bluuebunny/crossref_metadata_2025 huggingface dataset:
Reducing Warpage in Additive Manufacturing With Novel Toolpath Design
Authors: Godderidge Todd , Tekinalp Halil , Ozcan Soydan , Garg Nikhil , Kim Seokpum
Published: August 2024

Warpage in Additive Manufacturing (AM) is one of the major unsolved problems, especially with Fused Filament Fabrication (FFF). As layers cool, internal stresses cause non-uniform shrinkage, resulting in undesirable shapes and therefore limited applicability in precision industrial manufacturing. Existing solutions include methods to increase bed adhesion such as brims, rafts, and methods to control the environment such as uniformly heated enclosures, and materials with less shrinkage such as carbon fiber-reinforce polymers to improve stability and resistance to warpage. Recent approaches utilizing pre-deformation involve modifying the initial part geometry to compensate for the warpage rather than preventing it, such that the shrinkage process itself transforms the part into the desired final shape. However, designing such inverse geometries is often imprecise because shrinkage does not occur the same way reversely and it depends strongly on the part shape. Therefore, all of these approaches have pros and cons. In this technical paper, we propose a novel concept to reduce the warpage, demonstrate through FFF printing, and verify the concept by measuring the warpage amount. We provide this novel approach as an additional option as a solution for the users to choose when it comes to a warpage issue.

The novel approach we present in this paper, currently filed as a patent application, involves adding extra material into each bead using customizable out-of-plane deposition toolpaths. This method preserves the original part dimensions, allows for compensation in unavoidable shrinkage during solidification, and keeps the total bounding volume constant. We present 3D printing experiments with large shrinkage polymers, Polypropylene and Nylon-11, verifying the applicability of the method with FFF test parts, and demonstrate a warpage reduction by over 40% compared with conventional printing approaches. We intend to extend our method by including various materials, applying them to a larger scale AM and a large range of user-defined input geometries.
Site-Specific Property Informed Interface Design of Multi-Material Laser Powder Bed Fusion
Authors: Griffis Jacklyn , Masker Andrew , Schreiber Jeremy , Manogharan Guha
Published: August 2024

Laser powder bed fusion (LPBF) is a widely used metal additive manufacturing (AM) method, capable of complex geometry fabrication with high resolution and surface quality. Recent advances have introduced multi-material powder bed AM, which allows for selective powder deposition across multiple layers or within a single layer to truly achieve 3D voxel gradation As this process may combine two dissimilar metals with varying thermal properties along with effects of AM-induced defects, such as as-built cracking, delamination, or residual stresses, are common. Preliminary work has demonstrated that thermomechanical induced cracking at the fusion boundary, leads to premature failure which propagates along the defects at or near the fusion plane. The novelty in this study lies in combining nanoindentation-informed finite element analysis (FEA) to evaluate the use of mechanical interlocking improve mechanical performance in the face of defective interfacial adhesion.

To assess the local mechanical properties across multi-material fusion boundary, nanoindentation is applied to determine the gradient of material hardness. Oliver and Pharr’s analytical method to determine Young’s modulus from nanoindentation is then used to inform FEA. The fusion boundary was modeled as an effective third material partition to generate a digital twin of the fusion boundary. By designing interlocking patterns, we aimed to alternate tensile and compressive stress across the metamaterial structure for an overall reduction in the stress concentration at the site of as-built cracks to reduce the defect’s likelihood of propagating to the state of premature failure. Three mechanically interlocked designs are evaluated to demonstrate the capacity to locally load regions of the fusion boundary in compression despite global tensile loading.
Integrated Data Processing and Model Selection in Machine Learning Framework Development to Predict Dimensional Errors in Wire Arc Additive Manufacturing (WAAM)
Authors: Valizadeh Sotubadi Saleh , Hendrickson Nicholas , Nguyen Vinh
Published: August 2024

In-situ monitoring of Wire Arc Additive Manufacturing (WAAM) is crucial to provide real-time insights into the process for corrective feedback. Machine Learning (ML) approaches have proven to provide reasonable correlations between the input data and the process outputs in WAAM. However, there is a lack of knowledge with the development of an integrated ML development framework to address the simultaneous consideration of data processing and ML model development. This study aims to provide a search method to select ML frameworks with the combination of data processing and ML models with holistic performance metrics. Acoustic, welding current, welding fume, and the plate temperature datasets were collected during each printing operation. Subsequently, the collected datasets were preprocessed and used for feature extraction of the input data based on the intrinsic physical behavior of each time series dataset. The processed and extracted features were used to train six ML regression models to predict the corresponding measured height of the WAAM-printed workpieces. Mean Square Error (MSE), Mean Absolute Percentage Error (MAPE), and R-Squared metrics were then used to compare the performance of each of the regression models. Therefore, this study efficiently searches among different integrated ML frameworks to result in the combination of the data processing method and ML model with the best performance for the prediction of height in WAAM.
Toward Rapid Process Qualification of Laser Powder Bed Fusion: Model Predictive Control of Part Thermal History
Authors: Riensche Alexander , Bevans Benjamin , Sions John , Snyder Kyle , Plotnikov Yuri , Hass Derek , Rao Prahalada
Published: August 2024

