bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling of Metal Matrix Concentrated Solar Receivers for Supercritical Carbon Dioxide Power Blocks
Authors: Duggirala Vyas , Hegde Venkatanarasimha , Kumar Pramod , Reddy Venkateswara 
Published: August 2024

Abstract
Supercritical carbon dioxide (sCO2) power blocks for concentrating solar power (CSP) with novel metal matrix solar receivers have the potential to reduce operating expenses while improving overall system efficiencies. These concentrated solar receivers integrated with a metal matrix-based phase change material (PCM) thermal storage medium provide the compounding effect of an efficient heat exchanger while also integrating thermal storage within the receiver. Detailed numerical modeling of such devices with enthalpy–porosity-based formulation for phase change and turbulent convective heat transfer for the sCO2 microchannels is described in the current work. With sCO2 power blocks operating at temperatures and pressures beyond 800 °C and 200 bar, different high-temperature PCMs are studied. Steady-state charging and discharging cycles in addition to transient charging are simulated to analyze the thermal performance of the device. Energy storage density of the PCM is evaluated by tracking the movement of the melt-pool interface along the streamwise direction in a highly corrugated wavy microchannel. A detailed scaling analysis carried out to estimate the order of magnitude of the heat transfer coefficients is found to agree well with the numerical predictions. The outcomes from the current work can be utilized for sizing and detailed design of integrated solar receivers for high temperature sCO2 power block applications.
Experimental Study of the Dynamics of Lean Premixed Hydrogen Flames in a Multi Jet Combustor
Authors: Beuth Jan Paul , Reumschüssel Johann Moritz , von Saldern Jakob G. R. , Ćosić Bernhard , Paschereit Christian Oliver , Oberleithner Kilian 
Published: August 2024

Abstract
In this study, the flame dynamics of lean premixed hydrogen jet flames are experimentally investigated. Acoustic and optical measurement devices are used to capture the response of a bundle of jet flames to acoustic forcing. Using helium as a fuel surrogate, we simulate the change in acoustic properties in the burner during the determination of cold burner transfer matrix (BTM) measurements in order to avoid dangerous experiments. We investigate the influence of the equivalence ratio and the addition of methane as well as the interaction of the individual flames to evaluate the scalability of the results to systems with more flames. It is shown that the changes in the dynamic flame response can primarily be explained by the flame length, which changes both with the methane share and with the equivalence ratio. It can be observed that with small changes in the equivalence ratio, the flame length and the flame transfer function (FTF) change in the same way as with a small change in the gas composition. To assess the scalability of these results, we deactivate some of the jet flames and analyze how the overall response to acoustic forcing changes. We find that the FTF phase is not affected by the number of active flames. Analyzing the respective gain values, significantly stronger responses are measured for a few flames, but only small difference can be measured above a certain number of neighboring flames so that the lab scale results can also be expected to be valid for industrial configurations with a high number of flames.
Centrifugal Compressor Surge in Closed-Loop Systems: Initial Modeling and Comparison With Experiments
Authors: Purushothaman Sreenath , Niccolini Marmont Du Haut Champ Carlo Alberto , Reggio Federico , Silvestri Paolo , Traverso Alberto , Halbe Chaitanya 
Published: August 2024

Abstract
Heat pumps are expected to play a primary role in electrification of thermal users in the residential and industrial sectors. Dynamic compressors are widely used in large size heat pumps, thanks to their industrial replicability, compact size, affordable costs, and good performance in terms of efficiency and low acoustic emissions. The instability, which may occur in a compressor installed in closed-loop cycle such as in a heat pump, is quite different from the classic open loop configuration involving dynamic compressors. This is mainly due to the complexity of the compressor instability mechanism coupled to a vapor compression system connected with two-phase heat exchangers, having different thermal and fluid dynamic capacitance properties, under a physical feedback loop. The aim of this paper is to investigate the behavior of a dynamic compressor installed in an innovative heat pump prototype, of laboratory scale, under stable and unstable conditions. A preliminary simple dynamic model of the compression system consisting of a radial compressor, condenser, and evaporator is developed to represent the heat pump compression system, aiming at its time-dependent representation during compressor instable behavior. The evaporator and condenser are modeled using empirical correlations representing the heat exchange and phase change phenomena and including the thermal capacitances due to refrigerant mass and heat exchanger pipes. The preliminary validation of the dynamic model results is done through a dedicated experimental campaign, under different operating conditions. Results show the complexity of the interaction between the centrifugal compressor and the heat pump loop, discerning the different contributions to the time-dependent response of the system. Future steps will encompass a more detailed modeling of the heat pump loop and the use of updated field measurements, including liquid-level meters in the heat exchangers.
Raffinocyclicin is a novel plasmid-encoded circular bacteriocin produced by
Lactococcus raffinolactis
with broad-spectrum activity against many gram-positive food pathogens
Authors: Miceli de Farias Felipe , O'Connor Paula M. , Buttimer Colin , Kamilari Eleni , Soria Maria Cecilia , Johnson Crystal Nicole , Deliephan Aiswariya , Hill Daragh , Fursenko Oxana , Wiese Jonathan , Draper Lorraine A. , Stanton Catherine , Hill Colin , Ross R. Paul 
Published: August 2024

