Avoidance Protocol Research Articles

Enhanced Communication in Void Region of Underwater Wireless Sensor Network using Vector-Based Void Avoidance Comparing with Void Aware Pressure Routing Protocol

The aim of the proposed work is to improve the energy efficiency of sensor nodes in underwater wireless sensor networks using Vector-based void avoidance (VBVA) in comparison with void-aware pressure routing (VAPR). The performance of vector-based void avoidance uses the vector shift and backpressure mechanisms compared with the void-aware pressure routing protocol. A total of 34 samples are collected and 17 samples for each group is taken to the data sets. The proposed algorithm is tested in an underwater virtual environment by Aquasim in the NS2 simulator. The throughput, energy consumption, and packet delivery ratio are calculated to evaluate the performance of the proposed VBVA Protocol. The energy efficiency of the proposed vector-based void avoidance protocol is improved by avoids of void nodes and forward data packets. The Throughput mean value is (1.3297), Energy consumption mean value is (0.9960) and Packet delivery ratio mean value is (91.1735) achieved using VBVA protocol. This work has obtained significance (<0.01). The simulation results show that reduction of packet loss and improve the energy efficiency of the sensor network using the proposed VBVA algorithm in comparison with VAPR.

A Collision Avoidance Based Energy Efficient Medium Access Control Protocol for Clustered Underwater Wireless Sensor Networks

Underwater Wireless Sensor Networks (UWSNs) are typically deployed in energy constrained environments where recharging energy sources and replacing batteries are not viable. This makes energy efficiency in UWSNs a crucial directive to be followed during Medium Access Control (MAC) design. Multiplexing and scheduling based protocols are not ideal for UWSNs because of their strict synchronization requirements, longer latencies and constrained bandwidth. This paper presents the development and simulation analysis of a novel cross-layer communication based MAC protocol called Energy Efficient Collision Avoidance (EECA) MAC protocol. EECA-MAC protocol works on the principle of adaptive power control, controlling the transmission power based on the signal strength at the receiver. EECA-MAC enhances the conventional 4-way handshake to reduce carrier sensing by implementing an enhanced Request to Send (RTS) and Clear to Send (CTS) handshake and an improved back-off algorithm. Simulation analysis shows that the measures taken to achieve energy efficiency have a direct effect on the number of packet retransmissions. Compared to the Medium Access with Collision Avoidance (MACA) protocol, EECA-MAC shows a 40% reduction in the number of packets that are delivered after retransmissions. This reduction, coupled with the reduced signal interference, results in a 16% drop in the energy utilized by the nodes for data transmission.

Performance Analysis of Mobile Edge Computing in Resource-Limited CSMA/CA Networks

Mobile Edge Computing (MEC) has proved its great potential for supporting the delay-stringent services in wireless networks. We notice that offloading performance of the MEC system is not only determined by the PHY-layer transmission rate, but also closely related to the performance of channel access and computation at the server. To this end, in this correspondence, we investigate a multiuser MEC system, where each user offloads packet to a single AP equipped with an MEC server by preempting the channel according to carrier sense multiple access with collision avoidance (CSMA/CA) protocol. We derive the effective offloading rate and delay by considering transmission outage caused by the poor channel condition, the MAC-layer channel competition, and the packet overflow due to the limited service capability of the server, where the service process is modelled as an M/M/1/B queue. The theoretical analysis is verified by extensive simulations, which has shown that the competition intensity indicated by the number of users and the packet length, as well as the processing capability of the MECserver including the buffer size and the computation speed, has profound impact on the offloading performance.

Reinforcement Learning-Based Power Control for MACA-Based Underwater MAC Protocol

A major amount of the energy of battery-powered sensors is spent during packet transmissions. This issue has led to the development of power-control-based multiple-access collision avoidance (MACA) protocols that can reduce the packet transmission power and conserve energy. However, the reduction in transmission power renders the packets susceptible to collisions. To reduce these collisions while maintaining high energy efficiency, we propose a power control protocol that utilizes reinforcement learning to choose the optimal transmission power. The total reward is determined by the occurrence of a collision, amount of transmission power used, frequency of DATA packet retransmissions, and update of the interference range. A key feature of the proposed protocol is that it enables sensors to prevent collisions without any prior knowledge of interferences, thus eliminating the need for additional signaling. Further, simulation results reveal that compared with benchmark protocols such as collision avoidance power control media access control (MAC), two-level power control MAC, and MACA-based power control MAC protocols, the proposed protocol improves network throughput while minimizing the network energy consumption and collisions per packet. The efficacy of the proposed protocol is demonstrated through results obtained using varying average traffic loads.

