During sustained voluntary contractions, the variability in motor unit interspike intervals increases with fatigue. This increase in variability may represent an adaptive mechanism to prevent fatigue. We investigated whether randomly modulating interpulse intervals (IPI) in a constant frequency stimulation protocol reduces force loss over time compared to a non-modulated constant frequency protocol. A second purpose of this study was to investigate the role of the M-wave in force generation during evoked contractions. Eight healthy subjects participated in three 3-minute fatigue protocols of the thenar muscles elicited by supramaximal stimulation of the median nerve. All three protocols had a mean IPI of 33.3ms and only differed in the type of modulation. One protocol consisted of 0% modulation ('Constant'), another protocol consisted of uniformly distributed modulation of [plus or minus]20% ('Variable'), and a third protocol consisted of ramped modulation from 0 to [plus or minus]20% ('Ramp'). There was no significant difference between overall force-time integrals for the three protocols. There was a significant reduction in M-wave amplitude for all three protocols; however, the M-wave immediately following the 'Ramp' protocol was significantly larger than the M-wave immediately following the 'Constant' protocol. We conclude that modulation is ineffective at preserving force output and somewhat effective at preserving the M-wave amplitude. The varied reductions in fatigued M-waves suggest that it is not necessarily a limiting factor in force output and that it was not necessarily linked to the force loss in this experiment. / text

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ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / During a recent U.S. Army Yuma Proving Ground (YPG) ground test, an unexpected change in test location resulted in the implementation of an innovative ad hoc network solution to complete the planned test matrix. The original plan was to use an aircraft ground test facility; however, safety requirements resulted in the aircraft being placed 50 meters away from the facility. This distance was too great to use the existing connections; consequently, data collection and analysis were adversely affected until this time expedient solution was implemented.

Issues around Quality of Service (QoS) and security for Voice over IP (VoIP) have been extensively investigated separately, due to the great attention this technology currently attracts. The specific problem this work addresses centres upon the selection of optimal parameters for QoS and security for VoIP streams integrating both network impairments and user perception metrics into a novel empirically-driven approach. Specifically, the simulation model seeks the optimal parameters in terms of variable VoIP payloads, iterative block ciphers, codecs and authentication mechanisms to be used, so that optimum tradeoff between a set of conflicting factors is achieved. The model employs the widely used Transmission Rating Factor, R, as the methodology to predict and measure the perceived QoS based on current transmission and network impairments. The R factor is then used to map perceived QoS to the corresponding Mean Opinion Score value, which gives the average estimation of perceived voice quality (Quality of Experience). Furthermore, a genetic algorithm (GA) has been developed that uses the output from the simulation model as an input into an offline optimisation routine that simultaneously maximises the VoIP call volumes and the Level of Encryption (LoE) per call basis, without degrading the perceived quality of service under a specific threshold as dictated by the R factor. The solutions reflect the optimum combination of parameters for each codec used and due to the small size of the search space the actual speed of GA has been validated against an exhaustive search algorithm. The results extracted from this study demonstrate that under strict and pre-defined parameters the default payload size supported by the codecs is not the optimal selection in terms of call volume maximisation and perceived QoS when encryption is applied.

As the data rates supported by the physical layer increase, overheads increasingly dominate the throughput of wireless networks. A promising approach for reducing overheads is to group a number of frames together into one transmission. This can reduce the impact of overheads by sharing headers and the time spent waiting to gain access to the transmission floor. Traditional aggregation schemes require that frames that are aggregated all be destined to the same receiver. These approaches neglect the fact that transmissions are broadcast and a single transmission will potentially be received by many receivers. Thus, by taking advantage of the broadcast nature of wireless transmissions, overheads can be amortized over more data and achieve more performance gain. To show this, we design a series of MAC-based aggregation protocols that take advantage of rate adaptation and the broadcast nature of wireless transmissions. We first show the design of a system that can aggregate both unicast and broadcast frames. Further, the system can classify TCP ACK segments so that they can be aggregated with TCP data flowing in the opposite direction. Second, we develop a rate-adaptive frame aggregation scheme that allows us to find the best aggregation size by tracking the size based on received data frames and the data rate chosen by rate adaptation. Third, we develop a multi-destination frame aggregation scheme to aggregate broadcast frames and unicast frames that are destined for different receivers using delayed ACKs. Using a delayed ACK scheme allows multiple receivers to control transmission time of the ACKs. Finally, we extend multi-destination rate-adaptive frame aggregation to allow piggybacking of various types of metadata with user packets. This promises to lower the impact of metadata-based control protocols on data transport. A novel aspect of our work is that we implement and validate the designs not through simulation, but rather using our wireless node prototype, Hydra, which supports a high performance PHY based on 802.11n. To validate our designs, we conduct extensive experiments both on real and emulator-based channels and measure system performance. / text

