Does the choice of neighbourhood supermarket access measure influence associations with individual-level fruit and vegetable consumption? A case study from Glasgow

Background
Previous studies have provided mixed evidence with regards to associations between food store access and dietary outcomes. This study examines the most commonly applied measures of locational access to assess whether associations between supermarket access and fruit and vegetable consumption are affected by the choice of access measure and scale.

Method
Supermarket location data from Glasgow, UK (n = 119), and fruit and vegetable intake data from the 'Health and Well-Being' Survey (n = 1041) were used to compare various measures of locational access. These exposure variables included proximity estimates (with different points-of-origin used to vary levels of aggregation) and density measures using three approaches (Euclidean and road network buffers and Kernel density estimation) at distances ranging from 0.4 km to 5 km. Further analysis was conducted to assess the impact of using smaller buffer sizes for individuals who did not own a car. Associations between these multiple access measures and fruit and vegetable consumption were estimated using linear regression models.

Results
Levels of spatial aggregation did not impact on the proximity estimates. Counts of supermarkets within Euclidean buffers were associated with fruit and vegetable consumption at 1 km, 2 km and 3 km, and for our road network buffers at 2 km, 3 km, and 4 km. Kernel density estimates provided the strongest associations and were significant at a distance of 2 km, 3 km, 4 km and 5 km. Presence of a supermarket within 0.4 km of road network distance from where people lived was positively associated with fruit consumption amongst those without a car (coef. 0.657; s.e. 0.247; p0.008).

Conclusions
The associations between locational access to supermarkets and individual-level dietary behaviour are sensitive to the method by which the food environment variable is captured. Care needs to be taken to ensure robust and conceptually appropriate measures of access are used and these should be grounded in a clear a priori reasoning.

Stability analysis and resource allocation for space-based multi-access systems

In space-based networks, the data relay satellites can assist low-earth-orbit satellites in relaying data to other satellites or the ground station and improve the real time system throughput. To take full advantage of transmission resource of the cooperative relays, this paper proposes a multiple access and resource allocation strategy, in which relays can receive and transmit simultaneously according to channel characteristics of space-based systems. Based on the queueing theoretic formulation, the stability of the proposed protocol is analyzed and the maximum stable throughput region is derived, which would provide the appropriate guidance for the design of the system optimal control. Simulation results exhibit multiple factors that affect the stable throughput and verify the theoretical analysis.

Convergence analysis of multi-stage PIC detectors

This paper analyses the convergence behaviour of the parallel interference cancellation (PIC) detector in code division multiple access (CDMA) systems. Using the results from previous stability analysis of an iterated-map neural network, the paper derives a general condition from which the sufficient condition for convergence of the PIC detector with tentative decision functions that are monotonically increasing at a sublinear rate can be calculated. As examples, the paper derives the sufficient conditions for convergence of the PIC detector with the clip decision and the hyperbolic tangent decision functions. The paper also examines the convergence behaviour of the PIC detector with hyperbolic tangent decision function via computer simulation and compares it with the analytical results.

Peak to average power ratio analysis for LTE systems

The 3rd generation partnership project (3GPP) long term evolution (LTE) standard uses single carrier frequency division multiple access (SCFDMA) scheme for the uplink transmissions and orthogonal frequency division multiplexing access (OFDMA) in downlink. SCFDMA uses DFT spreading prior to OFDMA modulation to map the signal from each user to a subset of the available subcarriers i.e., single carrier modulation. The efficiency of a power amplifier is determined by the peak to average power ratio (PAPR) of the modulated signal. In this paper, we analyze the PAPR in 3GPP LTE systems using root raised cosine based filter. Simulation results show that the SCFDMA subcarrier mapping has a significantly lower PAPR compared to OFDMA. Also comparing the three forms of SCFDMA subcarrier mapping, results show that interleave FDMA (IFDMA) subcarrier mapping with proposed root raised cosine filter reduced PAPR significantly than localized FDMA (LFDMA) and distributed (DFDMA) mapping. This improves its radio frequency (RF) power amplifier efficiency and also the mean power output from a battery driven mobile terminal.

