bluuebunny/crossref_metadata_2025 huggingface dataset:
Racial disparities among older adults with acute myocardial infarction: The SILVER‐AMI study
Authors: Demkowicz Patrick C. , Hajduk Alexandra M. , Dodson John A. , Oladele Carol R. , Chaudhry Sarwat I.
Published: November 2022

Background

Despite an aging population, little is known about racial disparities in aging‐specific functional impairments and mortality among older adults hospitalized for acute myocardial infarction (AMI).

Methods

We analyzed data from patients aged 75 years or older who were hospitalized for AMI at 94 US hospitals from 2013 to 2016. Functional impairments and geriatric conditions were assessed in‐person during the AMI hospitalization. The association between race and risk of mortality (primary outcome) was evaluated with logistic regression adjusted sequentially for age, clinical characteristics, and measures of functional impairment and other conditions associated with aging.

Results

Among 2918 participants, 2668 (91.4%) self‐identified as White and 250 (8.6%) as Black. Black participants were younger (80.8 vs 81.7 years; p = 0.010) and more likely to be female (64.8% vs 42.5%; p < 0.001). Black participants were more likely to present with impairments in cognition (37.6% vs 14.5%; p < 0.001), mobility (66.0% vs 54.6%; p < 0.001) and vision (50.1% vs 35.7%; p < 0.001). Black participants were also more likely to report a disability in one or more activities of daily living (22.4% vs 13.0%; p < 0.001) and an unintentional loss of more than 10 lbs in the year prior to hospitalization (37.2% vs 13.0%; p < 0.001). The unadjusted odds of 6‐month mortality among Black participants (odds ratio [OR] 2.0, 95% confidence interval [CI] 1.4–2.8) attenuated to non‐significance after adjustment for age, clinical characteristics (OR 1.70, 95% CI 1.7, 1.2–2.5), and functional/geriatric conditions (OR 1.5, 95% CI 1.0–2.2).

Conclusions

Black participants had a more geriatric phenotype despite a younger average age, with more functional impairments. Controlling for functional impairments and geriatric conditions attenuated disparities in 6‐month mortality somewhat. These findings highlight the importance of systematically assessing functional impairment during hospitalization and also ensuring equitable access to community programs to support post‐AMI recovery among Black older adults.
Phylogenomics and the flowering plant tree of life
Authors: Guo Cen , Luo Yang , Gao Lian‐Ming , Yi Ting‐Shuang , Li Hong‐Tao , Yang Jun‐Bo , Li De‐Zhu
Published: November 2022

The advances accelerated by next‐generation sequencing and long‐read sequencing technologies continue to provide an impetus for plant phylogenetic study. In the past decade, a large number of phylogenetic studies adopting hundreds to thousands of genes across a wealth of clades have emerged and ushered plant phylogenetics and evolution into a new era. In the meantime, a roadmap for researchers when making decisions across different approaches for their phylogenomic research design is imminent. This review focuses on the utility of genomic data (from organelle genomes, to both reduced representation sequencing and whole‐genome sequencing) in phylogenetic and evolutionary investigations, describes the baseline methodology of experimental and analytical procedures, and summarizes recent progress in flowering plant phylogenomics at the ordinal, familial, tribal, and lower levels. We also discuss the challenges, such as the adverse impact on orthology inference and phylogenetic reconstruction raised from systematic errors, and underlying biological factors, such as whole‐genome duplication, hybridization/introgression, and incomplete lineage sorting, together suggesting that a bifurcating tree may not be the best model for the tree of life. Finally, we discuss promising avenues for future plant phylogenomic studies.
Petrochronology of polygenetic white micas (Naxos, Greece)
Authors: Villa Igor M. , Glodny Johannes , Peillod Alexandre , Skelton Alasdair , Ring Uwe
Published: November 2022

Naxos in the Greek Cyclades preserves a type example of polymetamorphism. The southern and northern parts of the island record different Tertiary P–T histories between Eocene and Miocene times, including a blueschist facies event, one or more amphibolite/greenschist facies overprint(s) and contact metamorphism. Age attributions for these events are inconsistent in the literature. Here, we propose a new approach that combines electron probe microanalyzer (EPMA) characterization of the white mica (WM) with 39Ar‐40Ar–Rb‐Sr multichronometry. Textural–petrographic–compositional observations reveal that the polygenetic WM consists of five different generations: pre‐Eocene relicts, paragonite, high‐Si phengite, low‐Si phengite and muscovite. EPMA mapping of four WM samples, previously analysed by Rb‐Sr, reveals major element compositions heterogeneous down to the μm scale. Each WM consists of chemically distinct generations, documenting submicron‐scale retrogression of high‐pressure (HP) phengite grains to muscovite. Four WM samples from a N‐S traverse across the island were analysed by 39Ar‐40Ar stepheating, comparing coarse and fine sieve size fractions to obtain overdetermined K‐Ar systematics. Fine sieve fractions are richer in Cl than coarse ones. Linear arrays in Cl/K‐age isotope correlation diagrams show two predominant WM generations (one Cl‐poor at ca. 38 Ma and one Cl‐rich at <20 Ma). A lower‐grade sample from southern Naxos was less pervasively recrystallized, provides older ages and preserves at least three WM generations, including a relict WM with a pre‐Palaeocene K‐Ar age, consistent with the high Ar retentivity of WM in the absence of complete recrystallization. The age of the Cl‐poor end‐member WM approximates the age of the HP event, 38 Ma. Ar inheritance in Cretaceous mica relicts is heterogeneous at the single‐grain scale. Comparing the degassing rates of the WM fractions rules out ‘multidomain’ diffusion. As no sample is monomineralic, the degassing rate of each polygenetic mica is instead controlled by the mass balanced sum of the unrelated rate constants of its constituent minerals. Given the commonness of zoned and composite micas, the approach detailed here is potentially useful for reconstructing polyphase metamorphic histories worldwide.
Individual differences in revising the life story—Personality and event characteristics influence change in the autobiographical meaning of life events
Authors: Peters Isabel , Kemper Nina F. , Schmiedek Florian , Habermas Tilmann
Published: November 2022

