bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Strength Characterization of Sintered Silicon Nitride Containing Oxide Additives
Authors: Govila R. K. 
Published: March 2015

The flexural strength of a commercially available sintered silicon nitride (NGK-SN73) material containing various oxide additives (ceria, magnesia, zirconia and SrO) was determined in 4-point bending as a function of temperature (20 to 1200 C) in an air environment. Significantly, high strength (790 MPa) is maintained from room temperature to 800 C. At 900 C. and above, flexural strength decreased sharply. The sudden decrease in strength at temperatures of 900 and 1000 C is believed due to softening of the residual glass phase present in the material, and led to the presence of sub-critical crack growth. The extent of sub-critical crack growth and large viscous flow increased with increasing temperature (1100–1200 C) and led to degradation of material’s strength. In addition, the material was susceptible to oxidation at these temperatures as displayed by discoloration (dark gray to white) of the specimens.
Extensive flexural stress rupture testing was carried out in the temperature range 800 to 1000 C in order to determine (i) the material’s susceptibility for low temperature oxidation instability, (ii) the presence of sub-critical crack growth at low temperatures (700 to 800 C) and high temperatures (900 to 1000 C) and (iii) to identify allowable stress levels for limited time (≤ 100 h) without showing degradation of materials strength (failure, creep or oxidation).
Detailed fractographic evidence is presented to illustrate the type of strength controlling flaws present in the material at 20 C and above, and to reveal the presence of sub-critical crack growth displayed by the material in the temperature range 800 to 1000 C under stres-rupture mode.
Numerical Solution of Three-Dimensional Turbulent Flows for Modern Gas Turbine Components
Authors: Hah C. , Leylek J. H. 
Published: March 2015

This paper describes the development and assessment of a computer code for three-dimensional compressible turbulent flows in modern gas turbine components. The code is based on a high-order upwinding relaxation scheme with fully conservative control volume. A three-dimensional Reynolds-averaged Navier-Stokes equation is solved with a two-equation turbulence model that has a low Reynolds number modification near the solid wall.
The code is applied to the study of compressible flow inside turbine blade rows of modern gas turbines. Measured data and calculations are carefully compared for the production and convection of aerodynamic loss to evaluate the code as an advanced design technique. The predicted aerodynamic performance is further compared with predictions based on current design techniques.
Semiautomatic segmentation of atherosclerotic carotid artery wall volume using 3D ultrasound imaging
Authors: Hossain Md. Murad , AlMuhanna Khalid , Zhao Limin , Lal Brajesh K. , Sikdar Siddhartha 
Published: March 2015

Purpose:Rupture of atherosclerotic plaques in the carotid artery has been implicated in 20% of strokes. 3D ultrasound (US) imaging is emerging as an attractive method to quantify plaque burden and track changes in plaque longitudinally over time. However, plaque segmentation from US images is challenging because of poor boundary contrast and shadowing. The objective of this study is to develop and evaluate a semiautomatic segmentation algorithm with a novel stopping criterion for segmenting outer wall boundary (OWB) and lumen intima boundary (LIB) of common, internal, and external carotid artery from 3D US images for quantifying the vessel wall volume (VWV).Methods:3D US image volumes were acquired from ten subjects with asymptomatic carotid stenoses. Volumes were acquired using a mechanically scanned linear probe, and the reconstructed volume consisted of 21 slices acquired at an interslice distance of 1 mm. The authors used distance regularized level set method with edge‐based energy, region‐based energy, smoothness energy, and a novel stopping criterion to segment the LIB and OWB of carotid artery. The algorithm was initialized by six user‐selected points on the LIB and OWB in seven 2D cross‐sectional slices in each volume. An ellipse fitting and a stopping boundary‐based energy is proposed to smooth the OWB contour and to stop leaking of the evolving contour, respectively. The algorithm was compared against ground truth boundaries generated from manual segmentations. The dice similarity coefficient (DSC), Hausdorff distance (HD), and modified HD (MHD) were used as error metrics.Results:The authors’ proposed stopping boundary energy‐based stopping criterion was compared with percentage change of area and change of the MHD between evolving contours at successive iterations stopping criteria. The performance of the proposed algorithm was better than other two stopping criteria and yielded mean of LIBDSC = 88.78%, OWBDSC = 94.81%, LIBMHD = 0.26 mm, OWBMHD = 0.25 mm, LIBHD = 0.74 mm, and OWBHD = 0.80 mm. The Bland–Altman plot and correlation coefficient (r = 0.99) indicated a high agreement between ground truth and algorithm‐generated boundaries. The coefficient of variation (COV) and minimum detectable change of the VWV are 5.2% and 57.2 mm3 (5.18% of mean VWV), calculated from repeated measurements of the VWV by algorithm. The mean absolute distance between corresponding points of the algorithm‐generated and the ground truth boundaries was 0.25 mm.Conclusions:The authors have developed a semiautomatic segmentation algorithm for measuring the VWV of the carotid artery using 3D US images with reduced operator interaction and computational time and higher reproducibility using a commercially available 3D US transducer. Their method is a step forward toward routine longitudinal monitoring of 3D plaque progression.
Amphibian Symbiotic Bacteria Do Not Show a Universal Ability To Inhibit Growth of the Global Panzootic Lineage of Batrachochytrium dendrobatidis
Authors: Antwis Rachael E. , Preziosi Richard F. , Harrison Xavier A. , Garner Trenton W. J. 
Published: March 2015

