bluuebunny/crossref_metadata_2025_split huggingface dataset:
Utilizing a Multi-Degree of Freedom Reduced-Order Model for Identifying Non-Synchronous Vibrations in Turbomachinery
Authors: Hollenbach Richard 
Published: August 2024

Abstract
The interaction between an unsteady aerodynamic instability with a natural mode of vibration causes large, undesired vibration in turbomachinery. In a simple form, an unsteady instability might be von Karman vortex shedding; on the other hand, it might be as complex as tip gap flow, jet core flow, or even a rotating stall. If the aerodynamic event occurs at frequencies away from shaft rotational harmonics, it is described as non-synchronous. Thus, an unsteady aerodynamic instability occurring at a frequency which excites a natural bending or torsional blade mode can be described as Non-Synchronous Vibrations (NSV), or often referred to as Vortex-Induced Vibrations (VIV). Compared to other aeroelastic phenomena, NSV has no industry accepted design tool. That leaves NSV as the most important issue to tackle for the need of an industry design tool is great.
This paper is a conclusion of multiple papers on utilizing a reduced-order model for NSV. For a pitching airfoil model, the first degree-of-freedom is the structure, while the second is the oscillating vortex shedding, captured using a Van der Pol and Duffing oscillator equation. These coupled equations create a fluid-structure interaction model which is tuned to replicate the experimental results of a wind tunnel airfoil exhibiting NSV. For the three-degree-of-freedom model, the compressor blade is given the motions of plunge and pitch, which the third degree is again the fluid. The tuned model is compared to experimental turbomachinery data. For both models, phase shift and work done per cycle are calculated and analyzed; the former depicts times for constructive and deconstructive interference, the latter demonstrates the dominant contributors to work. Finally, a framework for a full NSV design tool for industry is described including next steps for the eventually implementation of it within the research stages of turbomachinery geometry. Immediate next steps as well as long term future work are also described for this tool.
Experimental Investigation on Combustion Instabilities in a Lean Premixed Bluff Body Combustor Producing Acoustically Long Flame
Authors: Ikwubuo Melvin , Lee Jong Guen 
Published: August 2024

Abstract
The global and local characteristics of thermoacoustic instability occurring in a bluff body combustor which produces an acoustically non-compact flame (the Helmholtz number, He = kLflame, between 0.29 to 0.60) are reported. Over the flow conditions employed (Mach number of 0.05–0.13 and equivalence ratio of 0.60–0.85), the unstable flames are observed for a short combustor (CL = 0.66 m) with partially-closed combustor exit and a long combustor (CL = 1.22 m) with open combustor exit. The dominant peaks of pressure oscillation are found over a frequency range of 150–230Hz for the former and a frequency range of 200–280Hz for the latter. The discrepancy between the estimated and measured frequency is far greater for the short combustor than for the long combustor, which is attributed to the relatively longer flame length for the short combustor with respect to the combustor length than that for the long combustor, suggesting the relative flame length with respect to the characteristic wavelength is an important factor in determining the instability frequency and hence the prediction of thermoacoustic instability. The phase-averaged chemiluminescence image sequence during one period of pressure oscillation shows that the flame length changes significantly, responding to the pressure fluctuation during unstable combustion. Further analysis shows that for unstable flames, a region of flame where the local heat release fluctuation is out of phase with respect to the local pressure fluctuation and a region of flame where the local heat release fluctuation is in phase with respect to the local pressure fluctuation coexist over the flame length. The peak values of both damping and growing acoustic energy source increase as the Mach number increases, but the total acoustic source term becomes positive and its total value increases as the instability becomes strong.
Large-Eddy Simulation of a Non-Premixed Ammonia-Hydrogen Flame: NOx Emission and Flame Characteristics Validation
Authors: Ansari Naseem , Orsino Stefano , Meloni Roberto , Pucci Egidio , Castellani Simone , Andreini Antonio , Valera-Medina A. 
Published: August 2024

