bluuebunny/crossref_metadata_2025 huggingface dataset:
Human responses to bright light of different durations
Authors: Chang Anne‐Marie , Santhi Nayantara , St Hilaire Melissa , Gronfier Claude , Bradstreet Dayna S. , Duffy Jeanne F. , Lockley Steven W. , Kronauer Richard E. , Czeisler Charles A.
Published: April 2012

Key points

Light is the strongest time cue for entrainment and phase resetting of the circadian clock.

In humans, exposure to long‐duration light (6.5 h) in the late evening/early night causes phase delays, suppresses melatonin and increases alertness.

Here we studied the effects of different durations of exposure to a single high‐intensity (∼10,000 lux) light pulse (0.2 h, 1 h, 2.5 h and 4.0 h) on phase shifting, suppression of melatonin and self‐reported sleepiness in young men and women.

Phase‐resetting and melatonin‐suppression responses were dose dependent and non‐linear; shorter light exposures more efficiently phase‐shift the clock, suppress melatonin and induce alertness.

Abstract  Light exposure in the early night induces phase delays of the circadian rhythm in melatonin in humans. Previous studies have investigated the effect of timing, intensity, wavelength, history and pattern of light stimuli on the human circadian timing system. We present results from a study of the duration–response relationship to phase‐delaying bright light. Thirty‐nine young healthy participants (16 female; 22.18 ± 3.62 years) completed a 9‐day inpatient study. Following three baseline days, participants underwent an initial circadian phase assessment procedure in dim light (<3 lux), and were then randomized for exposure to a bright light pulse (∼10,000 lux) of 0.2 h, 1.0 h, 2.5 h or 4.0 h duration during a 4.5 h controlled‐posture episode centred in a 16 h wake episode. After another 8 h sleep episode, participants completed a second circadian phase assessment. Phase shifts were calculated from the difference in the clock time of the dim light melatonin onset (DLMO) between the initial and final phase assessments. Exposure to varying durations of bright light reset the circadian pacemaker in a dose‐dependent, non‐linear manner. Per minute of exposure, the 0.2 h duration was over 5 times more effective at phase delaying the circadian pacemaker (1.07 ± 0.36 h) as compared with the 4.0 h duration (2.65 ± 0.24 h). Acute melatonin suppression and subjective sleepiness also had a dose‐dependent response to light exposure duration. These results provide strong evidence for a non‐linear resetting response of the human circadian pacemaker to light duration.
C1 neurons excite locus coeruleus and A5 noradrenergic neurons along with sympathetic outflow in rats
Authors: Abbott S. B. , Kanbar R. , Bochorishvili G. , Coates M. B. , Stornetta R. L. , Guyenet P. G.
Published: April 2012

Key points

C1 neurons activate sympathetic tone and stimulate the hypothalamic–pituitary–adrenal axis in circumstances such as pain, hypoxia or hypotension.

C1 neurons innervate pontine noradrenergic cell groups, including the locus coeruleus (LC) and A5.

In this study, using an optogenetic approach in anaesthetized rats, we show that C1 neurons form excitatory synapses with LC neurons and that selective stimulation of C1 neurons activates LC and A5 neurons.

These results show that the C1 neurons activate pontine noradrenergic neurons through the release of glutamate. This effect may be important in the arousal‐promoting effects of hypoxia and pain.
Fault Diagnostics of Helicopter Gearboxes Based on Multi-Sensor Mixtured Hidden Markov Models
Authors: Chen Zhongsheng , Yang Yongmin
Published: April 2012

Accurate identification of faults in gearboxes is of vital importance for the safe operation of helicopters. Although hidden Markov models (HMMs) with Gaussian observations have been successfully used for fault diagnostics of mechanical systems, a Gaussian HMM must assume that the observation sequence is generated from a Gaussian process. Conversely, vibration signals from helicopter gearboxes are often non-Gaussian and non-stationary. Also, it always needs to use multi-sensors for more accurate fault diagnostics in practice. Thus, a classical Gaussian HMM may not meet the need of helicopter gearboxes, and it needs to study novel HMMs to model multi-sensor, non-Gaussian signals. This paper presents a multi-sensor mixtured HMM (MSMHMM), which is built on multi-sensor signals. For a MSMHMM, each sensor signal will be considered as the mixture of non-Gaussian sources, so it can depict non-Gaussian observation sequences very well. Then, learning mechanisms of MSMHMM parameters are formulated in detail based on the expectation-maximization (EM) algorithm and a framework of MSMHMM-based fault diagnostics is proposed. In the end, the proposed method is validated on a helicopter gearbox, and the results are very exciting.
Overall Motion Planning for Kinematically Redundant Parallel Manipulators
Authors: Carretero Juan A. , Ebrahimi Iman , Boudreau Roger
Published: April 2012

In this work, a new approach for motion planning of kinematically redundant parallel manipulators is proposed and compared with a method previously proposed by the authors called point-to-point motion planning (PPMP). Overall motion planning (OMP) consists of determining actuation schemes that optimize the manipulator’s performance while considering the entire given trajectory of the end-effector at once. The results of OMP are compared with those of PPMP of a kinematically redundant manipulator. It is shown that the proposed OMP strategy can generate actuation schemes for given trajectories such that the manipulator avoids singular configurations better than the PPMP strategy.
Drug Efflux by a Small Multidrug Resistance Protein Is Inhibited by a Transmembrane Peptide
Authors: Poulsen Bradley E. , Deber Charles M.
Published: April 2012

