The impact of the access point power model on the energy-efficient management of infrastructured wireless LANs

The reduction of the energy footprint of large and mid-sized IEEE 802.11 access networks is gaining momentum. When operating at the network management level, the availability of an accurate power model of the APs becomes of paramount importance, because different detail levels have a non-negligible impact on the performance of the optimisation algorithms. The literature is plentiful of AP power models, and choosing the right one is not an easy task. In this paper we report the outcome of a thorough study on the impact that various inflections of the AP power model have when minimising the energy consumption of the infrastructure side of an enterprise wireless LAN. Our study, performed on several network scenarios and for various device energy profiles, reveals that simple one- and two-component models can provide excellent results in practically all cases. Conversely, employing accurate and detailed power models rarely offers substantial advantages in terms of power reduction, but, on the other hand, makes the solving algorithms much slower to execute

Transcriptome analysis of haploid male gametophyte development in Arabidopsis

BACKGROUND: The haploid male gametophyte generation of flowering plants consists of two- or three-celled pollen grains. This functional specialization is thought to be a key factor in the evolutionary success of flowering plants. Moreover, pollen ontogeny is also an attractive model in which to dissect cellular networks that control cell growth, asymmetric cell division and cellular differentiation. Our objective, and an essential step towards the detailed understanding of these processes, was to comprehensively define the male haploid transcriptome throughout development. RESULTS: We have developed staged spore isolation procedures for Arabidopsis and used Affymetrix ATH1 genome arrays to identify a total of 13,977 male gametophyte-expressed mRNAs, 9.7% of which were male-gametophyte-specific. The transition from bicellular to tricellular pollen was accompanied by a decline in the number of diverse mRNA species and an increase in the proportion of male gametophyte-specific transcripts. Expression profiles of regulatory proteins and distinct clusters of coexpressed genes were identified that could correspond to components of gametophytic regulatory networks. Moreover, integration of transcriptome and experimental data revealed the early synthesis of translation factors and their requirement to support pollen tube growth. CONCLUSIONS: The progression from proliferating microspores to terminally differentiated pollen is characterized by large-scale repression of early program genes and the activation of a unique late gene-expression program in maturing pollen. These data provide a quantum increase in knowledge concerning gametophytic transcription and lay the foundations for new genomic-led studies of the regulatory networks and cellular functions that operate to specify male gametophyte development

A phase I study of the nitroimidazole hypoxia marker SR4554 using 19F magnetic resonance spectroscopy

SR4554 is a fluorine-containing 2-nitroimidazole, designed as a hypoxia marker detectable with 19F magnetic resonance spectroscopy (MRS). In an initial phase I study of SR4554, nausea/vomiting was found to be dose-limiting, and 1400 mg m−2 was established as MTD. Preliminary MRS studies demonstrated some evidence of 19F retention in tumour. In this study we investigated higher doses of SR4554 and intratumoral localisation of the 19F MRS signal. Patients had tumours 3 cm in diameter and 4 cm deep. Measurements were performed using 1H/19F surface coils and localised 19F MRS acquisition. SR4554 was administered at 1400 mg m−2, with subsequent increase to 2600 mg m−2 using prophylactic metoclopramide. Spectra were obtained immediately post infusion (MRS no. 1), at 16 h (MRS no. 2) and 20 h (MRS no. 3), based on the SR4554 half-life of 3.5 h determined from a previous study. 19Fluorine retention index (%) was defined as (MRS no. 2/MRS no. 1)*100. A total of 26 patients enrolled at: 1400 (n=16), 1800 (n=1), 2200 (n=1) and 2600 mg m−2 (n=8). SR4554 was well tolerated and toxicities were all grade 1; mean plasma elimination half-life was 3.7±0.9 h. SR4554 signal was seen on both unlocalised and localised MRS no. 1 in all patients. Localised 19F signals were detected at MRS no. 2 in 5 out of 9 patients and 4 out of 5 patients at MRS no. 3. The mean retention index in tumour was 13.6 (range 0.6-43.7) compared with 4.1 (range 0.6-7.3) for plasma samples taken at the same times (P=0.001) suggesting 19F retention in tumour and, therefore, the presence of hypoxia. We have demonstrated the feasibility of using 19F MRS with SR4554 as a potential method of detecting hypoxia. Certain patients showed evidence of 19F retention in tumour, supporting further development of this technique for detection of tumour hypoxia

