bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonpremixed Approaches for Fuel Flexible, Low NOx Combustors in High-Efficiency Gas Turbines
Authors: Emerson Benjamin , Patel Shivam J. , Gubbi Srujan , McKinney Randal G. , Wu David , Noble David R. , Lieuwen Tim 
Published: August 2024

Abstract
Lean, premixed combustor designs have almost completely replaced nonpremixed combustors for industrial gas turbine applications where NOx emissions are regulated. Nonetheless, these designs have also introduced turndown and fuel flexibility constraints and made combustion instabilities and flashback more problematic. Future gas turbine applications will require combustors to accommodate a range of alternative fuels, provide operational flexibility, and compete for services with a host of new technologies, including energy storage and fuel cells. The purpose of this paper is to propose nonpremixed, multistage designs for the next generation of high turndown, high fuel flexibility, low NOx combustion designs—referred to here as a Nonpremixed, Rich, Relaxation, Lean (NRRL) combustor. The key concept, we explore is nonpremixed combustion, followed by additional fuel mixing to locally fuel-rich conditions, a relaxation stage, and then a lean stage. This nonpremixed approach can handle essentially any fuel composition, including pure hydrogen, liquid fuels, pure methane, pure ammonia, and any combination in between while breaking the NOx-CO tradeoff and reducing combustion instability risk. This paper provides chemical reactor network modeling calculations to identify key kinetic processes and time scales required for such a concept. This concept has completely inverted sensitivities from lean, premixed systems which prefer short residence times, low pressures, and low temperatures to minimize NO formation. This concept prefers long residence times, high pressures, and high temperatures, indicating a very different set of design trades for part load and off-design performance.
Analysis of Thermo-Acoustic Instabilities Induced by Hydrogen Swirling Flames
Authors: Vaysse Nicolas , Durox Daniel , Vicquelin Ronan , Candel Sébastien , Renaud Antoine 
Published: August 2024

Abstract
A considerable research effort has been concerned combustion dynamics of systems fed with hydrocarbon fuels. The case of pure hydrogen/air flames deserves to be specifically considered because hydrogen is highly reactive, has a tendency to develop thermo-diffusive instabilities, is envisaged in many future applications, most notably in gas turbines, and is less well documented. Thermo-acoustic instabilities of pure hydrogen flames are here investigated in a configuration where hydrogen is injected in-crossflow in a swirling stream of air. The study is focused on operating conditions that lead to oscillatory regimes. Using Abel-transformed phase-averaged images of OH* emission and visible light emission in burnt gases, it is shown that the OH* signal evolves approximately in phase with the heat release rate. This signal is then used to determine the local Rayleigh source term that feeds acoustic energy in the oscillation. The contributions of this term are examined using a space–time analysis based on an integration of the source term in the transverse direction. This procedure allows a detailed analysis of the processes that contribute to the acoustic energy in the system, showing, in particular, that a strong positive addition of acoustic energy results from a roll-up of the flame tip and from the quick cyclic back propagation of the flame to the injector tip. A global integration of the Rayleigh source term is then used together with a volume-integrated acoustic energy to estimate the growth rate associated with these driving processes and estimate the damping rate. A special experimental method is then exploited to determine the effective growth rate of the instability. The system allowing a sweep in frequency, self-sustained instabilities obtained at different frequencies are used to extract the specific instability frequency band of the burner. Finally, the flame is externally forced in order to measure its flame-describing function.
Mass and Heat Exchange in Rotating Compressor Cavities With Variable Cob Separation
Authors: Nicholas Tom E. W. , Pernak Mikolaj J. , Lock Gary D. , Scobie James A. , Tang Hui 
Published: August 2024