A Randomized Controlled Trial on Safety of Steroid Avoidance in Immunologically Low-Risk Kidney Transplant Recipients

IntroductionSteroid-based immunosuppression after transplantation increases the risk of post-transplant diabetes mellitus (PTDM), with adverse effects on patient and graft survival. In the SAILOR study, we investigated the safety and efficacy of complete steroid avoidance in immunologically low-risk kidney recipients without diabetes on the current standard-of-care maintenance regimen with tacrolimus/mycophenolate mofetil (MMF).MethodsIn this 2-year, multicenter, open-label trial, a total of 222 patients were randomized to receive either steroid avoidance protocol (tacrolimus/MMF/antithymocyte globulin [ATG] induction [n = 113]) or steroid maintenance protocol (tacrolimus/MMF/prednisolone/basiliximab-induction [n = 109]).ResultsAt 1 year, no significant differences were found between steroid avoidance and steroid maintenance arms in the incidence of PTDM, the primary end point (12.4% vs. 18.3%, respectively, P = 0.30, CI: 16.3–4.4), or in overall biopsy-proven rejections (15% vs. 13.8%, respectively, P = 0.85). At 2 years, the composite end point of freedom from acute rejection, graft loss, and death (81% vs. 85%, respectively, P = 0.4), kidney function, or adverse events was comparable between the 2 arms. Moreover, 63.9% of the patients in the steroid avoidance arm remained free from steroids at 2 years.ConclusionThe SAILOR study provides further evidence for the feasibility, safety, and efficacy of early steroid-free treatment at 2 years in immunologically low-risk kidney recipients with tacrolimus/MMF maintenance regimen.

Is Perfusion Dose-Response Different Than Ventilation Dose-Response for Lung Cancer Patients Treated With Radiotherapy?

Ventilation-perfusion dose-response studies have focused on using functional imaging to characterize a dose-response and to assess whether the dose-response can predict subsequent pulmonary toxicity. Current dose-response studies typically focus on a single modality (ventilation or perfusion) and perform assessments on a population-based basis. There is no work evaluating whether ventilation dose-response differs from perfusion dose-response for individual lung cancer patients. The purpose of this study was to use single photon emission computed tomography (SPECT)-CT ventilation-perfusion imaging to quantitatively and clinically evaluate whether lung cancer patients treated with radiotherapy have differences between their ventilation and perfusion dose-responses.Twenty patients with biopsy proven lung cancer enrolled on a prospective functional avoidance protocol underwent SPECT-CT perfusion-ventilation scans pre- and 3-month post-radiotherapy. The SPECT-CT, planning CT, and dose distribution were rigidly registered. We calculated the relative changes in pre- to post-treatment ventilation-perfusion in lung regions receiving ≥ 20 Gy (referred to as ΔPV20 for perfusion and ΔVV20 for ventilation). Differences between perfusion-based ΔPV20 and ventilation-based ΔVV20 were assessed and referred to as ΔfV20. A radiologist read each pre- and post-treatment ventilation-perfusion scans using a semi-quantitative scale that assigned a score ranging from 1 to 8 that reflected functional defect and heterogeneity in each lung. The difference between radiologist scores for the pre- and post-treatment scans was calculated for both ventilation and perfusion. Differences between ventilation-based and perfusion-based radiologist scores were assessed.Twenty-five percent of patients had a difference of ΔfV20 > 35% between ventilation-perfusion pre- to post-treatment changes (ΔVV20 and ΔPV20) and 20% of patients had opposite directions for ventilation-perfusion pre- to post-treatment changes. Radiologist assessment resulted in 20% of patients having different ventilation-perfusion semi-quantitative change scores for ipsilateral lungs.The current work employed quantitative metrics and clinical assessments to evaluate whether ventilation dose-response differs from perfusion dose-response for individual lung cancer patients. Our data showed that ventilation dose-response can differ from perfusion dose-response for 20% to 30% of patients. Our study demonstrates that when evaluating functional dose-response for lung cancer patients, it is insufficient to look at ventilation or perfusion alone for a subset of patients; but rather both modes of functional imaging may be needed when predicting for clinical outcomes.