Abstract
The interest in ammonia and ammonia-hydrogen combustion as fuel for Gas Turbine (GT) applications implies the resolution of many technical challenges. The prediction of their flame characteristics, like flame morphology and pollutant emissions, through numerical simulations and specifically through Computational Fluid Dynamics (CFD) is one of them. In terms of NOx and unburnt emissions, the main roadblock is often related to a wide discrepancy of the results changing the employed chemistry set.
In the present work a non-premixed ammonia-hydrogen flame is investigated numerically and compared with the experimental findings retrieved in a test condition of the atmospheric pressure test campaign presented by Pugh et al. [1]. The CFD simulation is based on the species transport model with a different closure of the chemical source term depending on the cell-based combustion regime. The numerical case is based on a skeletal mechanism retrieved ad hoc to optimize the computational effort and preserve the main species needed for the calculation of the NOx emission. A detailed assessment of the CFD calculated NOx is carried out comparing it with experimental data. Following that a Chemical Reactor Network (CRN) model is used for NOx evaluation leveraging the time-averaged numerical solution from CFD. Some of the most accurate detailed chemical mechanisms present in literature are tested using the CRN model. The results from CFD and CRN reveal that there is a need to improve the pollutant emission for ammonia-hydrogen flame operating under lean non-premixed conditions.
A Comparative Analysis of Various Machine Learning Approaches for Fault Diagnostics of Hydrogen Fueled Gas Turbines
Authors: Hashmi Muhammad Baqir , Fentaye Amare Desalegn , Mansouri Mohammad , Kyprianidis Konstantinos G. 
Published: August 2024

Abstract
Global energy transition efforts towards decarbonization requires significant advances within the energy sector. In this regard, hydrogen is envisioned as a long-term alternative fuel for gas turbines. Accordingly, the gas turbine industry has expedited their efforts in developing 100% hydrogen compliant burners and associated auxiliary components for retrofitting the existing gas turbines. The utilization of hydrogen in gas turbines has some underlying challenges such as corrosion mainly originating from increased steam content in the hot gas path. In addition to corrosion, the gas turbine compressor is vulnerable to fouling which is the most commonly occurring fault in gas turbine operating over certain time window. Both faults are susceptible to performance and health degradation. To avoid expensive asset loss caused by unexpected downtimes and shutdowns, timely maintenance decision making is required. Therefore, simple, accurate and computationally efficient fault detection and diagnostics models become crucial for timely assessment of health status of the gas turbines.
The present study encompassed development of a physics-based performance model of a 100-kWe micro gas turbine running on 100% hydrogen fuel. The model is validated with experimental data acquired from test campaigns at the University of Stavanger. Data synthesized from experimentally validated performance model are utilized further for training machine learning algorithms. To identify an accurate algorithm, various algorithms such as support vector machine, decision tree, random forest algorithm, k-nearest neighbors, and artificial neural network were tested. The findings from fault diagnostics process (classification) revealed that ANN outperformed its counterpart algorithm by giving accuracy of 94.55%. Similarly, ANN also showed higher accuracy in performance degradation estimation process (regression) by showing the MSE of training loss as low as ∼0.14. The comparative analysis of all the chosen algorithms in the present study revealed ANN as the most accurate algorithm for fault diagnostics of hydrogen fueled gas turbines. However, there is need to further implement the ensemble machine learning models or deep learning model to explore and expedite the real time fault diagnostic accuracy to avoid false alarms and missed detections in context of hydrogen fuel.
Adjoint Optimization of Non-Axisymmetric Endwall Contours to Reduce Losses in a High-Pressure Turbine
Authors: Hendrickson Austin , Sperling Spencer , Nguyen Bao , Celestina Richard , Liu Jong , Aksoy Hakan , Nickol Jeremy , Mathison Randall 
Published: August 2024

