287 research outputs found
Deadline Constrained Cloud Computing Resources Scheduling through an Ant Colony System Approach
Cloud computing resources scheduling is essential for executing workflows in the cloud platform because it relates to both execution time and execution cost. In this paper, we adopt a model that optimizes the execution cost while meeting deadline constraints. In solving this problem, we propose an Improved Ant Colony System (IACS) approach featuring two novel strategies. Firstly, a dynamic heuristic strategy is used to calculate a heuristic value during an evolutionary process by taking the workflow topological structure into consideration. Secondly, a double search strategy is used to initialize the pheromone and calculate the heuristic value according to the execution time at the beginning and to initialize the pheromone and calculate heuristic value according to the execution cost after a feasible solution is found. Therefore, the proposed IACS is adaptive to the search environment and to different objectives. We have conducted extensive experiments based on workflows with different scales and different cloud resources. We compare the result with a particle swarm optimization (PSO) approach and a dynamic objective genetic algorithm (DOGA) approach. Experimental results show that IACS is able to find better solutions with a lower cost than both PSO and DOGA do on various scheduling scales and deadline conditions
Model-Independent Determination of and using Time-Delay Galaxy Lenses and Gamma-Ray Bursts
Combining the `time-delay distance' () measurements from galaxy
lenses and other distance indicators provides model-independent determinations
of the Hubble constant () and spatial curvature (), only
based on the validity of the Friedmann-Lema\^itre-Robertson-Walker (FLRW)
metric and geometrical optics. To take the full merit of combining measurements in constraining , we use gamma-ray burst (GRB) distances
to extend the redshift coverage of lensing systems much higher than that of
Type Ia Supernovae (SNe Ia) and even higher than quasars, whilst the general
cosmography with a curvature component is implemented for the GRB distance
parametrizations. Combining Lensing+GRB yields ~km
sMpc and (1). A
flat-universe prior gives slightly an improved ~km
sMpc. When combining Lensing+GRB+SN Ia, the error bar falls by 25\%, whereas is not improved due to the
degeneracy between SN Ia absolute magnitude, , and along with the
mismatch between the SN Ia and GRB Hubble diagrams at . Future
increment of GRB observations can help to moderately eliminate the
degeneracy in SN Ia distances and ameliorate the restrictions on cosmographic
parameters along with when combining Lensing+SN Ia+GRB. We
conclude that there is no evidence of significant deviation from a (an) flat
(accelerating) universe and is currently determined at 3\% precision. The
measurements show great potential to arbitrate the tension between the
local distance ladder and cosmic microwave background measurements and provide
a relevant consistency test of the FLRW metric.Comment: Accepted for publication in MNRA
Thiomicrorhabdus marina sp.nov., an obligate chemolithoautotroph isolated from tidal zone sediment, and genome insight into the genus Thiomicrorhabdus
The contribution of microbes to the marine sulfur cycle has received considerable attention in recent years. In this study, a new Gram-stain-negative, aerobic sulfur-oxidizing bacterium, designated strain 6S2-11T, was isolated from tidal zone sediment of the coast of Weihai, China. Strain 6S2-11T was an obligate chemolithoautotroph utilizing thiosulfate as the energy source. Physiological and biochemical experiments, phylogenetic analysis, and comparative genomic analysis were done with strain 6S2-11T. According to genomic analysis, strain 6S2-11T owned a complete thiosulfate oxidation pathway and an untypical nitrogen metabolism pathway. Its relatively small genome also has multiple environmental adaptation mechanisms. The DNA G+C content of strain 6S2-11T was 44.1%. Strain 6S2-11T was observed to grow at 20-37°C (optimum, 35°C), pH 6.0-9.5 (optimum, pH 7.5), and 0.5-5% (w/v) NaCl (optimum, 2.5%). The major cellular fatty acids (>10%) of strain 6S2-11T were Summed Feature 8 (C18:1ω7c/C18:1ω6c), C16:0 and Summed Feature 3 (C16:1ω7c/C16:1ω6c). The comparison of 16S rRNA gene sequences indicated that strain 6S2-11T was most closely to Thiomicrorhabdus xiamenensis G2T (96.8%). Based on the results of phylogenetic analysis, the strain 6S2-11T is a novel specie of the genus Thiomicrorhabdus, for which name Thiomicrorhabdus marina sp.nov. is proposed with the type strain 6S2-11T (=MCCC 1H00523T=KCTC 82994T)
Leader peptide removal in lasso peptide biosynthesis based on penultimate isoleucine residue
