bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability Analysis Hinged Vertical Flat Plate Rotation in a Uniform Flow
Authors: Sefat Sina Mirzaei , Fernandes Antonio Carlos 
Published: August 2013

The free falling of objects is a phenomenon that has been observed in the nature. The Pendulous Installation Method (PIM) of heavy devices is an example of free falling which occurs in the installation of heavy offshore devices on sea bed. Hence, the motivation of the present research is to study the fluttering and tumbling (autorotation) motions that may occur during the free fall of object. The fluttering is a periodic or chaotic oscillation of body about a vertical axis. On the other hand, the tumbling is end-over-end rotation of body. In order to access the main physical aspects, the present work decided to attack a more fundamental problem and describes the investigations on fluttering and autorotation motions of the interaction of uniform current and freely rotating plate about a fixed vertical axis.
A quasi-steady model is suggested to model the trajectories of flow induced rotation phenomenon and a stability analysis performed to gain insight into the nature of the bifurcation from fluttering to autorotation. At first, the fixed points for different models of motion is obtained and each point analyzed by using the linearized equation. Secondly, the phase diagrams as a function of angular velocity and angle of rotation have been presented for different dynamic models.
Scaling of Flexural and Compressive Ice Failure
Authors: Jordaan Ian , Taylor Rocky , Derradji-Aouat Ahmed 
Published: August 2013

Physical model tests are a powerful means of obtaining solutions to a variety of engineering problems. The applications in hydraulics and aerospace engineering are prominent, where the use of similitude and dimensionless numbers is well developed. The first step is to understand the mechanics of the process. In the case of ice, the theory has not been developed to the same degree as in fluid mechanics. The use of scale models in test basins has often focused on resistance to ship motion and on flexural failure of the ice. This has been reasonably well addressed. The properties of the model ice have often been modified to permit scaling of flexural strength as well as elastic modulus to achieve appropriate behaviour.
Extension of testing to situations where ice fails in compression or combined flexure and crushing leads to additional complication. At low rates of loading, ice creeps and also demonstrates enhanced rates of creep if the stress is sufficient to cause damage (microstructural change) in the ice. At higher rates of loading, fracture processes result in a localization of loading, and in the formation of high-pressure zones, which have their own special failure process.
In the paper a review of scaled ice testing is given, with associated mechanics including flexural failure. This is followed by a discussion of the failure processes in compression and related mechanics such as creep, damage and fracture. Suggestions as to scaling of these processes are made. An important aspect that is considered is the randomness of ice loads as measured in the full scale. Modelling this aspect and determination of appropriate extreme values is discussed. The Weibull modulus is suggested as an appropriate parameter.
Vibration Analysis and Evaluation for the Offshore Structure Using Simplified Model and RSS Method
Authors: Lee Chan Hui , Song Keun Bok , Kim Heui Won 
Published: August 2013

The evaluation of the vibration characteristics of offshore structure in the design stage is important to ensure the safety of structure, equipment and worker. Conventionally, the vibration analysis of the offshore structure is carried out according to its own analysis procedure including the selection of vibrating equipment, FE modeling, evaluation of excitation forces and criteria. The efficient modeling of the vibration equipment and the consideration of the phase of excitation forces are necessary to reduce the calculation time and to increase the accuracy of analysis.
In this paper, the efficient and accurate vibration analysis method is introduced including the simplified model of equipment and the RSS (root squared summation) method. The vibration equipment was modeled as the simplified model of which mesh size is reduced by 90%, however, its vibration characteristics such as natural frequency and vibration modes are not changed. In addition, the RSS method was applied in the forced vibration analysis to consider appropriate phase of excitation forces. As the RSS method is the summation of all the vibration response with respect to each excitation forces, it presents more reasonable and conservative vibration evaluation. The proposed vibration analysis method has been confirmed by conducting various offshore projects and is expected to be more efficient for the design of offshore structure.
Comprehensive Riser VIV Model Tests in Uniform and Sheared Flow
Authors: Lie Halvor , Braaten Henning , Jhingran Vikas Gopal , Sequeiros Octavio E. , Vandiver Kim 
Published: August 2013