ABSTRACT

Microbiomes associated with multicellular organisms influence the disease susceptibility of hosts. The potential exists for such bacteria to protect wildlife from infectious diseases, particularly in the case of the globally distributed and highly virulent fungal pathogen
Batrachochytrium dendrobatidis
of the global panzootic lineage (
B. dendrobatidis
GPL), responsible for mass extinctions and population declines of amphibians.
B. dendrobatidis
GPL exhibits wide genotypic and virulence variation, and the ability of candidate probiotics to restrict growth across
B. dendrobatidis
isolates has not previously been considered. Here we show that only a small proportion of candidate probiotics exhibited broad-spectrum inhibition across
B. dendrobatidis
GPL isolates. Moreover, some bacterial genera showed significantly greater inhibition than others, but overall, genus and species were not particularly reliable predictors of inhibitory capabilities. These findings indicate that bacterial consortia are likely to offer a more stable and effective approach to probiotics, particularly if related bacteria are selected from genera with greater antimicrobial capabilities. Together these results highlight a complex interaction between pathogens and host-associated symbiotic bacteria that will require consideration in the development of bacterial probiotics for wildlife conservation. Future efforts to construct protective microbiomes should incorporate bacteria that exhibit broad-spectrum inhibition of
B. dendrobatidis
GPL isolates.
Immunogenicity in Swine of Orally Administered Recombinant Lactobacillus plantarum Expressing Classical Swine Fever Virus E2 Protein in Conjunction with Thymosin α-1 as an Adjuvant
Authors: Xu Yi-Gang , Guan Xue-Ting , Liu Zhong-Mei , Tian Chang-Yong , Cui Li-Chun 
Published: March 2015

ABSTRACT

Classical swine fever, caused by classical swine fever virus (CSFV), is a highly contagious disease that results in enormous economic losses in pig industries. The E2 protein is one of the main structural proteins of CSFV and is capable of inducing CSFV-neutralizing antibodies and cytotoxic T lymphocyte (CTL) activities
in vivo
. Thymosin α-1 (Tα1), an immune-modifier peptide, plays a very important role in the cellular immune response. In this study, genetically engineered
Lactobacillus plantarum
bacteria expressing CSFV E2 protein alone (
L. plantarum
/pYG-E2) and in combination with Tα1 (
L. plantarum
/pYG-E2-Tα1) were developed, and the immunogenicity of each as an oral vaccine to induce protective immunity against CSFV in pigs was evaluated. The results showed that recombinant
L. plantarum
/pYG-E2 and
L. plantarum
/pYG-E2-Tα1 were both able to effectively induce protective immune responses in pigs against CSFV infection by eliciting immunoglobulin A (IgA)-based mucosal, immunoglobulin G (IgG)-based humoral, and CTL-based cellular immune responses via oral vaccination. Significant differences (
P
< 0.05) in the levels of immune responses were observed between
L. plantarum
/pYG-E2-Tα1 and
L. plantarum
/pYG-E2, suggesting a better immunogenicity of
L. plantarum
/pYG-E2-Tα1 as a result of the Tα1 molecular adjuvant that can enhance immune responsiveness and augment specific lymphocyte functions. Our data suggest that the recombinant
Lactobacillus
microecological agent expressing CSFV E2 protein combined with Tα1 as an adjuvant provides a promising strategy for vaccine development against CSFV.
Vernalophrys algivore gen. nov., sp. nov. (Rhizaria: Cercozoa: Vampyrellida), a New Algal Predator Isolated from Outdoor Mass Culture of Scenedesmus dimorphus
Authors: Gong Yingchun , Patterson David J. , Li Yunguang , Hu Zixuan , Sommerfeld Milton , Chen Yongsheng , Hu Qiang 
Published: March 2015