ABSTRACT

This study describes the discovery and characterization of raffinocyclicin, a novel plasmid-encoded circular bacteriocin, produced by the raw milk isolate
Lactococcus raffinolactis
APC 3967. This bacteriocin has a molecular mass of 6,092 Da and contains 61 amino acids with a three-amino acid leader peptide. It shows the highest identity to the circular bacteriocins bacicyclicin XIN-1 (42.62%), aureocyclicin 4185 (42.62%), and garvicin ML (41.53%). A broad inhibitory spectrum includes strains from
Staphylococcus
,
Enterococcus
,
Streptococcus
,
Micrococcus
,
Lactobacillus
,
Leuconostoc,
and
Listeria
, in addition to a pronounced inhibitory effect against
Lactococcus
and
Clostridium
. It displays low sensitivity to trypsin, most likely as a result of its circular nature. The raffinocyclicin gene cluster is composed of 10 genes: 6 core genes, genes encoding an accessory three-component ABC transporter (
rafCDE
), and a putative transcriptional regulator related to the MutR family. A lack of inhibitory activity in the cell-free supernatant combined with the pronounced activity of cell extracts suggests that the majority of raffinocyclicin is associated with the cell rather than being released to the extracellular environment. This is the first report of a bacteriocin produced by the
L. raffinolactis
species.

IMPORTANCE

The present study aimed to characterize raffinocyclicin, a novel circular bacteriocin produced by the lactic acid bacteria
Lactococcus raffinolactis
APC 3967. Bacteriocins are generally cationic and hydrophobic peptides with antimicrobial activity, which present diverse biotechnological properties of interest for the food industry. Raffinocyclicin inhibits a wide range of bacteria, including foodborne pathogens, and is stable against different treatments which suggest its potential as a natural biopreservative. Whole-genome sequencing and the genetic analysis of the raffinocyclicin gene cluster showed that it is encoded by plasmid that could be used in the future to transfer the ability to produce the bacteriocin to other lactic acid bacteria for industrial applications. These results together highlight the potential of this novel antimicrobial as a biopreservative to be used by the food industry.
Serosurveillance of
Coxiella burnetii
in feral swine populations of Hawaiʻi and Texas identifies overlap with human Q fever incidence
Authors: McMillan Ian A. , Norris Michael H. , Golon Samuel J. , Franckowiak Gregory A. , Grinolds James M. , Goldstein Samuel M. , Phelps Darrin M. , Bodenchuk Michael J. , Leland Bruce R. , Bowen Richard A. , Brown Vienna R. , Borlee Bradley R. 
Published: August 2024

ABSTRACT

Feral swine are invasive in the United States and a reservoir for infectious diseases. The increase in feral swine population and the geographic range are a concern for the spread of zoonotic diseases to humans and livestock. Feral swine could contribute to the spread of
Coxiella burnetii,
the causative agent of human Q fever. In this study, we characterized the seroprevalence of
C. burnetii
in feral swine populations of Hawaiʻi and Texas, which have low and high rates of human Q fever, respectively. Seropositivity rates were as high as 0.19% and 6.03% in Hawaiʻi and Texas, respectively, indicating that feral swine cannot be ruled out as a potential reservoir for disease transmission and spread. In Texas, we identified the overlap between seropositivity of feral swine and human Q fever incidence. These results indicate that there is a potentially low but detectable risk of
C. burnetii
exposure associated with feral swine populations in Hawaiʻi and Texas.
Advanced biology students’ individual conceptions of scientific researchers after participating in biomedically relevant CRE
Authors: Waring-Sparks Ashley L. , Waring-Sparks Rachel A. , Darner Rebekka , Mortimer Nathan T. 
Published: August 2024