Despite of considerable research activity during the last decades considerable uncertainties still remain in prediction of Vortex Induced Vibrations (VIV) of risers. Model tests of risers subjected to current have been shown to be a useful method for investigation of the VIV behavior of risers with and without suppression devices.
In order to get further insight on VIV of risers, an extensive hydrodynamic test program of riser models subjected to vortex-induced vibrations was undertaken during the winter 2010 by Shell Oil Company.
The VIV-model test campaign was performed in the MARINTEK Offshore Basin Laboratory. A new test rig was constructed and showed to give good test conditions. Three different 38m long riser models were towed horizontally at different speeds, simulating uniform and linearly varying sheared current. Measurements were made In-Line (IL) and Cross-Flow (CF) of micro bending strains and accelerations along the risers. The test program compromised about 400 tests, which give a rich test material for further studies.
In the present paper the test set-up and program are presented and selected results are reported.
Fractional Flow Analysis of Displacement in a CO2 Enhanced Gas Recovery Process for Carbonate Reservoirs
Authors: Odi Uchenna , Gupta Anuj 
Published: August 2013

This paper presents fractional flow analysis of displacement of gas/condensate in a wet/condensate gas reservoir by CO2 that includes interactions between CO2 and condensate.
Phase behavior affects the performance of carbon dioxide enhanced oil/ gas recovery processes in a significant manner. It also controls the effectiveness of carbon dioxide sequestration processes. In the past, there has been a focus on understanding interactions of CO2 with matrix and other fluids in oil reservoirs by various researchers. However, there is now an increasing interest in understanding carbon dioxide interactions in gas condensate reservoirs so that CO2 can be used to increase recovery. For a carbonate reservoir containing gas-condensates, this new focus requires a fundamental understanding of the interactions of carbon dioxide with condensate and gas phases. This paper describes the relative effect that these mechanisms have by conducting a fractional flow analysis for Enhanced Gas Recovery. These mechanisms include miscibility and partitioning of CO2 in various phases. Understanding these mechanisms is essential to modeling Enhanced Oil/Gas Recovery using CO2.
The analysis honors the material balance and accounts for miscibility between carbon dioxide and condensate. The results of the fractional flow analysis are important for validation of computer simulation of the comparable processes. This work is expected to serve as a foundation work in understanding the mechanisms involved in CO2 assisted enhanced oil and gas recovery.
Pore-Pressure Accumulation and Soil Softening Around Pile Foundations for Offshore Wind Turbines
Authors: Cuéllar Pablo , Baeßler Matthias , Rücker Werner 
Published: August 2013

The foundation of offshore wind turbines usually involves the installation of large-diameter steel piles in the seabed, either in monopile or multi-pile configurations (jacket, tripod, etc…), which have to ensure a proper fixity of the turbine during its whole service life-time.
However, such foundations raise several challenges and novel questions, partly due to the special characteristics of the offshore environment (for instance, the large numbers of load cycles from wind and waves and the possible influence of transient changes of pore water pressure around the pile) and aggravated by their large diameter, reduced slenderness and elevated ratio of lateral to vertical loads (see Fig. 1).
This paper studies the effects of cyclic lateral loading on the offshore piles focusing on the possibility of a progressive accumulation of residual pore water pressure within the saturated embedding soil. As it will be shown, this can lead to significant changes of their behaviour under external loading, which can potentially compromise the foundation’s stability or serviceability.
The paper will also analyse some singular effects of an irregular loading (e.g. cyclic loading with variable amplitude), in particular the so-called “order effects” and the phenomena arising during a realistic storm of moderate magnitude, and discuss their potential for transient damages to the foundation’s stiffness.
All these phenomena, which can lead to a loss of serviceability of the structure, have been investigated by the authors by means of a coupled bi-phasic analytical model of the offshore foundation featuring a versatile constitutive law suitable for the soil. The constitutive model, in the frame of the theory of Generalized Plasticity, can reproduce some complex features of cyclic soil behaviour such as the tendency for a progressive densification under cyclic loading, which is responsible for the soil liquefaction phenomena in undrained conditions.
Finally, some implications of these issues for the practical design of offshore monopiles will be discussed and some specific recommendations for the design procedures will be outlined.
A Comprehensive Approach for Assessing the Impacts of Wettability on Oil Production in Carbonate Reservoirs
Authors: Faerstein Marcos , Couto Paulo , Alves José 
Published: August 2013