Drug-resistant bacteria use several families of membrane-embedded transporters to remove antibiotics from the cell. One such family is the small multidrug resistance proteins (SMRs) that, because of their relatively small size (ca. 110 residues with four transmembrane [TM] helices), must form (at least) dimers to efflux drugs. Here, we use a Lys-tagged synthetic peptide with exactly the same sequence as TM4 of the full-length SMR Hsmr from
Halobacterium salinarum
[TM4 sequence: AcA(Sar)
3
-VAGVVGLALIVAGVVVLNVAS-KKK (Sar =
N
-methylglycine)] to compete with and disrupt the native TM4-TM4 interactions believed to constitute the locus of Hsmr dimerization. Using a cellular efflux assay of the fluorescent SMR substrate ethidium bromide, we determined that bacterial cells containing Hsmr are able to remove cellular ethidium via first-order exponential decay with a rate constant (
k
) of 10.1 × 10
−3
± 0.7 × 10
−3
s
−1
. Upon treatment of the cells with the TM4 peptide, we observed a saturable ∼60% decrease in the efflux rate constant to 3.7 × 10
−3
± 0.2 × 10
−3
s
−1
. In corresponding experiments with control peptides, including scrambled sequences and a sequence with
d
-chirality, a decrease in ethidium efflux either was not observed or was marginal, likely from nonspecific effects. The designed peptides did not evoke bacterial lysis, indicating that they act via the α-helicity and membrane insertion propensities of the native TM4 helix. Our overall results suggest that this approach could conceivably be used to design hydrophobic peptides for disruption of key TM-TM interactions of membrane proteins and represent a valuable route to the discovery of new therapeutics.
Malachite Green Interferes with Postantibiotic Recovery of Mycobacteria
Authors: Gelman Ekaterina , McKinney John D. , Dhar Neeraj
Published: April 2012

The genus
Mycobacterium
comprises slow-growing species with generation times ranging from hours to weeks. The protracted incubation time before colonies appear on solid culture medium can result in overgrowth by faster-growing microorganisms. To prevent contamination, the solid media used in laboratories and clinics for cultivation of mycobacteria contain the arylmethane compound malachite green, which has broad-spectrum antimicrobial activity. Malachite green has no impact on the plating efficiency of mycobacteria when cells are grown under normal conditions. However, we found that malachite green interfered with colony formation when bacteria were preexposed to antibiotics targeting cell wall biogenesis (isoniazid, ethionamide, ethambutol). This inhibitory effect of malachite green was not observed when bacteria were preexposed to antibiotics targeting cellular processes other than cell wall biogenesis (rifampin, moxifloxacin, streptomycin). Sputum specimens from tuberculosis patients are routinely evaluated on solid culture medium containing high concentrations of malachite green. This practice could lead to underestimation of bacterial loads and overestimation of chemotherapeutic efficacy.
Role of Common
bla
OXA-24/OXA-40
-Carrying Platforms and Plasmids in the Spread of OXA-24/OXA-40 among Acinetobacter Species Clinical Isolates
Authors: Grosso Filipa , Quinteira Sandra , Poirel Laurent , Novais Ângela , Peixe Luísa
Published: April 2012

The spread of OXA-24/OXA-40 (OXA-24/40)-producing
Acinetobacter
spp. in the Iberian Peninsula has been strongly influenced by clonal expansion, but the role of horizontal gene transfer has scarcely been explored.
bla
OXA-24/40
-carrying plasmids and genetic environments were characterized in representative (
n
= 15)
Acinetobacter
species clinical isolates (obtained between 2001 and 2007) by
Acinetobacter baumannii
PCR-based replicon typing, sequencing, hybridization, and restriction fragment length polymorphism. Besides the identification of
bla
OXA-24/40
within the chromosomes of some isolates, the circulation of common
bla
OXA-24/40
-carrying plasmids (30-kb
repA_AB
; 10-kb
aci2
) and genetic backbones among
Acinetobacter
spp. was demonstrated.
Chromosome-Encoded Extended-Spectrum Class A β-Lactamase MIN-1 from Minibacterium massiliensis
Authors: Bercot Béatrice , Nordmann Patrice , Drancourt Michel , Poirel Laurent
Published: April 2012

Minibacterium massiliensis
strain CIP107820 is a recently discovered waterborne Gram-negative rod isolated from hospital water samples. It harbors a chromosomally located gene encoding an Ambler class A extended-spectrum β-lactamase termed MIN-1, sharing 56%, 54%, and 51% amino acid identities with β-lactamases LUT-1, KPC-2, and CTX-M-2, respectively. β-Lactamase MIN-1 hydrolyzes penicillins, narrow-spectrum cephalosporins, cefotaxime, and, less efficiently, cefepime, while ceftazidime and carbapenems are very poor substrates, and cephamycins and aztreonam are not hydrolyzed.
Enterohemorrhagic Escherichia coli O157:H7 Shiga Toxins Inhibit Gamma Interferon-Mediated Cellular Activation
Authors: Ho Nathan K. , Ossa Juan C. , Silphaduang Uma , Johnson Roger , Johnson-Henry Kathene C. , Sherman Philip M.
Published: April 2012