Objective

Repeated autobiographical narratives have recently received increased attention as measures of the stability of narrative identity. We propose that one way to map change in life narratives is to rate the degree to which the autobiographical meaning of renarrated events changes. We aimed to test the influence of age, traits (openness, extraversion), and event characteristics on how much autobiographical meaning changes.

Method

In waves 3 and 4 of theMainLifestudy, 123 participants (15–72 years) narrated their lives twice, 4 years apart. Life events that were told both times were rated for change in autobiographical meaning (n = 531). Multilevel models tested individual and event characteristics as predictors.

Results

Autobiographical meaning changed more the more individuals were open to experience, the more recently the events had happened, and the more negative emotions the event narratives contained. It was unrelated to extraversion and to the use of autobiographical arguments. A decrease in change with age was due to older individuals narrating older events.

Conclusion

Our findings add to understanding how traits and life story are related and underscore the need to further study the role of event characteristics for stability and change in narrative identity.
Procyanidins regulate colonic metabolome, inflammatory response and antioxidant capacity in lambs fed a high‐concentrate diet
Authors: Mu Chuntang , Zhang Xuanzi , Zhang Jianxin , Hao Xiaoyan
Published: November 2022

This study explored the mechanism by which grape seed procyanidins (GSPs) alleviate colon inflammatory injury induced by a high‐concentrate diet in lambs. Forty‐eight 1/2 Dorper (♂) × 1/2 Small thin‐tailed (♀) crossed male lambs were randomly assigned into four groups: the control group (CON), fed with a high‐concentrate diet (concentrate:forage = 7:3) and three GSPs groups fed a high‐concentrate diet + 10 (LGSP), 20 (MGSP) and 40 (HGSP) mg/kg body weight (BW) GSPs per day, respectively. The results showed that the levels of interleukin (IL)−1β and tumour necrosis factor (TNF)‐α in plasma of lambs of the MGSP (0.155 and 38.52 pg/ml) and HGSP (0.165 and 39.60 pg/ml) groups were significantly lower than those in the CON (0.248 and 48.74 pg/ml) and LGSP (0.245 and 50.52 pg/ml) group (p < 0.05), and levels of IL‐1β in colon tissue in the MGSP (28.49 ng/g) and HGSP (26.67 ng/g) groups were also lower (p < 0.05) than that in CON (40.55 ng/g). Metabonomics analysis of colon tissue showed that differentially expressed metabolites were mainly enriched in the arachidonic acid metabolism, citric acid cycle, glycine, serine and threonine metabolism, and peroxisome proliferator‐activated receptor signalling pathway (p < 0.05). In conclusion, GSPs alleviate the colonic epithelium inflammatory response induced by a high‐concentrate diet by increasing energy metabolism, amino acid metabolism, antioxidant metabolism and inhibiting arachidonic acid metabolism.
Understanding the Diversity of Catholic Higher Education: A New Empirical Guide for Evaluating the Influence of Catholic Identity
Authors: Glanzer Perry L. , Cockle Theodore F. , Martin Jessica , Alexander Scott
Published: November 2022

Although scholars have often described faith‐based universities in America as “church‐related,” we argue this classification tells us virtually nothing about how the Catholic identity influences the mission, rhetoric, curriculum, or policies of Catholic institutions. Although Morey and Piderit (2006, Catholic higher education: A culture in crisis) created a more sophisticated four‐part typology of Catholic institutions, we find that students, parents, administrators, and scholars, particularly scholars interested in institutional secularization, need a better means of empirical analysis to determine the degree to which the Catholic identity of an institution influences key administrative decisions of the university. Thus, we propose a method of content analysis that can quantify how the Catholic identity shapes key administrative, curricular, and cocurricular decisions and thereby places Catholic institutions upon a continuum. We then apply our new Operationalizing Faith Identity Guide (OFIG) to Catholic institutions in the United States to demonstrate the helpfulness of its application.

Replication: The data needed to duplicate and replicate the findings in the paper will be made available immediately following publication.
A novelMRI‐based three‐dimensional model of stomach volume, surface area, and geometry in response to gastric filling and emptying
Authors: Bertoli Davide , Mark Esben Bolvig , Liao Donghua , Brock Christina , Frøkjær Jens Brøndum , Drewes Asbjørn Mohr
Published: November 2022

Background

Gastric motility and accommodation have a critical role in maintaining normal gastrointestinal homeostasis. Different modalities can be adopted to quantify those processes, that is, scintigraphy to measure emptying time and intragastric Barostat for accommodation assessment. However, magnetic resonance imaging (MRI) can assess the same parameters noninvasively without ionizing radiation. Our study aimed to develop a detailed three‐dimensional (3D) MRI model of the stomach to describe gastric volumes, surface areas, wall tension distribution, and interobserver agreement.