Low complexity MMSE based channel estimation technique for LTE OFDMA systems

Long term evolution (LTE) is designed for high speed data rate, higher spectral efficiency, and lower latency as well as high-capacity voice support. LTE uses single carrierfrequency division multiple access (SC-FDMA) scheme for the uplink transmission and orthogonal frequency division multiple access (OFDMA) in downlink. The one of the most important challenges for a terminal implementation are channel estimation (CE) and equalization. In this paper, a minimum mean square error (MMSE) based channel estimator is proposed for an OFDMA systems that can avoid the ill-conditioned least square (LS) problem with lower computational complexity. This channel estimation technique uses knowledge of channel properties to estimate the unknown channel transfer function at non-pilot subcarriers.

PAPR reduction technique for LTE OFDMA systems

Long term evolution (LTE) is the final step toward the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile networks. LTE uses orthogonal frequency division multiple access (OFDMA) for the downlink transmission and single carrier-frequency division multiple access (SC-FDMA) for uplink. OFDMA meets the 4G requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates. However, the potentially large peak-to-average power ratio (PAPR) of the transmitting signals has limited its application. This high PAPR causes interference when the OFDM signals are passed through an amplifier which does not have enough linear range. In this article, we investigate a clipping based PAPR reduction method for LTE OFDMA systems. Simulation results show that the clipping method is reduced PAPR significantly which decreases as the number of clip and filtering level is increased. As a results, increase the mean transmit power, and improve the power amplifier efficiency. This comes at the outlay of complexity, efficiency as well as cost.

Channel estimation scheme for 3.9G wireless communication systems using RLS algorithm

Main challenges for a terminal implementation are efficient realization of the receiver, especially for channel estimation (CE) and equalization. In this paper, training based recursive least square (RLS) channel estimator technique is presented for a long term evolution (LTE) single carrier-frequency division multiple access (SC-FDMA) wireless communication system. This CE scheme uses adaptive RLS estimator which is able to update parameters of the estimator continuously, so that knowledge of channel and noise statistics are not required. Simulation results show that the RLS CE scheme with 500 Hz Doppler frequency has 3 dB better performances compared with 1.5 kHz Doppler frequency.