This work pertains to the laser powder bed fusion (LPBF) additive manufacturing process. The goal of this work is to mitigate the expense and time required for qualification of laser powder bed fusion processed parts. In pursuit of this goal, the objective of this work is to develop and apply a physics-based model predictive control strategy to modulate the thermal history before the part is built. The key idea is to determine a desired thermal history for a given part a priori to printing using a physics-based model. Subsequently, a model predictive control strategy is developed to attain the desired thermal history by changing the laser power layer-by-layer. This is an important area of research because the spatiotemporal distribution of temperature within the part (also known as the thermal history) influences flaw formation, microstructure evolution, and surface/geometric integrity, all of which ultimately determine the mechanical properties of the part. Currently, laser powder bed fusion parts are qualified using a build-and-test approach wherein parameters are optimized by printing simple test coupons, followed by examining their properties via materials characterization and testing — a cumbersome and expensive process that often takes years. These parameters, once optimized, are maintained constant throughout the process for a part. However, thermal history is a function of over 50 processing parameters including material properties and part design, consequently, the current approach of parameter optimization based on empirical testing of simple test coupons seldom transfers successfully to complex, practical parts. Rather than instinctive process parameter optimization, the model predictive control strategy presents a radically different approach to LPBF part qualification that is based on understanding and modulating the causal thermal physics of the process. The approach has three steps: (Step 1) Predict – given a part geometry, use a rapid, mesh-less physics-based simulation model to predict its thermal history, analyze the predicted thermal history trend, isolate potential red flag problems such as heat buildup, and set a desired thermal history that corrects deleterious trends. (Step 2) Parse – iteratively simulate the thermal history as a function of various laser power levels layer-by-layer over a fixed time horizon. (Step 3) Select – the laser power that provides the closest match to the desired thermal history. Repeat Steps 2 and 3 until the part is completely built. We demonstrate through experiments with various geometries two advantages of this model predictive control strategy when applied to laser powder bed fusion: (i) prevent part failures due to overheating and distortion, while mitigating the need for anchoring supports; and (ii) improve surface integrity of hard to access internal surfaces.
Brief Paper: Adaptive Layer Height Control for WAAM Oscillatory Toolpaths Enabled by In-Situ 3D Scanning
Authors: Molla Bemnet , Kosmal Tadek , Williams Christopher
Published: August 2024

Wire Arc Additive Manufacturing (WAAM) is a relatively low-cost, high throughput additive manufacturing technology that uses arc welding to deposit metal beads in a layer-wise fashion to produce large-scale, complex parts. Oscillatory deposition strategies in WAAM are known for increasing deposition rate, obtaining more uniform layer surfaces, and their ability to reduce thermal cycling. In addition, small changes to the oscillatory path planning can result in a wide variety of bead shapes, which can be used to enable adaptive layer height throughout the build. The ability to build part regions at different layer heights could further mitigate process constraints (e.g. thermal input) during fabrication, compensate for build defects to enable manufacture of unique geometries, and ultimately increase throughput. However, to enable adaptive build height in WAAM, both predictive bead geometry models and in-situ control must be used to manage the interface between varying deposition regions and obtain consistent geometries.

This study compares a bead geometry prediction model to enable adaptive layer height via oscillatory toolpathing with an in-situ 3D scanning strategy. The bead geometry prediction model incorporates multiple processing parameters, including arc voltage, arc current, mass flow rate, travel speed, along with intrinsic material properties. This model, in concert with oscillatory path frequency and amplitude, can be used to predict bead geometry (width and height). During manufacturing, in-situ top-down 3D scans are collected at every layer to gather depth information of as-built geometries. This depth information is used to evaluate the efficacy of the oscillatory deposition with respect to each deposition type/region. This comparison is demonstrated with the manufacture of large-scale, functional metal parts.
A Novel Synthesized Thermography (SynTG) Approach for In-Situ Defect Detection During Laser Powder Bed Fusion
Authors: Fu Xianzhe , Son Kwangtae , Fan Zhaoyan
Published: August 2024