Methods

Twelve healthy volunteers underwent an MRI protocol of six axial T2‐weighted acquisitions. Each dataset was used to construct a 3D model of the stomach: First, the volumes of the whole stomach, gastric liquid, and air were segmented. After landmark placing, a raw 3D model was generated from segmentation data. Subsequently, irregularities were removed, and the model was divided into compartments. Finally, surface area and 3D geometry parameters (inverse curvatures) were extracted. The inverse curvatures were used as a proxy for wall tension distribution without measuring the intragastric pressure.

Key Results

The model was able to describe changes in volume and surface geometry for each compartment with a distinct pattern in response to filling and emptying. The surface tension was distributed nonhomogeneously between compartments and showed dynamical changes at various time points.

Conclusion & Inferences

The presented model offers a detailed tool for evaluating gastric volumes, surface geometry, and wall tension in response to filling and emptying and will provide insights into gastric emptying and accommodation in diseases such as diabetic gastroparesis.
Statins and oral biofilm: Simvastatin as a promising drug to control periodontal dysbiosis
Authors: Parolina de Carvalho Rafaela D. , de Andrade Moreno Jéssica , Roque Sindy Magri , Chan Daniel Cheuk Hong , Torrez Willy Bustillos , Stipp Rafael Nóbrega , Bueno‐Silva Bruno , de Lima Patricia Oliveira , Cogo‐Müller Karina
Published: November 2022

Objectives

This study evaluated antimicrobial activity of atorvastatin, pravastatin, rosuvastatin, and simvastatin against oral bacteria, and the interaction of simvastatin with standard antimicrobials (amoxicillin and metronidazole).

Methods

Minimal inhibitory concentration assays were performed with Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Actinomyces odontolyticus, Streptococcus oralis, Streptococcus mitis, Streptococcus salivarius, Streptococcus sanguinis, and Streptococcus gordonii; checkerboard microdilution assays between simvastatin and standard antimicrobials; monospecies and multispecies biofilms.

Results

Simvastatin showed the best antimicrobial activity against most species (MIC range from 3.12 to 25 μg/ml), highlighting the sensitivity of P. gingivalis. In the checkerboard assay, synergistic interaction was found between simvastatin and amoxicillin against S. oralis and S. sanguinis. P. gingivalis biofilm was inhibited by simvastatin at 10 and 50× Minimal inhibitory concentration, with similar effects to metronidazole. For multispecies biofilm, SMV reduced the biofilm metabolic activity (79%) and total counts (87%), comparable to amoxicillin. Simvastatin also reduced bacterial counts of Veilonnella parvula, P. gingivalis, Streptococcus mutans, Actinomyces naeslundii, P. intermedia, and Capnocytophaga ochracea in the multispecies biofilm.

Conclusions

Simvastatin showed antimicrobial and antibiofilm activity against oral bacteria and may contribute to the control of dysbiosis, and may be considered in clinical studies as an adjuvant in the treatment of periodontitis.
Is critical flicker‐fusion frequency a valid measure of visual fatigue? A post‐hoc analysis of a double‐masked randomised controlled trial
Authors: Singh Sumeer , Downie Laura E. , Anderson Andrew J.
Published: November 2022

Purpose

Critical flicker‐fusion frequency (CFF) has been used in clinical studies as a measure of visual fatigue. We examine the correlation between CFF and subjective reports of visual fatigue in a group of symptomatic computer users, to consider whether CFF may be used as a surrogate measure of visual fatigue symptoms.

Methods

We analysed data from a previous randomised controlled trial. One hundred and twenty adults, diagnosed with computer vision syndrome, had CFF and visual fatigue symptoms quantified before and after a visually demanding 2‐h computer task. Symptoms were assessed using a questionnaire with nine subcomponents that summed to a total score of 900. CFF was measured using a two‐interval forced‐choice method, with the flicker rate altered by a computer‐controlled staircase procedure. For our primary analysis, we determined Spearman correlation coefficients between post‐task symptom scores and CFF, and between change from baseline symptom scores and CFF. We also used a bootstrap procedure to consider whether symptom score subcomponents were significantly (Bonferroni‐corrected) different from overall scores with regard to their correlations with CFF.

Results

Although visual fatigue symptom scores altered significantly post‐task (mean change: 92 units; 95% confidence interval [CI]: 11 to 122), CFF did not (mean change −0.7 Hz; 95% CI: −1.7 to 0.3). There was no significant correlation between overall symptom scores and CFF, either for the post‐task (r = −0.13; 95% CI: −0.31 to 0.05) or the change from baseline (r = −0.18; 95% CI: −0.35 to 0.01) analysis. Subcomponents of the symptom questionnaire did not show a significant correlation with CFF, either for the post‐task or the change from baseline analysis.

