The Jahn Teller and surface interactions in C60 nano systems

Scanning Tunnelling Microscopy (STM) is the fastest possible method of imaging the molecular orbitals of the C[subscript]60 anions with resolution at the single atom level. For the particular anions of fullerene C[subscript]60, the splitting of the molecular orbitals due to the internal Jahn-Teller effects (JT) add further difficulties in understanding the published experimental images. In the current work, the effect of JT interaction on STM recorded images is studied. For higher charged states, the Coulomb interaction affects the distribution of electrons around the ion, and then as a consequence, the STM current. The external interaction between the molecule and the surface substrate is equally important. Symmetry analysis using group theory and Hückel molecular orbital (HMO) theory are applied in order to describe the influence of the surface interactions on JT minima associated with D[subscript]3d, D[subscript]5d, D[subscript]2h, and C[subscript]2h symmetries. It represents some fullerene anions, which are adsorbed to the surface with different orientations, such as pentagon, hexagon, and double-bond prone toward the surface. Several ions with higher charges are investigated, such as C2−60, C3−60, and C4−60. In case of high symmetry orientations, the JT minima of the ions on a surface are split into subgroups with equal energies, depending on the type of orientation. The interpretation of the experimental observations is always possible for any orientation from the JT minima distribution and the contribution to the images from different components of the degenerate molecular orbitals

The Jahn Teller and surface interactions in C60 nano systems

Scanning Tunnelling Microscopy (STM) is the fastest possible method of imaging the molecular orbitals of the C[subscript]60 anions with resolution at the single atom level. For the particular anions of fullerene C[subscript]60, the splitting of the molecular orbitals due to the internal Jahn-Teller effects (JT) add further difficulties in understanding the published experimental images. In the current work, the effect of JT interaction on STM recorded images is studied. For higher charged states, the Coulomb interaction affects the distribution of electrons around the ion, and then as a consequence, the STM current. The external interaction between the molecule and the surface substrate is equally important. Symmetry analysis using group theory and Hückel molecular orbital (HMO) theory are applied in order to describe the influence of the surface interactions on JT minima associated with D[subscript]3d, D[subscript]5d, D[subscript]2h, and C[subscript]2h symmetries. It represents some fullerene anions, which are adsorbed to the surface with different orientations, such as pentagon, hexagon, and double-bond prone toward the surface. Several ions with higher charges are investigated, such as C2−60, C3−60, and C4−60. In case of high symmetry orientations, the JT minima of the ions on a surface are split into subgroups with equal energies, depending on the type of orientation. The interpretation of the experimental observations is always possible for any orientation from the JT minima distribution and the contribution to the images from different components of the degenerate molecular orbitals

Jahn-Teller effects and surface interactions in multiply-charged fullerene anions and the effect on scanning tunneling microscopy images

We investigate the combined effects of Jahn-Teller (JT) coupling and interactions with a surface substrate on fullerene anions C$_{60}^{2-}$ to C$_{60}^{4-}$. JT coupling alone causes the C$_{60}$ ions to instantaneously distort from the icosahedral symmetry of the neutral molecule to a lower symmetry, with the molecule moving dynamically between a set of equivalent distortions. When adsorbed on a surface, the number of equivalent minimum-energy distortions is reduced. The implications of this on observed scanning tunneling microscopy (STM) images will be discussed, and comparisons made with existing experimental data. We show that a consistent interpretation of the images from all of the charge states of C$_{60}$ can only be obtained using a JT model in which the symmetry is further reduced by surface interactions. The comparison with experimental data also allows us to determine relationships between the quadratic Jahn-Teller coupling and surface interaction parameters

Cooling quasiparticles in A(3)C(60) fullerides by excitonic mid-infrared absorption