Laser Powder Bed Fusion (L-PBF) is one of the most widely applied additive manufacturing processes to fabricate metallic parts with high geometric accuracy. Due to the highly concentrated heating power and fast scanning speed used in the L-PBF process, voids could be produced during printing for multiple reasons. The new method measures the cooling rate at a specific temperature and melt pool temperature of each location on the powder bed and then synthesizes the results into images representing the defect-induced thermal property variation on each printed layer. Analytical models have been built based on a simplified L-PBF process scenario to theoretically prove the relationship between the thermal signatures and the voids-induced conductivity reduction. The relationship is then validated in experiments on a commercial L-PBF platform with a high-speed IR sensor. Ex-situ X-ray CT scanning was employed to validate the detection results of SynTG. The comparison results show a good match between the SynTG methods and the X-ray CT results. The conclusive findings demonstrate the potential of the SynTG method in defect detection, thereby enhancing the quality of the printed parts.
Viscosity Inference of Hybrid Bioink Using Decision Tree-Based Machine Learning Method
Authors: Limon Shah , Sarah Rokeya , Habib Md Ahasan
Published: August 2024

Among various 3D bioprinting methods, the extrusion-based approach stands out for its ability to achieve high cell release rates and construct intricate scaffold structures. However, the use of synthetic semi-solid polymers or natural hydrogels with shear-thinning properties requires ongoing research into rheological properties, especially hydrogel viscosity. Researchers are exploring hybrid hydrogels, a combination of various materials, to ensure scaffold shape fidelity and cell viability. Current practices involve extensive experimentation to achieve the required viscosity for smooth hydrogel release through the nozzle, a process often resource-intensive and time-consuming. Addressing this challenge, computational methods, particularly machine learning, are gaining attention for fine-tuning process parameters and optimizing bio-ink components. This study adopts a decision tree-based machine learning method, demonstrating its efficacy in predicting bioink viscosity for 300 combinations of shear rates and Alginate, Carboxymethyl Cellulose (CMC), and Tempo Mediated Nano-fibrillated Cellulose (TO-NFC) material compositions. The inference model has been trained using 75% of the initial data and tested the model for the rest of the unused 25% of data. The model exhibits excellent accuracy, highlighting its potential to significantly reduce trial-and-error experiments. This approach offers a streamlined and efficient bioprinting process, paving the way for further innovations in the dynamic field of 3D bioprinting.
Dynamic Geometric Modeling for Directed Energy Deposition Process
Authors: Zhang Wenze , Chen Siqi , Dong Boge , Chen Yuanzhi , Deng Xiaoke , Duan Molong , Tang Kai
Published: August 2024

Directed energy deposition (DED) is a prominent additive manufacturing technology for manufacturing metal parts. High-fidelity simulation can reconstruct the DED process but is typically too computationally complex for process control and planning. On the other hand, experimental-based models typically only consider the static relationship between the printed bead geometry and the printing parameters, leading to significant geometry deviations. To address this issue, we propose a dynamic model that correlates the printing parameters, such as energy deposition rate and energy moving speed, with the printed geometry, such as the width and height of the printed bead. A mirrored sigmoid model was developed to fit the geometry profile of the printed bead, and a nonlinear time-invariant system was constructed to simulate the extracted geometry. This system comprises a nonlinear static model and a linear time-invariant system that respectively handles the static relationship and the high-frequency dynamic signal increments decomposed from the whole input signals. Experimental results have verified the effectiveness of the proposed method in predicting the dynamic printed bead geometry and reducing geometry deviations.
Experimental and Computational Study of Transport Phenomena in Laser Melting-Based Metal Additive Manufacturing
Authors: Deb Abhik , Panda Priti Ranjan , Viswanathan Koushik , Dutta Pradip
Published: August 2024

The present study reports an experimentally validated three-dimensional computational model for studying the transport phenomena associated with the molten pool produced by a laser melting based direct energy deposition process. In the present study, the substrate used is SS 316, while the powder feed material is Inconel 718, which is introduced co-spatially with the moving laser beam. The model considers alloy solidification, as the powder material is different from that of the substrate. An enthalpy-based technique is used for modelling the phase change processes so that the solid-liquid interface need not be tracked separately. The reference co-ordinate system is kept moving with the scanning laser beam while solving the mass, momentum, energy, and species conservation equations. The model considers differential melting points of various elements (major elements being nickel, chromium, and iron), their vaporization above the respective boiling points, Marangoni convection arising out of high temperature gradients on the top surface of molten-pool, and the momentum of powder feed particles (being carried by pressurized nitrogen as carrier gas) along with that of the shielding gas (nitrogen). For a fixed laser spot size and constant powder feed rate, other process parameters including the laser scanning speed and laser power have been varied for parametric studies. This transient simulation has been carried out till a steady state of the melt pool is attained, whereafter there is no significant change in the temperature and composition of the molten pool with time. The computational model predicts the velocity distribution, temperature profile with recognition of the melting isotherm, and species distribution in the melt pool, along with the geometry, i.e., width and depth, of the dilution zone. Corresponding experiments have been performed using the same process parameters for depositing IN 718 on a SS 316 substrate. The transient temperature profile in the melt-pool is captured using an IR Camera, whereas the deposited samples are processed and characterized to view the dilution zone. The results obtained from computations with respect to the temperature profile, particularly the melting isotherm, and the dimensions, viz., width and depth, of the dilution zone are validated against the experimental results. This model can then be utilized for designing and optimizing laser melting based direct energy deposition processes. The findings from this model including the local temperature at the solidification front, and concentration of alloying element in the melt-pool region can also serve as inputs for studying the micro-structure evolution of the deposited layers.
Brief Paper: Discrete Element Based Modeling of Powder Spreading Dynamics for Laser Powder Bed Fusion Process
Authors: Tripathi Saurabh , Kumar Cheruvu Siva
Published: August 2024

