Autonomous flying WiFi access point

Unmanned aerial vehicles (UAVs), aka drones, are widely used civil and commercial applications. A promising one is to use the drones as relying nodes to extend the wireless coverage. However, existing solutions only focus on deploying them to predefined locations. After that, they either remain stationary or only move in predefined trajectories throughout the whole deployment. In the open outdoor scenarios such as search and rescue or large music events, etc., users can move and cluster dynamically. As a result, network demand will change constantly over time and hence will require the drones to adapt dynamically. In this paper, we present a proof of concept implementation of an UAV access point (AP) which can dynamically reposition itself depends on the users movement on the ground. Our solution is to continuously keeping track of the received signal strength from the user devices for estimating the distance between users devices and the drone, followed by trilateration to localise them. This process is challenging because our on-site measurements show that the heterogeneity of user devices means that change of their signal strengths reacts very differently to the change of distance to the drone AP. Our initial results demonstrate that our drone is able to effectively localise users and autonomously moving to a position closer to them

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Multi-messenger Observations of a Binary Neutron Star Merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ∼ 1.7 {{s}} with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of {40}-8+8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 {M}ȯ . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ∼ 40 {{Mpc}}) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ∼ 9 and ∼ 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.</p

The Occurrence of Primary Hepatic Adenoma in Deceased Donor Renal Transplant Recipient

Main findings: We reported a case of new-onset, multi-focal hepatic adenoma in an 18 year-old man with no classic risk factors occurring forty months after a renal transplant from a cadaver donor. Histopathology of the adenoma was examined and genotype and phenotype were also analyzed. Histopathologic examination of the adenoma showed no malignancy. Genotype and phenotype analysis revealed no HNIF 1 alpha or beta-catenin gene mutations and no inflammatory infiltration. The patient was well and disease-free postoperatively. Case hypothesis: Hepatic adenoma occurs mostly in those taking oral contraceptives or androgenic-anabolic steroids or in those with hereditary diseases. Hepatic adenoma in a renal transplant recipient is rare and has only been reported in one case with glycogen storage disease type Ia. Immunosuppressive treatment might have contributed to the development of the neoplasm. Promising future implications: Although malignant change occurs most often in beta-catenin gene mutation hepatic adenoma, surgical resection of the adenoma in a patient under immunosuppressive therapy should be considered in order to avoid the possibility of malignant transformation or hemorrhagic rupture

Learning Curve of Single-Port Laparoscopic Appendectomy for Noncomplicated Acute Appendicitis: A Preliminary Analysis Compared with Conventional Laparoscopic Appendectomy

Background: The aim of this study was to delineate the learning curve of single-port laparoscopic appendectomy for noncomplicated appendicitis. Patients and Methods: Thirty patients who underwent single-port laparoscopic appendectomy between July 2009 and June 2010 were compared retrospectively with 30 prior consecutive patients who underwent surgery in the three-port manner. Operative duration, number of conversions, time to resumption of oral intake, length of hospital stay, and complications were used as the indicators of the learning curve. Results: Demographics were similar between the single-port and three-port groups. A significant decrease in operative duration was noted after a surgical experience of 10 patients. An operative duration equivalent to that of the conventional three-port method could be achieved after 30 cases. Conclusions: Single-port laparoscopic appendectomy is a safe and feasible procedure. The learning curve could be overcome safely without major complications. Our preliminary analysis showed that 30 cases are sufficient to achieve an equivalent operative duration compared with conventional three-port laparoscopic appendectomy

Laparoscopic Resection for Submucosal Tumors Near the Esophagogastric Junction: Feasibility and Short-term Outcome

