bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat Transfer in Drop-Laden Turbulent Flows
Authors: Mangani Francesca , Zonta Francesco , Roccon Alessio , Soldati Alfredo 
Published: September 2024

Abstract
We study the heat transfer process in a multiphase turbulent system composed by a swarm of large and deformable drops and a continuous carrier phase. For a shear Reynolds number of Re = 300 and a constant drops volume fraction of Θ = 5.4%, we perform a campaign of direct numerical simulations (DNS) of turbulence coupled with a phase-field method and the energy equation; the Navier-Stokes equations are used to describe the flow field, while the phase-field method and the energy equation are used to describe the dispersed phase topology and the temperature field, respectively. Considering four Prandtl numbers, Pr = 1, 2, 4 and 8 and two Weber numbers, We = 1.5 and 3.0, we investigate the heat transfer process from warm drops to a colder turbulent flow. Using detailed statistics, we first characterize the time evolution of the temperature field in both the dispersed and carrier phase. Then, we develop an analytic model able to accurately reproduce the behaviour of the dispersed and continuous phase temperature. We find that an increase of the Prandtl number, obtained via a decrease of the thermal diffusivity, leads to a slower heat transfer between the dispersed and carrier phase. Finally, we correlate the drop diameters and their average temperatures.
A Computational Analysis of Fluid-Structure Interaction in Metachronal Propulsion
Authors: Lou Zhipeng , Lei Menglong , Byron Margaret L. , Li Chengyu 
Published: September 2024

Abstract
Ctenophores employ flexible rows of appendages called ctenes that form the metachronal beating pattern. A complete cycle of such paddling consists of a power stroke that strokes backward to produce propulsion and a recovery stroke that allows the appendage to recover its initial position. Effective locomotion in these creatures relies on maximizing propulsion during the power stroke while minimizing drag in the recovery stroke. Unlike rigid oars, the ctenes are flexible during both the power stroke and the recovery stroke, and notably, their strokes are asymmetric, with faster movement during the power stroke. As previous research assumed uniform material properties. This assumption will eventually make the ctene deform more intensively in the power stroke than the recovery stroke due to the asymmetrical hydrodynamic forces. However, observations contradict these assumptions. One explanation posits that ctenes stiffen during the power stroke, enhancing their propulsive force, and become more flexible in the recovery stroke, reducing drag by minimizing the water-countering area. This study focusses on the influence of asymmetric stiffness on their propulsion mechanism. Inspired by nature, we conducted three-dimensional fluid-structure interaction (FSI) using an in-house immersed-boundary-method-based flow solver integrated with a nonlinear finite-element solid-mechanics solver. This integrated solver uses a two-way coupling that ensures a higher accuracy regarding the complexity due to the involvement of the multiple ctenes in a ctene row. The preliminary results show that the anisotropic stiffness of the ctene have better accuracy of deformation as compared to the deformation recorded by the high-speed camera. The asymmetric properties of the ctene material allow both the spatial and temporal asymmetry of the ctene beating pattern. Our investigation suggests that while symmetrical beating can only generate negative net thrust, a slightly asymmetrical beating can make the thrust positive. We find that power stroke period that cost 30% whole period can generates the highest thrust. As multiple ctenes involves, the interaction among ctenes can amplified the effects of the asymmetrical beating, so that the thrust generation is enhanced by 9 to 13 times because of it.
Investigation on Design Parameters of a Francis Turbine Runner for Optimization Based on 3-D Inverse Design Method
Authors: Nagata Shunsuke , Tamada Yoichiro , Irie Tatsuya , Miyagawa Kazuyoshi 
Published: September 2024