In the domain of non-conventional manufacturing processes the use of lasers for metal-based additve-manufacturing (AM) processes has got immense push from both industry and academia. And among these processes the use of Laser powder bed fusion (L-PBF) has seen quite interest. But like any other manufacturing process the quality of part produced by l-PBF is a function of raw material characteristics such as size and morphology of the feedstock powder & material-processing conditions throughout the build cycle which includes powder layering and laser melting parameters.Hence, the current study focuses and deals with the study of powder dynamics, especially spreading dynamics in powder-bed based AM systems. This dynamics of powder spreading which can be categorized as bulk phenomenon gets influenced by the particle size distribution, recoater-speed & shape and size of the recoating object employed. The metal powders having approximately spherical shape, with sizes in μm scale, which are used to form a layer of powder and the dynamics associated with them can modeled using Discrete element based approach, which describes the bulk behaviour of powder using a lagrangian approach of tracking the motion of every particle in the bulk medium which is governed by equations of motion & which are differential form of the popular newton’s laws of motion. These equations in terms of force & moment balance laws are then integrated in each time-step to obtain positions & velocities of each particle hence describing their motion in a given domain. The model herein considers the actual size distribution of the Ti6Al4V alloy powder, which was obtained using laser-diffraction analysis. Non-linear force laws were used to model the contact and non-contact interactions among the particles in the bulk. Thus, enabling the model to study how various powder spreading parameters influence the different powder-bed characteristics such as particle segregation and particle packing density.
Brief Paper: Judicious Hybridization of Incremental Forming and Additive Manufacturing to Enhance Product Complexity Through Non-Planar Substrate/Deposition
Authors: Cherukupally Shivaprasad , Nagallapati Vishwanath , Konka Praveen , Simhambhatla Suryakumar , Nallagundla Venkata Reddy
Published: August 2024

Hybrid manufacturing is the combination of two or more different processes to overcome their individual limitations and take advantage of their combined strengths to produce components more efficiently and eco-friendly than existing processes. Double-sided incremental forming (DSIF) and metal additive manufacturing (MAM) using direct energy deposition are the most flexible processes that do not require geometry-specific tooling to produce customized and complex metal parts. However, there is no absolute geometrical freedom, and each process and machine has certain limitations (MAM process has gravity and torch accessibility constraints due to lower surface inclinations and intricate shapes, respectively). Hence, the main objective of the present work is to demonstrate the feasibility thereof from the judicious hybridization of DSIF and MAM processes (termed as HyDAM, Hybrid Deformation aided Additive Manufacturing) in terms of product complexity by exploiting the geometrical freedom offered from both processes. Non-planar substrates are formed using DSIF and deposition is carried out using wire-based direct energy deposition (W-DED). In the present work, two complex geometries which are difficult to fabricate by conventional AM process due to torch accessibility and gravity constraints are considered to demonstrate their feasibility through proposed hybrid process. An appropriate build orientation of the component is chosen, and the corresponding substrate is formed using DSIF. The material deposited on the formed substrate with a suitable deposition path. The feasibility of proposed HyDAM is successfully demonstrated by fabricating complex components using a three-axis machine during deposition. Future work includes the automatic feature recognition for HyDAM, role of process parameters on bead asymmetry, path planning, exploring complex geometries (for example: deposition of non-planar cellular/perforated structures), performing thermo-mechanical analysis, and achieving the good accuracy.
Measurement of Tool Edge Geometry Using Saturated Fluorescence From Cutting Fluid
Authors: Uenohara Tsutomu , Ito Taiyu , Mizutani Yasuhiro , Takaya Yasuhiro
Published: August 2024