Lasso peptides are ribosomally synthesized peptides that undergo post-translational modifications including leader peptide removal by B (or the segregated B1 and B2) proteins and core peptide macrolactamization by C proteins to form a unique lariat topology. A conserved threonine residue at the penultimate position of leader peptide is hitherto found in lasso peptide precursors and shown to be a critical recognition element for effective enzymatic processing. We identified a lasso peptide biosynthetic gene cluster (bsf) from Bradymonas sediminis FA350, a Gram-negative and facultatively prey-dependent bacterium that belongs to a novel bacterial order Bradymonadales in the class Deltaproteobacteria. The kinase BsfK specifically catalyzes the phosphorylation of the precursor peptide BsfA on the Ser3 residue. BsfB1 performs dual functions to accelerate the post-translational phosphorylation and assist BsfB2 in leader peptide removal. Most importantly, the penultimate residue of leader peptide is an isoleucine rather than the conserved threonine and this isoleucine has a marked impact on the phosphorylation of Ser3 as well as leader peptide removal, implying that BsfB1 and BsfB2 exhibit a new substrate selectivity for leader peptide binding and excision. This is the first experimentally validated penultimate isoleucine residue in a lasso peptide precursor to our knowledge. In silico analysis reveals that the leader peptide Ile/Val(-2) residue is rare but not uncommon in phosphorylated lasso peptides, as this residue is also discovered in Acidobacteriaceae and Sphingomonadales in addition to Bradymonadales
Corynebacterium marinum sp. nov. isolated from coastal sediment
A taxonomic study was performed on strain D7015T, which was isolated from coastal sediment close to a coal-fired power station in Qingdao, China. Strain D7015T comprised Gram-positive, non-motile diphtheroid rods, which grew in the presence of 0-8% (w/v) NaCl and at 4-37°C, with optimum growth at 1% (w/v) NaCl and 30-32°C. The G+C content was 65.0 mol%. The major fatty acids were C18:1ω9c (56.18%), C16:0 (38.02%), C16:1ω7c (4.45%), C18:0 (1.0%) and C14:0 (0.35%). On the basis of the morphological, physiological and phylogenetic characteristics, strain D7015T was classified in the genus Corynebacterium. It exhibited a 16S rRNA gene sequence similarity of 95.9% and a DNA:DNA relatedness value of 20.4% with Corynebacterium halotolerans DSM 44683T. Strain D7015T was sufficiently different from hitherto described Corynebacterium species to be considered as a novel species. The name Corynebacterium marinum sp. nov. is proposed, with strain D7015T (=CGMCC 1.6998T =NRRL B-24779T) as the type strain
Combining primary tumor features derived from conventional and contrast-enhanced ultrasound facilitates the prediction of positive axillary lymph nodes in Breast Imaging Reporting and Data System category 4 malignant breast lesions
PURPOSETo determine whether the primary tumor features derived from conventional ultrasound (US) and contrast-enhanced US (CEUS) facilitate the prediction of positive axillary lymph nodes (ALNs) in breast cancer diagnosed as Breast Imaging Reporting and Data System (BI-RADS) category 4.METHODSA total of 240 women with breast cancer who underwent preoperative conventional US, strain elastography, and CEUS between September 2016 and December 2019 were included. The multiple parameters of the primary tumor were obtained, and univariate and multivariate analyses were performed to predict positive ALNs. Then three prediction models (conventional US features, CEUS features, and the combined features) were developed, and the diagnostic performance was evaluated with receiver operating characteristic curves.RESULTSOn conventional US, the traits of large size and the non-circumscribed margin of the primary tumor were marked as two independent predictors. On CEUS, the features of vessel perforation or distortion and the enhanced range of the primary tumor were marked as two independent predictors for positive ALNs. Three prediction models were then developed: model A (conventional US features), model B (CEUS features), and model C (model A plus B). Model C yielded the highest area under the curve (AUC) of 0.82 [95% confidence interval (CI), 0.75–0.88] compared with model A (AUC 0.74; 95% CI, 0.68–0.81; P = 0.008) and model B (AUC 0.72; 95% CI, 0.65–0.80; P < 0.001) as per the DeLong test.CONCLUSIONCEUS, as a non-invasive examination technique, can be used to predict ALN metastasis. Combining conventional US and CEUS may produce favorable predictive accuracy for positive ALNs in BI-RADS category 4 breast cancer
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