ABSTRACT

Microbial contamination is the main cause of loss of biomass yield in microalgal cultures, especially under outdoor environmental conditions. Little is known about the identities of microbial contaminants in outdoor mass algal cultures. In this study, a new genus and species of vampyrellid amoeba,
Vernalophrys algivore
, is described from cultures of
Scenedesmus
dimorphus
in open raceway ponds and outdoor flat-panel photobioreactors. This vampyrellid amoeba was a significant grazer of
Scenedesmus
and was frequently associated with a very rapid decline in algal numbers. We report on the morphology, subcellular structure, feeding behavior, molecular phylogeny, and life cycle. The new amoeba resembles
Leptophrys
in the shape of trophozoites and pseudopodia and in the mechanism of feeding (mainly by engulfment). It possesses two distinctive regions in helix E10_1 (nucleotides 117 to 119, CAA) and E23_1 (nucleotides 522 and 523, AG) of the 18S rRNA gene. It did not form a monophyletic group with
Leptophrys
in molecular phylogenetic trees. We establish a new genus,
Vernalophrys
, with the type species
Vernalophrys algivore
. The occurrence, impact of the amoeba on mass culture of
S. dimorphus
, and means to reduce vampyrellid amoeba contamination in
Scenedesmus
cultures are addressed. The information obtained from this study will be useful for developing an early warning system and control measures for preventing or treating this contaminant in microalgal mass cultures.
Polyphenolic Extract from Maple Syrup Potentiates Antibiotic Susceptibility and Reduces Biofilm Formation of Pathogenic Bacteria
Authors: Maisuria Vimal B. , Hosseinidoust Zeinab , Tufenkji Nathalie 
Published: March 2015

ABSTRACT

Phenolic compounds are believed to be promising candidates as complementary therapeutics. Maple syrup, prepared by concentrating the sap from the North American maple tree, is a rich source of natural and process-derived phenolic compounds. In this work, we report the antimicrobial activity of a phenolic-rich maple syrup extract (PRMSE). PRMSE exhibited antimicrobial activity as well as strong synergistic interaction with selected antibiotics against Gram-negative clinical strains of
Escherichia coli
,
Proteus mirabilis
, and
Pseudomonas aeruginosa
. Among the phenolic constituents of PRMSE, catechol exhibited strong synergy with antibiotics as well as with other phenolic components of PRMSE against bacterial growth. At sublethal concentrations, PRMSE and catechol efficiently reduced biofilm formation and increased the susceptibility of bacterial biofilms to antibiotics. In an effort to elucidate the mechanism for the observed synergy with antibiotics, PRMSE was found to increase outer membrane permeability of all bacterial strains and effectively inhibit efflux pump activity. Furthermore, transcriptome analysis revealed that PRMSE significantly repressed multiple-drug resistance genes as well as genes associated with motility, adhesion, biofilm formation, and virulence. Overall, this study provides a proof of concept and starting point for investigating the molecular mechanism of the reported increase in bacterial antibiotic susceptibility in the presence of PRMSE.
Genome Sequence and Transcriptome Analysis of Meat-Spoilage-Associated Lactic Acid Bacterium Lactococcus piscium MKFS47
Authors: Andreevskaya Margarita , Johansson Per , Laine Pia , Smolander Olli-Pekka , Sonck Matti , Rahkila Riitta , Jääskeläinen Elina , Paulin Lars , Auvinen Petri , Björkroth Johanna 
Published: March 2015

