be performed safely during the COVID-19 pandemic with appropriate perioperative protocols. There was no relationship between preoperative testing for COVID-19 and self-isolation with symptomatic postoperative COVID-19. The risk of postoperative COVID-19 risk was greater in non-whites or if BS was performed during a local peak

Safety of Bariatric Surgery in ≥ 65-Year-Old Patients During the COVID-19 Pandemic

Background Age >= 65 years is regarded as a relative contraindication for bariatric surgery. Advanced age is also a recognised risk factor for adverse outcomes with Coronavirus Disease-2019 (COVID-19) which continues to wreak havoc on global populations. This study aimed to assess the safety of bariatric surgery (BS) in this particular age group during the COVID-19 pandemic in comparison with the younger cohort.Methods We conducted a prospective international study of patients who underwent BS between 1/05/2020 and 31/10/2020. Patients were divided into two groups - patients >= 65-years-old (Group I) and patients < 65-years-old (Group II). The two groups were compared for 30-day morbidity and mortality.Results There were 149 patients in Group 1 and 6923 patients in Group II. The mean age, preoperative weight, and BMI were 67.6 +/- 2.5 years, 119.5 +/- 24.5 kg, and 43 +/- 7 in Group I and 39.8 +/- 11.3 years, 117.7 +/- 20.4 kg, and 43.7 +/- 7 in Group II, respectively. Approximately, 95% of patients in Group 1 had at least one co-morbidity compared to 68% of patients in Group 2 (p = < 0.001). The 30-day morbidity was significantly higher in Group I ( 11.4%) compared to Group II (6.6%) (p = 0.022). However, the 30-day mortality and COVID-19 infection rates were not significantly different between the two groups.Conclusions Bariatric surgery during the COVID-19 pandemic is associated with a higher complication rate in those >= 65 years of age compared to those < 65 years old. However, the mortality and postoperative COVID-19 infection rates are not significantly different between the two groups