Conclusions

We find that CFF is not a useful surrogate for symptoms of visual fatigue, given its low correlation with scores on a visual fatigue symptom questionnaire.
Tumor‐suppressive miR‐323a inhibits pancreatic cancer cell proliferation and glycolysis through targeting HK‐2
Authors: Wei Yangnian , Wang Mingdong , Liang Mingkun , Liu Ling , Mo Shifa , Zhang Hongchang , Chen Yunhui , Li Nianfeng
Published: November 2022

Pancreatic ductal adenocarcinoma (PDAC) accounts for more than 85% of all malignant pancreatic exocrine tumors and is one of the main causes of cancer‐related fatalities. PDAC is characterized by a high glycolytic rate to ensure its survival as a result of hypovascularization and the desmoplastic reaction. In this study, microRNA 323a (miR‐323a) was shown to be downregulated within pancreatic cancer tissues and cells, and enriched in the glucose metabolism pathway. In vitro, overexpression of miR‐323a suppressed cell viability, DNA synthesis, and colony formation; in vivo, miR‐323a overexpression suppressed the tumor growth within a xenograft mouse model. Regarding cellular glycolysis, miR‐323a overexpression decreased glucose‐6‐phosphate levels, inhibited glucose uptake, and reduced lactate and adenosine triphosphate production. miR‐323a was found to directly target hexokinase 2 (HK‐2) and negatively regulated HK‐2 expression. HK‐2 overexpression exerted oncogenic effects on pancreatic cancer cells and promoted cellular glycolysis; more importantly, HK‐2 overexpression partially eliminated the effects of miR‐323a overexpression. In conclusion, miR‐323a is downregulated within pancreatic cancer and serves as a tumor‐suppressive miRNA through inhibiting cancer cell proliferation and glycolysis. miR‐323a exerts its tumor‐suppressive effects through targeting HK‐2.
Learning new meanings for known L2 words: Long‐term semantic representation is updated to integrate new information after consolidation
Authors: Chen Jiayan , Chen Baoguo
Published: November 2022

Previous research about learning new meanings for known words in second language (L2) has found that semantic relatedness, i.e., congruency, between new and existing meanings benefits encoding and explicit memory of new meanings, and reduces instant interference on accessing existing meanings. However, they did not take the memory consolidation process into account. Thus, integration of new meaning into long‐term semantic memory, update of existing meaning representation, and the impact of semantic relatedness between new and existing meanings in this process remain unclear. The present study used the event‐related potential (ERP) technique to explore these questions. We asked Chinese students to learn English known words' subdominant meanings variedly related to existing meanings and probed semantic representations with EEG recorded in primed lexical decision tasks four times before and after consolidation. We found that new meaning needs to go through offline consolidation to get integrated. Semantic relatedness/congruency boosted new meaning integration, not by directly expediting it during encoding or preliminary offline consolidation, but by promoting the update of existing meaning representation first, which presumably paved the way for better incorporation of new meaning in the long run. The whole pattern of results implies that long‐term semantic representation of existing meaning is updated to integrate related new meaning after consolidation, which not only draws a clearer picture of L2 ambiguous word acquisition but also bears broader implications for research on memory updating.
Experience of using expired lyophilized snake antivenom during a medical emergency situation in Lao People's Democratic Republic––A possible untapped resource to tackle antivenom shortage in Southeast Asia
Authors: Blessmann Jörg , Hanlodsomphou Soulaphab , Santisouk Bounlom , Krumkamp Ralf , Kreuels Benno , Ismail Ahmad Khaldun , Yong Mun Yee , Tan Kae Yi , Tan Choo Hock
Published: November 2022

Objectives

To evaluate the safety and efficacy of expired lyophilized snake antivenom of Thai origin during a medical emergency in 2020/2021 in Lao People's Democratic Republic.

Methods

Observational case series of patients with potentially life‐threatening envenoming who consented to the administration of expired antivenom between August 2020 and May 2022.

Results

A total of 31 patients received the expired antivenom. Malayan pit vipers (Calloselasma rhodostoma) were responsible for 26 (84%) cases and green pit vipers (Trimeresurus species) for two cases (6%). In three patients (10%) the responsible snake could not be identified. Of these, two presented with signs of neurotoxicity and one with coagulopathy. A total of 124 vials of expired antivenom were administered. Fifty‐nine vials had expired 2–18 months earlier, 56 vials 19–36 months and nine vials 37–60 months before. Adverse effects of variable severity were observed in seven (23%) patients. All 31 patients fully recovered from systemic envenoming.

Conclusions

Under closely controlled conditions and monitoring the use of expired snake antivenom proved to be effective and safe. Discarding this precious medication is an unnecessary waste, and it could be a valuable resource in ameliorating the current shortage of antivenom. Emergency use authorization granted by health authorities and preclinical testing of expired antivenoms could provide the support and legal basis for such an approach.
Ageing and endothelium‐mediated vascular dysfunction: the role of the NADPH oxidases
Authors: Kwon Oh Sung , Noh Sung Gi , Park Soung Hun , Andtbacka Robert H. I. , Hyngstrom John R. , Richardson Russell S.
Published: November 2022

