Analysis of power-saving techniques over a large multi-use cluster with variable workload

Reduction of power consumption for any computer system is now an important issue, although this should be carried out in a manner that is not detrimental to the users of that computer system. We present a number of policies that can be applied to multi-use clusters where computers are shared between interactive users and high-throughput computing. We evaluate policies by trace-driven simulations to determine the effects on power consumed by the high-throughput workload and impact on high-throughput users. We further evaluate these policies for higher workloads by synthetically generating workloads based around the profiled workload observed through our system. We demonstrate that these policies could save 55% of the currently used energy for our high-throughput jobs over our current cluster policies without affecting the high-throughput users’ experience

Substrate preferences of coexisting invasive amphipods, Dikerogammarus villosus and Dikerogammarus haemobaphes, under field and laboratory conditions

Two Ponto-Caspian amphipods, Dikerogammarus villosus and Dikerogammarus haemobaphes, have expanded their geographical ranges from eastern Europe into Great Britain in recent years. This study represents one of the first examining the distribution and habitat preferences of coexisting populations of D. haemobaphes and D. villosus via field and laboratory experiments in the UK. Field surveys of a recently invaded lowland reservoir in the UK are complimented with ex situ laboratory mesocosm experiments examining the substrate preferences of coexisting populations of D. villosus and D. haemobaphes. Results from the field study indicated that D. haemobaphes dominated the macroinvertebrate community within the reservoir and demonstrated a strong affinity for large cobble and artificial substrates. D. villosus occurred at lower abundances but displayed a strong preference for coarse cobble substrates. A third invasive amphipod, Crangonyx pseudogracilis, was largely confined to sand/silt habitats. Laboratory mesocosm experiments clearly supported the field observations of D. villosus and D. haemobaphes with both species demonstrating a preference for cobble substrates. Results from the study highlight the importance of characterising physical habitat when investigating biological invasions and suggest that habitat availability may influence the extent and speed at which range expansion of new amphipod invaders occurs

Characterisation of acute respiratory infections at a United Kingdom paediatric teaching hospital: observational study assessing the impact of influenza A (2009 pdmH1N1) on predominant viral pathogens

Background According to the World Health Organisation, influenza A (2009 pdmH1N1) has moved into the post-pandemic phase, but there were still high numbers of infections occurring in the United Kingdom in 2010-11. It is therefore important to examine the burden of acute respiratory infections at a large children’s hospital to determine pathogen prevalence, occurrence of co-infection, prevalence of co-morbidities and diagnostic yield of sampling methods. Methods This was a retrospective study of respiratory virus aetiology in acute admissions to a paediatric teaching hospital in the North West of England between 1st April 2010 and 31st March 2011. Respiratory samples were analysed either with a rapid RSV test if the patient had symptoms suggestive of bronchiolitis, followed by multiplex PCR testing for ten respiratory viruses, or with multiplex PCR testing alone if the patient had suspected other ARI. Patient demographics and data regarding severity of illness, presence of co-morbidities and respiratory virus sampling method were retrieved from case notes. Results 645 patients were admitted during the study period. 82/645 (12.7%) patients were positive for 2009 pdmH1N1, of whom 24 (29.2%) required PICU admission, with 7.3% mortality rate. Viral co-infection occurred in 48/645 (7.4%) patients and was not associated with more severe disease. Co-morbidities were present more frequently in older children, but there was no significant difference in prevalence of co-morbidity between 2009 pdmH1N1 patients and those with other ARI. NPA samples had the highest diagnostic yield with 192/210 (91.4%) samples yielding an organism. Conclusions Influenza A (2009 pdmH1N1) is an ongoing cause of occasionally severe disease affecting both healthy children and those with co-morbidities. Surveillance of viral pathogens provides valuable information on patterns of disease

Model-Based Security Testing

Security testing aims at validating software system requirements related to security properties like confidentiality, integrity, authentication, authorization, availability, and non-repudiation. Although security testing techniques are available for many years, there has been little approaches that allow for specification of test cases at a higher level of abstraction, for enabling guidance on test identification and specification as well as for automated test generation. Model-based security testing (MBST) is a relatively new field and especially dedicated to the systematic and efficient specification and documentation of security test objectives, security test cases and test suites, as well as to their automated or semi-automated generation. In particular, the combination of security modelling and test generation approaches is still a challenge in research and of high interest for industrial applications. MBST includes e.g. security functional testing, model-based fuzzing, risk- and threat-oriented testing, and the usage of security test patterns. This paper provides a survey on MBST techniques and the related models as well as samples of new methods and tools that are under development in the European ITEA2-project DIAMONDS.Comment: In Proceedings MBT 2012, arXiv:1202.582

Model-based inference of conditional extreme value distributions with hydrological applications

Multivariate extreme value models are used to estimate joint risk in a number of applications, with a particular focus on environmental fields ranging from climatology and hydrology to oceanography and seismic hazards. The semi-parametric conditional extreme value model of Heffernan and Tawn involving a multivariate regression provides the most suitable of current statistical models in terms of its flexibility to handle a range of extremal dependence classes. However, the standard inference for the joint distribution of the residuals of this model suffers from the curse of dimensionality because, in a d-dimensional application, it involves a d−1-dimensional nonparametric density estimator, which requires, for accuracy, a number points and commensurate effort that is exponential in d. Furthermore, it does not allow for any partially missing observations to be included, and a previous proposal to address this is extremely computationally intensive, making its use prohibitive if the proportion of missing data is nontrivial. We propose to replace the d−1-dimensional nonparametric density estimator with a model-based copula with univariate marginal densities estimated using kernel methods. This approach provides statistically and computationally efficient estimates whatever the dimension, d, or the degree of missing data. Evidence is presented to show that the benefits of this approach substantially outweigh potential misspecification errors. The methods are illustrated through the analysis of UK river flow data at a network of 46 sites and assessing the rarity of the 2015 floods in North West England