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Introduction: A protocol for management of sedation and pain for mechanically ventilated patients at Flagstaff Medical Center (FMC) was implemented in August 2013. It was unknown whether the protocol is being adhered to or whether it has had an impact on patient outcomes. Objectives: To develop an audit and feedback mechanism to monitor adherence to sedation protocol at FMC and determine whether the protocol has impacted patient outcomes. Methods: A retrospective manual chart review was conducted including all mechanically ventilated adult patients for four, one-month periods: 1) pre-protocol; and 2) one month, 3) six months, and 4) 12 months post-protocol implementation. Results: 132 total patients were included (32 pre; 100 post-protocol). Mean weighted adherence score for post-protocol study groups were 5.0±0.6, 5.0±0.7, and 5.2±0.7 (p=0.926) out of ten. Time of mechanical ventilation (p=0.003) and hospital length of stay (LOS) (p=0.023) were reduced post (56±58h; 9.8±7.9days) vs. pre-protocol (90±67h; 13±7days). The adherence score was weakly correlated with hospital LOS but not time of mechanical ventilation. Conclusion: This project demonstrates improvements in patient outcomes from utilization of a sedation protocol. However, this project also highlights several challenges associated with the monitoring of protocol adherence. A lack of audit and feedback may be a factor in the observed unchanged adherence over time. Both research and monitoring activities are impaired by EHR systems that do not allow for the easy extraction of data. Ensuring that adequate audit and feedback strategies are designed and available prior to implementation of new protocols is an essential step in planning the implementation of a new protocol.

Στην εργασία αυτή, μελετήθηκε η δομή του σύγχρονου ίντερνετ από την σκοπιά του δικτύου και κατέστη σαφές το πως διασυνδέονται οι πάροχοι υπηρεσιών και οι τερματική χρήστες, πως γίνεται η δρομολόγηση και ποιοί αλγόριθμοι χρησιμοποιούνται για τιν επίτευξη της. / This diploma thesis focus on how modern networks connect together in order to create the internet and which algorithms used for the routing of informations that traverse through them.

Efficient utilization of the limited wireless spectrum while satisfying applications’ quality of service requirements is an essential design goal of forthcoming wireless networks and a key to their successful deployment. The need for spectrally efficient systems has motivated the development of adaptive transmission techniques. Enabling this adaptation requires protocols for information exchange as well as mathematical tools to optimize the controllable parameters. In this dissertation, we provide insights into such protocols and mathematical tools that target efficient utilization of the wireless spectrum. First, we propose a distributed CDMA-based medium access protocol for mobile ad hoc networks (MANETs). Our approach accounts for multiple access interference at the protocol level, thereby addressing the notorious near-far problem that undermines the throughput performance in MANETs. Second, we present a novel power-controlled MAC protocol, called POWMAC, which enjoys the same single-channel, single-transceiver design of the IEEE 802.11 Ad Hoc MAC protocol, but which achieves a significant throughput improvement over the 802.11 protocol. Third, we consider joint power/rate optimization in the context of orthogonal modulation (OM) and investigate the performance gains achieved through adaptation of the OM order using recently developed optimization techniques. We show that such adaptation can significantly increase network throughput while simultaneously reducing the per-bit energy consumption relative to fixed-order modulation systems. Finally, we determine the maximum achievable “performance” of a wireless CDMA network that employs a conventional matched filter receiver and that operates under optimal link-layer adaptation where each user individually achieves the Shannon capacity. The derived bounds serve as benchmarks against which adaptive CDMA systems can be compared.

To understand bovine oocytes meiotic maturation, developmental potential, gene expression is required. The gene expression studies in the preimplantation bovine oocytes has been difficult, because the procedures that are being employed for extracting total RNA are not specific for bovine oocytes and so far is not providing the required amount for further procedures. Quantification of genes generally requires large amounts of total RNA in order to overcome the problem of low amount of mRNA present, so a standardized specific protocol is recommended. These days most of the researchers are using commercial Kit protocols without knowing the significance of chemicals and how they are acting on cells. In present project a standardized protocol (modified trizol) was designed for bovine oocytes, which was specific and less expensive. The efficiency of this protocol compared with Pure Link (Kit Protocol), GNTC (Guanidinium thiocyanate) for extraction of total RNA from fresh oocytes, vitrified oocytes with PROH (1,2 propanediol) and DMSO (dimethylsulfoxide) cryoprotectans was much better. The RNA (absorbance 260/280) purity levels of the standardized protocol was ranging (1.50-2.10), whereas for GNTC protocol (1.05-1.36), Pure Link (kit protocol) (2.05-2.7). Amplification of housekeeping genes (SDHA and GAPDH gene) showed the specificity and efficiency of the standardized protocol over other protocols.