ABSTRACT

While undergraduate research has been shown to be a high-impact educational practice, it is logistically impossible for all undergraduate biology majors to have long-term faculty-mentored research experience. Therefore, biology educators and researchers must devise opportunities to engage more students in undergraduate research outside of working directly in their labs. Course-Based Research Experiences (CREs), structured as authentic research experiences, are one such opportunity. In this work, we describe the effects of a CRE with biomedical relevance on students’ research skills, attitudes toward science, and perceptions of scientific research and scientific researchers. Results demonstrate that students gained experience in independent research skills including designing their own research project, being accountable for part of a project, and writing a research proposal. Students’ perceptions of scientific research and researchers, assessed by the Draw-A-Researcher Task, did not show changes among the whole group, but individual analysis yielded meaningful results related to students’ personal changes in how they perceived research and researchers, including their perception of themselves as researchers. This work demonstrates the substantial impact of CREs on upper-level biology undergraduate and graduate students.
Algal exudates promote conjugation in marine Roseobacters
Authors: Duchin Rapp Yemima , Lipsman Valeria , Yuda Lilach , Kublanov Ilya V. , Matsliyah Dor , Segev Einat 
Published: August 2024

ABSTRACT

Horizontal gene transfer (HGT) is a pivotal mechanism driving bacterial evolution, conferring adaptability within dynamic marine ecosystems. Among HGT mechanisms, conjugation mediated by type IV secretion systems (T4SSs) plays a central role in the ecological success of marine bacteria. However, the conditions promoting conjugation events in the marine environment are not well-understood. Roseobacters, abundant marine bacteria commonly associated with algae, possess a multitude of T4SSs. Many Roseobacters are heterotrophic bacteria that rely on algal secreted compounds to support their growth. These compounds attract bacteria, facilitating colonization and attachment to algal cells. Algae and their metabolites bring bacteria into close proximity, potentially promoting bacterial HGT. Investigation across various Roseobacters revealed that algal exudates indeed enhance plasmid transfer through conjugation. While algal exudates do not influence the transcription of bacterial conjugative machinery genes, they promote bacterial attachment, potentially stabilizing proximity and facilitating HGT. Notably, under conditions where attachment is less advantageous, the impact of algal exudates on conjugation is reduced. These findings suggest that algae enhance bacterial conjugation primarily by fostering attachment and highlight the importance of studying bacterial HGT within the context of algal–bacterial interactions.

IMPORTANCE
This study explores how algal–bacterial interactions influence horizontal gene transfer (HGT) among marine bacteria. HGT, a key driver of bacterial evolution, is facilitated by conjugation mediated by type IV secretion systems (T4SSs). Through investigating Roseobacters, abundant marine bacteria often found to be associated with algae, the study reveals that algal exudates enhance plasmid transfer via conjugation. This enhancement is attributed to the promotion of bacterial attachment by algal compounds, emphasizing the role of algal–bacterial interactions in shaping genetic exchange within dynamic marine ecosystems. Understanding these mechanisms is crucial for elucidating bacterial adaptability and evolution in the marine environment.
Physiological role and complex regulation of O
2
-reducing enzymes in the obligate anaerobe
Clostridioides difficile
Authors: Caulat Léo C. , Lotoux Aurélie , Martins Maria C. , Kint Nicolas , Anjou Cyril , Teixeira Miguel , Folgosa Filipe , Morvan Claire , Martin-Verstraete Isabelle 
Published: August 2024