Molecular Foundations of Reproductive Lethality in Arabidopsis thaliana

The SeedGenes database (www.seedgenes.org) contains information on more than 400 genes required for embryo development in Arabidopsis. Many of these EMBRYO-DEFECTIVE (EMB) genes encode proteins with an essential function required throughout the life cycle. This raises a fundamental question. Why does elimination of an essential gene in Arabidopsis often result in embryo lethality rather than gametophyte lethality? In other words, how do mutant (emb) gametophytes survive and participate in fertilization when an essential cellular function is disrupted? Furthermore, why do some mutant embryos proceed further in development than others? To address these questions, we first established a curated dataset of genes required for gametophyte development in Arabidopsis based on information extracted from the literature. This provided a basis for comparison with EMB genes obtained from the SeedGenes dataset. We also identified genes that exhibited both embryo and gametophyte defects when disrupted by a loss-of-function mutation. We then evaluated the relationship between mutant phenotype, gene redundancy, mutant allele strength, gene expression pattern, protein function, and intracellular protein localization to determine what factors influence the phenotypes of lethal mutants in Arabidopsis. After removing cases where continued development potentially resulted from gene redundancy or residual function of a weak mutant allele, we identified numerous examples of viable mutant (emb) gametophytes that required further explanation. We propose that the presence of gene products derived from transcription in diploid (heterozygous) sporocytes often enables mutant gametophytes to survive the loss of an essential gene in Arabidopsis. Whether gene disruption results in embryo or gametophyte lethality therefore depends in part on the ability of residual, parental gene products to support gametophyte development. We also highlight here 70 preglobular embryo mutants with a zygotic pattern of inheritance, which provide valuable insights into the maternal-to-zygotic transition in Arabidopsis and the timing of paternal gene activation during embryo development

A streaming approach to reveal crowded events from cellular data

Anomaly detection has been a very popular research topics over the last few years and applies to many scenarios from different disciplines. This research focuses on crowded phenomena, and addresses the detection of popular events by looking for “anomalous” patterns in cellular traffic data. In particular, the paper elaborates upon previous proposals and presents two streaming algorithms based on the wavelet decomposition of traffic data. The new algorithms consume traffic samples as soon as they are available, elaborate the data in real time and possibly raise alarms upon threshold crossing. The effectiveness of the approach is assessed by using the public dataset containing the real cellular data acquired over the network of the most popular Italian traffic operator. The experiments prove that the streaming algorithms generally achieve performance comparable to that of their offline counterparts, and that the small degradation that may occasionally be observed is however well counterbalanced by the obvious advantage of detecting anomalies in real-time with no need to wait for the elaboration of overly long traffic timeseries

On the Build-Up of Large Queues in a Queueing Model with Fractional Brownian Motion Input

We analyze the way in which large queues build up in the single-server fractional Brownian motion queueing model. The large deviations problem for the queue-length process can be rephrased as a moderate deviations problem for the underlying white noise. This framework allows us to obtain not only an asymptotic expression for the probability of overflow, but also the most likely path followed by the queue-length process to reach the overflow level and prediction of post-overflow behaviour. The model we consider has stationary increments: there is also a non-stationary version of fractional Brownian motion, introduced by Levy, which formed the basis for a similar study by Chang, Yao and Zajic. We compare our results with theirs, and illustrate the essential differences between the two models

Orchestration and Control in Software-Defined 5G Networks: Research Challenges

The fifth generation (5G) of cellular networks promises to be a major step in the evolution of wireless technology. 5G is planned to be used in a very broad set of application scenarios. These scenarios have strict heterogeneous requirements that will be accomplished by enhancements on the radio access network and a collection of innovative wireless technologies. Softwarization technologies, such as Software-Defined Networking (SDN) and Network Function Virtualization (NFV), will play a key role in integrating these different technologies. Network slicing emerges as a cost-efficient solution for the implementation of the diverse 5G requirements and verticals. The 5G radio access and core networks will be based on a SDN/NFV infrastructure, which will be able to orchestrate the resources and control the network in order to efficiently and flexibly and with scalability provide network services. In this paper, we present the up-to-date status of the software-defined 5G radio access and core networks and a broad range of future research challenges on the orchestration and control aspects.publishedVersio