Long after its discovery, superconductivity in alkali fullerides A(3)C(60) still challenges conventional wisdom. The freshest inroad in such ever-surprising physics is the behaviour under intense infrared excitation. Signatures attributable to a transient superconducting state extending up to temperatures ten times higher than the equilibrium T-c similar to 20 K have been discovered in K3C60 after ultra-short pulsed infrared irradiation-an effect which still appears as remarkable as mysterious. Motivated by the observation that the phenomenon is observed in a broad pumping frequency range that coincides with the mid-infrared electronic absorption peak still of unclear origin, rather than to transverse optical phonons as has been proposed, we advance here a radically new mechanism. First, we argue that this broad absorption peak represents a 'super-exciton' involving the promotion of one electron from the t(1u) half-filled state to a higher-energy empty t(1g) state, dramatically lowered in energy by the large dipole-dipole interaction acting in conjunction with the Jahn-Teller effect within the enormously degenerate manifold of (t(1u))(2)(t(1g))(1) states. Both long-lived and entropy-rich because they are triplets, the infrared-induced excitons act as a sort of cooling mechanism that permits transient superconductive signals to persist up to much higher temperatures

Global overview of the management of acute cholecystitis during the COVID-19 pandemic (CHOLECOVID study)

Background: This study provides a global overview of the management of patients with acute cholecystitis during the initial phase of the COVID-19 pandemic. Methods: CHOLECOVID is an international, multicentre, observational comparative study of patients admitted to hospital with acute cholecystitis during the COVID-19 pandemic. Data on management were collected for a 2-month study interval coincident with the WHO declaration of the SARS-CoV-2 pandemic and compared with an equivalent pre-pandemic time interval. Mediation analysis examined the influence of SARS-COV-2 infection on 30-day mortality. Results: This study collected data on 9783 patients with acute cholecystitis admitted to 247 hospitals across the world. The pandemic was associated with reduced availability of surgical workforce and operating facilities globally, a significant shift to worse severity of disease, and increased use of conservative management. There was a reduction (both absolute and proportionate) in the number of patients undergoing cholecystectomy from 3095 patients (56.2 per cent) pre-pandemic to 1998 patients (46.2 per cent) during the pandemic but there was no difference in 30-day all-cause mortality after cholecystectomy comparing the pre-pandemic interval with the pandemic (13 patients (0.4 per cent) pre-pandemic to 13 patients (0.6 per cent) pandemic; P = 0.355). In mediation analysis, an admission with acute cholecystitis during the pandemic was associated with a non-significant increased risk of death (OR 1.29, 95 per cent c.i. 0.93 to 1.79, P = 0.121). Conclusion: CHOLECOVID provides a unique overview of the treatment of patients with cholecystitis across the globe during the first months of the SARS-CoV-2 pandemic. The study highlights the need for system resilience in retention of elective surgical activity. Cholecystectomy was associated with a low risk of mortality and deferral of treatment results in an increase in avoidable morbidity that represents the non-COVID cost of this pandemic

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Physical and Dynamical Properties of the Atomic Spectrum and Squeezing of Information Entropy of Su(1,1) Interacting with Single Qubit

In this work, the interaction of an algebraic system of su(1,1) with qubit is investigated. Through Heisenberg’s equations of motion, the constants of motion are calculated. By solving the Schro ̈ding equation, the wave function that defines the features of the proposed system is obtained. Some statistical quantities are studied to determine the properties of the interaction of the algebraic system su(1,1) with qubit. The mathematical formula for the atomic emission spectrum is calculated and its properties are studied for many parameter values. Moreover, the periods of squeezing are defined by the entropy squeezing. The results are also compared and statistical quantities are linked together

Interplay between Coulomb and Jahn-Teller effects in icosahedral systems with triplet electronic states coupled to h-type vibrations

We will consider the role played by electron-vibration and electron-electron interactions, through Jahn-Teller (JT) and Coulomb interactions, respectively, in icosahedral systems in which triplet electronic states are coupled to hg-type vibrations. Starting from the electronic terms that arise from consideration of Coulomb interactions, we introduce JT couplings both within the terms and between nondegenerate terms. We show how the symmetry of the JT distortion can change when extra electrons are added, and give the conditions under which JT distortions can be suppressed entirely when the Coulomb interactions are sufficiently large. The relevance of our results to anions of the fullerene molecule C60 are briefly discussed, and existing experimental measurements are used to estimate values for the quadratic JT coupling constants for these anions