Abstract
Next generation aeroengines will operate at ever-increasing pressure ratios with smaller cores, where the control of blade-tip clearances across the flight cycle is an emerging design challenge. Such clearances are affected by the thermal expansion of the compressor disks that hold the blades, where acute thermal stresses govern operating life. The cavities formed by corotating disks feature a heated shroud at high radius and cooler cobs at low radius. A three-dimensional, unsteady and unstable flow structure is induced by destabilizing buoyancy forces. The radial distribution of disk temperature is driven by a conjugate heat transfer at Grashof numbers of order 1013. Such flows are further influenced by the heat and mass exchange with an axial throughflow of cooling air at low radius, where the interaction depends on the Rossby number and separation of the disk cobs. This paper is the first to study the effect of cob separation ratio on mass and heat exchange for compressor cavities. A model is developed to predict the cavity-throughflow interaction, and disk and fluid-core temperatures. The judicious use of a physics-based methodology provides reliable, reduced-order solutions to the complex conjugate problem, thereby making it appropriate for practical engine thermo-mechanical design. The model is validated by detailed experimental measurements using the Bath Compressor Cavity Rig, where variable disk cob spacings were investigated over a range of engine-representative conditions. The unsteady pressure measurements collected in the frame of reference of the rotating disks reveal new insight into the fundamentally aperiodic nature of the flow structure. This new understanding of heat transfer informs an expedient reduced-order model and enables more efficient design of future high pressure-ratio aeroengines.
A Surrogate Model Approach to Predict Operations and Maintenance Cost for Combined Cycle Power Plant
Authors: Choi Woosung , Webb Bobby M. , Noble David R. 
Published: August 2024

Abstract
In the transition toward carbon neutrality by 2050, renewable energy sources are gaining prominence. The variability of renewable energy poses challenges for power grid stability. Gas turbine combined cycle (GTCC) power plants play a crucial role in grid stabilization, especially during peak loads. In GTCC power generation, operations and maintenance (O&M) cost is the next most important after fuel and initial investment cost, and it is necessary to predict O&M cost according to changes in the operating environment for efficient and stable operation of GTCC power plant. However, various uncertainties exist when estimating O&M costs because actual design information is limitedly disclosed due to maintenance contracts between operators and manufacturers, and it is difficult to obtain accurate variables according to the operation condition. In this paper, the correlation was analyzed considering the uncertainty of the factors affecting the O&M cost of the GTCC power plant through sensitivity analysis, and the main factors were defined. In addition, a surrogate model was proposed that can quickly calculate fixed and variable O&M cost according to changing operating scenarios such as shortening startup time, enhancing ramp rate, or lower minimum load. Through the case study, short-term and long-term O&M costs can be estimated in the operating environment of the GTCC power plant currently being operated. Additionally, the model facilitates cost projections for new hybrid GTCC facilities (combining gas turbines with energy storage systems), aiding long-term investment planning.
Reverse Thrust Aerodynamics of Variable Pitch Fans With Inlet Distortion
Authors: Ma Kwun Yeung , Hall Cesare A. , Wang Tianhou , Williams Tim S. 
Published: August 2024

Abstract
Variable pitch fans (VPFs) can improve the operability of low pressure ratio fan systems by repitching the rotor blades. If a variable pitch fan can generate sufficient reverse thrust on landing, it will also eliminate the need for heavy, cascade-type thrust reversers. However, any reverse thrust generation is impacted by high levels of inlet distortion generated as air is drawn into the exhaust nozzle. This paper uses both Reynolds-averaged Navier–Stokes (RANS) computations and low-speed rig experiments to explore how a representative inlet distortion from the engine installation affects the aerodynamics and performance of a variable pitch fan operating in reverse thrust mode. The simulations and the experiments both show that the distortion from the engine installation leads to a highly three-dimensional flow field with a large recirculation region within the bypass duct. This is in contrast to the primarily axial flow that is produced for a case with uniform freestream inlet conditions. The distortion substantially redistributes the mass flow, thrust, and power in the engine. Streamline tracking combined with a power balance analysis reveals that there is highly radial flow within the fan rotor and almost all of the power from the fan is used to drive the recirculating flow in the bypass duct, which generates high loss and has a high total temperature. The recirculation reduces the net mass flow through the engine to around 5% of a uniform inflow case and the effective reverse thrust is greatly reduced. With uniform inflow, the net reverse thrust was found to be 35% of the nominal takeoff thrust. With inlet distortion present, this was reduced to 20%. This demonstrates the importance of designing and operating variable pitch fan systems to minimize the reverse thrust inlet distortion.
Design-Point Techno-Economics of Brayton Cycle PTES for Combined Heat and Power
Authors: Neises Ty , McTigue Joshua 
Published: August 2024