UNOS/OPTN Data-guided Assessment of Focal Segmental Glomerulosclerosis After Kidney Transplantation and Evaluation of Immunosuppressive Protocols in a Steroid-free Center.

Background.Focal segmental glomerulosclerosis (FSGS) is a common recurrent glomerulopathy associated with graft loss and patient survival after kidney transplantation (KT). However, its natural history, clinical predictors, and treatment response are still poorly understood. Steroid withdrawal regimens in KT have been associated with improvements in cardiovascular risk and patient outcomes. The Scripps Center for Organ Transplantation (SCOT) uses a rapid low-dose steroid withdrawal immunosuppression (IS) protocol for KT maintenance.Methods.We assessed the impact of our protocol on FSGS disease recurrence over a 10-y period to reassess our steroid and IS protocols and to evaluate if our patient outcomes diverge from published data. We compared 4 groups: steroids always, steroid free, steroid switch on, and steroid weaned off. We used IS and induction-matched retrospective data from United Network for Organ Sharing (UNOS) to investigate patient and graft survival for FSGS at SCOT.Results.Our analysis results differ from earlier studies showing that FSGS was associated with a higher risk of graft loss, perhaps because of selection of a UNOS data set filtered to match the SCOT IS protocol for making direct comparisons. Overall outcomes of graft failure and recipient death did not differ between SCOT patients and steroid-free transplant patient data from the UNOS data for FSGS. SCOT recurrence rate for FSGS was 7.5%, which was lower than in most published single-center studies.Conclusions.Based on our results, we believe that it is safe to continue the steroid avoidance protocols at SCOT and the steroid-free protocol may not be detrimental when the adverse effects and toxicities associated with steroid use are considered.

Complication avoidance protocols in endoscopic pituitary adenoma surgery: a retrospective cohort study in 514 patients

PurposeTo evaluate the impact of using consistent complication-avoidance protocols in patients undergoing endoscopic pituitary adenoma surgery including techniques for avoiding anosmia, epistaxis, carotid artery injury, hypopituitarism, cerebrospinal fluid leaks and meningitis.MethodsAll patients undergoing endoscopic adenoma resection from 2010 to 2020 were included. Primary outcomes included 90-day complication rates, gland function outcomes, reoperations, readmissions and length of stay. Secondary outcomes were extent of resection, short-term endocrine remission, vision recovery.ResultsOf 514 patients, (mean age 51 ± 16 years; 78% macroadenomas, 19% prior surgery) major complications occurred in 18(3.5%) patients, most commonly CSF leak (9, 1.7%) and meningitis (4, 0.8%). In 14 of 18 patients, complications were deemed preventable. Four (0.8%) had complications with permanent sequelae (3 before 2016): one unexplained mortality, one stroke, one oculomotor nerve palsy, one oculoparesis. There were no internal carotid artery injuries, permanent visual worsening or permanent anosmia. New hypopituitarism occurred in 23/485(4.7%). Partial or complete hypopituitarism resolution occurred in 102/193(52.8%) patients. Median LOS was 2 days; 98.3% of patients were discharged home. Comparing 18 patients with major complications versus 496 without, median LOS was 7 versus 2 days, respectively p < 0.001. Readmissions occurred in 6%(31/535), mostly for hyponatremia (18/31). Gross total resection was achieved in 214/312(69%) endocrine-inactive adenomas; biochemical remission was achieved in 148/209(71%) endocrine-active adenomas. Visual field or acuity defects improved in 126/138(91.3%) patients.ConclusionThis study suggests that conformance to established protocols for endoscopic pituitary surgery may minimize complications, re-admissions and LOS while enhancing the likelihood of preserving gland function, although there remains opportunity for further improvements.

