Multiphoton Transitions in a Spin System Driven by Strong Bichromatic Field

EPR transient nutation spectroscopy is used to measure the effective field (Rabi frequency) for multiphoton transitions in a two-level spin system bichromatically driven by a transverse microwave (MW) field and a longitudinal radio-frequency (RF) field. The behavior of the effective field amplitude is examined in the case of a relatively strong MW field, when the derivation of the effective Hamiltonian cannot be reduced to first-order perturbation theory in w_{1} / w_{rf} (w_{1} is the microwave Rabi frequency, w_{rf} is the RF frequency). Experimental results are consistently interpreted by taking into account the contributions of second and third order in w_{1} / w_{rf} evaluated by Krylov-Bogolyubov-Mitropolsky averaging. In the case of inhomogeneously broadened EPR line, the third-order correction modifies the nutation frequency, while the second-order correction gives rise to a change in the nutation amplitude due to a Bloch-Siegert shift.Comment: 7 pages, 6 figure

Dissipative dynamics of qubits driven by a bichromatic field in the dispersive regime

We study the coherent dynamics of relaxing qubits driven by a bichromatic radiation in the dispersive regime, when detuning of the frequency $\omega_{rf}$ of a longitudinal radiofrequency field from the Rabi frequency $\omega_{1}$ in a transverse microwave field is comparable in magnitude to $\omega_{rf}$ and $\omega_{1}$. We analytically describe this regime beyond the rotating wave approximation and find that the dominant feature of dynamics of qubits is the shift of the Rabi frequency caused by the dynamical Zeeman and Bloch-Siegert-like effects. These fundamental effects can be experimentally separated because, unlike the Bloch-Siegert effect, the dynamical Zeeman effect depends on the detuning sign. Our theoretical results are in a good agreement with the experimental data obtained in pulse EPR for the $E'_{1}$ centers in crystalline quartz.Comment: 11 pages, 4 figure

Recent outcome of liver transplantation for Budd Chiari syndrome - analysis of the european liver transplant registry (ELTR) and affiliated centres

peer reviewedBackground: Maintenance anticoagulation and Transjugular Intrahepatic Portosystemic Shunt (TIPS) have improved management of Budd-Chiari Syndrome (BCS) over the last decades. Most published studies on outcomes of liver transplantation (LT) for BCS in Europe date before these changes. Methods: Data were obtained from the European Liver Transplantation Registry (ELTR). Age <16, secondary BCS and hepatocellular carcinoma were excluded. Patient (PS) and graft survival (GS) before and after 2000 was compared. Multivariate Cox regression analysis (with re-transplantation as time- dependent covariate) identified predictors of PS and GS after 2000. Supplementary data was requested from all ELTR affiliated centres and received from 39. Results: 811 patients were transplanted for primary BCS between 2000 and 2020. Median age was 37.2y, 60% were female, median MELD was 17 and 29% had high urgency (HU) listing. One-, five- and ten-year PS rates between 2000-2020 were 83%, 76% and 69%, compared to 71%, 66% and 61% for the 293 patients transplanted before 2000 (p<0.001), while GS was 78%, 69%, 62% vs. 63%, 58% and 52%, respectively (p<0.001). Since 2000, BCS recurred in 3% and 12% received a re-transplant. Older recipient age (HR 1.02; 95%CI 1.01-1.04) and higher MELD (HR 1.03; 95%CI 1.01-1.06) were associated with worse PS while HU listing was associated with improved PS (HR 0.57; 95%CI 0.35-0.92). Older donor age was the only independent predictor of worse GS (HR 1.01; 95%CI 1.00-1.02). In n=236 (29%) with additional centre-data, 38% had myeloproliferative disease, 25% received TIPS pre-LT and 82% used anticoagulation post-LT. In these, anticoagulation was the only independent factor associated with PS (HR 0.38; 95%CI 0.15-0.98).Conclusions: LT for BCS results in excellent patient and graft survival. Outcomes have improved since 2000. Older recipient age and higher MELD result in poorer survival. HU listing appears to select patients with most favourable outcome. Long-term anticoagulation seems beneficial. Further validation is needed

Recent outcome of liver transplantation for Budd Chiari syndrome - analysis of the european liver transplant registry (ELTR) and affiliated centres

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Diagnosis and treatment in chronic pancreatitis: an international survey and case vignette study

Background: The aim of the study was to evaluate the current opinion and clinical decision-making process of international pancreatologists, and to systematically identify key study questions regarding the diagnosis and treatment of chronic pancreatitis (CP) for future research.Methods: An online survey, including questions regarding the diagnosis and treatment of CP and several controversial clinical case vignettes, was send by e-mail to members of various international pancreatic associations: IHPBA, APA, EPC, ESGE and DPSG.Results: A total of 288 pancreatologists, 56% surgeons and 44% gastroenterologists, from at least 47 countries, participated in the survey. About half (48%) of the specialists used a classification tool for the diagnosis of CP, including the Mayo Clinic (28%), Mannheim (25%), or Buchler (25%) tools. Overall, CT was the preferred imaging modality for evaluation of an enlarged pancreatic head (59%), pseudocyst (55%), calcifications (75%), and peripancreatic fat infiltration (68%). MRI was preferred for assessment of main pancreatic duct (MPD) abnormalities (60%). Total pancreatectomy with auto-islet transplantation was the preferred treatment in patients with parenchymal calcifications without MPD abnormalities and in patients with refractory pain despite maximal medical, endoscopic, and surgical treatment. In patients with an enlarged pancreatic head, 58% preferred initial surgery (PPPD) versus 42% initial endoscopy. In patients with a dilated MPD and intraductal stones 56% preferred initial endoscopic +/- ESWL treatment and 29% preferred initial surgical treatment.Conclusion: Worldwide, clinical decision-making in CP is largely based on local expertise, beliefs and disbeliefs. Further development of evidence-based guidelines based on well designed (randomized) studies is strongly encouraged

Diagnosis and treatment in chronic pancreatitis: an international survey and case vignette study

Background The aim of the study was to evaluate the current opinion and clinical decision-making process of international pancreatologists, and to systematically identify key study questions regarding the diagnosis and treatment of chronic pancreatitis (CP) for future research. Methods An online survey, including questions regarding the diagnosis and treatment of CP and several controversial clinical case vignettes, was send by e-mail to members of various international pancreatic associations: IHPBA, APA, EPC, ESGE and DPSG. Results A total of 288 pancreatologists, 56% surgeons and 44% gastroenterologists, from at least 47 countries, participated in the survey. About half (48%) of the specialists used a classification tool for the diagnosis of CP, including the Mayo Clinic (28%), Mannheim (25%), or Büchler (25%) tools. Overall, CT was the preferred imaging modality for evaluation of an enlarged pancreatic head (59%), pseudocyst (55%), calcifications (75%), and peripancreatic fat infiltration (68%). MRI was preferred for assessment of main pancreatic duct (MPD) abnormalities (60%). Total pancreatectomy with auto-islet transplantation was the preferred treatment in patients with parenchymal calcifications without MPD abnormalities and in patients with refractory pain despite maximal medical, endoscopic, and surgical treatment. In patients with an enlarged pancreatic head, 58% preferred initial surgery (PPPD) versus 42% initial endoscopy. In patients with a dilated MPD and intraductal stones 56% preferred initial endoscopic ± ESWL treatment and 29% preferred initial surgical treatment. Conclusion Worldwide, clinical decision-making in CP is largely based on local expertise, beliefs and disbeliefs. Further development of evidence-based guidelines based on well designed (randomized) studies is strongly encouraged