Tool edge wear has a significant effect on machining accuracy. Therefore, to obtain high machining accuracy, the tool edge geometry must be measured with high accuracy. On-machine measurement of tool edge geometry is desirable to reduce re-installation errors and improve throughput. Although conventional optical measurement methods can generally achieve high measurement accuracy in a clean measurement environment, on-machine measurement is difficult because the cutting fluid adhering to the tool interferes with the measurement. We have proposed a tool edge profile measurement method based on confocal detection of fluorescence generated by laser excitation of cutting fluid, and have demonstrated its validity. In this study, we focused on the phenomenon of saturated fluorescence to further improve the measurement accuracy. The intensity of fluorescence from the cutting fluid depends on the intensity of the excitation laser. When the intensity of the excitation laser is relatively low, the fluorescence intensity is proportional to the intensity of the excitation laser. At higher excitation laser intensities, however, the fluorescence intensity saturates due to the limited number of fluorescent molecules that can be excited. In other words, when a focused laser beam is used to excite the cutting fluid, the fluorescence intensity saturates only in a localized region in the vicinity of the focal spot. Therefore, detecting only the saturated fluorescence improves the spatial resolution of tool edge geometry measurement. In this study, the excitation laser was time-modulated to detect the saturated fluorescence. When the excitation laser is modulated at frequency f, fluorescence is also emitted at frequency f when the fluorescence is not saturated. On the other hand, when the fluorescence saturates, it is known that a frequency component twice the modulation frequency of the excitation laser appears in the fluorescence intensity. In other words, by modulating the excitation laser at frequency f and extracting only the 2f frequency component of the emitted fluorescence intensity using a lock-in amplifier, only the saturated fluorescence can be detected. In this study, the geometry of a worn throw-away tip was measured to validate the proposed method. Compared to the conventional method that detects non-saturated fluorescence, the proposed method has a steeper rise in fluorescence intensity when the focal spot is scanned from the air to the cutting fluid and a steeper fall in fluorescence intensity when the focal spot is scanned from the cutting fluid to the tool. This experimentally confirmed that the measurement resolution of the tool surface was improved. The tool edge geometry was measured by scanning the focal spot at many points on the tool. As a result, wear of a few micrometers to several tens of micrometers could be measured with high accuracy. The proposed method is expected to be implemented on machine tools.
Remote plasma-enhanced chemical vapor deposition of GeSn on Si (100), Si (111), sapphire, and fused silica substrates
Authors: Claflin B. , Grzybowski G. J. , Zollner S. , Rogers B. R. , Cooper T. A. , Look D. C.
Published: August 2024

GeSn films were simultaneously deposited on Si (100), Si (111), c-plane sapphire (Al2O3), and fused silica substrates to investigate the impact of the substrate on the resulting GeSn film. The electronic, structural, and optical properties of these films were characterized by temperature-dependent Hall-effect measurements, x-ray diffractometry, secondary ion mass spectrometry, and variable angle spectroscopic ellipsometry. All films were polycrystalline with varying degrees of texturing. The film on Si (100) contained only GeSn (100) grains, 40.4 nm in diameter. The film deposited on Si (111) contained primarily GeSn (111) grains, 36.4 nm in diameter. Both films deposited on silicon substrates were fully relaxed. The layer deposited on Al2O3 contained primarily GeSn (111) grains, 41.3 nm in diameter. The film deposited on fused silica was not textured, and the average grain size was 35.0 nm. All films contained ∼5.6 at. % Sn throughout the layer, except for the film deposited on Al2O3, which contained 7.5% Sn. The films deposited on Si (111), Al2O3, and fused silica exhibit p-type conduction over the entire temperature range, 10–325 K, while the layer deposited on the Si (100) substrate shows a mixed conduction transition from p-type at low temperature to n-type above 220 K. From ∼175 to 260 K, both holes and electrons contribute to conduction. Texturing of the GeSn film on Si (100) was the only characteristic that set this film apart from the other three films, suggesting that something related to GeSn (100) crystal orientation causes this transition from p- to n-type conduction.
Tracking age-related changes in voice and speech production with Landmark-based analysis of speech
Authors: Ishikawa Keiko , Anand Supraja
Published: August 2024

Voice and speech production change with age, which can lead to potential communication challenges. This study explored the use of Landmark-based analysis of speech (LMBAS), a knowledge-based speech analysis algorithm based on Stevens' Landmark Theory, to describe age-related changes in adult speakers. The speech samples analyzed were sourced from the University of Florida Aging Voice Database, which included recordings of 16 sentences from the Speech Perception in Noise test of Bilger, Rzcezkowski, Nuetzel, and Rabinowitz [J. Acoust. Soc. Am. 65, S98–S98 (1979)] and Bilger, Nuetzel, Rabinowitz, and Rzeczkowski [J. Speech. Lang. Hear. Res. 27, 32–84 (1984)]. These sentences were read in quiet environments by 50 young, 50 middle-aged, and 50 older American English speakers, with an equal distribution of sexes. Acoustic landmarks, specifically, glottal, bursts, and syllabicity landmarks, were extracted using SpeechMark®, MATLAB Toolbox version 1.1.2. The results showed significant age effect on glottal and burst landmarks. Furthermore, the sex effect was significant for burst and syllabicity landmarks. While the results of LMBAS suggest its potential in detecting age-related changes in speech, increase in syllabicity landmarks with age was unexpected. This finding may suggest the need for further refinement and adjustment of this analytical approach
Fast time-domain solution of the cochlear transmission line model in real-time applications
Authors: Murakami Yasuki
Published: August 2024

