We study steady state transport through a double quantum dot array using the equation-of-motion approach to the nonequilibrium Green functions formalism. This popular technique relies on uncontrolled ...approximations to obtain a closure for a hierarchy of equations; however, its accuracy is questioned. We focus on 4 different closures, 2 of which were previously proposed in the context of the single quantum dot system (Anderson impurity model) and were extended to the double quantum dot array, and develop 2 new closures. Results for the differential conductance are compared to those attained by a master equation approach known to be accurate for weak system-leads couplings and high temperatures. While all 4 closures provide an accurate description of the Coulomb blockade and other transport properties in the single quantum dot case, they differ in the case of the double quantum dot array, where only one of the developed closures provides satisfactory results. This is rationalized by comparing the poles of the Green functions to the exact many-particle energy differences for the isolate system. Our analysis provides means to extend the equation-of-motion technique to more elaborate models of large bridge systems with strong electronic interactions.
The dynamics of correlated electrons in quantum impurity models is typically described within the nonequilibrium Green function formalism combined with a suitable approximation. One common approach ...is based on the equation-of-motion technique often used to describe different regimes of the dynamic response. Here, we show that this approach may violate certain symmetry relations that must be fulfilled by the definition of the Green functions. These broken symmetries can lead to unphysical behaviour. To circumvent this pathological shortcoming of the equation-of-motion approach we provide a scheme to restore basic symmetry relations. Illustrations are given for the Anderson and double Anderson impurity models.
Objectives
The dental field is gradually reducing the use of amalgam and moving towards adhesive restoration. This change is in accordance with the advancement and improvement of composite resin ...materials and adhesion systems. Consequently, posterior cavity preparations teaching should be re‐examined to determine whether dental schools are adapting their curriculum to fit the current trends in dentistry and what rationale supports their decisions.
Methods
An online questionnaire was constructed to assess the time dedicated to teaching composite materials and amalgam, in addition to the principles of posterior preparations, for composite restorations in North American dental schools.
Results
A total 33 schools responded to the questionnaire. A large variation was found in teaching methods and techniques of posterior restorations. The reasoning for teaching amalgam restorations was diverse as were the principles of composite resin preparation taught.
Conclusion
No agreed principles of cavity preparation for resin composite restorations were found, as opposed to explicit agreement on amalgam cavity preparations. The results demonstrate a lack of clear guidelines for cavity preparation of resin composite restorations. Dental schools may benefit when a consensus on this topic is achieved.
Energetic stress compels cells to evolve adaptive mechanisms to adjust their metabolism. Inhibition of mTOR kinase complex 1 (mTORC1) is essential for cell survival during glucose starvation. How ...mTORC1 controls cell viability during glucose starvation is not well understood. Here we show that the mTORC1 effectors eukaryotic initiation factor 4E binding proteins 1/2 (4EBP1/2) confer protection to mammalian cells and budding yeast under glucose starvation. Mechanistically, 4EBP1/2 promote NADPH homeostasis by preventing NADPH-consuming fatty acid synthesis via translational repression of Acetyl-CoA Carboxylase 1 (ACC1), thereby mitigating oxidative stress. This has important relevance for cancer, as oncogene-transformed cells and glioma cells exploit the 4EBP1/2 regulation of ACC1 expression and redox balance to combat energetic stress, thereby supporting transformation and tumorigenicity in vitro and in vivo. Clinically, high EIF4EBP1 expression is associated with poor outcomes in several cancer types. Our data reveal that the mTORC1-4EBP1/2 axis provokes a metabolic switch essential for survival during glucose starvation which is exploited by transformed and tumor cells.
Office‐based surgery (OBS) has emerged as a significant subspecialty of ambulatory surgery. There are few clinical trials and limited published data on patient characteristics, anesthesia, or ...outcomes distinguishing OBS from ambulatory surgery centers (ASCs). We examined retrospective data from a large mobile anesthesia practice for 89,999 procedures from 2016 to 2019. Data was ed from billing and an anesthesia‐specific electronic medical record, segregating procedures performed in ASCs versus OBS. The number and breadth of procedures increased substantially. Compared to ASCs, OBS patients were more likely male (52% vs. 48%), older (61 years vs. 55 years), and to have a higher American Society of Anesthesiologists (ASAs) status (33% vs. 20% ASA 3 or higher). The procedure mix varied substantially between the two settings. The major complication rate was 0.07% for the ASCs and 0.24% for OBS (p = 0.2, confidence interval CI −0.15 to 0.04). Minor complications were 11.2% in OBS versus 17.3% the ASCs (p < 0.0001, 95% CI 5.2–7). The practice demonstrates a low rate of complications, and despite the limitations of this study, the organization and structure of this large mobile anesthesia practice serves as a template for effective risk mitigation and patient safety.