This paper discusses the impacts that rock wettability may have upon the production and recovery of oil with waterflooding in carbonate reservoirs and how it should be modeled. A broad review of the state of the art has been conducted surveying existing disagreements and knowledge gaps, basic definitions, as well as the correct understanding of the physical phenomena and identification of the characteristics of the various wettability scenarios.
Case studies conducted with a black oil reservoir simulator evaluated the impact of different wettability scenarios on oil production and recovery. A comprehensive approach considering all the parameters involved in the wettability modeling was applied to the case studies, showing how the behavior of the reservoir varies as a function of their wettability.
This paper shows how relative permeability and capillary pressure should be varied to correctly represent different wettability scenarios and consequently assess its impacts on oil production and recovery.
The case studies show that the evaluation of the volume of oil in the reservoir is impacted by wettability through the irreducible water saturation and primary drainage capillary pressure and must be considered in the analyses. In long term analyses, mixed-wet scenarios have a higher oil production and recovery. In medium and short term, the water-wet scenarios have the higher recovery, but in relation to oil production, these scenarios are negatively influenced by the smaller volume of oil in place.
The main contribution of this paper is the simultaneous analyses of all the parameters involved in the modeling of wettability showing how they impact the behavior of a reservoir. It shows how the parameters must be varied in a heterogeneous reservoir and how heterogeneity impacts the relevance of wettability in the studies.
Tensile Strain Models for Strain-Based Design of Pipelines
Authors: Wang Yong-Yi , Liu Ming , Song Yaxin , Horsley David 
Published: August 2013

This paper covers the development of tensile strain design models using a multidisciplinary approach, including fundamental fracture mechanics, small-scale material characterization tests, and large-scale tests of full-size pipes. The tensile strain design models are formulated in a four-level format. The Level 1 procedure provides estimated tensile strain capacity (TSC) in a tabular format for quick initial assessment. The initiation toughness alternatively termed apparent toughness is estimated from upper shelf Charpy impact energy. The Level 2 procedure contains a set of parametric equations based on an initiation-control limit state. The tensile strain capacity can be computed from these equations with the input of a pipe’s dimensional and material property parameters. The apparent toughness is estimated from either upper shelf Charpy energy or upper shelf toughness of standard CTOD test specimens. The Level 3 procedure uses the same set of equations as in Level 2 and the toughness values are obtained from low-constraint tests. In the Level 3 procedure, two limit states based on either initiation control or ductile instability can be used. The Level 4 procedure allows the use of direct FEA calculation to develop crack driving force relations. The same limit states as those in Level 3 may be used. The Level 4 procedures should only be used by seasoned experts in special circumstances where lower level procedures are judged inappropriate.
The tensile strain design models may be used for the following purposes:
(1) The determination of tensile strain capacity for a given set of material properties and flaw size.
(2) The determination of acceptable flaw sizes for a given set of material properties and target tensile strain capacity.
(3) The selection of material properties to achieve a target strain capacity for a given flaw size.
(4) The optimization of the tensile strain capacity by balancing the requirements of material parameters, such as weld strength (thus weld strength mismatch level) versus toughness.
The application of the tensile strain design models is given in a companion paper.
Stationary Phase and Nutrient Levels Trigger Transcription of a Genomic Locus Containing a Novel Peptide (TM1316) in the Hyperthermophilic Bacterium Thermotoga maritima
Authors: Frock Andrew D. , Montero Clemente I. , Blumer-Schuette Sara E. , Kelly Robert M. 
Published: August 2013