Modified CSMA/CA protocol for real-time data fusion applications based on clustered WSN

The large amount of data generated by the Internet of Things (IoT) is exploited by the data fusion process to improve the quality of services (QoS) requested by the user. Data fusion systems typically collect and fuse data from various sensor nodes to achieve better data quality (more precision, accuracy, or global view) on the field of interest. For the specific case of the wireless sensor network (WSN) based on cluster-tree topology, the data transmission between nodes and the intermediate data fusion node (DFN) depends primarily on the channel access often managed by the Carrier-Sens Multiple Access with Collision Avoidance (CSMA/CA) protocol. In this article, a modified CSMA/CA is proposed to meet the requirements of the WSN real-time data fusion applications and, in particular, to ensure better management of the transmission channel. It takes into account a transmission time-delay, schedules the retransmission dynamically, and eliminates data packets scheduled beyond the predefined time-delay, thereby releasing the channel to the benefit of other nodes. Moreover, before proceeding with the fusion at the DFN level, it optimizes the probability of receiving data from each node in the specified time-delay. The proposed solution is implemented under the Contiki operating system; it aims to collect data from all nodes within a given time-delay. The results of simulations and experiments show increasing in the data received within time-delay, collisions reduction, and saving energy in the WSN. Moreover, two real-time data fusion applications, namely mobile localization and majority decision-making, are also simulated to support the found results. Compared to the use of CSMA/CA as implemented in Contiki, using the proposed modified CSMA/CA in both data fusion applications improves QoS.

Association of perioperative red blood cell transfusions with all-cause and cancer-specific death in patients undergoing surgery for gastrointestinal cancer.

464 Background: Perioperative anemia and red blood cell (RBC) transfusions are common in patients undergoing gastrointestinal cancer surgery. To adequately balance the risks and benefits of transfusion, clinicians must understand the potential effect of transfusions on long-term outcomes. Methodologic issues have limited previous studies exploring the association between RBC transfusion and survival in this specific patient population. Our objective was to determine, among patients who have undergone gastrointestinal cancer resection, if perioperative RBC transfusions are associated with higher risk of all-cause and cancer-specific death. Methods: In this population-based retrospective cohort study, we used administrative datasets containing routinely collected data from Ontario, Canada. Patients who underwent gastrointestinal cancer resection between January 1, 2007 and March 31, 2019 and survived at least 90 days postoperatively were eligible for inclusion. All-cause death from the ninetieth post-operative day was compared between groups using Kaplan-Meier methods and Cox proportional hazards models. Cancer-specific death was compared using competing risk methods. Regression adjusted for potential confounders. Sensitivity analyses, including the E-value, evaluated the robustness of estimates. Results: We identified 74,962 patients (mean age, 67.7 years; 55.4% male; 79.7% colorectal cancer) who underwent resection for gastrointestinal cancer and survived at least 90 days after surgery. Over a median follow-up of 4.1 years (interquartile range 1.9-5.0 years), patients who received RBC transfusions demonstrated increased hazards of all-cause and cancer-specific death relative to patients who were not transfused (hazard ratio: 1.39, 95% confidence interval 1.34 to 1.44; cause-specific hazards ratio: 1.36, 1.30 to 1.43). The adjusted risk of all-cause death was higher in early follow-up intervals (3-6 months post-operatively) but remained elevated in each subsequent interval over 5 years. Conclusions: RBC transfusion among patients with gastrointestinal cancer is associated with increased all-cause death; this persisted over time suggesting a long-term effect of perioperative transfusion. These findings should help clinicians balance the risks and benefits of transfusion and highlight the need for well-designed, multicenter randomized trials to determine if aggressive transfusion avoidance protocols could improve patient survival after gastrointestinal cancer surgery.

Q-Learning Based Routing Protocol for Congestion Avoidance

Q-Learning Based Routing Protocol for Congestion Avoidance

Deadlock Detection and Cooperative Avoidance Protocol Based on Connected and Autonomous Vehicle Technology

Deadlock Detection and Cooperative Avoidance Protocol Based on Connected and Autonomous Vehicle Technology

Distributed IDA-PBC for a Class of Nonholonomic Mechanical Systems

Nonholonomic mechanical systems encompass a large class of practically interesting robotic structures, such as wheeled mobile robots, space manipulators, and multi-fingered robot hands. However, few results exist on the cooperative control of such systems in a generic, distributed approach. In this work we extend a recently developed distributed Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC) method to such systems. More specifically, relying on port-Hamiltonian system modelling for networks of mechanical systems, we propose a full-state stabilization control law for a class of nonholonomic systems within the framework of distributed IDA-PBC. This enables the cooperative control of heterogeneous, underactuated and nonholonomic systems with a unified control law. This control law primarily relies on the notion of Passive Configuration Decomposition (PCD) and a novel, non-smooth desired potential energy function proposed here. A low-level collision avoidance protocol is also implemented in order to achieve dynamic inter-agent collision avoidance, enhancing the practical relevance of this work. Theoretical results are tested in different simulation scenarios in order to highlight the applicability of the derived method.