Enterohemorrhagic
Escherichia coli
(EHEC) serotype O157:H7 is a food-borne pathogen that causes significant morbidity and mortality in developing and industrialized nations. EHEC infection of host epithelial cells is capable of inhibiting the gamma interferon (IFN-γ) proinflammatory pathway through the inhibition of Stat-1 phosphorylation, which is important for host defense against microbial pathogens. The aim of this study was to determine the bacterial factors involved in the inhibition of Stat-1 tyrosine phosphorylation. Human HEp-2 and Caco-2 epithelial cells were challenged directly with either EHEC or bacterial culture supernatants and stimulated with IFN-γ, and then the protein extracts were analyzed by immunoblotting. The data showed that IFN-γ-mediated Stat-1 tyrosine phosphorylation was inhibited by EHEC secreted proteins. Using two-dimensional difference gel electrophoresis, EHEC Shiga toxins were identified as candidate inhibitory factors. EHEC Shiga toxin mutants were then generated and complemented in
trans
, and mutant culture supernatant was supplemented with purified Stx to confirm their ability to subvert IFN-γ-mediated cell activation. We conclude that while other factors are likely involved in the suppression of IFN-γ-mediated Stat-1 tyrosine phosphorylation,
E. coli
-derived Shiga toxins represent a novel mechanism by which EHEC evades the host immune system.
Phenotypic, Morphological, and Functional Heterogeneity of Splenic Immature Myeloid Cells in the Host Response to Tularemia
Authors: Rasmussen John W. , Tam Jason W. , Okan Nihal A. , Mena Patricio , Furie Martha B. , Thanassi David G. , Benach Jorge L. , van der Velden Adrianus W. M.
Published: April 2012

Recent studies have linked accumulation of the Gr-1+CD11b+cell phenotype with functional immunosuppression in diverse pathological conditions, including bacterial and parasitic infections and cancer. Gr-1+CD11b+cells were the largest population of cells present in the spleens of mice infected with sublethal doses of theFrancisella tularensislive vaccine strain (LVS). In contrast, the number of T cells present in the spleens of these mice did not increase during early infection. There was a significant delay in the kinetics of accumulation of Gr-1+CD11b+cells in the spleens of B-cell-deficient mice, indicating that B cells play a role in recruitment and maintenance of this population in the spleens of mice infected withF. tularensis. The splenic Gr-1+CD11b+cells in tularemia were a heterogeneous population that could be further subdivided into monocytic (mononuclear) and granulocytic (polymorphonuclear) cells using the Ly6C and Ly6G markers and differentiated into antigen-presenting cells followingex vivoculture. Monocytic, CD11b+Ly6ChiLy6G−cells but not granulocytic, CD11b+Ly6CintLy6G+cells purified from the spleens of mice infected withF. tularensissuppressed polyclonal T-cell proliferation via a nitric oxide-dependent pathway. Although the monocytic, CD11b+Ly6ChiLy6G−cells were able to suppress the proliferation of T cells, the large presence of Gr-1+CD11b+cells in mice that survivedF. tularensisinfection also suggests a potential role for these cells in the protective host response to tularemia.
CodY Deletion Enhances
In Vivo
Virulence of Community-Associated Methicillin-Resistant Staphylococcus aureus Clone USA300
Authors: Montgomery Christopher P. , Boyle-Vavra Susan , Roux Agnès , Ebine Kazumi , Sonenshein Abraham L. , Daum Robert S.
Published: April 2012

The
Staphylococcus aureus
global regulator CodY responds to nutrient availability by controlling the expression of target genes.
In vitro
, CodY represses the transcription of virulence genes, but it is not known if CodY also represses virulence
in vivo
. The dominant community-associated methicillin-resistant
S. aureus
(CA-MRSA) clone, USA300, is hypervirulent and has increased transcription of global regulators and virulence genes; these features are reminiscent of a strain defective in CodY. Sequence analysis revealed, however, that the
codY
genes of USA300 and other sequenced
S. aureus
isolates are not significantly different from the
codY
genes in strains known to have active CodY.
codY
was expressed in USA300, as well as in other pulsotypes assessed. Deletion of
codY
from a USA300 clinical isolate resulted in modestly increased expression of the global regulators
agr
and
saeRS
, as well as the gene encoding the toxin alpha-hemolysin (
hla
). A substantial increase (>30-fold) in expression of the
lukF-PV
gene, encoding part of the Panton-Valentine leukocidin (PVL), was observed in the
codY
mutant. All of these expression differences were reversed by complementation with a functional
codY
gene. Moreover, purified CodY protein bound upstream of the
lukSF-PV
operon, indicating that CodY directly represses expression of
lukSF-PV
. Deletion of
codY
increased the virulence of USA300 in necrotizing pneumonia and skin infection. Interestingly, deletion of
lukSF-PV
from the
codY
mutant did not attenuate virulence, indicating that the hypervirulence of the
codY
mutant was not explained by overexpression of PVL. These results demonstrate that CodY is active in USA300 and that CodY-mediated repression restrains the virulence of USA300.
Microbicidal Activity of Vascular Peroxidase 1 in Human Plasma via Generation of Hypochlorous Acid
Authors: Li Hong , Cao Zehong , Moore D. Ray , Jackson Patricia L. , Barnes Stephen , Lambeth J. David , Thannickal Victor J. , Cheng Guangjie
Published: April 2012