Abstract
As modern gas turbines continue to evolve, further efficiency gains become more difficult to realize. The parasitic loss from secondary flows become a larger component of the overall loss, making aerodynamic optimization of secondary effects ever more critical. Specifically, the secondary flow losses created by the passage vortex can become a dominant loss factor. There has been much research and development over the past 40 years into the mitigation of these secondary flow structures, but manufacturing advances are opening up the realm of what designs can be practically implemented.
This paper discusses the development of an adjoint optimization method for three-dimensional endwall contouring using an adjoint solver in commercially available software. The primary goals of the study are to establish best practices for a holistic process of endwall optimization and compare the optimized design to the baseline geometry. An array of CFD analyses has been conducted for a high-pressure turbine stage to investigate the impact of the sensitivity radius parameter with regard to isentropic efficiency convergence. The results of these simulations are discussed and the effectiveness of the use of the adjoint model with respect to endwall contouring is discussed. Comparisons between the baseline geometry and optimized endwall shape are used to highlight how small changes in the endwall geometry impact the development of secondary flow structures such as the passage vortex. It was found that the optimized endwall geometry drove secondary losses down through a pinching mechanism at vortex formation, with a critical sensitivity radius providing the highest gains.
Experimental Study of the Real Gas Effects of CO2 on the Aerodynamic Performance Characteristics of a 1.5-Stage Axial Compressor
Authors: Kang Jeongseek , Vorobiev Alex , Cameron Joshua D. , Morris Scott C. , Turner Mark G. , Sedlacko Kyle , Miller Jason D. , Held Timothy J. 
Published: August 2024

Abstract
The thermodynamic properties of CO2 do not obey the ideal gas law and the simplified equation of state. The enthalpy and sonic speed depend on both temperature and pressure whereas the enthalpy and the speed of sound of ideal gas, like atmospheric air, depend only on its temperature. These effects add additional complexity to the design and operation of CO2 compressors compared to compressors utilizing air as their working fluid. For example, if the compressor inlet pressure changes during operation, its flow Mach number changes due to the change of the sonic speed which is followed by the change of corrected speed and the performance.
This paper focused on the experimental investigation of the performance parameters of a 1.5 stage axial compressor with CO2 gas. The design speed and the design pressure ratio of the compressor are 19,800 rpm and 1.41 respectively. The testing was completed using a 10MW closed CO2 compressor test loop at the University of Notre Dame Turbomachinery Laboratory. The compressor performance was measured at various compressor inlet conditions to demonstrate the effectiveness of the generalized corrected speed and the corrected flow coefficient in the CO2 compressor performance. Additionally, it is shown that the Reynolds number is connected to other performance parameters through the sonic speed and a set of experimental data is presented with an attempt to separate the effect of the Reynolds number and the effect of the corrected speed on the compressor performance.
Onametostat, a PfPRMT5 inhibitor, exhibits antimalarial activity to
Plasmodium falciparum
Authors: Min Hui , Lucky Amuza Byaruhanga , Madsen Jesper J. , Chim-Ong Anongruk , Li Xiaolian , Cui Liwang , Miao Jun 
Published: August 2024

ABSTRACT

Protein arginine methyltransferases (PRMTs) play critical roles in
Plasmodium falciparum
, a protozoan causing the deadliest form of malaria, making them potential targets for novel antimalarial drugs. Here, we screened 11 novel PRMT inhibitors against
P. falciparum
asexual growth and found that onametostat, an inhibitor for type II PRMTs, exhibited strong antimalarial activity with a half-maximal inhibitory concentration (IC
50
) value of 1.69 ± 0.04 µM.
In vitro
methyltransferase activities of purified PfPRMT5 were inhibited by onametostat, and a shift of IC
50
to onametostat was found in the
PfPRTM5
disruptant parasite line, indicating that PfPRTM5 is the primary target of onametostat. Consistent with the function of PfPRMT5 in mediating symmetric dimethylation of histone H3R2 (H3R2me2s) and in regulating invasion-related genes, onametostat treatment led to the reduction of H3R2me2s level in
P. falciparum
and caused the defects on the parasite’s invasion of red blood cells. This study provides a starting point for identifying specific PRMT inhibitors with the potential to serve as novel antimalarial drugs.
Loss of glycerol catabolism confers carbon-source-dependent artemisinin resistance in
Mycobacterium tuberculosis
Authors: Martini Maria Carla , Alonso Maria Natalia , Cafiero Juan Hilario , Xiao Junpei , Shell Scarlet S. 
Published: August 2024