The present study aimed to determine the isoform‐specific role of the NADPH oxidases (NOX) in the endothelium‐mediated vascular dysfunction associated with ageing. Endothelium‐dependent [intraluminal flow‐ and acetylcholine (ACh)‐induced] vasodilatation in human skeletal muscle feed arteries (SMFAs) of young (24 ± 1 years, n = 16), middle aged (45 ± 1 years, n = 18) and old (76 ± 2 years, n = 21) subjects was assessed in vitro with and without the inhibition of NOX1 (ML090), NOX2 (gp91) and NOX4 (plumbagin). To identify the role of nitric oxide (NO) bioavailability in these responses, NO synthase blockade (l‐NG‐monomethyl arginine citrate) was utilized. SMFA NOX1, NOX2 and NOX4 protein expression was determined by western blotting. Age related endothelium‐dependent vasodilatory dysfunction was evident in response to flow (young: 69 ± 3; middle aged: 51 ± 3; old: 27 ± 3%, P < 0.05) and ACh (young: 89 ± 2; middle aged: 72 ± 3; old: 45 ± 4%, P < 0.05). NOX1 inhibition had no effect on SMFA vasodilatation, whereas NOX2 inhibition restored flow‐ and ACh‐induced vasodilatation in the middle aged and the old SMFAs (middle aged + gp91: 69 ± 3; 86 ± 3, old + gp91: 65 ± 5; 83 ± 2%, P < 0.05) and NOX4 inhibition tended to restore these vasodilatory responses in these two groups, but neither achieved statistical significance (P ≈ 0.06). l‐NG‐monomethyl arginine citrate negated the restorative effects of NOX2 and NOX4 blockade. Only NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function (r = 0.48 to 0.93, P < 0.05). NOX2 and, to a lesser extent, NOX4 appear to play an important, probably NO‐mediated, role in age‐related endothelial dysfunction.

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Key points

The present study aimed to determine the isoform‐specific role of the NADPH oxidases (NOX) in the endothelium‐mediated vascular dysfunction associated with ageing.

Age related endothelium‐dependent vasodilatory dysfunction was evident in skeletal muscle feed arteries in response to both flow and acetylcholine.

NOX2 inhibition (gp91) restored endothelium‐dependent vasodilatation in the middle aged and the old skeletal muscle feed arteries, and NOX4 inhibition (plumbagin) tended to restore these vasodilatory responses in these two groups. Nitric oxide synthase inhibition negated the restorative effects of NOX2 and NOX4 blockade.

NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function.

NOX2 and, to a lesser extent, NOX4 appear to play an important, probably nitric oxide‐mediated, role in age‐related endothelial dysfunction and could be important therapeutic targets to maintain vascular health with ageing.
Localized Damage Identification in the Last Stage Low-Pressure Steam Turbine Blade Using Dynamic Parameter Measurements
Authors: Shetkar Keshav Ramesh , Srinivas J.
Published: November 2022

Steam turbine blades are the important components in power system shaft lines subjected to severe temperatures, leading to low/high cycle fatigue failures. The transient conditions occurring during startup and shutdown events generate alternative stresses causing the fracture at the blade roots. The present work deals with the effect of localized damage on the vibration characteristics and damage identification study in the last stage low-pressure (LP) steam turbine blade. Initially, free vibration studies and transient analysis of the last row LP blade section are conducted using the finite element model. A crack near the root region is modeled by a torsional spring, whose stiffness is expressed in terms of crack depth ratio. Effects of crack depth ratio and location near the roots on the natural frequencies and transient response amplitudes are studied in detail. The relationship between the damage parameters and blade frequencies is established through the backpropagation neural network model.
Numerical Investigation of a Heavy Duty Compression Ignition Engine Converted to Ammonia Spark Ignition Operation
Authors: Liu Jinlong , Ulishney Christopher , Dumitrescu Cosmin E.
Published: November 2022

The need for global decarbonization in power generation requires the increased use of zero-carbon fuels. Compared to hydrogen, ammonia is easier to store, transport, and produce. In addition, the products of complete combustion of ammonia are water and nitrogen. As a result, ammonia is an ideal green fuel for generating power in internal combustion engines. The drawbacks in power generation relate to the high energy needed to ignite the combustible mixture and the low laminar flame speed of ammonia compared to conventional fuels. The three-dimensional numerical study presented here investigated the potential of converting existing diesel engines to ammonia spark ignition operation. The results indicated that the use of ammonia in a diesel-like combustion chamber produced a slower kernel inception process. But the speed of the fully developed turbulent flame was large enough to rapidly complete the bulk combustion process despite the lower laminar flame speed inside the ammonia-air mixture, and this was in the absence of any combustion promoters such as the addition of hydrogen. The problem with pure ammonia operation was the reduced combustion efficiency and the high level of unburned ammonia emissions, since the slow spark inception process can be compensated by a larger compression ratio. The results also suggested that emissions formation and subsequent oxidation were a more complex phenomena. For example, lean ammonia combustion produced higher nitrogen oxides (NOx) concentrations due to the nitrogen in the fuel, despite the lower combustion temperature. Moreover, advancing spark timing reduced the NOx emissions, which was opposite to the traditional spark ignition engines. Additionally, the ammonia in engine crevices that escaped the late oxidation process was the main source of nitrous oxide (N2O) species in the exhaust gas that usually do not appear in traditional engines. Overall, all these results suggested that more fundamental research on ammonia combustion is needed to understand its use in efficient, decarbonized engines.
Numerical Modeling and Analysis of Energy-Assisted Compression Ignition of Varying Cetane Number Jet Fuels for High-Altitude Operation
Authors: Sapra Harsh Darshan , Hessel Randy , Amezcua Eri , Stafford Jacob , Miganakallu Niranjan , Rothamer David , Kim Kenneth , Kweon Chol-Bum M. , Kokjohn Sage
Published: November 2022

