bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient Thermal Analysis of Gas Turbine Shut Down Physics: Normal and Forced Cooling
Authors: Selvam Kathiravan , De Prosperis Roberto , Vanga Nageswara Rao 
Published: August 2016

For industrial gas turbine plant, Reliability, Availability & Maintainability (RAM) are the critical parameters that yield maximum production. As gas turbines work in high temperature environment, periodic maintenance of the machine is important for life evaluation & to detect any early failures. During major inspection, all critical components need to be disassembled, which reduces the availability of gas turbine & impacts the plant production. Minimizing the duration of the scheduled outage helps to increase the availability of a gas turbine unit. During every major inspection, it’s necessary to ensure that the turbine is cooled below the allowable temperature. Gas turbine maintenance phases are often delayed because of slow natural convection cooling during normal shutdown. To reduce the cool-down time, it’s necessary to accelerate the cooling & one of industry practices is to spin the unit at a certain speed for an extended period of time which enables low temperature ambient air circulation. However, this forced cooling of the machine imposes additional thermal stresses on the components that may result in overall life reduction.
This paper compares the thermal behaviour of normal cool down and forced cool down phenomena by simulating the critical gas turbine components. A 2D axi-symmetric flange to flange thermal modelling approach is used to predict the temperature distribution of the gas turbine components. Conduction, convection and radiation effects are captured using GE in-house methodology. Compressor and turbine casings as well as rotors are studied in detail to understand the transient thermal gradients. The results show that a high rim to bore gradient exists during forced cool down, which results in high stresses in the compressor and turbine wheel regions.
Steady and Unsteady Simulations for Annular Internal Condensing Flows in a Channel
Authors: Naik Ranjeeth , Narain Amitabh , Mitra Soumya 
Published: August 2016

This paper highlights: (i) numerical methods developed to solve annular/stratified internal condensing flow problems, and (ii) the assessed effects of transverse gravity and surface tension on shear driven (horizontal channels) and gravity driven (inclined channels) internal condensing flows. A comparative study of the flow physics is presented with the help of steady and unsteady computational results obtained from the numerical solutions of the full two-dimensional governing equations for annular internal condensing flows. These simulations directly apply to recently-demonstrated innovative condenser operations which make the flow regime annular over the entire length of the condenser. The simulation algorithm is based on an active integration of our own codes developed on MATLAB with the standard single-phase CFD simulation codes available on COMSOL. The approach allows for an accurate wave simulation technique for the highly sensitive shear driven annular condensing flows.
This simulation approach employs a sharp-interface model and uses a moving grid technique to accurately locate the dynamic interface by the solution of the interface tracking equation (employing the method of characteristics) along with the rest of the governing equations. The 4th order time-step accuracy in the method of characteristics has enabled, for the first time, the ability to track time-varying interface locations associated with wave phenomena and accurate satisfaction of all the interface conditions — including the more difficult to satisfy interfacial mass-flux equalities.
A combination of steady and unsteady simulation results are also used to identify the effects of transverse gravity, axial gravity, and surface tension on the growth of waves. The results presented bring out the differences within different types of shear driven flows and differences between shear driven and gravity driven flows.
The unsteady wave simulation capability has been used here to do the stability analysis for annular shear-driven steady flows. In stability analysis, an assessment of the dynamic response of the steady solutions to arbitrary instantaneous initial disturbance are obtained. The results mark the location beyond which the annular regime transitions to a non-annular regime (experimentally known to be a plug-slug regimes).
The computational prediction of heat-flux values agree with the experimentally measured values (at measurement locations) obtained from relevant runs of our in-house experiments. Also, a comparison between the computationally predicted and experimentally measured values regarding the length of the annular regime is possible, and will be presented elsewhere.
Numerical Analysis of Heat Exchangers Used in a Liquid Piston Compressor Using a One-Dimensional Model With an Embedded Two-Dimensional Submodel
Authors: Zhang Chao , Wieberdink Jacob , Simon Terrence W. , Li Perry Y. , Van de Ven James , Loth Eric 
Published: August 2016