Abstract
Pumped thermal energy storage (PTES) systems are grid batteries that use heat pumps to create both hot and cold thermal energy stores when there is excess electricity and then use a power cycle to convert the thermal energy into electricity when there is demand for electricity. In normal operation, Joule–Brayton PTES discharges low-grade heat at temperatures useful for thermal energy consumers like district and industrial heating. Furthermore, PTES designs, like conventional combined heat and power (CHP) technology, can be modified to sacrifice some round-trip efficiency (RTE) to increase the temperature of heat rejection. This paper uses design-point performance and cost models that provide a detailed understanding of the efficiency and cost tradeoffs of rejecting heat at various temperatures in ideal-gas Brayton PTES configurations. First, we keep the heat rejection in its nominal location in the PTES system: in the discharge cycle after the low-pressure exit of the recuperator before the cold-storage heat exchanger. Next, we move the heat rejection to the discharge turbine exit. We define design-point metrics that isolate both the cost and performance penalty associated with the hotter heat rejection and attribute it exclusively to the heat economic metrics. Finally, we estimate the performance of electric heater technology to generate heat at equivalent temperatures. We find that the levelized cost of heat (LCOH), including the cost of thermal energy storage (TES) buffering the PTES and heat off-taker, compares favorably versus electric technologies and is less than the cost of natural gas for low temperature scenarios and competitive with the cost of natural gas in some regions of the contiguous U.S. in high temperature scenarios.
Does Attraction Toward Physical Activity Predict Physical Activity Behavior in Older Adults?
Authors: Hudgins Brynn L. , Seo Yeongjun , Bittel Kelsey M. , Williams Kemiah , Hevel Derek J. , Labban Jeffrey D. , Maher Jackie P. 
Published: August 2024

Background/Objectives: Few studies have investigated associations between the motivational outcome based on physical activity (PA) affective experiences (i.e., attraction vs. antipathy toward PA) and behavior. This study investigated cross-sectional and longitudinal associations between attraction (vs. antipathy) toward PA and device-based PA in older adults. Methods: Older adults (n = 139; 71% female, Mage = 70.5) completed assessments of attraction (vs. antipathy) toward PA and 14 days of device-based accelerometry at Times 1 and 2. Results: Greater attraction toward PA at Time 1 was associated with greater steps (β = 5.31, p < .01) and moderate to vigorous intensity PA (β = 3.08, p < .05) at Time 1. Greater attraction toward PA at Time 1 was not significantly associated with steps or moderate to vigorous intensity PA at Time 2. Conclusion: Greater emphasis on resultant motivation from PA affective experiences may be useful in promoting PA in older adults. Significance/Implications: In spite of mixed findings in the present study, there is strong evidence that positive affective responses during a single bout of PA play an important role in predicting future engagement. Yet, affective experiences during PA can be individualistic and often influenced by contextual factors. Interventions designed to increase PA should focus on factors that may create positive affective experiences for participants.
Extensive Familiarization Is Required Before Assessing Acute Changes in Multiple Object Tracking Performance
Authors: Moon Jessica M. , Pinette John , Khwaja Aneesa , Fontenot Aubrey , Gibbs Violette , Dufner Trevor J. , Wells Adam J. 
Published: August 2024

