Cooperative Multi-Bitrate Video Caching and Transcoding in Multicarrier NOMA-Assisted Heterogeneous Virtualized MEC Networks

Cooperative video caching and transcoding in mobile edge computing (MEC) networks is a new paradigm for future wireless networks, e.g., 5G and 5G beyond, to reduce scarce and expensive backhaul resource usage by prefetching video files within radio access networks (RANs). Integration of this technique with other advent technologies, such as wireless network virtualization and multicarrier non-orthogonal multiple access (MC-NOMA), provides more flexible video delivery opportunities, which leads to enhancements both for the network's revenue and for the end-users' service experience. In this regard, we propose a two-phase RAF for a parallel cooperative joint multi-bitrate video caching and transcoding in heterogeneous virtualized MEC networks. In the cache placement phase, we propose novel proactive delivery-aware cache placement strategies (DACPSs) by jointly allocating physical and radio resources based on network stochastic information to exploit flexible delivery opportunities. Then, for the delivery phase, we propose a delivery policy based on the user requests and network channel conditions. The optimization problems corresponding to both phases aim to maximize the total revenue of network slices, i.e., virtual networks. Both problems are non-convex and suffer from high-computational complexities. For each phase, we show how the problem can be solved efficiently. We also propose a low-complexity RAF in which the complexity of the delivery algorithm is significantly reduced. A Delivery-aware cache refreshment strategy (DACRS) in the delivery phase is also proposed to tackle the dynamically changes of network stochastic information. Extensive numerical assessments demonstrate a performance improvement of up to 30% for our proposed DACPSs and DACRS over traditional approaches.Comment: 53 pages, 24 figure

Dry Eye Syndrome

Our understanding of keratoconjunctivitis sicca (KCS), also known as dry eye syndrome, has been changed over recent years. Until lately, the condition was thought to be merely due to aqueous tear insufficiency. Today, it is understood that KCS is a multifactorial disorder due to inflammation of the ocular surface and lacrimal gland, neurotrophic deficiency and meibomian gland dysfunction. This change in paradigm has led to the development of new and more effective medications

Current Approaches for Management of Postpenetrating Keratoplasty Astigmatism

A successful corneal graft requires both clarity and an acceptable refraction. A clear corneal graft may be an optical failure if high astigmatism limits visual acuity. Intraoperative measures to reduce postkeratoplasty astigmatism include round and central trephination of cornea with an adequate size, appropriate sutures with evenly distributed tension, and perfect graft-host apposition. Suture manipulation has been described for minimising early postoperative astigmatism. If significant astigmatism remains after suture removal, which cannot be corrected by optical means, then further surgical procedures containing relaxing incisions, compression sutures, laser refractive surgery, insertion of intrastromal corneal ring segments, wedge resection, and toric intraocular lens implantation can be performed. When astigmatism cannot be reduced using one or more abovementioned approaches, repeat penetrating keratoplasty should inevitably be considered. However, none of these techniques has emerged as an ideal one, and corneal surgeons may require combining two or more approaches to exploit the maximum advantages

The Effect of Mitomycin-C on Corneal Endothelial Cells after Photorefractive Keratectomy

Purpose: To evaluate short-term changes in central corneal endothelial cell density and morphology after photorefractive keratectomy (PRK) with mitomycin-C (MMC) 0.02% in patients with moderate myopia. Methods: In this prospective interventional case series, patients with moderate myopia (spherical equivalent refractive error from ‑4.0 to ‑8.0 D) underwent PRK with a single intraoperative application of MMC 0.02% for 40 seconds. Specular microscopy was performed preoperatively and repeated 6 months after surgery to determine changes in central corneal endothelial cell density (ECD), mean cell area (MCA) and coefficient of variation in cell size (CV). Results: Overall, 42 eyes of 21 participants with mean age of 26.2±6.3 years underwent surgery. Mean preoperative spherical equivalent refractive error was ‑5.2}1.2 D which was reduced to ‑0.4}0.5 D postoperatively (P < 0.001). Mean ECD was reduced insignificantly from 2,920±363 cells/mm2 preoperatively to 2,802±339 cells/mm2 postoperatively (P = 0.59). Similarly, there was no significant change in MCA or CV at six months (P = 0.76 and 0.52, respectively). Conclusion: Application of MMC 0.02% for 40 seconds during PRK in patients with moderate myopia did not significantly affect central corneal endothelial cell density and morphology after a 6 month follow up period

The influence of mesiodistal dimension of abutment preparation design on stress distribution in fiber-reinforced composite inlay fixed partial dentures: a finite element study

Introduction: Fiber-reinforced composites (FRCs) arecomprised of fiber and composite resin. Use of this materialin conservative dentistry for fabricating fixed partialdentures is growing. Although different studies have investigatedFRC inlay fixed partial dentures, the reportedresults have been controversial. Due to the limitations ofexperimental studies for assessment of masticatory forcesin the oral cavity, computer software was used in thepresent study to simulate oral environment. The aim ofthis study was to compare stress distribution in FRC inlaybridges with two abutment preparation designs with differentmesiodistal (MD) dimensions using a 3-dimensionalfinite element analysis.Method: ABAQUS software version 6.3-1 (HKS Inc.) wasused to create a 3D design. Two 3-unit inlay bridges weredesigned with two different abutment preparations inthe anterior teeth with different MD dimensions: dovetailpreparation with larger MD dimension and box preparationwith smaller MD dimension. Next, 50 N load was appliedwithin one second to the cingulum.Results: The maximum stress in the two bridges was concentratedat the connector areas between the abutmentsand the pontic. The difference in this respect was statisticallysignificant. The stress was approximately 10 timeshigher in the box preparation with smaller MD dimensionthan dovetail preparation.Conclusion: The stress distribution was more uniform indovetail preparation with greater mesiodistal dimensionthan in the smaller box design