Members of the heme peroxidase family play an important role in host defense. Myeloperoxidase (MPO) is expressed in phagocytes and is the only animal heme peroxidase previously reported to be capable of using chloride ion as a substrate to form the highly microbicidal species hypochlorous acid (HOCl) at neutral pH. Despite the potent bacterial killing activity of HOCl, individuals who fail to express MPO typically show only a modest increase in some fungal infections. This may point to the existence of redundant host defense mechanisms. Vascular peroxidase 1 (VPO1) is newly discovered member of the heme peroxidase family. VPO1 is expressed in cells of the cardiovascular system and is secreted into the bloodstream. In the present study, we investigate whether VPO1 is capable of generating HOCl and its role in host defense. Like MPO, VPO1 in the presence of H
2
O
2
and chloride generates HOCl. VPO1-dependent HOCl generation was demonstrated by chlorination of taurine and tyrosine using mass spectrometry. In addition, the VPO1/H
2
O
2
/Cl
−
system can cause the chlorination of monochlorodimedone and the oxidation of 5-thio-2-nitrobenzoic acid. Purified VPO1 and VPO1 in plasma mediate bacterial killing that is dependent on chloride and H
2
O
2
; killing is inhibited by peroxidase inhibitors and by the H
2
O
2
scavenger catalase. In the presence of erythrocytes, bacterial killing by VPO1 is slightly reduced. Thus, VPO1, in addition to MPO, is the second member of the heme peroxidase family capable of generating HOCl under physiological conditions. VPO1 is likely to participate in host defense, with bactericidal activity mediated through the generation of HOCl.
Complete Genome Sequences of Newcastle Disease Virus Strains Circulating in Chicken Populations of Indonesia
Authors: Xiao Sa , Paldurai Anandan , Nayak Baibaswata , Samuel Arthur , Bharoto Eny E. , Prajitno Teguh Y. , Collins Peter L. , Samal Siba K.
Published: April 2012

Eight highly virulent Newcastle disease virus (NDV) strains were isolated from vaccinated commercial chickens in Indonesia during outbreaks in 2009 and 2010. The complete genome sequences of two NDV strains and the sequences of the surface protein genes (F and HN) of six other strains were determined. Phylogenetic analysis classified them into two new subgroups of genotype VII in the class II cluster that were genetically distinct from vaccine strains. This is the first report of complete genome sequences of NDV strains isolated from chickens in Indonesia.
Effects of recreational rock climbing and environmental variation on a sandstone cliff-face lichen community
Authors: Adams Matthew D. , Zaniewski Kamil
Published: April 2012

Lichen community composition was evaluated for both lichen cover and richness on a cliff face commonly used for recreational rock climbing. The sandstone outcrop is located on the Sibley Peninsula, which extends from the north shore of Lake Superior. One-hundred and twenty plots were examined. Each plot was 1 m2 in size, with 60 plots located on unclimbed cliff sections and 60 more located where recreational rock climbing regularly occurs. Lichen richness and cover were significantly lower on the rock climbing sections compared with unclimbed sections. Linear regression models indicated significant relationships with cover and richness to environmental response variables and climbing treatment. Detrended correspondence analysis indicated a separation of lichen community groups on this cliff, and major separations occurred between plots in each climbing treatment. Canonical correspondence analysis indicated a significant amount of community group variation between climbed and unclimbed locations related to climbing treatment and aspect of the plots. Climbing is found to have an impact on this sandstone cliff-face lichen community.
Reciprocal gender effects of a keystone alpine plant species on other plants, pollinators, and arthropods
Authors: Lortie Christopher J. , Reid Anya M.
Published: April 2012

The term facilitation generally describes positive interactions between plants, and a common approach in these studies is to identify a dominant plant to structure sampling. Unfortunately, whilst this field has rapidly expanded community ecology, it rarely includes other trophic levels such as insects and pollinators. Here, we combine facilitation, pollination, and reciprocity measures to explore the general hypothesis that sexual dimorphism in a benefactor plant species mediates its impact. The following three predictions were tested and supported using the gynodioecious alpine cushion plant Silene acaulis (L.) Jacq.: (i) that the trait set of a gynodioecious benefactor plant varies between genders; (ii) that dimorphism changes the facilitation of other plants, arthropods, and pollinators; and (iii) that insect selectivity, particularly pollinators, reciprocally impacts the reproductive output of the two genders. Female S. acaulis cushion plants produced significantly more flowers but they were smaller than those of hermaphrodites. Hermaphrodite cushions facilitated other plant species and pollinators more effectively than females, whilst females strongly facilitated more arthropods. Finally, female plants have significantly higher reproductive output as estimated by fruit and seed production, and this was directly related to visitation rate by pollinators. Hence, this study clearly establishes the value of combining some of the common themes of pollination biology such as sexual dimorphism, floral morphology, and measuring reproduction with the study of positive plant–plant interactions.
The response of flowering time to global warming in a high-altitude plant: the impact of genetics and the environment
Authors: Brunet Johanne , Larson-Rabin Zachary
Published: April 2012