ABSTRACT

Lactococcus piscium
is a psychrotrophic lactic acid bacterium and is known to be one of the predominant species within spoilage microbial communities in cold-stored packaged foods, particularly in meat products. Its presence in such products has been associated with the formation of buttery and sour off-odors. Nevertheless, the spoilage potential of
L. piscium
varies dramatically depending on the strain and growth conditions. Additional knowledge about the genome is required to explain such variation, understand its phylogeny, and study gene functions. Here, we present the complete and annotated genomic sequence of
L. piscium
MKFS47, combined with a time course analysis of the glucose catabolism-based transcriptome. In addition, a comparative analysis of gene contents was done for
L. piscium
MKFS47 and 29 other lactococci, revealing three distinct clades within the genus. The genome of
L. piscium
MKFS47 consists of one chromosome, carrying 2,289 genes, and two plasmids. A wide range of carbohydrates was predicted to be fermented, and growth on glycerol was observed. Both carbohydrate and glycerol catabolic pathways were significantly upregulated in the course of time as a result of glucose exhaustion. At the same time, differential expression of the pyruvate utilization pathways, implicated in the formation of spoilage substances, switched the metabolism toward a heterofermentative mode. In agreement with data from previous inoculation studies,
L. piscium
MKFS47 was identified as an efficient producer of buttery-odor compounds under aerobic conditions. Finally, genes and pathways that may contribute to increased survival in meat environments were considered.
The N-Terminal GH10 Domain of a Multimodular Protein from Caldicellulosiruptor bescii Is a Versatile Xylanase/β-Glucanase That Can Degrade Crystalline Cellulose
Authors: Xue Xianli , Wang Rong , Tu Tao , Shi Pengjun , Ma Rui , Luo Huiying , Yao Bin , Su Xiaoyun 
Published: March 2015

ABSTRACT

The genome of the thermophilic bacterium
Caldicellulosiruptor bescii
encodes three multimodular enzymes with identical C-terminal domain organizations containing two consecutive CBM3b modules and one glycoside hydrolase (GH) family 48 (GH48) catalytic module. However, the three proteins differ much in their N termini. Among these proteins, CelA (or
C. bescii
Cel9A [CbCel9A]/Cel48A) with a GH9/CBM3c binary partner in the N terminus has been shown to use a novel strategy to degrade crystalline cellulose, which leads to its outstanding cellulose-cleaving activity. Here we show that
C. bescii
Xyn10C (CbXyn10C), the N-terminal GH10 domain from CbXyn10C/Cel48B, can also degrade crystalline cellulose, in addition to heterogeneous xylans and barley β-glucan. The data from substrate competition assays, mutational studies, molecular modeling, and docking point analyses point to the existence of only one catalytic center in the bifunctional xylanase/β-glucanase. The specific activities of the recombinant CbXyn10C on Avicel and filter paper were comparable to those of GH9/CBM3c of the robust CelA expressed in
Escherichia coli
. Appending one or two cellulose-binding CBM3bs enhanced the activities of CbXyn10C in degrading crystalline celluloses, which were again comparable to those of the GH9/CBM3c-CBM3b-CBM3b truncation mutant of CelA. Since CbXyn10C/Cel48B and CelA have similar domain organizations and high sequence homology, the endocellulase activity observed in CbXyn10C leads us to speculate that CbXyn10C/Cel48B may use the same strategy that CelA uses to hydrolyze crystalline cellulose, thus helping the excellent crystalline cellulose degrader
C. bescii
acquire energy from the environment. In addition, we also demonstrate that CbXyn10C may be an interesting candidate enzyme for biotechnology due to its versatility in hydrolyzing multiple substrates with different glycosidic linkages.
The RpoE Stress Response Pathway Mediates Reduction of the Virulence of Enteropathogenic Escherichia coli by Zinc
Authors: Xue Yuan , Osborn Jossef , Panchal Anand , Mellies Jay L. 
Published: March 2015

ABSTRACT

Zinc supplements are an effective clinical treatment for infantile diarrheal disease caused by enteric pathogens. Previous studies demonstrated that zinc acts on enteropathogenic
Escherichia coli
(EPEC) bacteria directly to suppress several virulence-related genes at a concentration that can be achieved by oral delivery of dietary zinc supplements. Our
in vitro
studies showed that a micromolar concentration of zinc induced the envelope stress response and suppressed virulence in EPEC, providing a possible mechanistic explanation for zinc's therapeutic action. In this report, we investigated the molecular and physiological changes in EPEC induced by zinc. We found that micromolar concentrations of zinc reduced the bacterial growth rate without affecting viability. We observed increased membrane permeability caused by zinc. Zinc upregulated the RpoE-dependent envelope stress response pathway and suppressed EPEC virulence gene expression. RpoE alone was sufficient to inhibit virulence factor expression and to attenuate attaching and effacing lesion formation on human host cells. By mutational analysis we demonstrate that the DNA-binding motif of RpoE is necessary for suppression of the
LEE1
, but not the
LEE4
, operon. Predictably, inhibition of the RpoE-mediated envelope stress response in combination with micromolar concentrations of zinc reduced EPEC viability. In conclusion, zinc induces the RpoE and stress response pathways in EPEC, and the alternate sigma factor RpoE downregulates EPEC LEE and non-LEE virulence genes by multiple mechanisms.
Carbon Source Preference in Chemosynthetic Hot Spring Communities
Authors: Urschel Matthew R. , Kubo Michael D. , Hoehler Tori M. , Peters John W. , Boyd Eric S. 
Published: March 2015