ABSTRACT

Clostridioides difficile
, the major cause of antibiotic-associated diarrhea, is a strict anaerobic, sporulating Firmicutes. However, during its infectious cycle, this anaerobe is exposed to low oxygen (O
2
) tensions, with a longitudinal decreasing gradient along the gastrointestinal tract and a second lateral gradient with higher O
2
tensions in the vicinity of the cells. A plethora of enzymes involved in oxidative stress detoxication has been identified in
C. difficile
, including four O
2
-reducing enzymes: two flavodiiron proteins (FdpA and FdpF) and two reverse rubrerythrins (revRbr1 and revRbr2). Here, we investigated the role of the four O
2
-reducing enzymes in the tolerance to increasing physiological O
2
tensions and air. The four enzymes have different, yet overlapping, spectra of activity. revRbr2 is specific to low O
2
tensions (<0.4%), FdpA to low and intermediate O
2
tensions (0.4%–1%), revRbr1 has a wider spectrum of activity (0.1%–4%), and finally FdpF is more specific to tensions > 4% and air. These different O
2
ranges of action partly arise from differences in regulation of expression of the genes encoding those enzymes. Indeed, we showed that
revrbr2
is under the dual control of σ
A
and σ
B
. We also identified a regulator of the Spx family that plays a role in the induction of
fdp
and
revrbr
genes upon O
2
exposure. Finally,
fdpF
is regulated by Rex, a regulator sensing the NADH/NAD
+
ratio. Our results demonstrate that the multiplicity of O
2
-reducing enzymes of
C. difficile
is associated with different roles depending on the environmental conditions, stemming from a complex multi-leveled network of regulation.

IMPORTANCE

The gastrointestinal tract is a hypoxic environment, with the existence of two gradients of O
2
along the gut, one longitudinal anteroposterior decreasing gradient and one proximodistal increasing from the lumen to the epithelial cells. O
2
is a major source of stress for an obligate anaerobe such as the enteropathogen
C. difficile
. This bacterium possesses a plethora of enzymes capable of scavenging O
2
and reducing it to H
2
O. In this work, we identified the role of the four O
2
-reducing enzymes in the tolerance to the physiological O
2
tensions faced by
C. difficile
during its infectious cycle. These four enzymes have different spectra of action and protect the vegetative cells over a large range of O
2
tensions. These differences are associated with a distinct regulation of each gene encoding those enzymes. The complex network of regulation is crucial for
C. difficile
to adapt to the various O
2
tensions encountered during infection.
ResMAP—a saturation mutagenesis platform enabling parallel profiling of target-specific resistance-conferring mutations in
Plasmodium
Authors: Wall Richard J. , MacGowan Stuart A. , Hallyburton Irene , Syed Aisha J. , Ajay Castro Sowmya , Dey Gourav , Milne Rachel , Patterson Stephen , Phelan Jody , Wiedemar Natalie , Wyllie Susan 
Published: August 2024

ABSTRACT

New and improved drugs are required for the treatment and ultimate eradication of malaria. The efficacy of front-line therapies is now threatened by emerging drug resistance; thus, new tools to support the development of drugs with a lower propensity for resistance are needed. Here, we describe the development of a RESistance Mapping And Profiling (ResMAP) platform for the identification of resistance-conferring mutations in
Plasmodium
drug targets. Proof-of-concept studies focused on interrogating the antimalarial drug target,
Plasmodium falciparum
lysyl tRNA synthetase (
Pf
KRS). Saturation mutagenesis was used to construct a plasmid library encoding all conceivable mutations within a 20-residue span at the base of the
Pf
KRS ATP-binding pocket. The superior transfection efficiency of
Plasmodium knowlesi
was exploited to generate a high coverage parasite library expressing
Pf
KRS bearing all possible amino acid changes within this region of the enzyme. The selection of the library with
Pf
KRS inhibitors, cladosporin and DDD01510706, successfully identified multiple resistance-conferring substitutions. Genetic validation of a subset of these mutations confirmed their direct role in resistance, with computational modeling used to dissect the structural basis of resistance. The application of ResMAP to inform the development of resistance-resilient antimalarials of the future is discussed.

