Quench dynamics of Fano-like resonances in the presence of the on-dot superconducting pairing.

We explore the electron dynamics of a system composed of double quantum dot embedded between metallic and superconducting leads in a "T-shape" geometry. In nanoscopic systems, where electron transfer between electrodes can be realized via different paths, interference effects play an important role. For double quantum dot system in the chosen geometry, interference of electrons transferred between electrodes via the interfacial quantum dot and electrons scattered on the side dot gives rise to Fano-like interference. If such a system is additionally coupled to a superconducting electrode, together with the well-understood Fano resonance an additional resonance appears on the opposite side of the Fermi level. In the recent work (Baranski et al. in Sci Rep 10:2881, 2020), we showed that this resonance occurs solely as a result of the local pairing of non-scattered electrons with scattered ones. In this work, considering the quench dynamics, we explore how much time is required for formation of each of these resonances. In particular, (i) we analyze the charge oscillations between subsystems; (ii) we estimate the time required for each resonance to achieve stable equilibrium upon an abrupt change of interdot connection; (iii) we discuss a typical energy and time scales for experiments on similar architectures.

Evaluation of a tryptase depletion index for better pathologic identification of mast cell activation syndrome.

BACKGROUND: Laboratory evidence supporting diagnosis of the prevalent condition of mast cell activation syndrome (MCAS) currently includes elevated levels in blood or urine of mediators relatively specific to mast cells (MCs) and/or increased numbers of MCs in luminal gastrointestinal (GI) tract tissues. However, identification of elevated mediators is technically challenging and expensive, and controversy persists regarding the normal ranges of numbers/counts of MCs in various GI tract segments, let alone challenges in determining how many of the visualized MCs are activated. To aid diagnosis of MCAS, we developed a potential new approach for the pathologist to identify the extent of GI tract MC activation easily and inexpensively. PARTICIPANTS AND METHODS: Visualization of MCs in gastrointestinal biopsies from 251 patients vs. 95 controls using antibodies against CD117 and tryptase; MC counting per mm2; calculation of the difference between the CD117-positive MCs (identifying all MCs) vs. tryptase-positive MCs (identifying non-activated tryptase-containing MCs), which we define as the tryptase depletion index (TDI). RESULTS: Mean total MC counts did not differ significantly between patients and controls, but mean TDIs differed significantly. Non-overlapping confidence intervals at the 99.9% level identified cut-offs of TDIs between patients vs. controls of 26, 45 and 32 MCs/mm2 in gastric antrum, duodenum, and colon, respectively. CONCLUSIONS: The TDI may discriminate between MCAS patients vs. controls. If this preliminary work can be independently confirmed, the TDI may become a useful additional minor diagnostic criterion for MCAS.

Anomalous Fano Resonance in Double Quantum Dot System Coupled to Superconductor.

We analyze the influence of a local pairing on the quantum interference in nanoscopic systems. As a model system we choose the double quantum dot coupled to one metallic and one superconducting electrode in the T-shape geometry. The analysis is particularly valuable for systems containing coupled objects with considerably different broadening of energy levels. In such systems, the scattering of itinerant electrons on a discrete (or narrow) energy level gives rise to the Fano-type interference. Systems with induced superconducting order, along well understood Fano resonances, exhibit also another features on the opposite side of the Fermi level. The lineshape of these resonances differs significantly from their reflection on the opposite side of the Fermi level, and their origin was not fully understood. Here, considering the spin-polarized tunneling model, we explain a microscopic mechanism of a formation of these resonances and discuss the nature of their uncommon lineshapes. We show that the anomalous Fano profiles originate solely from the pairing of nonscattered electrons with scattered ones. We investigate also the interplay of each type of resonances with the Kondo physics and discuss the resonant features in differential conductivity.

Intramyocardial transplantation of bone marrow-derived stem cells: ultrasonic strain rate imaging in a model of hibernating myocardium.

BACKGROUND: The aim of this study was to evaluate potential cardioprotective effects of bone marrow-derived stem cells in chronic ischemic myocardium regarding strain rate parameters during dobutamine stress echocardiography. METHODS: An ameroid constrictor was placed around the circumflex artery in 23 pigs to induce hibernating myocardium. Pigs received autologous mesenchymal stem cells (auto MSCs), allogeneic MSC (allo MSC), autologous mononuclear cells (auto MNCs), or placebo injections into the ischemic region. During dobutamine stress echocardiography, peak systolic strain rates (SR(sys)) and systolic and postsystolic strain values (epsilon(sys), epsilon(ps)) were determined. The animals were evaluated regarding myocardial fibrosis, neovascularization, apoptosis, and myocardial beta-adrenergic receptor density. RESULTS: The median ejection fraction was reduced in the control group compared with the auto MSC-, allo MSC-, and auto MNC-treated pigs (36.5% vs 46.0% vs 46.0% vs 41.5%; P = .001, respectively). Histopathology revealed a decreased myocardial fibrosis in auto MSC- (16.3%), allo MSC- (11.3%), and auto MNC- (16.7%) treated pigs compared with controls (31.0%; P = .004). The fibrosis and echocardiographic deformation data correlated in the posterior walls: rest peak SR(sys)r = -0.92; epsilon(sys)r = -0.86; 10 microg dobutamine stimulation peak SR(sys)r = -0.88, epsilon(sys), r = -0.87 (P = .0001). CONCLUSION: Endocardial injection of stem cells may induce cardioprotective effects in chronic ischemic myocardium and helps to keep the ischemic myocardium viable.