The study on risk avoidance of transaction default based on the herding effect

There is a widespread phenomenon of trading goods ordered in advance in the commodity market, and consumers choose to imitate others for security reasons, to form a herd phenomenon of following the trend and following the crowd, this has become an important source of default by commodity booking party in transactions, causing a contingent loss to the producer of the goods. In this paper, the influence of the consumer herding effect is introduced into the characterization of default risk transmission, the herding conduction index is added to the intensity-based model of circular default, it makes the description of default risk more in line with the process of outbreak, aggregation and regression of actual risk. With the help of the credit default swap trading mechanism, the cost model of transaction default risk avoidance protocol is given. The simulation results of the model show that the herding effect has an important impact on the default probability of commodity booking party in transactions, it also makes the cost of default risk avoidance have a corresponding direction of change.

Safety and Efficacy of a Steroid Avoidance Immunosuppression Regimen in Renal Transplant Patients With De Novo or Preformed Donor-Specific Antibodies: A Single-Center Study

Although interest in the role of donor-specific antibodies (DSAs) in kidney transplant rejection, graft survival, and histopathological outcomes is increasing, their impact on steroid avoidance or minimization in renal transplant populations is poorly understood. Primary outcomes of graft survival, rejection, and histopathological findings were assessed in 188 patients who received transplants between 2012 and 2015 at the Scripps Center for Organ Transplantation, which follows a steroid avoidance protocol. Analyses were performed using data from the United Network for Organ Sharing. Cohorts included kidney transplant recipients with de novo DSAs (dnDSAs; n = 27), preformed DSAs (pfDSAs; n = 15), and no DSAs (nDSAs; n = 146). Median time to dnDSA development (classes I and II) was shorter (102 days) than in previous studies. Rejection of any type was associated with DSAs to class I HLA (P < .05) and class II HLA (P < .01) but not with graft loss. Although mean fluorescence intensity (MFI) independently showed no association with rejection, an MFI >5000 showed a trend toward more antibody-mediated rejection (P < .06), though graft loss was not independently associated. Banff chronic allograft nephropathy scores and a modified chronic injury score were increased in the dnDSA cohort at 6 months, but not at 2 years (P < .001 and P < .08, respectively). Our data suggest that dnDSAs and pfDSAs impact short-term rejection rates but do not negatively impact graft survival or histopathological outcomes at 2 years. Periodic protocol post-transplant DSA monitoring may preemptively identify patients who develop dnDSAs who are at a higher risk for rejection.

Creating Collision-Free Communication in IoT with 6G Using Multiple Machine Access Learning Collision Avoidance Protocol

Cloud computing is an important technology to offer consumer appliances a wide pool of elastic resources. The heterogeneous network faces collision while making communication, which reduces the entire network performance. The future cloud-edge networks will deal with a vast amount of clients and servers, such as the Internet of Things (IoT) and the 6G networks, which require flexible solutions. From these points, Multiple Machine Access Learning with Collision Carrier Avoidance (MMALCCA) protocol is proposed in the environment of 6G Internet of Things for creating an effective communication process. This protocol employs the Media Access Control (MAC) protocol for the sync of high-speed wireless communication networks in the Terahertz (THz) band. MMALCCA performs multiple machine access and collision control for improving the resource utilization and latency-less services of the users. The decisions of the protocol are made using the output of the classification and regression learning method for improving the efficiency of MAC sync. The performance of the proposed protocol is verified using the metrics latency, collision probability, service failure, and resource utilization by varying channels and user equipment density.

