Spatial Performance Analysis and Design Principles for Wireless Peer Discovery

In wireless peer-to-peer networks that serve various proximity-based applications, peer discovery is the key to identifying other peers with which a peer can communicate and an understanding of its performance is fundamental to the design of an efficient discovery operation. This paper analyzes the performance of wireless peer discovery through comprehensively considering the wireless channel, spatial distribution of peers, and discovery operation parameters. The average numbers of successfully discovered peers are expressed in closed forms for two widely used channel models, i.e., the interference limited Nakagami-m fading model and the Rayleigh fading model with nonzero noise, when peers are spatially distributed according to a homogeneous Poisson point process. These insightful expressions lead to the design principles for the key operation parameters including the transmission probability, required amount of wireless resources, level of modulation and coding scheme (MCS), and transmit power. Furthermore, the impact of shadowing on the spatial performance and suggested design principles is evaluated using mathematical analysis and simulations.Comment: 12 pages (double columns), 10 figures, 1 table, to appear in the IEEE Transactions on Wireless Communication

Application of Copula-Based Markov Model to Generate Monthly Precipitation

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Safety and feasibility of hybrid tracheostomy

Background Percutaneous dilatational tracheostomy (PDT) is widely used in intensive care units, but this conventional method has some disadvantages, such as requirement of a lot of equipment and experts at the site. Especially, in situations where the patient is isolated due to an infectious disease, difficulties in using the equipment may occur, and the number of exposed persons may increase. In this paper, we introduce hybrid tracheostomy that combines the advantages of surgical tracheostomy and PDT and describe our experiences. Methods Data from 55 patients who received hybrid tracheostomy without bronchoscopy from January 2020 to February 2021 were collected and reviewed retrospectively. Hybrid tracheostomy was performed at the bedside by a single thoracic surgeon. The hybrid tracheostomy method was as follows: after the skin was incised and the trachea was exposed, only the extent of the endotracheal tube that could not be removed was withdrawn, and then tracheostomy was performed by the Seldinger method using a PDT kit. Results The average age was 66.5 years, and the proportion of men was 69.1%. Among the patients, 21.8% were taking antiplatelet drugs and 14.5% were taking anticoagulants. The average duration of the procedure was 13.3 minutes. There was no major bleeding, and there was one case of paratracheal placement of the tracheostomy tube. Conclusions In most patients, the procedure can be safely performed without any major complications. However, patients with a short neck, a neck burn or patients who have received radiation therapy to the neck should be treated with conventional methods

Correlation of photoluminescent quantum efficiency and device characteristics for the soluble electrophosphorescent light emitter with interfacial layers

We have investigated the effects of interfacial layers on the properties of soluble phosphorescent organic light emitting devices. Two kinds of polyfluorene-based interfacial layer materials have been studied; both were spin coated on top of PEDOT:PSS to form the insoluble layers by thermal annealing. The molecular-doped, phosphorescent light emitting layer comprising a polymeric host, small molecular host, and guest molecule was fabricated onto the thin interfacial layer. The photoluminescence quantum yield (PLQY) of these layers was measured with an integrating sphere. We have calculated the PLQY values of the single phosphorescent light emitting layer and various organic multilayers incorporating the interfacial layers, showing that a reduction in PLQY due to the interfacial quenching is more significant in the thicker interfacial layer structures. In spite of the decrease in PLQY induced by the triplet energy mismatch, polyfluorene-based interfacial layers improved the charge injection from PEDOT:PSS to the emitting layer, which results in the enhanced brightness and current. The triplet quenching by the interfacial layer could explain the reduction in luminous efficiency of the devices compared to the reference. This was also investigated by studying the charge carrier trapping, change in the spectral characteristics induced by the shift in the emission zone, and the analysis on the carrier balance of devices.This research was supported by the Seoul R&BD support program (CR070048) and SystemIC2010 project, Ministry of Knowledge Economy, Korea

Nanovesicles derived from iron oxide nanoparticles-incorporated mesenchymal stem cells for cardiac repair