Guest editorial : In Journal of networks, v.7 n.3

Networking of computing devices has been going through rapid evolution and thus continuing to be an ever expanding area of importance in recent years. New technologies, protocols, services and usage patterns have contributed to the major research interests in this area of computer science. The current special issue is an effort to bring forward some of these interesting developments that are being pursued by researchers at present in different parts of the globe. Our objective is to provide the readership with some insight into the latest innovations in computer networking through this. This Special Issue presents selected papers from the thirteenth conference of the series (ICCIT 2010) held during December 23-25, 2010 at the Ahsanullah University of Science and Technology. The first ICCIT was held in Dhaka, Bangladesh, in 1998. Since then the conference has grown to be one of the largest computer and IT related research conferences in the South Asian region, with participation of academics and researchers from many countries around the world. Starting in 2008 the proceedings of ICCIT are included in IEEExplore. In 2010, a total of 410 full papers were submitted to the conference of which 136 were accepted after reviews conducted by an international program committee comprising 81 members from 16 countries. This was tantamount to an acceptance rate of 33%. From these 136 papers, 14 highly ranked manuscripts were invited for this Special Issue. The authors were advised to enhance their papers significantly and submit them to undergo review for suitability of inclusion into this publication. Of those, eight papers survived the review process and have been selected for inclusion in this Special Issue. The authors of these papers represent academic and/or research institutions from Australia, Bangladesh, Japan, Korea and USA. These papers address issues concerning different domains of networks namely, optical fiber communication, wireless and interconnection networks, issues related to networking hardware and software and network mobility. The paper titled “Virtualization in Wireless Sensor Network: Challenges and Opportunities” argues in favor of bringing in different heterogeneous sensors under a common virtual framework so that the issues like flexibility, diversity, management and security can be handled practically. The authors Md. Motaharul Islam and Eui-Num Huh propose an architecture for sensor virtualization. They also present the current status and the challenges and opportunities for further research on the topic. The manuscript “Effect of Polarization Mode Dispersion on the BER Performance of Optical CDMA” deals with impact of polarization mode dispersion on the bit error rate performance of direct sequence optical code division multiple access. The authors, Md. Jahedul Islam and Md. Rafiqul Islam present an analytical approach toward determining the impact of different performance parameters. The authors show that the bit error rate performance improves significantly by the third order polarization mode dispersion than its first or second order counterparts. The authors Md. Shohrab Hossain, Mohammed Atiquzzaman and William Ivancic of the paper “Cost and Efficiency Analysis of NEMO Protocol Entities” present an analytical model for estimating the cost incurred by major mobility entities of a NEMO. The authors define a new metric for cost calculation in the process. Both the newly developed metric and the analytical model are likely to be useful to network engineers in estimating the resource requirement at the key entities while designing such a network. The article titled “A Highly Flexible LDPC Decoder using Hierarchical Quasi-Cyclic Matrix with Layered Permutation” deals with Low Density Parity Check decoders. The authors, Vikram Arkalgud Chandrasetty and Syed Mahfuzul Aziz propose a novel multi-level structured hierarchical matrix approach for generating codes of different lengths flexibly depending upon the requirement of the application. The manuscript “Analysis of Performance Limitations in Fiber Bragg Grating Based Optical Add-Drop Multiplexer due to Crosstalk” has been contributed by M. Mahiuddin and M. S. Islam. The paper proposes a new method of handling crosstalk with a fiber Bragg grating based optical add drop multiplexer (OADM). The authors show with an analytical model that different parameters improve using their proposed OADM. The paper “High Performance Hierarchical Torus Network Under Adverse Traffic Patterns” addresses issues related to hierarchical torus network (HTN) under adverse traffic patterns. The authors, M.M. Hafizur Rahman, Yukinori Sato, and Yasushi Inoguchi observe that dynamic communication performance of an HTN under adverse traffic conditions has not yet been addressed. The authors evaluate the performance of HTN for comparison with some other relevant networks. It is interesting to see that HTN outperforms these counterparts in terms of throughput and data transfer under adverse traffic. The manuscript titled “Dynamic Communication Performance Enhancement in Hierarchical Torus Network by Selection Algorithm” has been contributed by M.M. Hafizur Rahman, Yukinori Sato, and Yasushi Inoguchi. The authors introduce three simple adapting routing algorithms for efficient use of physical links and virtual channels in hierarchical torus network. The authors show that their approaches yield better performance for such networks. The final title “An Optimization Technique for Improved VoIP Performance over Wireless LAN” has been contributed by five authors, namely, Tamal Chakraborty, Atri Mukhopadhyay, Suman Bhunia, Iti Saha Misra and Salil K. Sanyal. The authors propose an optimization technique for configuring the parameters of the access points. In addition, they come up with an optimization mechanism in order to tune the threshold of active queue management system appropriately. Put together, the mechanisms improve the VoIP performance significantly under congestion. Finally, the Guest Editors would like to express their sincere gratitude to the 15 reviewers besides the guest editors themselves (Khalid M. Awan, Mukaddim Pathan, Ben Townsend, Morshed Chowdhury, Iftekhar Ahmad, Gour Karmakar, Shivali Goel, Hairulnizam Mahdin, Abdullah A Yusuf, Kashif Sattar, A.K.M. Azad, F. Rahman, Bahman Javadi, Abdelrahman Desoky, Lenin Mehedy) from several countries (Australia, Bangladesh, Japan, Pakistan, UK and USA) who have given immensely to this process. They have responded to the Guest Editors in the shortest possible time and dedicated their valuable time to ensure that the Special Issue contains high-quality papers with significant novelty and contributions.

Intelligent DDoS packet filtering in high-speed networks

Currently high-speed networks have been attacked by successive waves of Distributed Denial of Service (DDoS) attacks. There are two major challenges on DDoS defense in the high-speed networks. One is to sensitively and accurately detect attack traffic, and the other is to filter out the attack traffic quickly, which mainly depends on high-speed packet classification. Unfortunately most current defense approaches can not efficiently detect and quickly filter out attack traffic. Our approach is to find the network anomalies by using neural network, deploy the system at distributed routers, identify the attack packets, and then filter them quickly by a Bloom filter-based classifier. The evaluation results show that this approach can be used to defend against both intensive and subtle DDoS attacks, and can catch DDoS attacks’ characteristic of starting from multiple sources to a single victim. The simple complexity, high classification speed and low storage requirements make it especially suitable for DDoS defense in high-speed networks.