In high-altitude habitats, an increase in temperature and greater precipitation in the form of rain represent climate changes typically associated with global warming. We determined whether phenotypic plasticity and genetic changes in the mean phenotype could affect the adaptation of flowering time to changes in the environment resulting from global warming in a montane plant species, Aquilegia coerulea James. We collected seeds from 17 plants from each of three natural populations. For each of these 51 families, we assigned 3–4 individuals to each of four water and temperature treatments. We observed phenotypic plasticity in flowering time in response to both temperature and water availability but no genetic variance or genetic differentiation in phenotypic plasticity. These results indicate that phenotypic plasticity could provide a quick response to environmental changes but provides little evolutionary potential. In contrast to phenotypic plasticity in flowering time, the mean flowering time did vary among families and among populations, suggesting a genetic basis to flowering time and adaptation in the different populations. The most likely scenario for the adaptation of this plant species to climate change is a rapid response via phenotypic plasticity followed by selection and micro-evolutionary changes in the mean phenotype.
CHAOTIC DETECTOR FOR BPSK SIGNALS IN VERY LOW SNR CONDITIONS
Authors: ZHANG SONG , RUI GUO-SHENG
Published: April 2012

Chaotic detection of weak signals based on Duffing oscillator uses the property of sensitive dependence on initial conditions (SDIC). A small signal can cause a transition between the states of the system and thus be detected. Different from the early works, we concentrate on using chaotic oscillator as a detector for BPSK signals in very low signal-to-noise ratio (SNR) conditions. Phase transition identification is the key step of weak signals detection by using Duffing oscillator. In this paper, we expose a novel algorithm to use Teager energy operator (TEO) to identify the phase transition, which is more easily to be calculated than the usually used methods. According to this algorithm, a methodology is proposed for detection for BPSK signals using Duffing oscillator. A powerline carrier communication system is studied as an example to illustrate the bit error performance of the proposed chaotic detector. The simulation results show that the proposed detector works much better than the traditional coherent demodulation in strong background noise, and it can improve the error performance of uncoded BPSK signal approaching the Shannon limit curve. The proposed chaotic detector gives us another way to approach the Shannon limit without using any complex channel code technology.
COALESCENCE OF THE TWO SECONDARY RESPONSES IN COUPLED DUFFING EQUATIONS
Authors: LAI TING-YU , TUNG PI-CHENG , HSIAO YUNG-CHIA
Published: April 2012

The novel coalescence of the secondary responses for the coupled Duffing equations are observed in this study. Two secondary responses that do not bifurcate from the primary responses merge into one due to saddle-node bifurcation generation within a specific parameter range. The frequency responses of the coupled Duffing equations are calculated using the harmonic balance method while the periodic orbits are detected by the shooting method. The stability of the periodic orbits is determined on utilizing Floquet theory. The parametric continuation algorithm is used to obtain the bifurcation points and bifurcation lines for a Duffing system with two varying parameters. The analytical results demonstrate the novel phenomenon that occurs in the Duffing equations.
ITERATION OF QUADRATIC MAPS ON MATRIX ALGEBRAS
Authors: NASCIMENTO BAPTISTA ALEXANDRA , CORREIA RAMOS CARLOS , MARTINS NUNO
Published: April 2012

We study the iteration of a quadratic family in the algebra of 2 × 2 real matrices, parameterized by a matrix C. We analyze and classify the existing cycles (periodic orbits) and their dependence on the parameter matrix. We discuss how new dynamical phenomena occur as a consequence of the noncommutativity of the matrix product. In particular, we show that the commutator of the initial condition with parameter matrix C has a decisive role in the overall dynamics.
Rapid earth modelling for appraisal and development studies of deep-water clastic reservoirs and the concept of ‘procycling’
Authors: Larue D. K. , Hovadik J.
Published: April 2012

Creating earth models for deep-water appraisal and development studies is perhaps the most challenging task confronting the petroleum geologist today. Data are limited (few wells, limited core, untested seismic quality), time is limited and drilling, testing and facilities costs are very high. Uncertainty in geological characterization of the reservoir can have the greatest potential impact on project value. How can a thorough characterization of reservoir uncertainty be made based on limited data and in a timely fashion? A workflow for creation of suites of models for appraisal and development studies of deep-water reservoirs is described. The goal of the workflow is to rapidly construct suites of earth models based on limited data that capture the full range of uncertainty in reservoir characteristics and properties. After characterizing possible distributions for individual parameters, suites of earth models are built in a single step using an experimental design framework, aided by a powerful workflow manager which automates earth model construction. Earth models created using the experimental design framework are seamlessly linked to flow simulation software. Plackett–Burman, folded Plackett–Burman and Full Factorial experimental designs were used in different appraisal and development cases. Multiple experimental designs were produced by adding and modifying uncertainty parameters as additional data arrived, and ideas about the possible character of the reservoir evolved. In the appraisal case described here, 6 experimental designs were made, 388 earth models were created and studied, and 79 of those models were dynamically simulated. The process of quickly building and re-building suites of earth models using experimental designs to address changing perceptions and concerns about uncertainty in reservoir character is termed here ‘procycling’. Procycling is complementary to experimental design studies, in that multiple experimental designs are employed over time: procycling focuses on changes in predictions made by individual experimental design studies. The results of procycling are not necessarily to change the perception of uncertainty (for example the range of possible outcomes), but to anchor what the limits of uncertainty are and what the most important uncertainties are with the given data.
How to trim a MST
Authors: Fujito Toshihiro
Published: April 2012