Background. Minimally invasive surgery has proved to be effective and efficient in the management of gastric submucosal tumors (SMT). However, confronting a SMT near the esophagogastric junction (EGJ) is still challenging because of the potentially devastating risks of stenosis or leakage. This study evaluated the safety, feasibility, and oncological efficacy of laparoscopic resection for SMTs located near the EGJ. Methods. From December 2008 to November 2011, we enrolled a total of 19 patients diagnosed with gastric SMTs located near the EGJ who underwent laparoscopic surgery. The clinicopathological characteristics and surgical outcomes of the 19 patients were recorded and reviewed retrospectively. Results. All 19 patients underwent laparoscopic resections of their gastric SMTs without complications during the study period. There were 9 men and 10 women, with a mean age of 63.3 +/- 15.1 years (range 33-86 years). The operative duration was 187.8 +/- 58.9 minutes (range 90-310 minutes). Intraoperative localization included endoscopy (n = 3), tattooing (n = 2), and combined modalities (n = 1). The exogastric (n = 12) and transgastric methods (n = 7) were used. The histopathology showed 10 gastrointestinal stromal tumors, 7 leiomyomas, 1 hyperplastic polyp, and 1 lipoma. The postoperative courses for all cases were uneventful. The mean follow-up period was 16.7 +/- 9.4 months, with no recurrence noted. Conclusions: Laparoscopic resections for gastric SMTs near the EGJ are safe and feasible, with satisfactory oncological outcomes in the short term

Healable and Foldable Carbon Nanotube/Wax Conductive Composite

In this study, a composite material with healable and foldable features is formulated to print conductive patterns on rough surfaces, such as paper, cloth, and three-dimensional (3D) printed objects. Carbon nanotubes (CNTs) are mixed with wax to formulate a solid composite for pen writing. The composite has a low percolation threshold of 2.5 wt % CNTs and can be written on various rough substrates, such as paper and cloth, to create conductive patterns for electronic conductors. Because of the strong infrared (IR) absorption of CNTs, the printed patterns can be selectively sintered by noncontact IR radiation efficiently to show great electrical conductivity. The electrical resistance of the written patterns on paper also show an insignificant increase after bending, folding, and crumpling. Furthermore, the conductive composite exhibits great healability after destructive damages. The conductivity of the damaged patterns after severe folding or knife cutting recovers to its original value with thermal or IR heating. Several examples, such as conductive tracks on paper, cloth, or 3D printed objects, are also demonstrated to show the potential of this healable conductive composite for electronic applications

The Occurrence of Primary Hepatic Adenoma in Deceased Donor Renal Transplant Recipient

Main findings: We reported a case of new-onset, multi-focal hepatic adenoma in an 18 year-old man with no classic risk factors occurring forty months after a renal transplant from a cadaver donor. Histopathology of the adenoma was examined and genotype and phenotype were also analyzed. Histopathologic examination of the adenoma showed no malignancy. Genotype and phenotype analysis revealed no HNF1&#945; or &#946;-catenin gene mutations and no inflammatory infiltration. The patient was well and disease-free postoperatively. Case hypothesis: Hepatic adenoma occurs mostly in those taking oral contraceptives or androgenic-anabolic steroids or in those with hereditary diseases. Hepatic adenoma in a renal transplant recipient is rare and has only been reported in one case with glycogen storage disease type Ia. Immunosuppressive treatment might have contributed to the development of the neoplasm. Promising future implications: Although malignant change occurs most often in &#946;-catenin gene mutation hepatic adenoma, surgical resection of the adenoma in a patient under immunosuppressive therapy should be considered in order to avoid the possibility of malignant transformation or hemorrhagic rupture

Multi-agent reinforcement learning based 3D trajectory design in aerial-terrestrial wireless caching networks

This paper investigates a dynamic 3D trajectory design of multiple cache-enabled unmanned aerial vehicles (UAVs) in a wireless device-to-device (D2D) caching network with the goal of maximizing the long-term network throughput. By storing popular content at the nearby mobile user devices, D2D caching is an efficient method to improve network throughput and alleviate backhaul burden. With the attractive features of high mobility and flexible deployment, UAVs have recently attracted significant attention as cache-enabled flying base stations. The use of cache-enabled UAVs opens up the possibility of tracking the mobility pattern of the corresponding users and serving them under limited cache storage capacity. However, it is challenging to determine the optimal UAV trajectory due to the dynamic environment with frequently changing network topology and the coexistence of aerial and terrestrial caching nodes. In response, we propose a novel multi-agent reinforcement learning based framework to determine the optimal 3D trajectory of each UAV in a distributed manner without a central coordinator. In the proposed method, multiple UAVs can cooperatively make flight decisions by sharing the gained experiences within a certain proximity to each other. Simulation results reveal that our algorithm outperforms the traditional single- and multi-agent Q-learning algorithms. This work confirms the feasibility and effectiveness of cache-enabled UAVs which serve as an important complement to terrestrial D2D caching nodes