IMPORTANCE

An increase in treatment failures for malaria highlights an urgent need for new tools to understand and minimize the spread of drug resistance. We describe the development of a RESistance Mapping And Profiling (ResMAP) platform for the identification of resistance-conferring mutations in
Plasmodium
spp, the causative agent of malaria. Saturation mutagenesis was used to generate a mutation library containing all conceivable mutations for a region of the antimalarial-binding site of a promising drug target,
Plasmodium falciparum
lysyl tRNA synthetase (
Pf
KRS). Screening of this high-coverage library with characterized
Pf
KRS inhibitors revealed multiple resistance-conferring substitutions including several clinically relevant mutations. Genetic validation of these mutations confirmed resistance of up to 100-fold and computational modeling dissected their role in drug resistance. We discuss potential applications of this data including the potential to design compounds that can bypass the most serious resistance mutations and future resistance surveillance.
A group B streptococcal type VII-secreted LXG toxin mediates interbacterial competition and colonization of the murine female genital tract
Authors: Job Alyx M. , Doran Kelly S. , Spencer Brady L. 
Published: August 2024

ABSTRACT

Group B
Streptococcus
(GBS) asymptomatically colonizes the vagina but can opportunistically ascend to the uterus and be transmitted vertically during pregnancy, resulting in neonatal pneumonia, bacteremia, and meningitis. GBS is a leading etiologic agent of neonatal infection and understanding the mechanisms by which GBS persists within the polymicrobial female genital mucosa has the potential to mitigate subsequent transmission and disease. Type VIIb secretion systems (T7SSb) are encoded by Bacillota and often mediate interbacterial competition using LXG toxins that contain conserved N-termini important for secretion and variable C-terminal toxin domains that confer diverse biochemical activities. Our recent work characterized a role for the GBS T7SSb in vaginal colonization and ascending infection but the mechanisms by which the T7SSb promotes GBS persistence in this polymicrobial niche remain unknown. Herein, we investigate the GBS T7SS in interbacterial competition and GBS niche establishment in the female genital tract. We demonstrate GBS T7SS-dependent inhibition of mucosal pathobiont
Enterococcus faecalis
both
in vitro
using predator-prey assays and
in vivo
in the murine genital tract and found that a GBS LXG protein encoded within the T7SS locus (herein named group
B
streptococcal
L
XG
T
oxin
A
) contributes to these phenotypes. We identify BltA as a T7SS substrate that is toxic to
E. coli
and
S. aureus
upon induction of intracellular expression along with associated chaperones. Finally, we show that BltA and its chaperones contribute to GBS vaginal colonization. Altogether, these data reveal a role for a novel T7b-secreted toxin in GBS mucosal persistence and competition.

IMPORTANCE

Competition between neighboring, non-kin bacteria is essential for microbial niche establishment in mucosal environments. Gram-positive bacteria encoding T7SSb have been shown to engage in competition through the export of LXG-motif-containing toxins, but these have not been characterized in group B
Streptococcus
(GBS), an opportunistic colonizer of the polymicrobial female genital tract. Here, we show a role for GBS T7SS in competition with mucosal pathobiont
Enterococcus faecalis
, both
in vitro
and
in vivo
. We further find that a GBS LXG protein contributing to this antagonism is exported by the T7SS and is intracellularly toxic to other bacteria; therefore, we have named this protein group
B
streptococcal
L
XG
T
oxin
A
(BltA). Finally, we show that BltA and its associated chaperones promote persistence within female genital tract tissues,
in vivo
. These data reveal previously unrecognized mechanisms by which GBS may compete with other mucosal opportunistic pathogens to persist within the female genital tract.
Draft genome of an anaerobic nitrate-reducing, benzene-degrading member of the order
Thermincolales
Authors: Xiao Johnny Z. , Nesbø Camilla L. , Molenda Olivia , Toth Courtney R. A. , Edwards Elizabeth A. 
Published: August 2024

ABSTRACT

We present a metagenome assembled genome (MAG) of an anaerobic bacterium from a nitrate-reducing, benzene-degrading enrichment culture (NRBC). The draft
Thermincolales
genome consists of 20 contigs with a total length of 4.09 Mbp and includes putative carboxylase genes likely involved in benzene activation.
Genomic sequences and annotations of two
Pseudomonas
species isolated from marine and terrestrial habitats
Authors: Manirakiza Eric , Chaumier Timothée , Tirichine Leïla 
Published: August 2024

ABSTRACT

Here, we present the complete genome sequences and annotations of two species of the
Pseudomonas
genus isolated from marine and terrestrial environments. Both genomes and their annotations are available on BacBrowse (
https://BacBrowse.univ-nantes.fr
). This study will contribute to a better understanding of the diversity present within the
Pseudomonas
genus.