ABSTRACT

In view of the urgent need for new antibiotics to treat human infections caused by multidrug-resistant pathogens, drug repurposing is gaining strength due to the relatively low research costs and shorter clinical trials. Such is the case of artemisinin, an antimalarial drug that has recently been shown to display activity against
Mycobacterium tuberculosis
(Mtb), the causative agent of tuberculosis. To gain insight into how Mtb is affected by artemisinin, we used RNAseq to assess the impact of artemisinin on gene expression profiles, revealing the induction of several efflux pumps and the KstR2 regulon. To anticipate the artemisinin resistance-conferring mutations that could arise in clinical Mtb strains, we performed an
in vitro
evolution experiment in the presence of lethal concentrations of artemisinin. We obtained artemisinin-resistant isolates displaying different growth kinetics and drug phenotypes, suggesting that resistance evolved through different pathways. Whole-genome sequencing of nine isolates revealed alterations in the
glpK
and
glpQ1
genes, both involved in glycerol metabolism, in seven and one strains, respectively. We then constructed a
glpK
mutant and found that loss of
glpK
increases artemisinin resistance only when glycerol is present as a major carbon source. Our results suggest that mutations in glycerol catabolism genes could be selected during the evolution of resistance to artemisinin when glycerol is available as a carbon source. These results add to recent findings of mutations and phase variants that reduce drug efficacy in carbon-source-dependent ways.
Construction nanobiotechnology approach for performance enhancement of microbially induced biomineralization (MIB) using a biopolymer encapsulated spore-based system
Authors: Debnath Ankita , Sen Ramkrishna 
Published: August 2024

ABSTRACT

The integration of green construction practices within the built environment has been significantly advanced by biotechnological innovations, among which microbially induced biomineralization (MIB), predominantly facilitated by various strains of spore-forming bacilli, emerges as a pivotal mechanism for the self-healing of concrete. However, the practical deployment of this technology faces challenges, notably the compromised viability of bacterial spores due to germination triggered by severe shear stress during concrete mixing. To address this limitation, a water-insoluble polymer (extracellular polymeric substance) produced by
Cellulomonas flavigena
was utilized to encapsulate and protect the spores. The encapsulation process was rigorously verified through physicochemical methodologies, including X-ray diffraction (XRD) analysis, which revealed alterations in the interlayer spacings of the extracellular polymeric substance (EPS) structure during the encapsulation process, indicating successful EPS coating of the spores. Furthermore, a proof of concept for the enhanced biomineralization capacity of EPS-coated spores was demonstrated. Standard analytical techniques confirmed the precipitation of calcite and vaterite among other minerals, underscoring the effectiveness of this novel approach. This breakthrough paves the way for the development of innovative, sustainable bioconcrete applications, aligning with broader environmental objectives and advancing the field of green construction technology.

IMPORTANCE
Development of bioconcrete with self-healing capability through MIB constitutes an important sustainable construction biotechnology approach for restoration and repair of built environment. Like every promising technology, MIB also suffers from certain shortcomings in terms of compromised viability of the microbial cells after premature germination of the spores on exposure to shear stress caused during concrete mixing. In this study, these challenges were adequately addressed by successfully providing a protective coating of indigenously extracted EPS to the bacterial spores and elucidating the interactive mechanisms between them. The results showed stable encapsulation of the spores while providing mechanistic insights of the encapsulation phenomenon. The data also showed enhanced rate of biomineralization by encapsulated microbes when subjected to stress conditions.
TolC and EmrA1 contribute to
Francisella novicida
multidrug resistance and modulation of host cell death
Authors: Kopping Erik J. , Benziger P. Todd , Thanassi David G. 
Published: August 2024