The
minimum cost-tree cover
problem is to compute a minimum cost-tree
T
in a given connected graph
G
with costs on the edges, such that the vertices spanned by
T
form a vertex cover for
G
. The problem is supposed to occur in applications of vertex cover and in edge-dominating sets when additional connectivity is required for solutions. Whereas a linear-time
2
-approximation algorithm for the unweighted case has been known for quite a while, the best approximation ratio known for the weighted case is
3
. Moreover, the
3
-approximation algorithms for such cases are far from practical due to their inefficiency.

In this article we present a fast, purely combinatorial
2
-approximation algorithm for the minimum cost-tree cover problem. It constructs a good approximate solution by trimming some leaves within a minimum spanning tree (MST); and, to determine which leaves to trim, it uses both the primal-dual schema and an instance layering technique adapted from the local ratio method.
Automating scientific discovery
Authors: Savage Neil
Published: April 2012

Computer scientists are teaching machines to run experiments, make inferences from the data, and use the results to conduct new experiments.
Digitization and copyright
Authors: Waldfogel Joel
Published: April 2012

Examining the effects of stealing on producers and consumers.
An
n
-gram analysis of
Communications
2000--2010
Authors: Soper Daniel S. , Turel Ofir
Published: April 2012

Applied to almost 3,500 articles it reveals computing's (and
Communications'
) culture, identity, and evolution.
Sharp utilization thresholds for some realtime scheduling problems
Authors: Gopalakrishnan Sathish
Published: April 2012

Scheduling policies for real-time systems exhibit threshold behavior that is related to the utilization of the task set they schedule, and in some cases this threshold is sharp. A task set is considered
schedulable
if it can be scheduled to meet all associated deadlines.
A schedulability test for a chosen policy is a test of feasibility: given a task set, can all deadlines be met?
For the rate monotonic scheduling policy, we show that periodic workload with utilization less than a threshold U
RM
can be scheduled almost surely and that all workload with utilization greater than U
RM
is almost surely not schedulable. We study such sharp threshold behavior in the context of processor scheduling using static task priorities, not only for periodic real-time tasks but for aperiodic real-time tasks as well. The notion of a utilization threshold provides a simple schedulability test for most real-time applications. These results improve our understanding of scheduling policies and provide an interesting characterization of the typical behavior of policies. The threshold is sharp (small deviations around the threshold cause schedulability, as a property, to appear or disappear) for most policies; this is a happy consequence that can be used to address the limitations of existing utilization-based tests for schedulability. We demonstrate the use of such an approach for balancing power consumption with the need to meet deadlines in web servers.
Synthesis of local-rule processes
Authors: Coffman Edward G.
Published: April 2012

How does one systematically program global computations in systems of a vast number of components restricted to local-rule interaction in a flat hierarchy? This question has been around since the 50's when cellular automata were introduced as models of such systems. The question posed here is known as the synthesis problem, and remains poorly understood. Terms like self-assembling and self-organizing are often used to describe computations on such systems. We mention a number of instances of local-rule processes at widely different scales in computer and network engineering: molecular computation, sensor-network computation, and computation on the Web. Typical performance questions that we address include the convergence to useful, non-degenerate behavior: does it always occur, and if so, how long does it take.
Bilateral matrix-exponential distributions (abstract only)
Authors: Bladt Mogens , Esparza Luz Judith R. , Nielsen Bo Friis
Published: April 2012

In this article we define the classes of bilateral and multivariate bilateral matrix-exponential distributions. These distributions have support on the entire real space and have rational moment-generating functions. These distributions extend the class of bilateral phasetype distributions of [1] and the class of multivariate matrix-exponential distributions of [9]. We prove a characterization theorem stating that a random variable has a bilateral multivariate distribution if and only if all linear combinations of the coordinates have a univariate bilateral matrix-exponential distribution. As an application we demonstrate that certain multivariate disions, which are governed by the underlying Markov jump process generating a phasetype distribution, have a bilateral matrix-exponential distribution at the time of absorption, see also [4].
Stochastic decomposition in production inventory with service time (abstract only)
Authors: Krishnamoorthy A. , Narayanan Viswanath C.
Published: April 2012