A fast numerical time-domain solution for a one-dimensional cochlear transmission-line model was proposed for real-time applications. In this approach, the three-dimensional solver developed by Murakami [J. Acoust. Soc. Am. 150(4), 2589–2599 (2021)] was modified to develop a solution for the one-dimensional model. This development allows the solution to accurately and quickly calculate cochlear responses. The present solution can solve the model in real-time under coarse grid conditions. However, under fine-grid conditions, the computation time is significantly longer than the duration of the signal. Nevertheless, calculations can be performed under the fine grid condition, which previously required much computation time. This fact is essential to applications.
Stroke of DNA
Authors: Baek Amy E.
Published: August 2024

Inflammasome activation by circulating DNA leads to recurrent stroke associated with atherosclerosis.
Structural basis of paramyxo- and pneumovirus polymerase inhibition by non-nucleoside small-molecule antivirals
Authors: Wolf Josef D. , Sirrine Michael R. , Cox Robert M. , Plemper Richard K.
Published: August 2024

Small-molecule antivirals can be used as chemical probes to stabilize transitory conformational stages of viral target proteins, facilitating structural analyses. Here, we evaluate allosteric pneumo- and paramyxovirus polymerase inhibitors that have the potential to serve as chemical probes and aid the structural characterization of short-lived intermediate conformations of the polymerase complex. Of multiple inhibitor classes evaluated, we discuss in-depth distinct scaffolds that were selected based on well-understood structure-activity relationships, insight into resistance profiles, biochemical characterization of the mechanism of action, and photoaffinity-based target mapping. Each class is thought to block structural rearrangements of polymerase domains albeit target sites and docking poses are distinct. This review highlights validated druggable targets in the paramyxo- and pneumovirus polymerase proteins and discusses discrete structural stages of the polymerase complexes required for bioactivity.
A time-course analysis of
Aspergillus terreus
secretomes reveals the importance of pectin-degrading enzymes to increase the digestibility of soybean meal
Authors: Plouhinec Lauriane , Bonnin Estelle , Kielbasa Mélodie , Armengaud Jean , Neugnot Virginie , Berrin Jean-Guy , Lafond Mickael
Published: August 2024

Considering an ever-growing global population, which hit 8 billion people in the fall of 2022, it is essential to find solutions to avoid croplands competition between human food and animal feed. Agricultural co-products such as soybean meals have become important components of the circular economy thanks to their use in animal feed. Their implementation was made possible by the addition of exogenous enzymes in the diet of monogastric animals, especially fungal carbohydrate-active enzymes (CAZymes). Here, we describe a time-course production and analysis of
Aspergillus terreus
secretomes for the identification of CAZymes able to enhance the digestibility of soybean meals. Functional assays revealed that the release of nutrients and the degradation of pectins in soybean meals can be tightly interconnected. Using a comparative proteomics approach, we identified several fungal pectin-degrading enzymes leading to increased assimilable nutrients in the soluble fraction of soybean meals. Our results reinforce the importance of deconstructing pectic polysaccharides in feedstuffs and contribute to sharpen our understanding of the fungal enzymatic interplays involved in pectin hydrolysis.

IMPORTANCE

In the present study, we developed a strategy to identify the key fungal enzymatic activities involved in the improvement of soybean meal (SBM) digestibility. Our data unravel the importance of pectin degradation for the release of nutrients from SBM and provide some insights regarding the degradation of rhamnogalacturonan-I (RG-I) by ascomycetes. Indeed, the hydrolysis of pectins and RG-I by human microbiota is well documented in the literature, but our knowledge of the fungal CAZymes at play for the degradation of soybean pectins remains hitherto underexplored. Due to its wide use in animal feed, improving the digestibility of SBM by enzymatic treatments is a current challenge for feed additive suppliers. Since non-starch polysaccharides and pectins have often been reported for their anti-nutritional role in SBM, we believe this study will provide new avenues toward the improvement of enzymatic cocktails for animal nutrition and health.
Demystifying anaerobic respiration: a problem-solving exercise
Authors: Linder Tomas
Published: August 2024

Anaerobic respiration reactions are of fundamental importance to global biogeochemical cycling of elements. Yet, the idea that cellular respiration can occur not only in the absence of oxygen but also involve the oxidation of inorganic substrates (e.g., AsO
3
3–
, Fe
2+
, H
2
, H
2
S, Mn
2+
, NH
3
, and S
0
) is often foreign to many undergraduate students. This article describes a problem-solving exercise where students are introduced to the thermodynamic fundamentals of respiration with a particular focus on the role of redox (reduction-oxidation) potentials (

E
0
´

). In the exercise, the students investigate how the difference in redox potential (

ΔE
0
´

) between different pairs of reductants and oxidants affects the range of permissible microbial metabolic reactions in natural environments when oxygen is absent.
Incompatible packaging signals and impaired protein functions hinder reassortment of bat H17N10 or H18N11 segment 7 with human H1N1 influenza A viruses
Authors: Wang Liping , Shi Lei , Liu Heidi , Zhang Jialin , Yang Wenyu , Schountz Tony , Ma Wenjun
Published: August 2024