ABSTRACT

Francisella
spp. are Gram-negative, facultative intracellular pathogens.
Francisella tularensis
causes the human disease tularemia and is considered a biological threat agent due to its high infectivity and virulence. A central aspect of
Francisella
virulence is its ability to dampen host immune responses. We previously identified the outer membrane channel (OMC) protein TolC as a critical
F. tularensis
virulence factor required for suppression of apoptotic and proinflammatory responses during macrophage infection. TolC functions as part of multidrug efflux systems and the type I secretion pathway that exports bacterial effector proteins. In these systems, TolC forms tripartite complexes together with an inner membrane transporter and periplasmic membrane fusion protein (MFP). To advance understanding of TolC function in
Francisella
, we analyzed OMC and MFP homologs in
Francisella novicida
, a widely used model species that causes a tularemia-like disease in mice. In agreement with the previous
F. tularensis
studies, all three OMCs present in
F. novicida
contributed to multidrug resistance, but only TolC was important for suppressing macrophage cell death. In addition, we identified the EmrA1 MFP as important for resisting antimicrobial compounds and dampening host cell death. In contrast to results obtained with
F. tularensis
, the cell death triggered during infection with the
F. novicida tolC
and
emrA1
mutants was dominated by pyroptosis rather than apoptosis. These data expand our understanding of TolC function in
Francisella
and underscore both conserved and differential aspects of
F. novicida
and
F. tularensis
.

IMPORTANCE

Francisella tularensis
is a Gram-negative intracellular bacterial pathogen and causative agent of tularemia. We previously identified the outer membrane channel protein TolC as contributing to antimicrobial resistance and subversion of host responses by
F. tularensis
. To advance understanding of TolC function in
Francisella
and to identify components that might work together with TolC, we took advantage of a transposon mutant library in
F. novicida
, a model species that causes a tularemia-like disease in mice. Our findings identify TolC and the membrane fusion protein EmrA1 as important for both antimicrobial resistance and suppression of macrophage cell death. This study also revealed differences in cell death pathways triggered by
F. novicida
versus
F. tularensis
infection that may relate to differences in virulence.
Subnanometer structure of medusavirus capsid during maturation using cryo-electron microscopy
Authors: Watanabe Ryoto , Song Chihong , Takemura Masaharu , Murata Kazuyoshi 
Published: August 2024

ABSTRACT

Medusavirus is a giant virus classified into an independent family of
Mamonoviridae
. Amoebae infected with medusavirus release immature particles in addition to virions. These particles were suggested to exhibit the maturation process of this virus, but the structure of these capsids during maturation remains unknown. Here, we apply a block-based reconstruction method in cryo-electron microscopy (cryo-EM) single particle analysis to these viral capsids, extending the resolution to 7–10 Å. The maps reveal a novel network composed of minor capsid proteins (mCPs) supporting major capsid proteins (MCPs). A predicted molecular model of the MCP fitted into the cryo-EM maps clarified the boundaries between the MCP and the underlining mCPs, as well as between the MCP and the outer spikes, and identified molecular interactions between the MCP and these components. Several structural changes of the mCPs under the fivefold vertices of the immature particles were observed, depending on the presence or absence of the underlying internal membrane. In addition, the lower part of the penton proteins on the fivefold vertices was also missing in mature virions. These dynamic conformational changes of mCPs indicate an important function in the maturation process of medusavirus.

IMPORTANCE
The structural changes of giant virus capsids during maturation have not thus far been well clarified. Medusavirus is a unique giant virus in which infected amoebae release immature particles in addition to mature virus particles. In this study, we used cryo-electron microscopy to investigate immature and mature medusavirus particles and elucidate the structural changes of the viral capsid during the maturation process. In DNA-empty particles, the conformation of the minor capsid proteins changed dynamically depending on the presence or absence of the underlying internal membranes. In DNA-full particles, the lower part of the penton proteins was lost. This is the first report of structural changes of the viral capsid during the maturation process of giant viruses.