Evidence based drug therapy : are optimal doses and multiple medication therapies realistic in patients with chronic heart failure

Background: Chronic Heart Failure (CHF) has a high mortality and morbidity. Large scale randomised controlled trials have proven the benefits of beta blockade and ACE inhibitors in reducing mortality in patients with CHF and expert guidelines mandate their use. In spite of these recommendations, important therapies are under-prescribed and under-utilised.

Method: 1015 consecutive patients enrolled in CHF management programs across Australia were surveyed during 2005-2006 to determine prescribing patterns in heart failure medications. These patients were followed-up for a period of 6 months.

Results: The survey revealed that beta blockers were prescribed to 80% of patients (more than 85% were on sub-optimal doses) and 70% were prescribed Angiotensin converting enzyme (ACE) inhibitors (approximately 50% were on sub-optimal dose). 19% of patients were prescribed Angiotensin receptor blockers (ARBs). By 6 months <25% of the patients who were on sub-optimal dose beta blockers or ACE inhibitors at baseline, had been up-titrated to maximum dose (p<0.0001). In CHF programs, were nurses were able to titrate medications, 75% of patients reached optimal dose of beta blockers compared to those programs with no nurse-led medication titration, where only 25% of patients reached optimal dose (p<0.004). When examining optimal dosage for any two of these mandatory medications, less patients were on optimal therapy. Beta blockers and ACE inhibitors, were both prescribed in combination in 60% of patients. While beta blockers and ARBs were prescribed to 15% of patients.

Conclusion: Whilst prescribing rates for a single medication strategy of beta blockers, or ACE inhibitors were greater than 70%, an increase in dosage of these medications and utilisation of proven combination therapy of these medications was poor. It is suggested that clinical outcomes for this cohort of patients could be further improved by adherence to evidence-based practice, ESC guidelines, and optimisation of these medications by heart failure nurses in a CHF program. On the basis of these findings and in the absence of ready access to a polypill, focussing on evidence-based practice to increase utilisation and optimal dosage of combination medication therapy is critical.

Design of multiple sequence alignment algorithms on parallel, distributed memory supercomputers

The challenge of comparing two or more genomes that have undergone recombination and substantial amounts of segmental loss and gain has recently been addressed for small numbers of genomes. However, datasets of hundreds of genomes are now common and their sizes will only increase in the future. Multiple sequence alignment of hundreds of genomes remains an intractable problem due to quadratic increases in compute time and memory footprint. To date, most alignment algorithms are designed for commodity clusters without parallelism. Hence, we propose the design of a multiple sequence alignment algorithm on massively parallel, distributed memory supercomputers to enable research into comparative genomics on large data sets. Following the methodology of the sequential progressiveMauve algorithm, we design data structures including sequences and sorted k-mer lists on the IBM Blue Gene/P supercomputer (BG/P). Preliminary results show that we can reduce the memory footprint so that we can potentially align over 250 bacterial genomes on a single BG/P compute node. We verify our results on a dataset of E.coli, Shigella and S.pneumoniae genomes. Our implementation returns results matching those of the original algorithm but in 1/2 the time and with 1/4 the memory footprint for scaffold building. In this study, we have laid the basis for multiple sequence alignment of large-scale datasets on a massively parallel, distributed memory supercomputer, thus enabling comparison of hundreds instead of a few genome sequences within reasonable time.

Family support and ease of access link socio-economic status and sports club membership in adolescent girls : a mediation study

Background Much research has been conducted into the determinants of physical activity (PA) participation among adolescent girls. However, the more specific question of what are the determinants of particular forms of PA participation, such as the link between participation through a sports club, has not been investigated. Accordingly, the aim of this study was to investigate the relationships between participation in a sports club and socio-economic status (SES), access to facilities, and family and peer support, for female adolescents.

Methods A survey of 732 female adolescent school students (521 metropolitan, 211 non-metropolitan; 489 Year 7, 243 Year 11) was conducted. The survey included demographic information (living arrangements, ethnicity indicators, and indicators of SES such as parental education and employment status and locality); access to facilities; and family and peer support (travel, encouragement, watching, praise, joint participation). For each characteristic, sports club participants and non-participants were compared using chi-square tests. Multiple mediation analyses were used to investigate the role of access, family and peer support in the link between SES and sport participation.