Computational Fluid Dynamics (CFD) simulations are performed to study the potential of Energy-Assisted Compression Ignition (EACI) strategy for enabling ignition and enhancing combustion of different cetane number jet fuels during high-altitude operation. EACI employs an ignition assistant (IA), which is an advanced glow-plug design with the ability to sustain higher temperatures for prolonged periods, to provide the necessary ignition energy for precise ignition control and enhanced combustion. In the numerical simulations, the combustion chemistry solver is coupled with a multi-component wide distillation fuel mechanism, energy source modeling, and a turbulence-chemistry interaction model to accurately capture the Ignition Assisted-combustion. The simulation is first validated against optical engine measurements for CN 48 jet fuel and then transferred to another single-cylinder test engine to study the ignition and combustion characteristics of EACI with CN 35 jet fuel at varying IA temperatures. Simulation results show that EACI significantly improves fuel ignitability. Ignition delay reductions for CN 48 fuel of 57% and CN 35 fuel of 25% are noted at IA temperatures of 1550 K and 1405 K compared to when the IA is switched off. Furthermore, EACI improved the combustion efficiency to 99.7% compared to the 90% estimated for the IA off case in the optical engine.
Evaluation of Spray and Combustion Models for Simulating Dilute Combustion in a Direct-Injection Spark-Ignition Engine
Authors: Kim Joohan , Ameen Muhsin , Scarcelli Riccardo , Kim Namho , Singh Eshan , Sjöberg Magnus
Published: November 2022

Dilute combustion in spark-ignition engines has the potential to improve thermal efficiency by mitigating knock and by reducing throttling and wall heat losses. However, ignition and combustion processes can become unstable for dilute operation due to a lowered laminar flame speed, resulting in excessive cycle-to-cycle variability (CCV) of the combustion process. To compensate for the slower combustion in less reactive mixtures, a modified intake port geometry can be employed to generate a strong tumble flow in the cylinder and elevate turbulence levels around the spark plug, thereby promoting a faster transition to turbulent deflagration. Consequently, optimizing combustion chamber geometry and operating strategy is crucial to maximizing the benefits of using dilute combustion with enhanced in-cylinder turbulence across a wide range of operating conditions. Computational fluid dynamics (CFD) simulations can be utilized for virtual engine optimization tasks, but this would require the models to be truly predictive regarding the impact of changes to the engine design and operational parameters.

In this study, multi-cycle large-eddy simulations (LES) are performed for a direct-injection spark-ignition engine to investigate the model performance in predicting engine combustion characteristics with respect to changes in the intake configuration. A tumble plate that blocks the lower part of the intake port inlet is used to vary the tumble. A set of CFD models that have been recently developed are employed, which takes into account the drag of non-spherical droplets, flash-boiling behavior of liquid sprays, spray-wall interaction, surrogate formulation of a research-grade E10 gasoline, and fast chemical kinetic solvers. Simulation results are compared to experimental engine data in terms of cylinder pressure, apparent heat release rate, mass fraction burned timing, and flame images. It is found that LES employing the state-of-the-art CFD models are capable of properly predicting the spray processes and reproducing the measured mean cylinder pressure for the case with the tumble plate. On the other hand, the LES over-predicts the combustion rate during the early combustion stage and under-estimates the CCV, and these discrepancies become larger when the tumble plate is removed.
Design Optimization of an Ethanol Heavy-Duty Engine Using Design of Experiments and Bayesian Optimization
Authors: Tekgul Bulut , Liu I-Han , Vittal Manohar , Schanz Robert , Blumreiter Julie , Johnson Bernard H. , Magnotti Gina M.
Published: November 2022

Diesel-fueled engines still hold a large market share in the medium and heavy-duty transportation sector. However, the increase in fossil fuel prices and the strict emission regulations are leading engine manufacturers to seek cleaner alternatives without a compromise in performance. Alcohol-based fuels, such as ethanol, offer a promising alternative to diesel fuel in meeting regulatory demands. Ethanol provides cleaner combustion and lower levels of soot due to its chemical properties, in particular its lower level of carbon content. In addition, the stoichiometric operating conditions of alcohol fueled engines enable the mitigation of NOx emissions in aftertreatment stage. With the promise of retrofitting diesel engines to run on ethanol to reduce emissions, the thermal efficiency of these engines remains the primary optimization target. In order to find the optimal ethanol-fueled engine design that maximizes the thermal efficiency, a large design space needs to be investigated using engineering tools.

In this study, previous research by the authors on optimizing the design of a single-cylinder ethanol-fueled engine was extended to explore the design space for a heavy-duty multi-cylinder engine configuration. A heavy-duty engine setup with multiple operating conditions at different engine speeds and loads were considered. A design optimization analysis was performed to identify the potential designs that maximize the indicated thermal efficiency in an ethanol-fueled compression ignition engine. First, a computational fluid dynamics (CFD) model of the engine was validated using experimental data for four drive cycle points. Using a design of experiments (DoE) approach and a parameterized piston bowl geometry, the model was then exercised to explore the relationship among geometric features of the piston bowl and spray targeting angle and indicated thermal efficiency across all tested operating conditions. After evaluating 165 candidate designs, a piston bowl geometry was identified that yielded an increase between 1.3 to 2.2 percentage points in indicated thermal efficiency for all tested conditions, while satisfying the operational design constraints for peak pressure and maximum pressure rise rate. The increased performance was attributed to enhanced mixing that led to the formation of a more homogeneous distribution of in-cylinder temperature and equivalence ratio, higher combustion temperatures, and shorter combustion duration. Finally, a Bayesian optimization (BOpt) analysis was employed to find the optimal piston bowl geometry with a fixed spray injector angle for one of the operating conditions. Using BOpt, a piston candidate was identified that resulted in a 1.9 percentage point increase in thermal efficiency from the baseline design, yet only required 65% of the design samples investigated using the DoE approach.
A Study of Seizure Mechanism at Around the Piston Pin of a Medium Duty Diesel Engine
Authors: Shirotori Yunosuke , Watanabe Takuya , Ito Akemi
Published: November 2022