Abstract
In this paper, an effect of a blade loading and a lean angle at a runner inlet are investigated to understand the internal flow and the loss in the turbine runner. Furthermore, a new Francis turbine runner is designed to improve the turbine performance by the optimization method using the 3D Inverse Design Method and Computational Fluid Dynamics (CFD). According to the investigation of the blade loading and the internal flow, the pressure gradient and the centrifugal forces cause the spanwise secondary flow on the meridional plane of the runner. Also, it is confirmed that designing a runner with the after-loading at every span on the blade is effective in reducing the pressure gradient near the runner inlet, minimizing the spanwise secondary flow, and improving the performance. For the lean angle at the runner inlet, the positive blade lean angle, i.e., the band side forward inclination in the direction of runner rotation, is effective in reducing the pressure gradient on the meridional plane and controlling the secondary flow. The performance of the new runner optimized based on the discussion above has demonstrated the effectiveness of this investigation. These findings and the optimization method will be of great use for designers to develop or improve the turbine performance.
An Experimental Study on the Emission Dynamics in Fused Deposition Modelling (FDM) 3D Printing Process
Authors: Misztal Tad Jerzy , Addasi Omar , Albano Jooi , Liu Yang 
Published: September 2024

Abstract
Fused Deposition Modeling (FDM) 3D printing is a manufacturing process that involves the melting and layering of thermoplastic to create 3D objects. Concerns have arisen from the volatile organic compounds (VOCs) emitted when 3D printing filaments are heated to their melting points, posing environmental and health risks. In the present study, a series of experiments were conducted to characterize the thermal flow phenomena during FDM 3D printing, specifically focused on investigating the VOCs emission dynamics along with the thermal flow during heating and melting in the printing processes. A high-speed Schlieren imaging system and an infrared thermal imaging system were temporally synchronized to both qualitatively and quantitatively characterize the thermal effects and the thermal-induced multiphase flows during the 3D printing process within an FDM 3D printer. In addition, the VOC emissions during the printing process were quantified by using a spatially-distributed-and-temporally-synchronized metal-oxide sensor array system, which can achieve fast spatial tracking of the VOC emissions. By correlating the data from the multiple measurement systems, the VOC emission transport behaviors in the convective gas current were characterized in detail. The findings in this paper offer insights into off-gassing profiles of different filaments, aiding in the development of customized ventilation approaches.
Accessing the Melting Dynamics of Phase Change Material Under Reduced Gravity Conditions
Authors: Singh Shobhana , Kansara Keyur , Dwivedi Navin K. , Khodachenko Maxim L. 
Published: September 2024

Abstract
Phase Change Materials (PCMs) are widely used materials in thermal management applications. The passive working, good thermal stability and inherent thermophysical properties make PCM a natural fit for thermal control devices. However, their performance in real working conditions is often different from the behavior measured at lab scale owing to the effects occurring from varied heat sources, length scale, gravity forces, enthalpy and supercooling effects, etc. In this study, a two-dimensional computational fluid dynamic (CFD) model of a PCM-filled square enclosure with constant temperature bottom heating is developed to investigate the impact of reduced gravity on the melting process of PCMs and assess the dynamic characteristics that evolve with time. The control volume-based enthalpy porosity approach is utilized to simulate the melting process of paraffin-based PCM. Numerical simulations are carried out with reduced gravity environments by varying g to 0.2g. The evolution of flow regimes from conductive to convective through the destabilization of conductive state to the onset of Rayleigh-Benard convection, and chaotic flow is presented in terms of temperature and flow fields. It is found that when the gravity is reduced to 0.2g, the onset of convection delays by ∼ 3 times compared to the time taken by PCM under the standard gravity. In conclusion, the present study has provided valuable insights into the underlying physical phenomena of PCM melting in reduced gravity important in developing design strategies for PCM-based thermal energy storage systems that can operate effectively in reduced gravity environments.
Migration of a Leaky-Dielectric Droplet in the Fringe Electric Fields of Parallel Plate Capacitors
Authors: Melbye Julie , Wang Danling , Wang Yechun 
Published: September 2024