Etiology of Childhood Bacteremia and Timely Antibiotics Administration in the Emergency Department

BACKGROUND: Bacteremia is now an uncommon presentation to the children’s emergency department (ED) but is associated with significant morbidity and mortality. Its evolving etiology may affect the ability of clinicians to initiate timely, appropriate antimicrobial therapy. METHODS: A retrospective time series analysis of bacteremia was conducted in the Alder Hey Children’s Hospital ED between 2001 and 2011. Data on significant comorbidities, time to empirical therapy, and antibiotic susceptibility were recorded. RESULTS: A total of 575 clinical episodes were identified, and Streptococcus pneumoniae (n = 109), Neisseria meningitidis (n = 96), and Staphylococcus aureus (n = 89) were commonly isolated. The rate of bacteremia was 1.42 per 1000 ED attendances (95% confidence interval: 1.31–1.53). There was an annual reduction of 10.6% (6.6%–14.5%) in vaccine-preventable infections, and an annual increase of 6.7% (1.2%–12.5%) in Gram-negative infections. The pneumococcal conjugate vaccine was associated with a 49% (32%–74%) reduction in pneumococcal bacteremia. The rate of health care–associated bacteremia increased from 0.17 to 0.43 per 1000 ED attendances (P = .002). Susceptibility to empirical antibiotics was reduced (96.3%–82.6%; P < .001). Health care–associated bacteremia was associated with an increased length of stay of 3.9 days (95% confidence interval: 2.3–5.8). Median time to antibiotics was 184 minutes (interquartile range: 63–331) and 57 (interquartile range: 27–97) minutes longer in Gram-negative bacteremia than in vaccine-preventable bacteremia. CONCLUSIONS: Changes in the etiology of pediatric bacteremia have implications for prompt, appropriate empirical treatment. Increasingly, pediatric bacteremia in the ED is health care associated, which increases length of inpatient stay. Prompt, effective antimicrobial administration requires new tools to improve recognition, in addition to continued etiological surveillance

Functional status predicts acute care readmissions from inpatient rehabilitation in the stroke population

Objective: Acute care readmission risk is an increasingly recognized problem that has garnered significant attention, yet the reasons for acute care readmission in the inpatient rehabilitation population are complex and likely multifactorial. Information on both medical comorbidities and functional status is routinely collected for stroke patients participating in inpatient rehabilitation. We sought to determine whether functional status is a more robust predictor of acute care readmissions in the inpatient rehabilitation stroke population compared with medical comorbidities using a large, administrative data set. Methods: A retrospective analysis of data from the Uniform Data System for Medical Rehabilitation from the years 2002 to 2011 was performed examining stroke patients admitted to inpatient rehabilitation facilities. A Basic Model for predicting acute care readmission risk based on age and functional status was compared with models incorporating functional status and medical comorbidities (Basic-Plus) or models including age and medical comorbidities alone (Age-Comorbidity). C-statistics were compared to evaluate model performance. Findings: There were a total of 803,124 patients: 88,187 (11%) patients were transferred back to an acute hospital: 22,247 (2.8%) within 3 days, 43,481 (5.4%) within 7 days, and 85,431 (10.6%) within 30 days. The C-statistics for the Basic Model were 0.701, 0.672, and 0.682 at days 3, 7, and 30 respectively. As compared to the Basic Model, the best-performing Basic-Plus model was the Basic+Elixhauser model with C-statistics differences of +0.011, +0.011, and + 0.012, and the best-performing Age-Comorbidity model was the Age+Elixhauser model with C-statistic differences of -0.124, -0.098, and -0.098 at days 3, 7, and 30 respectively. Conclusions: Readmission models for the inpatient rehabilitation stroke population based on functional status and age showed better predictive ability than models based on medical comorbidities

Infectivity of Plasmodium falciparum in malaria-naive individuals is related to knob expression and cytoadherence of the parasite

Plasmodium falciparum is the most virulent human malaria parasite because of its ability to cytoadhere in the microvasculature. Nonhuman primate studies demonstrated relationships among knob expression, cytoadherence, and infectivity. This has not been examined in humans. Cultured clinical-grade P. falciparum parasites (NF54, 7G8, and 3D7B) and ex vivo-derived cell banks were characterized. Knob and knob-associated histidine-rich protein expression, CD36 adhesion, and antibody recognition of parasitized erythrocytes (PEs) were evaluated. Parasites from the cell banks were administered to malaria-naive human volunteers to explore infectivity. For the NF54 and 3D7B cell banks, blood was collected from the study participants for in vitro characterization. All parasites were infective in vivo. However, infectivity of NF54 was dramatically reduced. In vitro characterization revealed that unlike other cell bank parasites, NF54 PEs lacked knobs and did not cytoadhere. Recognition of NF54 PEs by immune sera was observed, suggesting P. falciparum erythrocyte membrane protein 1 expression. Subsequent recovery of knob expression and CD36-mediated adhesion were observed in PEs derived from participants infected with NF54. Knobless cell bank parasites have a dramatic reduction in infectivity and the ability to adhere to CD36. Subsequent infection of malaria-naive volunteers restored knob expression and CD36-mediated cytoadherence, thereby showing that the human environment can modulate virulence