We study an (s, S) inventory system with positive service time (for an overview of the work reported so far in inventory with positive service time one may refer to Krishnamoorthy, Lakshmi and Manikandan: A survey on inventory models with positive service time, OPSEARCH, DOI 10.1007/s12597-010-0032-z). This leads to a queue of demands being formed. The process of demand arrival constitutes a Poisson process. The duration of each service is exponentially distributed. Our model is a supply chain where items are added to the inventory through a production process. This starts each time the inventory level goes down to s and continues to be on until inventory level reaches S with the time required to add one unit of the item into the inventory when the production is on, are independent, identically distributed exponential random variables. Further all distributions involved in this paper are assumed to be mutually independent. We assume that no customer joins the queue when the inventory level is 0. This assumption leads us to an explicit product form solution for the steady state probability vector, using a simple approach. This is despite the fact that there is a strong correlation between lead time (the time required to add an item into the inventory) and the number of customers joining the queue during the lead time (except when the inventory level is zero during which time no customer joins the queue). The technique is to combine the steady state probability vector of the classical M/M/1 queue and that of the production inventory system where each service requires negligible time and no backlogs are allowed. Using a similar technique, the expected length of a production cycle is also obtained explicitly. The optimality of the highest inventory level S and the production switching on level s has been studied using a cost function constructed using the steady state system performance measures. Since we have obtained explicit expressions for these measures, analytic expressions have been derived for the optimal values of S and s.

To show that our method can be applied to other similar problems, we analyze in detail a variant of the above problem (discussed in Schwarz M, Sauer. C, Daduna, H., Kulik, R and Szekli, R: M/M/1 Queueing systems with inventory, Queueing Systems, 54,55-78, 2006). For that model, we assume that in a production run, production occurs only once in a cycle and the amount produced is sufficient to take the inventory level back to S. A brief discussion on the application of our method to inventory system with lead time for replenishment has also been provided.
The multi-armed bandit, with constraints
Authors: Denardo Eric V. , Feinberg Eugene A. , Rothblum Uriel G.
Published: April 2012

The colorfully-named and much-studied multi-armed bandit is the following Markov decision problem: At epochs 1, 2, ... , a decision maker observes the current state of each of several Markov chains with rewards (bandits) and plays one of them. The Markov chains that are not played remain in their current states. The Markov chain that is played evolves for one transition according to its transition probabilities, earning an immediate reward (possibly negative) that can depend upon its current state and on the state to which transition occurs. Henceforth, to distinguish the states of the individual Markov chains from those of the Markov decision problem, the latter are called multi-states. Each multi-state prescribes a state for each of the Markov chains.

This version of the multi-armed bandit problem was originally solved by John Gittins. It has a large range of operations research applications including applications to resource allocation, scheduling, project management, and search.

A key result for the multi-armed bandit is that attention can be restricted to a simple class of decision procedures. A label is assigned to each state of each bandit such that no two states have the same label, even if they are in different bandits. A priority rule is a policy that, given each multistate, plays the Markov chain whose current state has the lowest label. The literature includes several different proofs of the optimality of a priority rule. Nearly all of these proofs rest on a family of optimal stopping times, one for each state of each bandit.

A different approach is taken here. Pair-wise comparison, rather than optimal stopping, is used to demonstrate the optimality of a priority rule. This is accomplished for models having linear and exponential utility functions. Elementary row operations are used to identify an optimal priority rule and to compute its expected utility for a given starting state.

Our analysis covers the cases of linear and exponential utilities. In the case of a linear utility function, the model is generalized to include constraints that link the bandits. With C constraints, an optimal policy is shown to take the form of an initial randomization over C + 1 priority rules, and column generation is proposed as a solution method.

The proposed computational methods are based on several matrix algorithms. First, an algorithm, called the Triangularizer, transforms the one-step rewards and transition probability matrixes for individual bandits by applying elementary row operations. The transformed matrixes, called finalized, are triangle: all their elements on diagonals and below diagonals are equal to zero. For a given index policy, running the transformed bandits is equivalent to running the original bandits. Second, the transition probabilities and one-step rewards of the transformed bandits are used to compute the performance characteristics of index policies in polynomial times. These computations are used by the column generation algorithm for multi-armed bandits with constraints.
Performance evaluation of large-scale dynamic systems
Authors: Anceaume Emmanuelle , Ludinard Romaric , Sericola Bruno
Published: April 2012

In this paper we present an in-depth study of the dynamicity and robustness properties of large-scale distributed systems, and in particular of peer-to-peer systems. When designing such systems, two major issues need to be faced. First, population of these systems evolves continuously (nodes can join and leave the system as often as they wish without any central authority in charge of their control), and second, these systems being open, one needs to defend against the presence of malicious nodes that try to subvert the system. Given robust operations and adversarial strategies, we propose an analytical model of the local behavior of clusters, based on Markov chains. This local model provides an evaluation of the impact of malicious behaviors on the correctness of the system. Moreover, this local model is used to evaluate analytically the performance of the global system, allowing to characterize the global behavior of the system with respect to its dynamics and to the presence of malicious nodes and then to validate our approach.
A novel key management scheme for wireless embedded systems
Authors: Lu Yung-Feng , Kuo Chin-Fu , Pang Ai-Chun
Published: April 2012