The present study presents a one-dimensional liquid-piston compressor model with an embedded two-dimensional submodel. The submodel is for calculating heat conduction across a representative internal plate of a porous heat exchanger matrix within the compression space. The liquid-piston compressor is used for Compressed Air Energy Storage (CAES). Porous-media-type heat exchangers are inserted in the compressor to absorb heat from air as it is compressed. Compression without heat transfer typically results in a temperature rise of a gas and a drop in efficiency, for the elevated temperature leads to wasted thermal energy, due to cooling during subsequent cooling back to ambient temperature. The use of heat exchangers can reduce the air temperature rise during the compression period.
A typical numerical model of a heat exchanger is a one-dimensional simplification of the two-energy-equation porous media model. The present authors proposed a one-dimensional model that incorporates the Volume of Fluid (VOF) method for application to the two-phase flow, liquid piston compressor with exchanger inserts. Important to calculating temperature distributions in both the solid and fluid components of the mixture is heat transfer between the two, which depends on the local temperature values, geometry, and the velocity of fluid through the matrix. In the one-dimensional model, although the axial temperatures vary, the solid is treated as having a uniform temperature distribution across the plate at any axial location. This may be in line with the physics of flow in most heat exchangers, especially when the exchangers are made of metal with high thermal conductivity. However, it must be noted that for application to CAES, the gas temperature in the compression chamber rises rapidly during compression and the core of the solid wall may heat up to a different temperature than that of the surface, depending on the geometry, solid material of the exchanger and fluid flow situation. Therefore, a new, one-dimensional model with embedded two-dimensional submodel is developed to consider two-dimensional heat conduction in a representative solid plate. The VOF concept is used in the model to handle the moving liquid-gas interface (liquid piston).
The model gives accurate solutions of temperature distributions in the liquid piston compression chamber. Six different heat exchangers with different length scales and different materials are simulated and compared.
Application of the MSMD Framework in the Simulation of Battery Packs
Authors: Li Genong , Li Shaoping , Cao Jing 
Published: August 2016

Lithium-ion battery has been widely used in electric vehicles (EVs). Battery’s performance, life and safety are of great engineering importance. Using simulation tools, battery’s electric performance and thermal behavior can be computed to provide useful information in the design of a battery pack and its thermal management system.
The muti-scale muti-dimensional (MSMD) methodology has been proven to be very effective in the simulation of battery at the battery’s geometry dimension scale. The method has been demonstrated in the literature for a single battery cell simulation. However, in the EV applications, battery packs where individual battery is connected in series and/or parallel are often used to provide the required power input during a real driving cycle. In this paper the MSMD methodology is extended to the battery pack simulation.
Plasmid with Colistin Resistance Gene
mcr-1
in Extended-Spectrum-β-Lactamase-Producing Escherichia coli Strains Isolated from Pig Slurry in Estonia
Authors: Brauer Age , Telling Kaidi , Laht Mailis , Kalmus Piret , Lutsar Irja , Remm Maido , Kisand Veljo , Tenson Tanel 
Published: August 2016

ABSTRACT

A plasmid carrying the colistin resistance gene
mcr-1
was isolated from a pig slurry sample in Estonia. The gene was present on a 33,311-bp plasmid of the IncX4 group.
mcr-1
is the only antibiotic resistance gene on the plasmid, with the other genes mainly coding for proteins involved in conjugative DNA transfer (
taxA
,
taxB
,
taxC
,
trbM
, and the
pilX
operon). The plasmid pESTMCR was present in three phylogenetically very different
Escherichia coli
strains, suggesting that it has high potential for horizontal transfer.
Complex Class 1 Integron Carrying
qnrB62
and
bla
VIM-2
in a Citrobacter freundii Clinical Isolate
Authors: Lee Jae Jin , Kim Mi-Na , Park Kwang Seung , Lee Jung Hun , Karim Asad Mustafa , Park Moonhee , Kim Ji Hwan , Lee Sang Hee 
Published: August 2016

ABSTRACT

The coexistence of
qnrB62
and
bla
VIM-2
was detected in a
Citrobacter
clinical isolate. The reduced fluoroquinolone susceptibility is attributable to
qnrB62
, mutations of quinolone-resistance-determining regions, and an efflux pump or pumps. The genetic context surrounding chromosomal
qnrB62
was a novel complex class 1 integron (In1184::IS
CR1
::
qnrB62
) containing a unique gene array (
bla
VIM-2
-
aacA4′-8
-
gucD
). An 18-nucleotide deletion at the 3′ end of the
pspA
gene [
pspA
(Δ
18
)], upstream of
qnrB62
, and an inverted repeat region (IRR2) were detected in In1184::IS
CR1
::
qnrB62
, indicating past transposition events.
Clinical Features and Risk Factors for Development of Breakthrough Gram-Negative Bacteremia during Carbapenem Therapy
Authors: Lee Ji-Yong , Kang Cheol-In , Ko Jae-Hoon , Lee Woo Joo , Seok Hye-Ri , Park Ga Eun , Cho Sun Young , Ha Young Eun , Chung Doo Ryeon , Lee Nam Yong , Peck Kyong Ran , Song Jae-Hoon 
Published: August 2016