Novel bat H17N10 and H18N11 influenza A viruses (IAVs) are incapable of reassortment with conventional IAVs during co-infection. To date, the underlying mechanisms that inhibit bat and conventional IAV reassortment remain poorly understood. Herein, we used the bat influenza M gene in the PR8 H1N1 virus genetic background to determine the molecular basis that restricts reassortment of segment 7. Our results showed that NEP and M1 from bat H17N10 and H18N11 can interact with PR8 M1 and NEP, resulting in mediating PR8 viral ribonucleoprotein (vRNP) nuclear export and formation of virus-like particles with single vRNP. Further studies demonstrated that the incompatible packaging signals (PSs) of H17N10 or H18N11 M segment led to the failure to rescue recombinant viruses in the PR8 genetic background. Recombinant PR8 viruses (rPR8psH18M and rPR8psH17M) containing bat influenza M coding region flanked with the PR8 M PSs were rescued but displayed lower replication in contrast to the parental PR8 virus, which is due to a low efficiency of recombinant virus uncoating correlating with the functions of the bat M2. Our studies reveal molecular mechanisms of the M gene that hinder reassortment between bat and conventional IAVs, which will help to understand the biology of novel bat IAVs.

IMPORTANCE

Reassortment is one of the mechanisms in fast evolution of influenza A viruses (IAVs) and responsible for generating pandemic strains. To date, why novel bat IAVs are incapable of reassorting with conventional IAVs remains completely understood. Here, we attempted to rescue recombinant PR8 viruses with M segment from bat IAVs to understand the molecular mechanisms in hindering their reassortment. Results showed that bat influenza NEP and M1 have similar functions as respective counterparts of PR8 to medicating viral ribonucleoprotein nuclear export. Moreover, the incompatible packaging signals of M genes from bat and conventional IAVs and impaired bat M2 functions are the major reasons to hinder their reassortment. Recombinant PR8 viruses with bat influenza M open reading frames were generated but showed attenuation, which correlated with the functions of the bat M2 protein. Our studies provide novel insights into the molecular mechanisms that restrict reassortment between bat and conventional IAVs.
A new mechanism of respiratory syncytial virus entry inhibition by small-molecule to overcome K394R-associated resistance
Authors: Song Qiaoyun , Zhu Haoyue , Qiu Manlan , Cai Jialiao , Hu Yun , Yang Haixia , Rao Shuwen , Li Yaolan , Li Manmei , Hu Lijun , Wang Shuqin , Hong Jian , Ye Wencai , Chen Heru , Wang Ying , Tang Wei
Published: August 2024

Infection with respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract disease in young children and older people. Despite intensive efforts over the past few decades, no direct-acting small-molecule agents against RSV are available. Most small-molecule candidates targeting the RSV fusion (F) protein pose a considerable risk of inducing drug-resistant mutations. Here, we explored the
in vitro
and
in vivo
virological properties of the K394R variant, a cross-resistant mutant capable of evading multiple RSV fusion inhibitors. Our results demonstrated that the K394R variant is highly fusogenic
in vitro
and more pathogenic than the parental strain
in vivo
. The small molecule (2
E
,2′
E
)-
N
,
N
′-((1
R
,2
S
,3
S
)−3-hydroxycyclohexane-1,2-diyl)bis(3-(2-bromo-4-fluorophenyl) acrylamide) (CL-A3-7), a structurally optimized compound derived from a natural caffeoylquinic acid derivative, substantially reduced
in vitro
and
in vivo
infections of both wild-type RSV and the K394R variant. Mechanistically, CL-A3-7 significantly inhibited virus–cell fusion during RSV entry by blocking the interaction between the viral F protein and the cellular insulin-like growth factor 1 receptor (IGF1R). Collectively, these results indicate severe disease risks caused by the K394R variant and reveal a new anti-RSV mechanism to overcome K394R-associated resistance.

IMPORTANCE

Respiratory syncytial virus (RSV) infection is a major public health concern, and many small-molecule candidates targeting the viral fusion (F) protein are associated with a considerable risk of inducing drug-resistant mutations. This study investigated virological features of the K394R variant, a mutant strain conferring resistance to multiple RSV fusion inhibitors. Our results demonstrated that the K394R variant is highly fusogenic in cell cultures and more pathogenic than the parental strain in mice. The small-molecule inhibitor CL-A3-7 substantially reduced
in vitro
and
in vivo
infections of both wild-type RSV and the K394R variant by blocking the interaction of viral F protein with its cellular receptor, showing a new mechanism of action for small-molecules to inhibit RSV infection and overcome K394R-associated resistance.
The SaeRS two-component system regulates virulence gene expression in group B
Streptococcus
during invasive infection
Authors: Coppolino Francesco , De Gaetano Giuseppe Valerio , Claverie Cosme , Sismeiro Odile , Varet Hugo , Legendre Rachel , Pellegrini Angelica , Berbiglia Alessia , Tavella Luca , Lentini Germana , Famà Agata , Barbieri Giulia , Pietrocola Giampiero , Teti Giuseppe , Firon Arnaud , Beninati Concetta
Published: August 2024