A Cross-Layer Analysis for Symbiotic Network Using CSMA/CN Protocol

The Internet-of-Things (IoT) paradigm holds the promise to revolutionize the way we live and work through connecting various machine-type communication terminals. In this work, we investigate a symbiotic network from a cross-layer perspective, where passive IoT devices coexist in symbiosis with an ambient network that uses carrier sense multiple access with collision notifications (CSMA/CNs) MAC protocol. In the ambient network, each full-duplex mobile user (MU) aims to transmit its own packets to the common access point (AP) while receiving the signal backscattered from its associated backscatter device (BD). Considering the imperfectness of carrier sensing of the MU, two key parameters, i.e., the probability of detection and the probability of false alarm, are quantified. Then we derive the PHY-layer outage probabilities and analyze the corresponding diversity orders for both the CSMA/CN and the BD system. By incorporating the outage probabilities and the carrier sensing metrics into the MAC-layer analysis, the cross-layer outage capacities of the CSMA/CN and the BD system are derived. Simulation results demonstrate that the system performance can be improved by appropriately setting the PHY-layer parameters, such as the BD reflection coefficient α and the number of samples for carrier sensing K, as well as the MAC-layer parameters, such as the sensing duration and the initial contention window. With the BD reflection coefficient being 0.05, the outage capacity of the overall system has improved by 41.85% compared with carrier sense multiple access with collision avoidance protocol.

Mitigating message dissemination issues in safety applications for vehicular ad hoc networks

SummaryIn a vehicular ad hoc network (VANET) each node is required to transmit periodic and event‐driven messages. The periodic messages are also known as beacons and consist of the basic vehicle status, such as position, speed, direction, and any additional information required by a safety application. One of the main concerns faced with this technology is channel congestion, which often happens in scenarios with a high vehicular density like traffic jams. When the channel is congested, there are no guarantees for a reliable message delivery. For this purpose, several protocols have been proposed to resolve this issue. In this work we propose neighbor congestion avoidance protocol (NCAP) as a novel solution employing a proactive strategy with vehicle position prediction using Kalman filter and an efficient event‐driven message delivery scheme. When compared with other strategies in congested scenarios, NCAP was able to significantly decrease the number of beacons by 49%, while also reducing the number of event‐driven message retransmissions by approximately 81%. NCAP also presented better performance in regard to the number of collisions between messages and channel busy ratio.

Results of using the infection avoidance Protocol for postoperative wounds in spinal surgery

Background. We developed a Protocol based on the results of a previous study of risk factors for infection of a postoperative wound: do not use monopolar coagulation on the skin and subcutaneous fat; remove hemostatic material from the wound; relax the established wound expander every 65 minutes; refuse to suture the muscles in the area of laminectomy, refuse to use an intradermal suture.The study objective is a verification of the received Protocol.Materials and methods. A comprehensive retrospective cohort study evaluated the results of surgical treatment of 575 spinal patients who were under the authors’ supervision in 2014–2016. Patients were divided into groups: operated in the period from 2014 to 2016 (control group), operated in 2017, in the treatment of which the Protocol for reducing complications was applied (main group).Results. It was found that after the introduction of the Protocol, the percentage of patients with postoperative wound infection decreased from 6.0 to 1.3 %.Conclusion. The resulting Protocol is an effective tool for reducing wound infection and can be recommended for prevention of the postoperative wound infection in patients with spinal with diseases and injuries.

Embryonic Exposure to Ethanol Increases Anxiety-Like Behavior in Fry Zebrafish.

Fetal alcohol spectrum disorder (FASD) is an umbrella term to describe the effects of ethanol (Eth) exposure during embryonic development, including several conditions from malformation to cognitive deficits. Zebrafish (Danio rerio) are a translational model popularly applied in brain disorders and drug screening studies due to its genetic and physiology homology to humans added to its transparent eggs and fast development. In this study, we investigated how early ethanol exposure affects zebrafish behavior during the initial growth phase. Fish eggs were exposed to 0.0 (control), 0.25 and 0.5% ethanol at 24h post-fertilization. Later, fry zebrafish (10days old) were tested in a novel tank task and an inhibitory avoidance protocol to inquire about morphology and behavioral alterations. Analysis of variance showed that ethanol doses of 0.25 and 0.5% do not cause morphological malformations and did not impair associative learning but increased anxiety-like behavior responses and lower exploratory behavior when compared to the control. Our results demonstrate that one can detect behavioral abnormalities in the zebrafish induced by embryonic ethanol as early as 10days post-fertilization and that alcohol increases anxious behavior during young development in zebrafish.