Wireless Embedded Systems (WEBs) has attracted significant interest in recent years, for instance, Wireless Sensor Networks (WSN), have recently been in the limelight for many domains. The characteristics of WEBs have imposed various restrictions on their system designs. Since embedded systems usually are developed by low-cost hardware, one major challenge in the development of many WEBs applications is to provide high-security features with limited resources. In this paper, we propose a novel key establishment scheme, named half-key scheme that based on the well-known random key pre-distribution scheme and DDHV-D deployment knowledge to provide resource-efficient key management in WEBs with reduced memory space requirements and better security enforcement. The capability of the proposed approach is evaluated by an analytical model and a series of experiments.
SSO 2011 Workshop Report: 1st ACM SIGSPATIAL International Workshop on Spatial Semantics and Ontologies (SSO) 2011
Authors: Wiegand Nancy , Berg-Cross Gary , Varanka Dalia
Published: April 2012

We were pleased to organize the 1st Spatial Semantics and Ontologies (SSO) international workshop as part of the 19th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM SIGSPATIAL GIS 2011). Semantic technologies are an emerging topic. This workshop was motivated by the need for semantics-related research for geospatial data and to provide a place for discussion and distribution of the work in this area. ACM SIGSPATIAL GIS 2011 offered a perfect venue to bring together computer scientists with spatial/geospatial domain experts, and this workshop was designed to help engage and create a synergy with computer and spatial scientists interested in the semantic area. We anticipated that technical advancements would be made by computer specialists focusing on the spatial area in collaboration with domain specialists who know the semantic problems they face. Having this workshop at ACM GIS opened the research to include wide areas of computer science.
Highlights from ACM SIGSPATIAL China Chapter in 2011
Authors: Xie Xing
Published: April 2012

In order to promote ACM SIGSPATIAL and corresponding research area in China, and encourage collaboration between SIGSPATIAL researchers in China and researchers worldwide, in Oct. 2009, we have established ACM SIGSPATIAL China chapter, with the strong support of SIGSPATIAL executive committee. Till now, we have 31 professional members in SIGSPATIAL China. They come from Chinese universities/research institutes such as Wuhan University, Renmin University, University of Science and Technology of China, Zhejiang University, Chinese Academy of Sciences, and industry labs such as Microsoft Research Asia and Nokia Research China.
Tarazu
Authors: Ahmad Faraz , Chakradhar Srimat T. , Raghunathan Anand , Vijaykumar T. N.
Published: April 2012

Data center-scale clusters are evolving towards heterogeneous hardware for power, cost, differentiated price-performance, and other reasons. MapReduce is a well-known programming model to process large amount of data on data center-scale clusters. Most MapReduce implementations have been designed and optimized for homogeneous clusters. Unfortunately, these implementations perform poorly on heterogeneous clusters (e.g., on a 90-node cluster that contains 10 Xeon-based servers and 80 Atom-based servers, Hadoop performs worse than on 10-node Xeon-only or 80-node Atom-only homogeneous sub-clusters for many of our benchmarks). This poor performance remains despite previously proposed optimizations related to management of straggler tasks. In this paper, we address MapReduce's poor performance on heterogeneous clusters. Our first contribution is that the poor performance is due to two key factors: (1) the non-intuitive effect that MapReduce's built-in load balancing results in excessive and bursty network communication during the Map phase, and (2) the intuitive effect that the heterogeneity amplifies load imbalance in the Reduce computation. Our second contribution is Tarazu, a suite of optimizations to improve MapReduce performance on heterogeneous clusters. Tarazu consists of (1) Communication-Aware Load Balancing of Map computation (CALB) across the nodes, (2) Communication-Aware Scheduling of Map computation (CAS) to avoid bursty network traffic and (3) Predictive Load Balancing of Reduce computation (PLB) across the nodes. Using the above 90-node cluster, we show that Tarazu significantly improves performance over a baseline of Hadoop with straightforward tuning for hardware heterogeneity.
Study on Detailed Calculation and Experiment Methods of Neutronics, Fuel Materials, and Thermal Hydraulics for a Commercial Type Japanese Sodium-Cooled Fast Reactor
Authors: Takeda Toshikazu , van Rooijen W. F. G. , Yamaguchi Katsuhisa , Uno Masayoshi , Arita Yuji , Mochizuki Hiroyasu
Published: April 2012

This paper discusses the objectives and results of a multiyear R&D project to improve the modeling accuracy for the detailed calculation of the Japanese Sodium-cooled Fast Reactor (JSFR), although the preliminary design of JSFR is prepared using conventional methods. For detailed design calculations, new methods are required because the JSFR has special features, which cannot be accurately modeled with existing codes. An example is the presence of an inner duct in the fuel assemblies. Therefore, we have developed new calculational and experimental methods in three areas: (1) for neutronics, we discuss the development of methods and codes to model advanced FBR fuel subassemblies, (2) for fuel materials, modeling and measurement of the thermal conductivity of annular fuel is discussed, and (3) for thermal hydraulics, we describe advances in modeling and calculational models for the intermediate heat exchanger and the calculational treatment of thermal stratification in the hot plenum of an FBR under low flow conditions. The new methods are discussed and the verification tests are described. In the validation test, measured data from the prototype FBR Monju is partly used.