Context: The Neurotracker CORE assessment is an 8-minute multiple object tracking (MOT) program used in sport science research and clinical rehabilitation as a perceptual-cognitive training tool; however, it has garnered interest for its potential use as an acute assessment of cognitive performance. Although some data exist regarding the learning effect of repeated exposures, it is often overlooked with investigators focusing primarily on the presence of transfer effects to other cognitive realms. As a result, exclusive data on the effect of repeated testing, or subsequent periods of no testing (ie, detraining) on test–retest reliability, and on MOT performance are sparse. Design: Repeated-measures/reliability. Methods: Twenty-three recreationally active men and women completed 15 training sessions consisting of 2 CORE assessments per session (30 assessments). Participants were randomized to either 1 or 2 weeks of detraining prior to completing 15 retraining sessions (30 assessments). Training and retraining periods were divided into 10 blocks (3 assessments/block) for analysis. MOT speed threshold (MOT-ST), consistency, fastest trial score success speed, lowest trial score miss speed, the number of perfect, near misses, and significant miss trials within each block were used to determine performance. Intraclass correlation coefficient, standard error of measurement, and minimal detectable change were used to determine reliability. Results: Significant improvements in MOT-ST and fastest trial score success speed were noted within training blocks 1 to 6 and 1 to 7, respectively (P < .05). MOT-ST and fastest trial score success speed demonstrated excellent test–retest reliability between blocks 8 and 9. There was no effect of detraining period on performance during retraining. Conclusions: Eighteen tests are necessary to overcome training effects and establish a reliable baseline when MOT-ST is used as the performance outcome. Detraining periods up to 2 weeks did not impact performance. The average of 3 discrete tests should be used when assessing MOT-ST performance.
Systemic absorption and safety of topical terbinafine hydrochloride 10% solution (MOB015B): a phase 1 maximal usage trial in patients with moderate-to-severe onychomycosis
Authors: Tavakkol Amir , DuBois Janet C. , Gupta Aditya K. 
Published: August 2024

ABSTRACT

Topical antifungals may be considered to treat onychomycosis with minimal risk of systemic side effects. In this study, we assess the safety, tolerability, systemic exposure, and pharmacokinetic characteristics of topical terbinafine hydrochloride 10% solution (MOB015B) in adults with moderate-to-severe onychomycosis. Clinically and mycologically confirmed patients with toenail onychomycosis (
N
= 20) were enrolled in this single-center, open-label study . Each patient had ≥50% involvement of both great toenails and at least four additional toenails affected. MOB015B was applied once daily to all toenails for 28 days. Blood was drawn on days 1, 14, and 28. Plasma concentrations of MOB015B after the first dose were quantifiable in all subjects by 24 h. Steady-state levels in plasma were reached by day 28. The mean systemic exposure on day 28 of 0.72 ng/mL for maximum plasma concentration (C
max
) was approximately 2,000 times lower than the mean plasma level of 1.39 µg/mL seen after oral administration of 250 mg terbinafine for 28 days. Adverse events (five patients), such as headache (
n
= 3), seasonal allergy (
n
= 1), and neck pain (
n
= 1), were considered unrelated to MOB015B; no application site reactions or study discontinuations due to an adverse event were observed. MOB015B applied to all affected toenails under maximal usage conditions for 28 days demonstrated very low levels of terbinafine in plasma (C
max
<1 ng/mL after 28 days), consistent with a favorable safety and tolerability profile.

CLINICAL TRIALS

This study is registered with

ClinicalTrials.gov
as
NCT03244280

.
Multicenter evaluation of activity of aztreonam in combination with avibactam, relebactam, and vaborbactam against metallo-β-lactamase-producing carbapenem-resistant gram-negative bacilli
Authors: Tao Lili , Dahlquist Ashley , Harris Harley , Jacobs Emily , Wenzler Eric , Simner Patricia J. , Humphries Romney 
Published: August 2024