Downsizing and lowering engine speed is effective for fuel economy. However, such measures lead to severe lubrication condition and increase the risk of seizure because of higher load for the sliding surface. The bearing of the small end of a connecting rod is one of the sliding parts used under the severest lubrication conditions. Therefore, clarifying the mechanism of its seizure is an important subject. In the previous study, it is shown that higher the cylinder pressure thicker the oil film between the piston pin and bearing of the small end of the connecting rod. It derived a hypothesis that cylinder pressure causes a deformation of the pin and thicker oil film at around the center of the bearing and heavy contact at the bearing end. This study aimed clarifying the mechanism of the seizure occurring at around the piston pin. The calculated results showed that oil film could be generated by deformation of the piston pin. Further, oil film thickness was measured by laser induced fluorescence method for investigating the effect of pin stiffness. Measured result showed lower the stiffness of the piston pin thicker the oil film. It was found that the deformation of piston pin caused thick oil films. The fact that seizure occurred often the engine operation with the low stiffness piston pin also proved the hypothesis adequate.
Thermoelectric Exhaust Heat Recovery to Maximize Brake Thermal Efficiency of Advanced Diesel Engines: Modeling and Baseline Analysis
Authors: Sok Ratnak , Kusaka Jin
Published: November 2022

This work demonstrates the enhancement of brake thermal efficiency (BTE) of an advanced, turbocharged, production-intent 2.2 L diesel engine with a thermoelectric waste heat recovery system (TEG-WHR). The integrated engine model with the TEG is developed using 0D/1D software. Experimental data from the corrugated fin TEG under fin pitch = 1.0–2.0 mm, inlet gas temperatures (200–300 °C), and mass flow rates (5.0–15.0 g/s) are used for validating the model. The TEG model can reproduce measured pressure drop, heat transfer, and thermal performance characteristics. A 1-cylinder engine model parented from the advanced turbocharged diesel engine is developed. Under motoring and firing conditions, measured exhaust pressure, temperature, velocity, mass flow rate, and enthalpy are validated under various valve timings. Finally, the 3-layer TEG model is connected to the 4-cylinder engine to maximize its performance under a highly efficient (peak BTE) operating condition at 2250 RPM. Optimal size and thermoelectric module arrangement of the TEG system in the engine system considering a tradeoff between the TEG generated electrical power and engine pumping losses are suggested. The effective power of 1.1 kW and 1.1 % BTE improvement are obtained from the 3-sheet TEG system. As a result, a 49.9 % engine BTE is demonstrated without brake power loss.
Cooled Spray Technology for Particulate Reduction in a Heavy-Duty Engine
Authors: Klingbeil Adam , Heher Brett , Flores Manuel , Triana Padilla Antonio , Lavertu Thomas , Tinar Tristen , Ellis Scott
Published: November 2022

Diesel Engine Emission Reduction Technologies like Ducted Fuel Injection and Cooled Spray use passive hardware elements near the fuel injector spray holes to improve combustion and reduce particulate matter, with minimal impact on other performance parameters. This paper discusses the fabrication, installation and testing of Cooled spray inserts in a heavy-duty diesel engine. A cylinder head assembly with a Cooled Spray insert design, developed by Wabtec, allows use of multiple insert geometries for test purposes. As there are multiple test geometries planned and because proper alignment of the insert and injector is critical for the combustion process, manual alignment of the Cooled Spray device to the fuel injector is required. The location of injector holes within the cooled spray insert are imaged using a fiber-optic borescope. Imaging of the alignment with different injectors shows varying degrees of alignment success, suggesting that the injector nozzle variation may contribute to the misalignment between the individual nozzle holes and the fuel passages of the insert. Prior to the engine testing, a one-dimensional thermodynamic engine model provided boundary conditions for single cylinder engine testing. Finally, engine performance of the cooled spray insert is compared to the baseline engine performance. The test results show that an alignment improvement of 0.15mm reduced Filter Smoke Number by 85%. Additionally, Cooled Spray caused 70% reduction in Filter Smoke Number compared to the non-Cooled Spray for one condition while showing emissions parity or increases at other conditions.
Comparing the Injection Strategy of Gasoline Compression Ignition vs. Alcohol Compression Ignition: A Partial Review and Experimental Comparison
Authors: Gainey Brian , Yan Ziming , Gandolfo John , Lawler Benjamin
Published: November 2022