Abstract
This work numerically studies the dynamics of a droplet, uncharged and freely suspended in an immiscible fluid, driven to move by the fringe electric field generated by parallel plate capacitors. Both the droplet and the suspending fluid are considered as leaky dielectrics. The deformation and migration of the droplet through the fringe electric field into or away from the parallel plate capacitors is our focus. A three-dimensional spectral boundary element method for interfacial dynamics in electrical fields is modified and adopted for the current study. The influences of the material properties of the pair of immiscible fluids including the viscosity ratio, surface tension, conductivity, and permittivity on the direction and velocity of the droplet migration will be investigated. The effects of operational and design parameters on droplet motion, including the electrical field strength and the parallel plates’ gap width will be explored as well. In this preliminary study the numerical method will then be applied to investigate the entrapment processes of fine CO2 bubbles in two-dimensional MXene-membranes, a novel membrane technology newly developed for CO2 sensing, capture and reduction. This technology is being developed for an over-arching goal of understanding changes in ocean carbon cycle and controlling CO2 level globally. The efficiency of such a device will be discussed from the view point of fluid dynamics.
Direct Numerical Simulation of Mixing Phenomena in the Upper Plenum of Advanced Reactors
Authors: Nguyen Tri , Merzari Elia , Coppo Leite Victor , Jackson Brian 
Published: September 2024

Abstract
The conceptualization and development of advanced nuclear reactors encompasses challenging fluid-flow concerns that significantly impact their operational safety and efficacy. The establishment of a comprehensive numerical database focused on high-fidelity data holds promising potential in facilitating the formulation of accurate and cost-effective reduced-resolution heat transfer models. These models can be designed based on a multiscale hierarchy developed as part of the recent U.S. Department of Energy-funded Center of Excellence for Thermal Fluids Applications in Nuclear Energy, which represents a significant stride toward resolving industry-specific challenges associated with the heat transfer behavior of advanced reactors. In this paper, we consider Direct Numerical Simulation of the upper plenum with discharging jets of high-temperature gas-cooled reactors. Two isothermal cases at Re = 10622 and 4097 have been considered following the experimental setups of TAMU and MiGaDome facilities. The low Prandtl number fluid (Helium) is considered for all simulations. First and second-order statistics are investigated, and improvements of the agreement with experimental data have been observed compared to previous LES studies. Moreover, the Proper Orthogonal Decomposition (POD) is applied to reveal and illuminate the flow behaviors in the upper plenum. The generated high-fidelity DNS data will be utilized alongside data-driven methods to improve turbulence modeling closures.
Molecular characterization of clinically isolated
Pseudomonas aeruginosa
with varying resistance to ceftazidime-avibactam and ceftolozane-tazobactam collected as a part of the ATLAS global surveillance program from 2020 to 2021
Authors: Li H. , Oliver A. , Shields R. K. , Kamat S. , Stone G. , Estabrook M. 
Published: September 2024

ABSTRACT

Ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (C/T) are important agents for treating multidrug-resistant
P. aeruginosa
infections. In this study, we evaluated the molecular characteristics of 300 globally collected clinical
P. aeruginosa
isolates non-susceptible (NS) to CZA, C/T, or both agents. Isolates were CZA-NS and C/T-NS (
n
= 57), CZA-susceptible (S) and C/T-NS (
n
= 145), or CZA-NS and C/T-S (
n
= 98) selected from the Antimicrobial Testing Leadership and Surveillance (ATLAS) surveillance program from 2020 to 2021. Characterization was by whole-genome sequencing. Analysis was performed to identify β-lactamase genes and mutations that impact efflux regulation, AmpC regulation, and target binding (PBP3). Of the 57 CZA-NS+C/T-NS isolates, 64.9% carried a metallo-β-lactamase (MBL), and a cumulative 84.2% carried any non-intrinsic β-lactamase [i.e., not
Pseudomonas-
derived cephalosporinase (PDC) or OXA-50-like]. Of the 145 CZA-S+C/T-NS isolates, 26.2% carried an extended-spectrum β-lactamase (ESBL) and no carbapenemase, 17.9% carried a serine-carbapenemase, and 42.1% were negative for non-intrinsic β-lactamases. Of 98 CZA-NS+C/T-S isolates, 34.7% carried mutations previously described as causing an upregulation of the MexAB-OprM efflux pump, while only 9.2% carried a non-intrinsic β-lactamase, and no resistance mechanism was identified in 29.6% of these isolates. MBLs were present in most isolates NS to both agents. More than half of the CZA-S+C/T-NS isolates carried serine β-lactamases. The most frequently identified resistance mechanism identified in CZA-NS+C/T-S isolates was a marker indicating the upregulation of MexAB-OprM. No mechanism was identified that is thought to support resistance to these agents in numerous isolates. This may be due in part to the fact that whole genome sequencing (WGS) cannot directly measure gene expression of chromosomal resistance mechanisms.
Evolution toward extremely high imipenem resistance in
Mycobacterium abscessus
outbreak strains
Authors: Le Run Eva , Tettelin Hervé , Holland Steven M. , Zelazny Adrian M. 
Published: September 2024