Results There were significant associations (p<0.05) between sports club participation and: all demographic characteristics; all measures of family and peer support; and access to sport-related facilities. Highest levels of participation were associated with monolingual Australian-born families, with two parents, at least one of whom was well-educated, with both parents employed, and high levels of parental assistance, engagement and support. Participation in club sport among both younger and older adolescent girls was significantly positively associated with the SES of both their neighbourhoods and their households, particularly in metropolitan areas. These associations were most strongly mediated by family support and by access to facilities.

Conclusions To facilitate and promote greater participation in club sport among adolescent girls from low SES neighbourhoods and households, strategies should target modifiable determinants such as facility access and parental support. This will involve improving access to sports facilities and promoting, encouraging and assisting parents to provide support for their daughters’ participation in sport clubs.

Vascular access e-learning : the essentials

Objectives
Form a working group of renal vascular access nurses to develop peer reviewed, accessible, evidence based e-leaning modules related to vascular access principles and practice.

Key messages
Vascular access training and guidelines are often unit specific but the core principles of vascular access care are generally transferable. The vascular access e-learning module aims to utilize resources to minimize wasted time developing and keeping multiple individual vascular access training packages up to date.
Vascular access education is delivered from a variety of resources such as educators, senior staff and vascular access nurses. This e-learning module allows renal units the opportunity to provide a national learning package with general consensus on terminology and up to date evidence based practice.
Recently there has been a rise in the use of ultrasound to assess and perform image guided cannulation in vascular access to improve patient outcomes. There is only a small window of opportunity to provide education in ultrasound use. This module will provide education on this and other aspects of vascular access practices and patient care.

Implications for clinical practice
Implications include access to standardized learning packages based on current evidence based practice, eencouraging the utilization of new technology (e.g. Ultrasound observation and interpretation of results), reinforcing the underpinning knowledge of anatomy and physiology of vascular access, standardizing practice benefits to patients and nurses moving between dialysis units, improving accessibility by transitioning learning to smart phones and tablets and providing an opportunity for international collaboration related to vascular access e-learning concepts.

The influence of sighing respirations on infant lung function measured using multiple breath washout gas mixing techniques

There is substantial interest in studying lung function in infants, to better understand the early life origins of chronic lung diseases such as asthma. Multiple breath washout (MBW) is a technique for measuring lung function that has been adapted for use in infants. Respiratory sighs occur frequently in young infants during natural sleep, and in accordance with current MBW guidelines, result in exclusion of data from a substantial proportion of testing cycles. We assessed how sighs during MBW influenced the measurements obtained using data from 767 tests conducted on 246 infants (50% male; mean age 43 days) as part of a large cohort study. Sighs occurred in 119 (15%) tests. Sighs during the main part of the wash-in phase (before the last 5 breaths) were not associated with differences in standard MBW measurements compared with tests without sighs. In contrast, sighs that occurred during the washout were associated with a small but discernible increase in magnitude and variability. For example, the mean lung clearance index increased by 0.36 (95% CI: 0.11-0.62) and variance increased by a multiplicative factor of 2 (95% CI: 1.6-2.5). The results suggest it is reasonable to include MBW data from testing cycles where a sigh occurs during the wash-in phase, but not during washout, of MBW. By recovering data that would otherwise have been excluded, we estimate a boost of about 10% to the final number of acceptable tests and 6% to the number of individuals successfully tested.

Joint optimization of rule placement and traffic engineering for QoS provisioning in software defined network

Software-Defined Network (SDN) is a promising network paradigm that separates the control plane and data plane in the network. It has shown great advantages in simplifying network management such that new functions can be easily supported without physical access to the network switches. However, Ternary Content Addressable Memory (TCAM), as a critical hardware storing rules for high-speed packet processing in SDN-enabled devices, can be supplied to each device with very limited quantity because it is expensive and energy-consuming. To efficiently use TCAM resources, we propose a rule multiplexing scheme, in which the same set of rules deployed on each node apply to the whole flow of a session going through but towards different paths. Based on this scheme, we study the rule placement problem with the objective of minimizing rule space occupation for multiple unicast sessions under QoS constraints. We formulate the optimization problem jointly considering routing engineering and rule placement under both existing and our rule multiplexing schemes. Via an extensive review of the state-of-the-art work, to the best of our knowledge, we are the first to study the non-routing-rule placement problem. Finally, extensive simulations are conducted to show that our proposals significantly outperform existing solutions.