Using Hubble Parameter Measurements to Find Constraints on Dark Energy Based on Different Cosmological Models

In this paper, Hubble parameter versus redshift data, collected from multiple resources, is used to place constraints on the parameters of two current Cosmological dark energy models. The first dark energy model considered is the Standard Model of cosmology, also known as ΛCDM with spatial curvature, which is primarily based on Einstein’s General Theory of Relativity with a spatially homogeneous time-independent cosmological constant, Λ. The second is the XCDM model which parameterize dark energy as a fluid whose density can vary with time. The H(z) data collected through different experimental sources was used to put constraints on the parameters of these models. The constraints obtained are then compared with the previously obtained constraints using different probes like type-1a supernovae, distance modulus, CMB anisotropy, and baryonic acoustic oscillations peak length scale. The results of analyzing the Hubble parameter vs redshift data is consistent with previous conclusions that we live in an approximately flat, accelerating Universe. However, in order to deduct tighter constraints on cosmological models’ parameter, like the geometry of the Universe, more and better-quality data will be neede

Research challenges in 5G networks: a HetNets perspective

This paper highlights use cases, emerging machine type communication (MTC) technologies, ongoing research activities, and existing research challenges in 5G networks. 5G networks are faced with the following challenges: (i) handling large amounts of data, (ii) coping with different types of data traffic, i.e., human-type, machine-type, and combined-type (iii) connecting billions of machines, and (iv) severe resource limitations of devices. The ubiquitous nature of cellular networks make them the preferred choice for access networks, but a lack of communication resources is a problem. To address the resource scarcity issue, different wireless access networks may combine to form a heterogeneous network (HetNet) and hence become a single 5G network. For long-term success of 5G networks, we envision the following as important research outputs: (i) a scalable 5G network architecture that can handle a large number of human users and machines considering different constraints, (ii) a comprehensive quality of service (QoS) framework to satisfy heterogeneous users and machines requirements, (iii) a procedure for intelligent access network selection, and (iv) comprehensive inter-network handover mechanisms

RPL-based routing protocols for multi-sink wireless sensor networks

Recent studies demonstrate that the performance of a wireless sensor network (WSN) can be improved by deploying multiple sinks in the network. Therefore, in this paper we present different routing protocols for multi-sink WSNs based on the routing protocol for low-power and lossy networks (RPL). Our protocols use different routing metrics and objective functions (OFs). We use the available bandwidth, delay, MAC layer queue occupancy, and expected transmission count (ETX) as the tie-breaking metrics in conjunction with the shortest hop-count metric. Our OFs use the tie-breaking metrics on a greedy or end-to-end basis. Our simulation results demonstrate that the protocols based on the delay, buffer occupancy, and ETX metrics demonstrate best performance, increasing the packet delivery ratio by up to 25% and decreasing the number of retransmissions by up to 65%, compared to a version of the RPL protocol that only uses the hop-count metric. Another key insight is that, using the tie-breaking metrics on a greedy basis demonstrates a slight performance improvement compared to using the metrics on an end-to-end basis. Finally, our results also demonstrate that multiple sinks inside a WSN improve the RPL-based protocol performance

Evaluation of available bandwidth as a routing metric for delay-sensitive IEEE 802.15.4-based ad-hoc networks

In this paper, we evaluate available bandwidth as a routing metric for IEEE 802.15.4-based ad-hoc networks. The available bandwidth on a data forwarding path is an approximation of the forwarding path’s residual data relaying capacity. High available bandwidth on a data forwarding path implies low data traffic load on the path, therefore data flows may experience low delay and high packet delivery ratio (PDR). Our aim is to evaluate available bandwidth as a routing metric. We present different available-bandwidth-based routing protocols for IEEE 802.15.40-based networks, namely: end-to-end available-bandwidth-based routing protocol (ABR), available bandwidth and contention-aware routing protocol (ABCR), and shortest hop-count and available-bandwidth-based opportunistic routing protocol (ABOR). Moreover, we also present variants of ABR and ABCR capable of distributing a flow’s data packets on multiple paths by maintaining the top K downstream nodes (the downstream nodes that advertised best data forwarding paths towards a sink node) corresponding to each sink node in a routing table. We focus on both single-sink and multi-sink networks. We performed extensive simulations, and the simulation results demonstrate that the available bandwidth routing metric shows better results when combined with a routing metric that helps to limit a data forwarding path’s length, i.e., shortest hop-count or intra-flow contention count. For multi-path data forwarding towards the same sink node, and at high traffic volumes, the available bandwidth metric demonstrates best performance when combined with the shortest hop-count routing metric

Capacity and contention-based joint routing and gateway selection for machine-type communications

Typically, in machine-type communications (MTC) devices communicate with servers over the Internet. In a large-scale machine-to-machine area (M2M) network, the devices may not connect directly to the Internet due to radio transmission and energy limitations. Therefore, the devices collaborate wirelessly to relay their data to a gateway. A large-scale M2M area network may have multiple gateways, selecting a proper gateway for the devices can have immense impact on the networks performance. We present the channel capacity and contention-based joint routing and gateway selection methods for MTC. Based on channel capacity and contention, our methods select the best gateway on per-packet, per-flow, and per-node basis. We compare the methods performance with existing methods using simulation and test-bed experiments. We analyse the impact of the number of gateways, physical distribution of transmitters, control overhead, and duty-cycling on the performance of the gateway selection methods. Our results demonstrate that, in duty-cycled operations, the methods performance depends on control overhead and making a good trade-off between load imbalance to different gateways and a forwarding paths length. Otherwise only the latter impacts the methods performance. In general, our node-based best gateway selection method makes a better trade-off and exhibits lower control overhead, hence it demonstrates better performance. Moreover, our methods demonstrate better performance as compared to an existing state-of-the-art joint routing and gateway selection method

Design and analysis of RPL objective functions for multi-gateway ad-hoc low-power and lossy networks

RPL is a standard routing framework for low-power and lossy networks (LLNs). LLNs usually operate in challenged conditions, therefore RPL can be adapted to satisfy requirements of a particular LLN. RPL facilitates this through objective functions (OFs). An OF is used to discover and maintain data forwarding paths based on the requirements of LLNs. In RPL, different OFs can use different routing metrics in different ways. In this paper, we design different OFs and analyse their impact on RPL performance in multi-gateway ad-hoc LLNs. In conjunction with the shortest hop-count, our designed OFs also use the following tie-breaking metrics: available bandwidth, delay, buffer occupancy, and ETX. Our OFs use the tie-breaking metrics on a greedy or an end-to-end basis. In our experimental analysis, we consider the impact of duty-cycling, number of gateways, and data traffic load on the OFs’ performance. Our results demonstrate that, generally speaking, the performance improves with an increase in the number of gateways. In the absence of duty-cycling, the greedy approach is better compared to the end-to-end approach, and using delay, buffer occupancy, and ETX metrics as the tie-breaking metrics in conjunction with the shortest hop-count metric yield the best performance. In a relatively high data traffic load, all OFs perform similarly. In duty-cycling mode, frequent changes in the parent node incur extra synchronization time between a sender and receiver. OFs that use the tie-breaking metrics on an end-to-end basis do not frequently change parent nodes, hence they demonstrate better performance. Furthermore, in duty-cycling mode, the shortest hop-count metric demonstrates the best performance compared to the other metrics

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

Mapping genomic loci implicates genes and synaptic biology in schizophrenia

Schizophrenia has a heritability of 60-80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies