Clock Synchronisation Assisted Clock and Data Recovery for Sub-Nanosecond Data Centre Optical Switching

In current `Cloud' data centres, switching of data between servers is performed using deep hierarchies of interconnected electronic packet switches. Demand for network bandwidth from emerging data centre workloads, combined with the slowing of silicon transistor scaling, is leading to a widening gap between data centre traffic demand and electronically-switched data centre network capacity. All-optical switches could offer a future-proof alternative, with potentially under a third of the power consumption and cost of electronically-switched networks. However, the effective bandwidth of optical switches depends on their overall switching time. This is dominated by the clock and data recovery (CDR) locking time, which takes hundreds of nanoseconds in commercial receivers. Current data centre traffic is dominated by small packets that transmit in tens of nanoseconds, leading to low effective bandwidth, as a high proportion of receiver time is spent performing CDR locking instead of receiving data, removing the benefits of optical switching. High-performance optical switching requires sub-nanosecond CDR locking time to overcome this limitation. This thesis proposes, models, and demonstrates clock synchronisation assisted CDR, which can achieve this. This approach uses clock synchronisation to simplify the complexity of CDR versus previous asynchronous approaches. An analytical model of the technique is first derived that establishes its potential viability. Following this, two approaches to clock synchronisation assisted CDR are investigated: 1. Clock phase caching, which uses clock phase storage and regular updates in a 2km intra-building scale data centre network interconnected by single-mode optical fibre. 2. Single calibration clock synchronisation assisted CDR}, which leverages the 20 times lower thermal sensitivity of hollow core optical fibre versus single-mode fibre to synchronise a 100m cluster scale data centre network, with a single initial phase calibration step. Using a real-time FPGA-based optical switch testbed, sub-nanosecond CDR locking time was demonstrated for both approaches

Clock Synchronized Transmission of 51.2GBd Optical Packets for Optically Switched Data Center Interconnects

Optical switching has attracted significant attention in recent research on data center networks (DCNs) as it is a promising viable route for the further scaling of hyper scale data centers, so that DCNs can keep pace with the rapid growth of machine-to-machine traffic. It has been shown that optical clock synchronization enables sub-nanosecond clock and data recovery time and is crucial to high performance optically switched DCN. Moreover, the interconnect data rate is expected to increase from the current 100 Gb/s per fiber to scale to 800 Gb/s and beyond, requiring high baud rate signaling at >50 GBd. Thus, future optically switched DCN should support >50GBd data transmission with optical clock synchronization. Here, we demonstrate the clock- synchronized transmission of 128-byte optical packets at 51.2 GBd and study the impact of reference clock phase noise on system performance, focusing on the tolerance to the clock phase misalignment that affects the system scalability and reliability. By comparing the tolerable sampling clock phase offsets using different reference clocks, we show that a clock phase offset window of about 8ps could be achieved with a <0.2ps source clock. Furthermore, we model and numerically study the de- correlation of clock phase noise. This allows the total jitter to be estimated, and thereby, the estimation of the transmission performance for future generations of high baud rate, clock synchronized DC interconnects

How can we better support families living with cardiovascular disease and depression?

Published in accordance with the Publisher's Open Access policyPurpose – The purpose of this paper is to discuss the role of psychosocial treatments to support families living with cardiovascular disease (CVD) and depression. The paper highlights that depression in people with CVD is a predictor of non-adherence to both medicines and cardiovascular rehabilitation programmes. The authors believe there is a clinical need to develop a programme of care to support the whole family to adhere to cardiovascular rehabilitation programmes. Design/methodology/approach – A team of expert cardiovascular nurses, mental health nurses (MHN) and cardiologist clinical opinions and experiences. These opinions and experiences were supplemented by literature using MEDLINE as the primary database for papers published between December 2000 and December 2013. Findings – People with CVD who become depressed are more likely to stop taking their medicine and stop working with their health care worker. Most people with heart and mood problems live with their families. Health workers could have a role in supporting families living with heart and mood problems to their care and treatment. The paper has highlighted the importance of working with families living with heart and mood problems to help them to stick with care and treatment. Originality/value – Most people with heart and mood problems live with their families. The paper has highlighted the importance of working with families living with heart and mood problems to help them to persevere with care and treatment. MHN may have a role, though consideration should also be given to exploring the role of other health care workers and members of the community. As the population ages, clinicians and communities will need to consider the impact of depression on adherence when working with families living with CVD and depression

Low-latency wavelength-switched clock-synchronized intra-data center interconnects enabled by hollow core fiber

Fast (nanoseconds) optical wavelength switching is emerging as a viable solution to scaling the size and capacity of intra-data center interconnection. A key enabling technology for such systems is low-jitter optical clock synchronization, which enables sub-nanosecond clock and data recovery for optically switched frames using low-cost methods such as clock phase caching. We propose and demonstrate real-time low-latency wavelength-switched clock-synchronized intra-data center interconnection at 51.2 GBd using a fast tunable laser (with ns scale switching time) and ultra-stable-latency hollow core fiber (HCF) for optically-switched data center networks. For wavelength-switched systems, we achieve a physical layer latency below 46 ns, consisting of 28 ns transceiver latency and a 18 ns inter-packet gap. Finally, we show that by exploiting the low chromatic dispersion and thermally-stable latency features of HCF, active clock phase tracking can be entirely eliminated