ABSTRACT

With the increasing use of carbapenems, carbapenem-resistant Gram-negative bacteria have become a major concern in health care-associated infections. The present study was performed to evaluate the clinical and microbiological features of breakthrough Gram-negative bacteremia (GNB) during carbapenem therapy and to assess risk factors for development of breakthrough GNB. A case-control study was performed at a tertiary hospital from 2005 to 2014. Case patients were defined as individuals whose blood cultures grew Gram-negative bacteria while the patients were receiving carbapenems for at least 48 h before breakthrough GNB. Age-, sex-, and date-matched controls were selected from patients who received carbapenem for at least 48 h and did not develop breakthrough GNB during carbapenem treatment. A total of 101 cases of breakthrough GNB were identified and compared to 100 controls. The causative microorganisms for breakthrough GNB were
Stenotrophomonas maltophilia
(
n
= 33),
Acinetobacter baumannii
(
n
= 32),
Pseudomonas aeruginosa
(
n
= 21), and others (
n
= 15). Approximately 90% of
S. maltophilia
isolates were susceptible to levofloxacin and trimethoprim-sulfamethoxazole. The most common infection types were primary bacteremia (38.6%) and respiratory infections (35.6%). More than half of the patients died within a week after bacteremia, and the 30-day mortality rate was 70.3%. In a multivariate analysis, a longer hospital stay, hematologic malignancy, persistent neutropenia, immunosuppressant use, and previous colonization by causative microorganisms were significantly associated with breakthrough GNB. Our data suggest that
S. maltophilia
,
A. baumannii
, and
P. aeruginosa
are the major pathogens of breakthrough GNB during carbapenem therapy, in association with a longer hospital stay, hematologic malignancy, persistent neutropenia, immunosuppressant use, and previous colonization.
Molecular Characterization of Extended-Spectrum-Cephalosporin-Resistant Enterobacteriaceae from Wild Kelp Gulls in South America
Authors: Liakopoulos Apostolos , Olsen Björn , Geurts Yvon , Artursson Karin , Berg Charlotte , Mevius Dik J. , Bonnedahl Jonas 
Published: August 2016

ABSTRACT

Extended-spectrum-cephalosporin-resistant
Enterobacteriaceae
are a public health concern due to limited treatment options. Here, we report on the occurrence and the molecular characteristics of extended-spectrum-cephalosporin-resistant
Enterobacteriaceae
recovered from wild birds (kelp gulls). Our results revealed kelp gulls as a reservoir of various extended-spectrum cephalosporinase genes associated with different genetic platforms. In addition, we report for the first time the presence of a known epidemic clone of
Salmonella enterica
serotype Heidelberg (JF6X01.0326/XbaI.1966) among wild birds.
Distinct Effects of T-705 (Favipiravir) and Ribavirin on Influenza Virus Replication and Viral RNA Synthesis
Authors: Vanderlinden Evelien , Vrancken Bram , Van Houdt Jeroen , Rajwanshi Vivek K. , Gillemot Sarah , Andrei Graciela , Lemey Philippe , Naesens Lieve 
Published: August 2016

ABSTRACT
T-705 (favipiravir) is a new antiviral agent in advanced clinical development for influenza therapy. It is supposed to act as an alternative substrate for the viral polymerase, causing inhibition of viral RNA synthesis or virus mutagenesis. These mechanisms were also proposed for ribavirin, an established and broad antiviral drug that shares structural similarity with T-705. We here performed a comparative analysis of the effects of T-705 and ribavirin on influenza virus and host cell functions. Influenza virus-infected cell cultures were exposed to T-705 or ribavirin during single or serial virus passaging. The effects on viral RNA synthesis and infectious virus yield were determined and mutations appearing in the viral genome were detected by whole-genome virus sequencing. In addition, the cellular nucleotide pools as well as direct inhibition of the viral polymerase enzyme were quantified. We demonstrate that the anti-influenza virus effect of ribavirin is based on IMP dehydrogenase inhibition, which results in fast and profound GTP depletion and an imbalance in the nucleotide pools. In contrast, T-705 acts as a potent and GTP-competitive inhibitor of the viral polymerase. In infected cells, viral RNA synthesis is completely inhibited by T-705 or ribavirin at ≥50 μM, whereas exposure to lower drug concentrations induces formation of noninfectious particles and accumulation of random point mutations in the viral genome. This mutagenic effect is 2-fold higher for T-705 than for ribavirin. Hence, T-705 and ribavirin both act as purine pseudobases but profoundly differ with regard to the mechanism behind their antiviral and mutagenic effects on influenza virus.
Metabolomic Profiling of the Malaria Box Reveals Antimalarial Target Pathways
Authors: Allman Erik L. , Painter Heather J. , Samra Jasmeet , Carrasquilla Manuela , Llinás Manuel 
Published: August 2016

