Steady-state properties of multi-orbital systems using quantum Monte Carlo.

A precise dynamical characterization of quantum impurity models with multiple interacting orbitals is challenging. In quantum Monte Carlo methods, this is embodied by sign problems. A dynamical sign problem makes it exponentially difficult to simulate long times. A multi-orbital sign problem generally results in a prohibitive computational cost for systems with multiple impurity degrees of freedom even in static equilibrium calculations. Here, we present a numerically exact inchworm method that simultaneously alleviates both sign problems, enabling simulation of multi-orbital systems directly in the equilibrium or nonequilibrium steady-state. The method combines ideas from the recently developed steady-state inchworm Monte Carlo framework [Erpenbeck et al., Phys. Rev. Lett. 130, 186301 (2023)] with other ideas from the equilibrium multi-orbital inchworm algorithm [Eidelstein et al., Phys. Rev. Lett. 124, 206405 (2020)]. We verify our method by comparison with analytical limits and numerical results from previous methods.

Management of colorectal anastomotic stricture with multidiameter balloon dilation: long-term results.

BACKGROUND: Postoperative colorectal anastomotic strictures are quite common. As such, many techniques have been available to address such a problem, one of which is endoscopic dilation. The aim of the present study was to evaluate the long-term outcomes following endoscopic dilation using a multidiameter balloon. METHODS: A retrospective study was conducted on patients with postoperative anastomotic stenosis treated with endoscopic dilation using a multidiameter balloon at our institution, in January 2005-December 2019 were retrospectively reviewed, excluding those with tumor recurrence. Perioperative factors, complications, and recurrence rates were analyzed. RESULTS: There were 40 patients, (22 males and 18 females, mean age 64.6 ± 10.7 years, range 33-84 years). The median follow-up period was 56 months (interquartile range 22.5-99 months). Only 1 complication occurred, micro-perforation due to guided wire injury, which was managed conservatively. Five (12.5%) patients developed restenosis and underwent repeat balloon dilation. None of the five recurrences required more aggressive management, such as redo anastomosis. CONCLUSIONS: Endoscopic multidiameter balloon dilation is a safe and effective method for treating benign colorectal anastomotic strictures.

Ratcheting and transitions: short granular chain in a gradient of vibration.

We report our experimental work on a one-dimensional gradient of vibration with a short granular chain. The system exhibits transitions of ratcheting dynamics from passive monotonic creeping against the gradient, to rapid stochastic head swinging with a reversed bias in its direction, and to seemingly random fluctuations. The spontaneously emerged spatial pattern reflects bifurcations of the state of the chain. Evidence from counterpart experiments using uniform vibrations confirms a nonmonotonic development of accessible modes behind the transitions, whereas the reversed ratcheting reflects an interesting dialogue between the size of the object and the spatial gradient.

Noninvasive cutaneous blood flow as a response predictor for visible light therapy on segmental vitiligo: a prospective pilot study.

BACKGROUND: Visible light is a treatment option for segmental vitiligo (SV), and visible light-induced repigmentation is associated with normalization of sympathetic dysfunction. Currently, it is difficult to predict individual patients' response to visible light therapy. OBJECTIVES: To test whether cutaneous blood flow can serve as a response predictor for visible light on treating SV. METHODS: Fourteen patients with SV were recruited in this prospective pilot study. Laser Doppler flowmetry was used to evaluate the cutaneous blood flow over SV lesions and contralateral normal skin. The pretreatment blood flow evaluation consisted of two stages: stage 1, following cold stress without prior visible light irradiation, and stage 2, following cold stress with prior visible light irradiation. Subsequently, the patients received regular visible light treatment for 3months, and a comparison of the pretreatment blood flow patterns between the visible light responding and nonresponding groups was carried out at the end of the study period. RESULTS: The SV lesions showed different blood flow profiles as compared with the contralateral normal skin. At the end of the 3-month study period, seven (50%) patients showed clinical repigmentation of >25%. The visible light responding group showed a more consistent occurrence of increased blood flow after stage 2 of the pretreatment evaluation while the nonresponding counterpart showed no significant changes. CONCLUSIONS: Normalization of sympathetic dysfunction may account for the efficacy of visible light in treating SV. Evaluation of cutaneous blood flow with and without prior visible light irradiation on cold-stressed SV lesions may serve as a treatment response predictor.

Design optimization of multi-pinhole micro-SPECT configurations by signal detection tasks and system performance evaluations for mouse cardiac imaging.

An optimized configuration of multi-pinhole aperture can improve the spatial resolution and the sensitivity of pinhole SPECT simultaneously. In this study, an optimization strategy of the multi-pinhole configuration with a small detector is proposed for mouse cardiac imaging. A 14 mm-diameter spherical field-of-view (FOV) is used to accommodate the mouse heart. To accelerate the optimization process, the analytic models are applied to rapidly obtain the projection areas of the FOV, the sensitivities and the spatial resolutions of numerous system designs. The candidates of optimal multi-pinhole configuration are then decided by the preliminary evaluations with the analytic models. Subsequently, the pinhole SPECT systems equipped with the designed multi-pinhole apertures are modeled in GATE to generate the imaging system matrices (H matrices) for the system performance assessments. The area under the ROC curves (AUC) of the designed systems is evaluated by signal-known-exactly/background-known-statistically detection tasks with their corresponding H matrices. In addition, the spatial resolutions are estimated by the Fourier crosstalk approach, and the sensitivities are calculated with the H matrices of designed systems, respectively. Furthermore, a series of OSEM reconstruction images of synthetic phantoms, including the hot-rod phantom, mouse heart phantom and Defrise phantom, are reconstructed with the H matrices of designed systems. To quantify the sensitivity and resolution competition in the optimization process, the AUC from the detection tasks and the resolution estimated by the Fourier crosstalk are used as the figure of merits. A trade-off function of AUC and resolution is introduced to find the optimal multi-pinhole configuration. According to the examining results, a 22.5° rotated detector plus a 4-pinhole aperture with 22.5° rotation, 20% multiplexing and 1.52X magnification is the optimized multi-pinhole configuration for the micro pinhole-SPECT applied to mouse cardiac imaging with a camera of 49  ×  49 mm(2) active area.