Optical transitions between Landau levels: AA-stacked bilayer graphene

The low-frequency optical excitations of AA-stacked bilayer graphene are investigated by the tight-binding model. Two groups of asymmetric LLs lead to two kinds of absorption peaks resulting from only intragroup excitations. Each absorption peak obeys a single selection rule similar to that of monolayer graphene. The excitation channel of each peak is changed as the field strength approaches a critical strength. This alteration of the excitation channel is strongly related to the setting of the Fermi level. The peculiar optical properties can be attributed to the characteristics of the LL wave functions of the two LL groups. A detailed comparison of optical properties between AA-stacked and AB-stacked bilayer graphenes is also offered. The compared results demonstrate that the optical properties are strongly dominated by the stacking symmetry. Furthermore, the presented results may be used to discriminate AABG from MG, which can be hardly done by STM

Resource request dispatch in standalone and federated MEC systems: a matching game approach

This paper has been presented at : IEEE Wireless Communications and Networking Conference. 15-19 April 2019 Marrakech, MoroccoMulti-access edge computing (MEC) system con-sisting of geographically-distributed heterogeneous servers can provide low-latency virtualized resource to support computation offloading of smart devices. When bulk offloading requests comes to an MEC system, how to dispatch requests to servers so as to maximize divergent objectives of MEC service providers and users is challenging. The problem further involves money transfer when different MEC service providers can share resource to each other. In this paper, we address request dispatch issues in a standalone MEC and among federated MEC systems using matching game theory. We have adapted several classical matching algorithms to our problem. Simulation results show that we can serve more requests while still meeting latency constraints. For federated MEC systems, we can also have high revenue.This work was partially supported by the Ministry of Science and Technology, Taiwan, under grant numbers 106-2221-E-009-004 and by the H2020 collaborative Europe/Taiwan research project 5G-CORAL (grant number 761586)

Clinical Features of Ehlers-Danlos Syndrome

Background/PurposeEhlers-Danlos syndrome (EDS) is a clinically and genetically heterogeneous connective tissue disorder characterized by hyperextensibility of the skin, hypermobility of joints, and tissue fragility. This retrospective study analyzed the characteristics of patients with EDS.MethodsReview of medical records identified 16 cases of EDS during the study period from November 1997 to October 2002. Data on these patients, including clinical presentation, physical examinations, Beighton score, echocardiogram, bone mineral density findings and clinical classification, were analyzed.ResultsThe age of the patients ranged from 13 months to 36 years. All patients had skin hyperextensibility, joint hypermobility (Beighton score > 5 points), and tissue fragility. Complete bone mineral density study was performed in 11 patients and revealed that all had osteoporosis. Echocardiographic study was performed in 14 patients and showed aortic root dilatation/valve prolapse in 6/14 (43%). Other common features of EDS had the following prevalence: premature rupture of membranes in 3/16 (19%); prematurity in 3/16 (19%); neonatal hypotonia in 5/16 (31%); congenital hip dislocation in 3/16 (19%); unstable gait in 7/16 (44%); bone fracture(s) in 3/16 (19%); motor delay in 3/16 (19%); scoliosis in 3/16 (19%); short stature in 7/16 (44%); and positive family history in 8/16 (50%). All patients had a Beighton score of more than 5 points.ConclusionThe results of this study emphasize the importance of echocardiographic monitoring of aortic size and valvular condition, and assessment of bone mineral density in patients with EDS. Clinical evaluation and counseling should be undertaken prior to pregnancy in patients with EDS because of the risk from labor and vaginal delivery in patients with type IV and the inability to distinguish EDS subtypes in Taiwan due to the unavailability of biochemical assay or molecular mutation analysis as part of standard care