Because of poor engraftment and safety concerns regarding mesenchymal stem cell (MSC) therapy, MSC-derived exosomes have emerged as an alternative cell-free therapy for myocardial infarction (MI). However, the diffusion of exosomes out of the infarcted heart following injection and the low productivity limit the potential of clinical applications. Here, we developed exosome-mimetic extracellular nanovesicles (NVs) derived from iron oxide nanoparticles (IONPs)-incorporated MSCs (IONP-MSCs). The retention of injected IONP-MSC-derived NVs (IONP-NVs) within the infarcted heart was markedly augmented by magnetic guidance. Furthermore, IONPs significantly increased the levels of therapeutic molecules in IONP-MSCs and IONP-NVs, which can reduce the concern of low exosome productivity. The injection of IONP-NVs into the infarcted heart and magnetic guidance induced an early shift from the inflammation phase to the reparative phase, reduced apoptosis and fibrosis, and enhanced angiogenesis and cardiac function recovery. This approach can enhance the therapeutic potency of an MSC-derived NV therapy.

Implantable cardioverter defibrillator therapy in pediatric and congenital heart disease patients: a single tertiary center experience in Korea

PurposeThe use of implantable cardioverter defibrillators (ICDs) to prevent sudden cardiac death is increasing in children and adolescents. This study investigated the use of ICDs in children with congenital heart disease.MethodsThis retrospective study was conducted on the clinical characteristics and effectiveness of ICD implantation at the department of pediatrics of a single tertiary center between 2007 and 2011.ResultsFifteen patients underwent ICD implantation. Their mean age at the time of implantation was 14.5±5.4 years (range, 2 to 22 years). The follow-up duration was 28.9±20.4 months. The cause of ICD implantation was cardiac arrest in 7, sustained ventricular tachycardia in 6, and syncope in 2 patients. The underlying disorders were as follows: ionic channelopathy in 6 patients (long QT type 3 in 4, catecholaminergic polymorphic ventricular tachycardia [CPVT] in 1, and J wave syndrome in 1), cardiomyopathy in 5 patients, and postoperative congenital heart disease in 4 patients. ICD coils were implanted in the pericardial space in 2 children (ages 2 and 6 years). Five patients received appropriate ICD shock therapy, and 2 patients received inappropriate shocks due to supraventricular tachycardia. During follow-up, 2 patients required lead dysfunction-related revision. One patient with CPVT suffered from an ICD storm that was resolved using sympathetic denervation surgery.ConclusionThe overall ICD outcome was acceptable in most pediatric patients. Early diagnosis and timely ICD implantation are recommended for preventing sudden death in high-risk children and patients with congenital heart disease

Hypoxia-dependent mitochondrial fission regulates endothelial progenitor cell migration, invasion, and tube formation

Tumor undergo uncontrolled, excessive proliferation leads to hypoxic microenvironment. To fulfill their demand for nutrient, and oxygen, tumor angiogenesis is required. Endothelial progenitor cells (EPCs) have been known to the main source of angiogenesis because of their potential to differentiation into endothelial cells. Therefore, understanding the mechanism of EPC-mediated angiogenesis in hypoxia is critical for development of cancer therapy. Recently, mitochondrial dynamics has emerged as a critical mechanism for cellular function and differentiation under hypoxic conditions. However, the role of mitochondrial dynamics in hypoxia-induced angiogenesis remains to be elucidated. In this study, we demonstrated that hypoxia-induced mitochondrial fission accelerates EPCs bioactivities. We first investigated the effect of hypoxia on EPC-mediated angiogenesis. Cell migration, invasion, and tube formation was significantly increased under hypoxic conditions; expression of EPC surface markers was unchanged. And mitochondrial fission was induced by hypoxia time-dependent manner. We found that hypoxia-induced mitochondrial fission was triggered by dynamin-related protein Drp1, specifically, phosphorylated DRP1 at Ser637, a suppression marker for mitochondrial fission, was impaired in hypoxia time-dependent manner. To confirm the role of DRP1 in EPC-mediated angiogenesis, we analyzed cell bioactivities using Mdivi-1, a selective DRP1 inhibitor, and DRP1 siRNA. DRP1 silencing or Mdivi-1 treatment dramatically reduced cell migration, invasion, and tube formation in EPCs, but the expression of EPC surface markers was unchanged. In conclusion, we uncovered a novel role of mitochondrial fission in hypoxia-induced angiogenesis. Therefore, we suggest that specific modulation of DRP1-mediated mitochondrial dynamics may be a potential therapeutic strategy in EPC-mediated tumor angiogenesis