ABSTRACT

The threat of widespread drug resistance to frontline antimalarials has renewed the urgency for identifying inexpensive chemotherapeutic compounds that are effective against
Plasmodium falciparum
, the parasite species responsible for the greatest number of malaria-related deaths worldwide. To aid in the fight against malaria, a recent extensive screening campaign has generated thousands of lead compounds with low micromolar activity against blood stage parasites. A subset of these leads has been compiled by the Medicines for Malaria Venture (MMV) into a collection of structurally diverse compounds known as the MMV Malaria Box. Currently, little is known regarding the activity of these Malaria Box compounds on parasite metabolism during intraerythrocytic development, and a majority of the targets for these drugs have yet to be defined. Here we interrogated the
in vitro
metabolic effects of 189 drugs (including 169 of the drug-like compounds from the Malaria Box) using ultra-high-performance liquid chromatography–mass spectrometry (UHPLC-MS). The resulting metabolic fingerprints provide information on the parasite biochemical pathways affected by pharmacologic intervention and offer a critical blueprint for selecting and advancing lead compounds as next-generation antimalarial drugs. Our results reveal several major classes of metabolic disruption, which allow us to predict the mode of action (MoA) for many of the Malaria Box compounds. We anticipate that future combination therapies will be greatly informed by these results, allowing for the selection of appropriate drug combinations that simultaneously target multiple metabolic pathways, with the aim of eliminating malaria and forestalling the expansion of drug-resistant parasites in the field.
Metabolomics-Based Screening of the Malaria Box Reveals both Novel and Established Mechanisms of Action
Authors: Creek Darren J. , Chua Hwa H. , Cobbold Simon A. , Nijagal Brunda , MacRae James I. , Dickerman Benjamin K. , Gilson Paul R. , Ralph Stuart A. , McConville Malcolm J. 
Published: August 2016

ABSTRACT

High-throughput phenotypic screening of chemical libraries has resulted in the identification of thousands of compounds with potent antimalarial activity, although in most cases, the mechanism(s) of action of these compounds remains unknown. Here we have investigated the mode of action of 90 antimalarial compounds derived from the Malaria Box collection using high-coverage, untargeted metabolomics analysis. Approximately half of the tested compounds induced significant metabolic perturbations in
in vitro
cultures of
Plasmodium falciparum
. In most cases, the metabolic profiles were highly correlated with known antimalarials, in particular artemisinin, the 4-aminoquinolines, or atovaquone. Select Malaria Box compounds also induced changes in intermediates in essential metabolic pathways, such as isoprenoid biosynthesis (i.e., 2-C-methyl-
d
-erythritol 2,4-cyclodiphosphate) and linolenic acid metabolism (i.e., traumatic acid). This study provides a comprehensive database of the metabolic perturbations induced by chemically diverse inhibitors and highlights the utility of metabolomics for triaging new lead compounds and defining specific modes of action, which will assist with the development and optimization of new antimalarial drugs.
Prevalence of Quinolone Resistance in Enterobacteriaceae from Sierra Leone and the Detection of
qnrB
Pseudogenes and Modified LexA Binding Sites
Authors: Leski Tomasz A. , Stockelman Michael G. , Bangura Umaru , Chae Daniel , Ansumana Rashid , Stenger David A. , Vora Gary J. , Taitt Chris R. 
Published: August 2016

ABSTRACT

A collection of 74
Enterobacteriaceae
isolates found in Bo, Sierra Leone, were tested for quinolone antibiotic susceptibility and resistance mechanisms. The majority of isolates (62%) were resistant to quinolones, and 61% harbored chromosomal
gyrA
and/or
parC
mutations. Plasmid-mediated quinolone resistance genes were ubiquitous, with
qnrB
and
aac(6′)-Ib-cr
being the most prevalent. Mutated LexA binding sites were found in all
qnrB1
genes, and truncated
qnrB
pseudogenes were found in the majority of
Citrobacter
isolates.
CovR Regulates Streptococcus mutans Susceptibility To Complement Immunity and Survival in Blood
Authors: Alves Lívia A. , Nomura Ryota , Mariano Flávia S. , Harth-Chu Erika N. , Stipp Rafael N. , Nakano Kazuhiko , Mattos-Graner Renata O. 
Published: August 2016

