Buuskoch8145

We propose new symplectic networks (SympNets) for identifying Hamiltonian systems from data based on a composition of linear, activation and gradient modules. In particular, we define two classes of SympNets the LA-SympNets composed of linear and activation modules, and the G-SympNets composed of gradient modules. Correspondingly, we prove two new universal approximation theorems that demonstrate that SympNets can approximate arbitrary symplectic maps based on appropriate activation functions. We then perform several experiments including the pendulum, double pendulum and three-body problems to investigate the expressivity and the generalization ability of SympNets. The simulation results show that even very small size SympNets can generalize well, and are able to handle both separable and non-separable Hamiltonian systems with data points resulting from short or long time steps. In all the test cases, SympNets outperform the baseline models, and are much faster in training and prediction. We also develop an extended version of SympNets to learn the dynamics from irregularly sampled data. This extended version of SympNets can be thought of as a universal model representing the solution to an arbitrary Hamiltonian system.The structure of the brain network exhibits modularity at multiple spatial scales. The effect of the modular structure on the brain dynamics has been the focus of several studies in recent years but many aspects remain to be explored. For example, it is not well-known how the delays in the transmission of signals between the neurons and the brain regions interact with the modular structure to determine the brain dynamics. In this paper, we show an important impact of the delays on the collective dynamics of brain networks with modular structure; that is, the degree of the synchrony between different brain regions depends on the oscillating frequency. In particular, we show that when increasing the frequency of the nodes the network transits from a global synchrony state to an asynchronous state, through a transition region over which the local synchrony inside the modules is stronger than the global synchrony. Selleck GA-017 When the delays depend on the distance between the nodes, the modular structure of different spatial scales appears in the correlation matrix over different specific frequency bands, so that, finer spatial modular structures reveal in higher frequency bands. The results are corroborated by a simple theoretical argument and elaborated by simulations on several simplified modular networks and the connectome with different spatial resolutions.Poor bone quality and low bone mineral density (BMD) have been previously tied to higher rates of postoperative mechanical complications in patients undergoing spinal fusion. These include higher rates of proximal junctional kyphosis, screw pullout, pseudoarthrosis, and interbody subsidence. For these reasons, accurate preoperative assessment of a patient's underlying bone quality is paramount for all elective procedures. Dual-energy X-ray absorptiometry (DXA) is currently considered to be the gold standard for assessing BMD. However, a growing body of research has suggested that in vivo assessments of BMD using DXA are inaccurate and have, at best, moderate correlations to postoperative mechanical complications. Consequently, there have been investigations into using alternative methods for assessing in vivo bone quality, including using computed tomography (CT) and magnetic resonance imaging (MRI) volumes that are commonly obtained as part of surgical evaluation. Here we review the data regarding the accuracy of DXA for the evaluation of spine bone quality and describe the alternative imaging modalities currently under investigation.

Spinal fusion surgeries are one of the most common types of operations performed during inpatient stays in the United States. Successful wound closure, including watertight closure at the skin layer, plays in important role in patient outcomes.

To compare the economic and clinical outcomes of spinal fusion surgeries using one of two sutureless skin closure techniques skin staples plus waterproof wound dressings (SSWWD) or 2-octyl cyanoacrylate plus polymer mesh tape (2OPMT).

Retrospective study using a multi-hospital database.

Patients undergoing inpatient spinal fusion surgery for a spine disorder between October 1, 2015 and March 31, 2019.

Total costs from the hospital perspective, operating room time (ORT), hospital length of stay (LOS), non-home discharge, infection/wound complications during the 90-day global period (index surgery through 90 days post-discharge), and 30/60/90-day all-cause readmissions.

Outcomes were compared between study groups using nearest neighbor propensity score matchinificant (p>0.05).

In this retrospective observational study of patients undergoing elective inpatient spinal fusion surgery, the use of 2OPMT for skin closure was associated with significantly lower ORT, LOS, non-home discharge, and 90-day rates of infections/wound complications as compared with SSWWD.

In this retrospective observational study of patients undergoing elective inpatient spinal fusion surgery, the use of 2OPMT for skin closure was associated with significantly lower ORT, LOS, non-home discharge, and 90-day rates of infections/wound complications as compared with SSWWD.

Expandable cages (EXP) are being more frequently utilized in transforaminal lumbar interbody fusions (TLIF). EXP were designed to reduce complications related to neurological retraction, enable better lordosis restoration, and improve ease of insertion, particularly in the advent of minimally invasive surgical (MIS) techniques, however they are exponentially more expensive than the nonexpandable (NE) alternative.

To investigate the clinical results of expandable cages in single level TLIF.

Retrospective review at a single institution.

Two hundred and fifty-two single level TLIFs from 2012 to 2018 were included.

Clinical characteristics, perioperative and neurologic complication rates, and radiographic measures.

Patients ≥18 years of age who underwent single level TLIF with minimum 1 year follow-up were included.

clinical characteristics, perioperative and neurologic complications. Radiographic analysis included pelvic incidence-lumbar lordosis (PI-LL) mismatch, segmental lumbar lordosis (LL) mismatch, disc height restoration, and subsidence ≥2 mm.