ABSTRACT

Treatment options for carbapenem-resistant gram-negative bacilli (CR-GNB), especially metallo-β-lactamase (MBL)-producing CR-GNB, are limited. Aztreonam (ATM) in combination with avibactam (AVI) has shown potential for treating MBL-producing carbapenem-resistant Enterobacterales (CREs) and
Stenotrophomonas maltophilia
. However, data on ATM in combination with other β-lactamase inhibitors (BLIs) are limited. We performed a multicenter study to evaluate the
in vitro
activities of ATM in combination with AVI, vaborbactam (VAB), relebactam (REL), tazobactam (TAZ) as well as with their commercially available formulations against CREs and
S. maltophilia
using broth microdilution. AVI restored ATM activity for MBL-producing CREs (ATM: 9.8% vs ATM-AVI: 78.0%) and
S. maltophilia
(ATM: 0% vs ATM-AVI: 93.3%). REL also moderately restored activity of ATM in MBL-producing CREs (ATM: 9.8% vs ATM-REL: 42.7%) and
S. maltophilia
(ATM: 0% vs ATM-REL: 68.9%). VAB and TAZ demonstrated very limited effect on the activity of ATM against CR-GNB evaluated. The combination of ATM with ceftazidime-AVI (CAZ-AVI) demonstrated maximum activity against CREs. Although ATM-CAZ-AVI is the most potent regimen available for CREs and
S. maltophilia
, ATM-IMI-REL might be a reasonable alternative.
CRISPR-Cas inhibits plasmid transfer and immunizes bacteria against antibiotic resistance acquisition in manure
Authors: Upreti Chahat , Kumar Pranav , Durso Lisa M. , Palmer Kelli L. 
Published: August 2024

ABSTRACT

The horizontal transfer of antibiotic resistance genes among bacteria is a pressing global issue. The bacterial defense system clustered regularly interspaced short palindromic repeats (CRISPR)-Cas acts as a barrier to the spread of antibiotic resistance plasmids, and CRISPR-Cas-based antimicrobials can be effective to selectively deplete antibiotic-resistant bacteria. While significant surveillance efforts monitor the spread of antibiotic-resistant bacteria in the clinical context, a major, often overlooked aspect of the issue is resistance emergence in agriculture. Farm animals are commonly treated with antibiotics, and antibiotic resistance in agriculture is on the rise. Yet, CRISPR-Cas efficacy has not been investigated in this setting. Here, we evaluate the prevalence of CRISPR-Cas in agricultural
Enterococcus faecalis
strains and its antiplasmid efficacy in an agricultural niche: manure. Analyzing 1,986
E. faecalis
genomes from human and animal hosts, we show that the prevalence of CRISPR-Cas subtypes is similar between clinical and agricultural
E. faecalis
strains. Using plasmid conjugation assays, we found that CRISPR-Cas is a significant barrier against resistance plasmid transfer in manure. Finally, we used a CRISPR-based antimicrobial approach to cure resistant
E. faecalis
of erythromycin resistance, but this was limited by delivery efficiency of the CRISPR antimicrobial in manure. However, immunization of bacteria against resistance gene acquisition in manure was highly effective. Together, our results show that
E. faecalis
CRISPR-Cas is prevalent and effective in an agricultural setting and has the potential to be utilized for depleting antibiotic-resistant populations. Our work has broad implications for tackling antibiotic resistance in the increasingly relevant agricultural setting, in line with a One Health approach.

IMPORTANCE

Antibiotic resistance is a growing global health crisis in human and veterinary medicine. Previous work has shown technologies based on CRISPR-Cas—a bacterial defense system—to be effective in tackling antibiotic resistance. Here we test if CRISPR-Cas is present and effective in agricultural niches, specifically in the ubiquitously present bacterium,
Enterococcus faecalis
. We show that CRISPR-Cas is both prevalent and functional in manure and has the potential to be used to specifically kill bacteria carrying antibiotic resistance genes. This study demonstrates the utility of CRISPR-Cas-based strategies for control of antibiotic resistance in agricultural settings.