Abstract There is little data on suicide among elderly depressed patients seeking psychiatric help. Recent studies have demonstrated that physical illness may increase this risk. We aimed to assess, ...retrospectively, the association between suicide and physical illness among depressed elderly psychiatric patients. All medical records of patients admitted during a 10-year period to an acute psychiatric ward, after having attempted suicide, were reviewed. Inclusion criteria were: age > 65 years, diagnosis of a depressive disorder and intact cognition. The comparison group consisted of previous or subsequent admissions, closest (by date), of elderly patients, matching the inclusion criteria, but without previous record of attempting suicide, into the same ward. The cumulative illness rating scale (CIRS) score was calculated for each patient. 78 admissions of elderly depressed patients, who had attempted suicide before hospitalization, were examined. The comparison group ( n = 87) consisted of the subsequent admission of a similar but not suicidal pre-admission patient. The CIRS total score was significantly higher among suicidal patients (10.2 vs. 8.0; p = 0.0008). Suicidal patients scored higher in the vascular and the respiratory sections of CIRS. Our results support reported findings of higher rates of illness among suicidal elderly patients. The CIRS may be considered an additional tool in assessing risk for suicide in elderly psychiatric subjects.
Lattice spin models are useful for studying critical phenomena and allow the extraction of equilibrium and dynamical properties. Simulations of such systems are usually based on Monte Carlo (MC) ...techniques, and the main difficulty is often the large computational effort needed when approaching critical points. In this work, it is shown how such simulations can be accelerated with the use of NVIDIA graphics processing units (GPUs) using the CUDA programming architecture. We have developed two different algorithms for lattice spin models, the first useful for equilibrium properties near a second-order phase transition point and the second for dynamical slowing down near a glass transition. The algorithms are based on parallel MC techniques, and speedups from 70- to 150-fold over conventional single-threaded computer codes are obtained using consumer-grade hardware.
This paper proposes a new methodology for solving the well-known rank aggregation problem from pairwise comparisons using low-rank matrix completion. Partial and noisy data of pairwise comparisons is ...first transformed into a matrix form. We then use tools from matrix completion, which has served as a major component in the low-rank based completion solution for the Netflix challenge, to construct the preference of different objects. In our approach, the data from multiple comparisons is used to create an estimate of the probability of object i winning (or be chosen) over object j, where only a partial set of comparisons between the N objects is known. These probabilities can be transformed to take the form of a rank-one matrix. An alternating minimization algorithm, in which the target matrix takes a bilinear form, is used in combination with maximum likelihood estimation for both factors. The reconstructed matrix is used to obtain the true underlying preference intensity. We start by exploring the asymptotic case of an infinitely large number of comparisons (“noiseless case”). We then extend our solution to the case of a finite number of comparisons for a subset of pairs (“noisy case”). This work demonstrates the improvement of our proposed algorithm over the state-of-the-art techniques in both simulated scenarios and real data.
Brillouin microscopy (BM) is an emerging technique for all‐optical mechanical imaging without the need for physical contact with the sample or for an external mechanical stimulus. However, BM often ...retrieves a single Brillouin frequency shift for multiple mechanically different materials of structures and/or in regions—sufficiently larger than the phonon wavelength—inside the volume and its surroundings, resulting in significantly limited mechanical specificity in the Brillouin shift images produced. Here, a new physics‐driven model selection framework is developed based on information theory and a physical‐statistical overfit Brillouin water peak threshold that enables the robust identification of single‐ and multi‐peak Brillouin signatures in the sample pixels. The model selection framework is applied to Brillouin data of material interfaces and living NIH/3T3 cells measured by stimulated Brillouin scattering (SBS) microscopy, facilitating the quantification of the Brillouin frequency shift of materials in different regions of the sample and significantly improving mechanical specificity compared with the standard single peak fitting analysis.
A physics‐driven model selection scheme for improving the analysis of Brillouin microscopy images is proposed. The scheme is based on information theory and a physical‐statistical overfit Brillouin water peak threshold. The new analysis strategy together with the multi‐parameter contrast of stimulated Brillouin microscopy open new possibilities for an improved, more quantitative, mechanically‐specific analysis of Brillouin imaging data of materials and biological systems.
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