ABSTRACT

Streptococcus mutans
, a major pathogen of dental caries, may promote systemic infections after accessing the bloodstream from oral niches. In this study, we investigate pathways of complement immunity against
S. mutans
and show that the orphan regulator CovR (CovR

Sm

) modulates susceptibility to complement opsonization and survival in blood.
S. mutans
blood isolates showed reduced susceptibility to C3b deposition compared to oral isolates. Reduced expression of

covR
Sm

in blood strains was associated with increased transcription of CovR

Sm

-repressed genes required for
S. mutans
interactions with glucans (
gbpC
,
gbpB
, and
epsC
), sucrose-derived exopolysaccharides (EPS). Consistently, blood strains showed an increased capacity to bind glucan
in vitro
. Deletion of

covR
Sm

in strain UA159 (UAcov) impaired C3b deposition and binding to serum IgG and C-reactive protein (CRP) as well as phagocytosis through C3b/iC3b receptors and killing by neutrophils. Opposite effects were observed in mutants of
gbpC
,
epsC
, or
gtfBCD
(required for glucan synthesis). C3b deposition on UA159 was abolished in C1q-depleted serum, implying that the classical pathway is essential for complement activation on
S. mutans
. Growth in sucrose-containing medium impaired the binding of C3b and IgG to UA159, UAcov, and blood isolates but had absent or reduced effects on C3b deposition in
gtfBCD
,
gbpC
, and
epsC
mutants. UAcov further showed increased
ex vivo
survival in human blood in an EPS-dependent way. Consistently, reduced survival was observed for the
gbpC
and
epsC
mutants. Finally, UAcov showed an increased ability to cause bacteremia in a rat model. These results reveal that CovR

Sm

modulates systemic virulence by regulating functions affecting
S. mutans
susceptibility to complement opsonization.
Pyrroloquinoline Quinone Ethanol Dehydrogenase in Methylobacterium extorquens AM1 Extends Lanthanide-Dependent Metabolism to Multicarbon Substrates
Authors: Good Nathan M. , Vu Huong N. , Suriano Carly J. , Subuyuj Gabriel A. , Skovran Elizabeth , Martinez-Gomez N. Cecilia 
Published: August 2016

ABSTRACT

Lanthanides are utilized by microbial methanol dehydrogenases, and it has been proposed that lanthanides may be important for other type I alcohol dehydrogenases. A triple mutant strain (
mxaF xoxF1 xoxF2
; named MDH-3), deficient in the three known methanol dehydrogenases of the model methylotroph
Methylobacterium extorquens
AM1, is able to grow poorly with methanol if exogenous lanthanides are added to the growth medium. When the gene encoding a putative quinoprotein ethanol dehydrogenase,
exaF
, was mutated in the MDH-3 background, the quadruple mutant strain could no longer grow on methanol in minimal medium with added lanthanum (La
3+
). ExaF was purified from cells grown with both calcium (Ca
2+
) and La
3+
and with Ca
2+
only, and the protein species were studied biochemically. Purified ExaF is a 126-kDa homodimer that preferentially binds La
3+
over Ca
2+
in the active site. UV-visible spectroscopy indicates the presence of pyrroloquinoline quinone (PQQ) as a cofactor. ExaF purified from the Ca
2+
-plus-La
3+
condition readily oxidizes ethanol and has secondary activities with formaldehyde, acetaldehyde, and methanol, whereas ExaF purified from the Ca
2+
-only condition has minimal activity with ethanol as the substrate and activity with methanol is not detectable. The
exaF
mutant is not affected for growth with ethanol; however, kinetic and
in vivo
data show that ExaF contributes to ethanol metabolism when La
3+
is present, expanding the role of lanthanides to multicarbon metabolism.

IMPORTANCE
ExaF is the most efficient PQQ-dependent ethanol dehydrogenase reported to date and, to our knowledge, the first non-XoxF-type alcohol oxidation system reported to use lanthanides as a cofactor, expanding the importance of lanthanides in biochemistry and bacterial metabolism beyond methanol dehydrogenases to multicarbon metabolism. These results support an earlier proposal that an aspartate residue near the catalytic aspartate residue may be an indicator of rare-earth element utilization by type I alcohol dehydrogenases.