ABSTRACT

The genome of the hyperthermophilic bacterium
Thermotoga maritima
encodes numerous putative peptides/proteins of 100 amino acids or less. While most of these open reading frames (ORFs) are transcribed during growth, their corresponding physiological roles are largely unknown. The onset of stationary phase in
T. maritima
was accompanied by significant morphological changes and upregulation of several ORFs located in the TM1298-TM1336 genome locus. This region contains putative HicAB toxin-antitoxin pairs, hypothetical proteins, radical
S
-adenosylmethionine (SAM) enzymes, and ABC transporters. Of particular note was the TM1315-TM1319 operon, which includes a putative 31-amino-acid peptide (TM1316) that was the most highly transcribed gene in the transcriptome during stationary phase. Antibodies directed against a synthetic version of TM1316 were used to track its production, which correlated closely with transcriptomic data. Immunofluorescence microscopy revealed that TM1316 was localized to the cell envelope and prominent in cell aggregates formed during stationary phase. The only functionally characterized locus with an organization similar to that of TM1315-TM1319 is in
Bacillus subtilis
, which contains subtilosin A, a cyclic peptide with Cys–to–α-carbon linkages that functions as an antilisterial bacteriocin. While the organization of TM1316 resembled that of the
Bacillus
peptide (e.g., in its number of amino acids and spacing of Cys residues), preparations containing high levels of TM1316 affected the growth of neither
Thermotoga
species nor
Pyrococcus furiosus
, a hyperthermophilic archaeon isolated from the same locale as
T. maritima
. Several other putative Cys-rich peptides could be identified in the TM1298-TM1336 locus, and while their roles are also unclear, they merit examination as potential antimicrobial agents in hyperthermophilic biotopes.
Development of a DNA Microarray Method for Detection and Identification of All 15 Distinct O-Antigen Forms of Legionella pneumophila
Authors: Cao Boyang , Yao Fangfang , Liu Xiangqian , Feng Lu , Wang Lei 
Published: August 2013

ABSTRACT

Legionella
is ubiquitous in many environments. At least 50 species and 70 serogroups of the Gram-negative bacterium have been identified. Of the 50 species, 20 are pathogenic, and
Legionella pneumophila
is responsible for the great majority (approximately 90%) of the Legionnaires' disease cases that occur. Furthermore, of the 15
L. pneumophila
serogroups identified, O1 alone causes more than 84% of the Legionnaires' disease cases that occur worldwide. Rapid and reliable assays for the detection and identification of
L. pneumophila
in water, environmental, and clinical samples are in great demand.
L. pneumophila
bacteria are traditionally identified by their O antigens by immunological methods. We have recently developed an O serogroup-specific DNA microarray for the detection of all 15 distinct O-antigen forms of
L. pneumophila
, including serogroups O1 to O15. A total of 35 strains were used to verify the specificity of the microarray, including 15
L. pneumophila
O-antigen standard reference strains and seven
L. pneumophila
clinical isolates as target strains, seven reference strains of other non-
pneumophila Legionella
species as closely related strains, and six non-
Legionella
bacterial species as nonrelated strains. The detection sensitivity was 1 ng of genomic DNA or 0.4 CFU/ml in water samples with filter enrichment and plate culturing. This study demonstrated that the microarray allows specific, sensitive, and reproducible detection of
L. pneumophila
serogroups. To the best of our knowledge, this is the first report of a microarray serotyping method for all 15 distinct O-antigen forms of
L. pneumophila
.
Streptomycin Application Has No Detectable Effect on Bacterial Community Structure in Apple Orchard Soil
Authors: Shade Ashley , Klimowicz Amy K. , Spear Russell N. , Linske Matthew , Donato Justin J. , Hogan Clifford S. , McManus Patricia S. , Handelsman Jo 
Published: August 2013

ABSTRACT
Streptomycin is commonly used to control fire blight disease on apple trees. Although the practice has incited controversy, little is known about its nontarget effects in the environment. We investigated the impact of aerial application of streptomycin on nontarget bacterial communities in soil beneath streptomycin-treated and untreated trees in a commercial apple orchard. Soil samples were collected in two consecutive years at 4 or 10 days before spraying streptomycin and 8 or 9 days after the final spray. Three sources of microbial DNA were profiled using tag-pyrosequencing of 16S rRNA genes: uncultured bacteria from the soil (culture independent) and bacteria cultured on unamended or streptomycin-amended (15 μg/ml) media. Multivariate tests for differences in community structure, Shannon diversity, and Pielou's evenness test results showed no evidence of community response to streptomycin. The results indicate that use of streptomycin for disease management has minimal, if any, immediate effect on apple orchard soil bacterial communities. This study contributes to the profile of an agroecosystem in which antibiotic use for disease prevention appears to have minimal consequences for nontarget bacteria.
Engineered Escherichia coli with Periplasmic Carbonic Anhydrase as a Biocatalyst for CO2Sequestration
Authors: Jo Byung Hoon , Kim Im Gyu , Seo Jeong Hyun , Kang Dong Gyun , Cha Hyung Joon 
Published: August 2013