Gasoline compression ignition and compression ignition with a high cooling potential alcohol fuel, like wet ethanol 80 or methanol, are both promising alternatives to conventional diesel compression ignition that can improve efficiency and reduce criteria pollutants in the transportation sector. The fuel properties of gasoline are diametrically opposite of alcohol fuels and thus, the fuels behave differently in compression ignition. In this work the optimal compression ignition strategy with each fuel is studied. Data from the literature and experimental data presented in this work show that using a combination of partially-premixed and mixing-controlled combustion with gasoline in compression ignition enables robust control over the heat release process without incurring a significant efficiency penalty. Contrarily, the high cooling potential, of the alcohol fuels (∼6% of their lower heating value) means that heat absorption from evaporation and heating of the injected fuel can have a significant negative impact on efficiency if the fuel is injected near top dead center. However, the high cooling potential of the fuel enables robust control over the heat release process in a partially-premixed combustion strategy, which is not true of regular-grade gasoline (under all conditions). Overall, this work shows that on a light-duty diesel-engine architecture, compression ignition with gasoline, wet ethanol 80, and methanol can all achieve similar fuel conversion efficiencies. Compression ignition with gasoline resulted in a higher combustion efficiency compared to the alcohol fuels at the expense of higher engine-out NOx emissions and soot emissions. At 1500 rpm and 10 bar net indicated mean effective pressure, gasoline compression ignition achieved a net fuel conversion efficiency of 44.3% with an engine-out NOx level of 0.89 g/kWh and an FSN of 0.86. At the same operating condition, wet ethanol 80 compression ignition achieved a net fuel conversion efficiency of 44.0% with an engine-out NOx level of 0.21 g/kWh and an FSN of 0.03.
An Experimental Comparison of Cyclic Variations in Diesel-Natural Gas and POMDME-Natural Gas Dual Fuel Combustion
Authors: Narayanan Abhinandhan , Hariharan Deivanayagam , Krishnan Sundar , Srinivasan Kalyan
Published: November 2022

Cyclic variations in internal combustion engines are caused by various factors, including combustion mixture stratification, in-cylinder flows, local fluctuations in air-fuel ratio, etc. Cyclic variations have a profound impact on engine performance and emissions. In this study, cyclic variations in dual fuel combustion are analyzed, comparing diesel – natural gas (NG) and polyoxymethylene dimethyl ether (POMDME) – NG dual fuel combustion. Cyclic variability was initially quantified using the coefficient of variation (COV) of IMEPg computed from experimental cylinder pressure data. The cases analyzed in this study had a COV of IMEPg greater than or around 5%, which was the lower limit of onset of instability for this engine. Experiments were performed at two fixed start of injection (SOI) of high-cetane fuel: 310 CAD and 350 CAD. For all experiments, a constant load of 5 bar IMEPg was maintained and the intake boost pressure and rail pressure, were fixed at 1.5 bar and 500 bar respectively. For each case, 1000 cycles of cylinder pressure data were recorded, filtered, and processed using an in-house heat release analysis code for each cycle. A comparison between individual cycles and the “ensemble averaged cycle” was made for both diesel-NG and POMDME-NG combustion. For the early SOI of 310 CAD, the peak cylinder pressure fluctuations of individual cycle were found to be ± 15 bar for both fuel combinations, compared to the ensemble averaged cycle, and < 1/10th of the cycles had an IMEPg lower than 0.05 bar of the ensemble averaged cycle. However, the peak pressure fluctuations were found to be lower for POMDME-NG (± 3 bar) than diesel-NG dual fuel combustion at 350 CAD SOI, indicating lower cyclic variations. The higher reactivity of POMDME helped reduce fluctuations in combustion phasing in the retarded SOI. The presence of cycles of deterioration and cycles of recovery were also observed with diesel-NG combustion for 310 CAD SOI, and the scatter in the IMEPg return map was similar for both fuel combinations. The IMEPg return map for POMDME-NG combustion was less scattered at the 350 CAD SOI.
Operating Range and Emissions From Ammonia-Hydrogen Mixtures in Spark-Ignited Engines
Authors: Swift Evan , Kane Seamus , Northrop William F.
Published: November 2022

Ammonia combustion in engines is a promising approach for decarbonization of the energy sector. If made from renewable energy sources, anhydrous “green” ammonia combustion results in zero net carbon dioxide emissions. As a renewable energy storage medium, green ammonia is superior to both compressed hydrogen and batteries for long term energy storage. Combustion of pure ammonia in spark-ignited engines is challenged by low laminar flame speeds and high required ignition energy. Partially converting ammonia to hydrogen and nitrogen through local decomposition is a practical method for enhancing ammonia flame speed and reactivity. This work experientially examines anhydrous ammonia/hydrogen combustion and emissions using a single-cylinder variable compression ratio engine over a range of operating conditions. The study finds that high combustion stability (CoV < 2%) and high efficiency (gITE > 40%) are both possible using only 5% volumetric H2 addition. Experimental results show that rich operation is favorable due to low NOx (< 100ppm) and N2O (∼20 ppm). Roughly 1% unburned NH3 was found in the exhaust, which increased during rich operation. Hydrogen addition decreased NH3 emissions and aided smooth operation while worsening NOx emissions. While ammonia displayed a high knock tolerance like natural gas, heat release analysis indicated that spark-assisted compression ignition combustion was achieved at advanced spark timing and elevated intake temperature. Initial range finding experiments and modeling presented in this work provide a basis for further investigation into the role of rich engine operation and in-cylinder turbulence to enhance ammonia combustion at low hydrogen blending levels.