ABSTRACT

Treatment of
Mycobacterium abscessus
pulmonary disease requires multiple antibiotics including intravenous β-lactams (e.g., imipenem).
M. abscessus
produces a β-lactamase (Bla
Mab
) that inactivates β-lactam drugs but less efficiently carbapenems. Due to intrinsic and acquired resistance in
M. abscessus
and poor clinical outcomes, it is critical to understand the development of antibiotic resistance both within the host and in the setting of outbreaks. We compared serial longitudinally collected
M. abscessus
subsp.
massiliense
isolates from the index case of a cystic fibrosis center outbreak and four outbreak-related strains. We found strikingly high imipenem resistance in the later patient isolates, including the outbreak strain (MIC > 512 µg/mL). The phenomenon was recapitulated upon exposure of intracellular bacteria to imipenem. Addition of the β-lactamase inhibitor avibactam abrogated the resistant phenotype. Imipenem resistance was caused by an increase in β-lactamase activity and increased
bla
Mab
mRNA level. Concurrent increase in transcription of the preceding
ppiA
gene indicated upregulation of the entire operon in the resistant strains. Deletion of the porin
mspA
coincided with the first increase in MIC (from 8 to 32 µg/mL). A frameshift mutation in
msp2
responsible for the rough colony morphology and a SNP in ATP-dependent helicase
hrpA
cooccurred with the second increase in MIC (from 32 to 256 µg/mL). Increased Bla
Mab
expression and enzymatic activity may have been due to altered regulation of the
ppiA-bla
Mab
operon by the mutated HrpA alone or in combination with other genes described above. This work supports using carbapenem/β-lactamase inhibitor combinations for treating
M. abscessus
, particularly imipenem-resistant strains.
Engineering probiotic
Escherichia coli
Nissle 1917 to block transfer of multiple antibiotic resistance genes by exploiting a type I CRISPR-Cas system
Authors: Fang Mengdie , Zhang Ruiting , Wang Chenyu , Liu Zhizhi , Fei Mingyue , Tang Biao , Yang Hua , Sun Dongchang 
Published: September 2024

ABSTRACT

Many multidrug-resistant (MDR) bacteria have evolved through the accumulation of antibiotic resistance genes (ARGs). Although the potential risk of probiotics as reservoirs of ARGs has been recognized, strategies for blocking the transfer of ARGs while using probiotics have rarely been explored. The probiotic
Escherichia coli
Nissle 1917 (EcN) has long been used for treating intestinal diseases. Here, we demonstrate frequent transfer of ARGs into EcN both
in vitro
and
in vivo
, raising concerns about its potential risk of accumulating antibiotic resistance. Given that no CRISPR-Cas system was found in natural EcN, we integrated the type I-E CRISPR-Cas3 system derived from
E. coli
BW25113 into EcN. The engineered EcN was able to efficiently cleave multiple ARGs [i.e.,
mcr-1
,
bla
NDM-1
, and
tet
(X)] encoding enzymes for degrading last-resort antibiotics. Through co-incubation of EcN expressing Cas3-Cascade and that expressing Cas9, we showed that the growth of the former strain outcompeted the latter strain, demonstrating a better clinical application prospect of EcN expressing the type I-E CRISPR-Cas3 system. In the intestine of a model animal (i.e., zebrafish), the engineered EcN exhibited immunity against the transfer of CRISPR-targeted ARGs. Our work equips EcN with immunity against the transfer of multiple ARGs by exploiting the exogenous type I-E CRISPR-Cas3 system, thereby reducing the risk of the spread of ARGs while using it as a probiotic chassis for generating living therapeutics.