Communications with guaranteed bandwidth and low latency using frequency-referenced multiplexing

Emerging cloud applications such as virtual reality and connected car fleets demand guaranteed connections, as well as low and stable latency, to edge data centres. Currently, user–cloud communications rely on time-scheduled data frames through tree-topology fibre networks, which are incapable of providing guaranteed connections with low or stable latency and cannot be scaled to a larger number of users. Here we show that a frequency-referenced multiplexing method can provide guaranteed bandwidth and low latency for time-critical applications. We use clock and optical frequency synchronization, enabled by frequency comb and signal processing techniques, to provide each user with dedicated optical bandwidth, creating scalable user–cloud upstream communications. As a proof of concept, we demonstrate a frequency-division multiplexing system servicing up to 64 users with an aggregate bandwidth of 160 GHz, exhibiting a data rate of up to 4.3 Gbps per user (240.0 Gbps aggregated capacity considering a 200 GHz wavelength band) with a high receiver sensitivity of –35 dBm

Unpacking dimensions of evidentiary knowledge and reasoning in the teaching and learning of science

https://repository.isls.org/bitstream/1/601/1/273.pdfPublished versio

One and Only Campaign Nevada Evaluation of Educational Materials For Injection Safety Executive Summary

The goal of the evaluation was to measure the effectiveness of the Campaign’s educational materials in raising awareness among the general public and enhancing the knowledge of healthcare personnel. Through this measurement the evaluation results would then also provide recommendations for improvements to the materials. To achieve these goals the evaluation team at NICRP created a strategic dissemination plan designed to support a formal evaluation of messages within the materials, message delivery and general knowledge and understanding of safe injection practices by both providers and the general public. Methods utilized to conduct this evaluation included: Surveys of both patients and healthcare professionals collected in medical offices which frequently administer injections throughout Nevada; Focus groups with members of the general public (potential patients) as well as health care professionals statewide; An expert marketing review of campaign materials; A statewide telephone survey assessing public education and attitudes regarding safe injection practices; and A brief process evaluation of the Nevada Safe Injections Workgroup

Health Status of Children Entering Kindergarten: Results of the 2009-2010 (Year Two) Nevada Kindergarten Health Survey

Academic achievement for children is vital to their success in life. Those that do well in school have greater opportunities for post-secondary education, and later have better prospects for employment. One of the major factors that can affect a child’s academic achievement is his or her health status. Academic outcomes and health conditions are consistently linked in the literature (Taras & Potts-Datema, 2005). Children with poor health status, and especially those with common chronic health conditions, have increased numbers of school absences and more academic deficiencies (Taras & Potts-Datema, 2005). In a study concerning excused versus unexcused absences, children with greater absenteeism had lower academic performance, and those with excused absences performed better than those with unexcused absences (Gottfried, 2009). Therefore, to increase the likelihood for academic success in children, we need address their health concerns. Preventative care is crucial to a child’s ability to succeed in school.According to data from the KIDS COUNT Data Center at the Annie E. Casey Foundation (2009), 11 percent of Nevada’s teens are high school dropouts, compared to 7 percent nationally. The national dropout prevention center lists poor attendance and low achievement as two of the significant risk factors for school dropout (Hammond et al., 2007). Additionally studies examining school dropout rates indicate that early intervention is necessary to prevent students from dropping out of school. Middle and high school students that drop out likely stopped being engaged in school much earlier in their academic career. Therefore, early prevention and intervention is crucial to improving graduation rates. Ensuring that children have their basic needs met, including receiving adequate health care, can directly impact a child’s academic achievement as well as increase their likelihood for high school graduation.To gain baseline information on the health status of children entering the school system and better track student health status, the Nevada Institute for Children’s Research and Policy (NICRP), in partnership with the state’s 17 school districts, the Southern Nevada Health District (SNHD), and the Nevada State Health Division (NSHD), conducted a health survey examining the health status as well health insurance status of Nevada’s children entering kindergarten. This study was conducted with the goal of quantifying the health status of children as they enter school to be able to identify specific areas for improvement to eventually increase academic success among Nevada’s students

Experimental warming differentially affects vegetative and reproductive phenology of tundra plants

Rapid climate warming is altering Arctic and alpine tundra ecosystem structure and function, including shifts in plant phenology. While the advancement of green up and flowering are well-documented, it remains unclear whether all phenophases, particularly those later in the season, will shift in unison or respond divergently to warming. Here, we present the largest synthesis to our knowledge of experimental warming effects on tundra plant phenology from the International Tundra Experiment. We examine the effect of warming on a suite of season-wide plant phenophases. Results challenge the expectation that all phenophases will advance in unison to warming. Instead, we find that experimental warming caused: (1) larger phenological shifts in reproductive versus vegetative phenophases and (2) advanced reproductive phenophases and green up but delayed leaf senescence which translated to a lengthening of the growing season by approximately 3%. Patterns were consistent across sites, plant species and over time. The advancement of reproductive seasons and lengthening of growing seasons may have significant consequences for trophic interactions and ecosystem function across the tundra