ABSTRACT

Rates of dissolved inorganic carbon (DIC), formate, and acetate mineralization and/or assimilation were determined in 13 high-temperature (>73°C) hot springs in Yellowstone National Park (YNP), Wyoming, in order to evaluate the relative importance of these substrates in supporting microbial metabolism. While 9 of the hot spring communities exhibited rates of DIC assimilation that were greater than those of formate and acetate assimilation, 2 exhibited rates of formate and/or acetate assimilation that exceeded those of DIC assimilation. Overall rates of DIC, formate, and acetate mineralization and assimilation were positively correlated with spring pH but showed little correlation with temperature. Communities sampled from hot springs with similar geochemistries generally exhibited similar rates of substrate transformation, as well as similar community compositions, as revealed by 16S rRNA gene-tagged sequencing. Amendment of microcosms with small (micromolar) amounts of formate suppressed DIC assimilation in short-term (<45-min) incubations, despite the presence of native DIC concentrations that exceeded those of added formate by 2 to 3 orders of magnitude. The concentration of added formate required to suppress DIC assimilation was similar to the affinity constant (

K
m

) for formate transformation, as determined by community kinetic assays. These results suggest that dominant chemoautotrophs in high-temperature communities are facultatively autotrophic or mixotrophic, are adapted to fluctuating nutrient availabilities, and are capable of taking advantage of energy-rich organic substrates when they become available.
“Quorum Non-Sensing”: Social Cheating and Deception in Vibrio cholerae
Authors: Katzianer David S. , Wang Hui , Carey Ryan M. , Zhu Jun 
Published: March 2015

ABSTRACT

Quorum sensing (QS) is widely used by bacteria to coordinate behavior in response to external stimuli. In
Vibrio cholerae
, this process is important for environmental survival and pathogenesis, though, intriguingly, a large percentage of natural isolates are QS deficient. Here, we show that QS-deficient mutants can spread as social cheaters by ceasing production of extracellular proteases under conditions requiring their growth. We further show that mutants stimulate biofilm formation and are over-represented in biofilms compared to planktonic communities; on this basis, we suggest that QS-deficient mutants may have the side effect of enhancing environmental tolerance of natural populations due to the inherent resistance properties of biofilms. Interestingly, high frequencies of QS-deficient individuals did not impact production of QS signaling molecules despite mutants being unable to respond to these inducers, indicating that these variants actively cheat by false signaling under conditions requiring QS. Taken together, our results suggest that social cheating may drive QS deficiency emergence within
V. cholerae
natural populations.
Alamethicin Suppresses Methanogenesis and Promotes Acetogenesis in Bioelectrochemical Systems
Authors: Zhu Xiuping , Siegert Michael , Yates Matthew D. , Logan Bruce E. 
Published: March 2015

ABSTRACT

Microbial electrosynthesis (MES) systems with mixed cultures often generate a variety of gaseous and soluble chemicals. Methane is the primary end product in mixed-culture MES because it is the thermodynamically most favorable reduction product of CO
2
. Here, we show that the peptaibol alamethicin selectively suppressed the growth of methanogens in mixed-culture MES systems, resulting in a shift of the solution and cathode communities to an acetate-producing system dominated by
Sporomusa
, a known acetogenic genus in MES systems.
Archaea
in the methane-producing control were dominated by
Methanobrevibacter
species, but no
Archaea
were detected in the alamethicin-treated reactors. No methane was detected in the mixed-culture reactors treated with alamethicin over 10 cycles (∼3 days each). Instead, acetate was produced at an average rate of 115 nmol ml
−1
day
−1
, similar to the rate reported previously for pure cultures of
Sporomusa ovata
on biocathodes. Mixed-culture control reactors without alamethicin generated methane at nearly 100% coulombic recovery, and no acetate was detected. These results show that alamethicin is effective for the suppression of methanogen growth in MES systems and that its use enables the production of industrially relevant organic compounds by the inhibition of methanogenesis.