IMPORTANCE

To reduce the development of antibiotic resistance, probiotics have been considered as a substitute for antibiotics. However, probiotics themselves are reservoirs of antibiotic resistance genes (ARGs). This study introduces a new strategy for limiting the spread of ARGs by engineering the typical probiotic strain
Escherichia coli
Nissle 1917 (EcN), which has been used for treating intestinal diseases and developed as living therapeutics. We also demonstrate that the type I CRISPR-Cas system imposes a lower growth burden than the type II CRISPR-Cas system, highlighting its promising clinical application potential. Our work not only provides a new strategy for restricting the transfer of ARGs while using probiotics but also enriches the genetic engineering toolbox of EcN, paving the way for the safe use and development of probiotics as living therapeutics.
Phage-based biocontrol of
Porphyromonas gingivalis
through indirect targeting
Authors: Wu Chuncheng , Fujiki Jumpei , Mathieu Jacques , Schwarz Cory , Cornell Carolyn , Alvarez Pedro J. J. 
Published: September 2024

ABSTRACT

Bacteriophages offer an opportunity for chemical-free, precise control of problematic bacteria, but this approach can be limited when lytic phages are difficult to obtain for the target host. In such cases, phage-based targeting of cooperating or cross-feeding bacteria (e.g.,
Streptococcus gordonii
) can be an effective approach to control the problematic bacteria (e.g.,
Porphyromonas gingivalis
). Using a dual-species biofilm system, phage predation of
S. gordonii
(10
8
PFU·mL
−1
) decreased the abundance of pathogenic
P. gingivalis
by >99% compared with no-treatment controls, while also inhibiting the production of cytotoxic metabolic end products (butyric and propionic acids). Phage treatment upregulated genes associated with interspecies co-adhesion (5- to 8-fold) and quorum sensing (10-fold) in residual
P. gingivalis
, which is conducive to increased potential to bind to
S. gordonii
. Counterintuitively, lower-titer phage applications (10
4
PFU·mL
−1
) increased the production of extracellular polymeric substance (EPS) by 22% and biofilm biomass by 50%. This overproduction of EPS may contribute to the phenomenon where the biofilm separated into two distinct species layers, as observed by confocal laser scanning microscopy. Although more complex mixed-culture systems should be considered to delineate the merits and limitations of this novel biocontrol approach (which would likely require the use of phage cocktails), our results offer proof of concept that indirect phage-based targeting can expand the applicability of phage-based control of pathogenic bacteria for public health protection.

IMPORTANCE

Lytic phages are valuable agents for targeted elimination of bacteria in diverse applications. Nevertheless, lytic phages are difficult to isolate for some target pathogens. We offer proof of concept that this limitation may be overcome via indirect phage targeting, which involves knocking out species that interact closely with and benefit the primary problematic target bacteria. Our target (
P. gingivalis
) only forms a periodontal pathogenic biofilm if the pioneer colonizer (
S. gordonii
) offers its surface for
P. gingivalis
to attach. Phage predation of the co-adhesive
S. gordonii
significantly reduced abundance of the target pathogen by >99%, decreased the total biofilm biomass by >44%, and suppressed its production of cytotoxic metabolic byproducts. Thus, this research extends the scope of phage-based biocontrol for public health protection.