ABSTRACTCarbonic anhydrase is an enzyme that reversibly catalyzes the hydration of carbon dioxide (CO2). It has been suggested recently that this remarkably fast enzyme can be used for sequestration of CO2, a major greenhouse gas, making this a promising alternative for chemical CO2mitigation. To promote the economical use of enzymes, we engineered the carbonic anhydrase fromNeisseria gonorrhoeae(ngCA) in the periplasm ofEscherichia coli, thereby creating a bacterial whole-cell catalyst. We then investigated the application of this system to CO2sequestration by mineral carbonation, a process with the potential to store large quantities of CO2.ngCA was highly expressed in the periplasm ofE. coliin a soluble form, and the recombinant bacterial cell displayed the distinct ability to hydrate CO2compared with its cytoplasmicngCA counterpart and previously reported whole-cell CA systems. The expression ofngCA in the periplasm ofE. coligreatly accelerated the rate of calcium carbonate (CaCO3) formation and exerted a striking impact on the maximal amount of CaCO3produced under conditions of relatively low pH. It was also shown that the thermal stability of the periplasmic enzyme was significantly improved. These results demonstrate that the engineered bacterial cell with periplasmicngCA can successfully serve as an efficient biocatalyst for CO2sequestration.
Bimodular Peptide Synthetase SidE Produces Fumarylalanine in the Human Pathogen Aspergillus fumigatus
Authors: Steinchen Wieland , Lackner Gerald , Yasmin Sabiha , Schrettl Markus , Dahse Hans-Martin , Haas Hubertus , Hoffmeister Dirk 
Published: August 2013

ABSTRACT

The filamentous mold
Aspergillus fumigatus
causes invasive aspergillosis, a potentially life-threatening infectious disease, in humans. The
sidE
gene encodes a bimodular peptide synthetase and was shown previously to be strongly upregulated during initiation of murine lung infection. In this study, we characterized the two adenylation domains of SidE with the ATP-[
32
P]pyrophosphate exchange assay
in vitro
, which identified fumarate and
l
-alanine, respectively, as the preferred substrates. Using full-length
holo
-SidE, fumarylalanine (FA) formation was observed
in vitro
. Furthermore, FA was identified in
A. fumigatus
culture supernatants under inducing conditions, unless
sidE
was genetically inactivated. As FA is structurally related to established pharmaceutical products exerting immunomodulatory activity, this work may contribute to our understanding of the virulence of
A. fumigatus
.
Evidence for a Bacterial Lipopolysaccharide-Recognizing G-Protein-Coupled Receptor in the Bacterial Engulfment by Entamoeba histolytica
Authors: Brewer Matthew T. , Agbedanu Prince N. , Zamanian Mostafa , Day Tim A. , Carlson Steve A. 
Published: August 2013

ABSTRACT

Entamoeba histolytica
is the causative agent of amoebic dysentery, a worldwide protozoal disease that results in approximately 100,000 deaths annually. The virulence of
E. histolytica
may be due to interactions with the host bacterial flora, whereby trophozoites engulf colonic bacteria as a nutrient source. The engulfment process depends on trophozoite recognition of bacterial epitopes that activate phagocytosis pathways.
E. histolytica
GPCR-1 (EhGPCR-1) was previously recognized as a putative G-protein-coupled receptor (GPCR) used by
Entamoeba histolytica
during phagocytosis. In the present study, we attempted to characterize EhGPCR-1 by using heterologous GPCR expression in
Saccharomyces cerevisiae
. We discovered that bacterial lipopolysaccharide (LPS) is an activator of EhGPCR-1 and that LPS stimulates EhGPCR-1 in a concentration-dependent manner. Additionally, we demonstrated that
Entamoeba histolytica
prefers to engulf bacteria with intact LPS and that this engulfment process is sensitive to suramin, which prevents the interactions of GPCRs and G-proteins. Thus, EhGPCR-1 is an LPS-recognizing GPCR that is a potential drug target for treatment of amoebiasis, especially considering the well-established drug targeting to GPCRs.