Group B
Streptococcus
(GBS) is a pathobiont responsible for invasive infections in neonates and the elderly. The transition from a commensal to an invasive pathogen relies on the timely regulation of virulence factors. In this study, we characterized the role of the SaeRS two-component system in GBS pathogenesis. Loss-of-function mutations in the SaeR response regulator decrease virulence in mouse models of invasive infection by hindering the ability of bacteria to persist at the inoculation site and to spread to distant organs. Transcriptome and
in vivo
analysis reveal a specialized regulatory system specifically activated during infection to control the expression of only two virulence factors: the PbsP adhesin and the BvaP secreted protein. The
in vivo
surge in SaeRS-regulated genes is complemented by fine-tuning mediated by the repressor of virulence CovRS system to establish a coordinated response. Constitutive activation of the SaeRS regulatory pathway increases PbsP-dependent adhesion and invasion of epithelial and endothelial barriers, though at the cost of reduced virulence. In conclusion, SaeRS is a dynamic, highly specialized regulatory system enabling GBS to express a restricted set of virulence factors that promote invasion of host barriers and allow these bacteria to persist inside the host during lethal infection.

IMPORTANCE

Group B
Streptococcus
(or GBS) is a normal inhabitant of the human gastrointestinal and genital tracts that can also cause deadly infections in newborns and elderly people. The transition from a harmless commensal to a dangerous pathogen relies on the timely expression of bacterial molecules necessary for causing disease. In this study, we characterize the two-component system SaeRS as a key regulator of such virulence factors. Our analysis reveals a specialized regulatory system that is activated only during infection to dynamically adjust the production of two virulence factors involved in interactions with host cells. Overall, our findings highlight the critical role of SaeRS in GBS infections and suggest that targeting this system may be useful for developing new antibacterial drugs.
ASB3 expression aggravates inflammatory bowel disease by targeting TRAF6 protein stability and affecting the intestinal microbiota
Authors: Cheng Mingyang , Xu Bin , Sun Yu , Wang Junhong , Lu Yiyuan , Shi Chunwei , Pan Tianxu , Zhao Wenhui , Li Xiaoxu , Song Xiaomei , Wang Jianzhong , Wang Nan , Yang Wentao , Jiang Yanlong , Huang Haibin , Yang Guilian , Zeng Yan , Yang Dongqin , Wang Chunfeng , Cao Xin
Published: August 2024

E3 ubiquitin ligase (E3) plays a vital role in regulating inflammatory responses by mediating ubiquitination. Previous studies have shown that ankyrin repeat and SOCS box-containing protein 3 (ASB3) is involved in immunomodulatory functions associated with cancer. However, the impact of ASB3 on the dynamic interplay of microbiota and inflammatory responses in inflammatory bowel disease (IBD) is unclear. Here, we systematically identify the E3 ligase ASB3 as a facilitative regulator in the development and progression of IBD. We observed that ASB3 exhibited significant upregulation in the lesions of patients with IBD. ASB3
−/−
mice are resistant to dextran sodium sulfate-induced colitis. IκBα phosphorylation levels and production of proinflammatory factors IL-1β, IL-6, and TNF-α were reduced in the colonic tissues of ASB3
−/−
mice compared to WT mice. This colitis-resistant phenotype was suppressed after coprophagic microbial transfer and reversed after combined antibiotics removed the gut commensal microbiome. Mechanistically, ASB3 specifically catalyzes K48-linked polyubiquitination of TRAF6 in intestinal epithelial cells. In contrast, in ASB3-deficient organoids, the integrity of the TRAF6 protein is shielded, consequently decelerating the onset of intestinal inflammation. ASB3 is associated with dysregulation of the colitis microbiota and promotes proinflammatory factors’ production by disrupting TRAF6 stability. Strategies to limit the protein level of ASB3 in intestinal epithelial cells may help in the treatment of colitis.

IMPORTANCE

Ubiquitination is a key process that controls protein stability. We determined the ubiquitination of TRAF6 by ASB3 in intestinal epithelial cells during colonic inflammation. Inflammatory bowel disease patients exhibit upregulated ASB3 expression at focal sites, supporting the involvement of degradation of TRAF6, which promotes TLR-Myd88/TRIF-independent NF-κB aberrant activation and intestinal microbiota imbalance. Sustained inflammatory signaling in intestinal epithelial cells and dysregulated protective probiotic immune responses mediated by ASB3 collectively contribute to the exacerbation of inflammatory bowel disease. These findings provide insights into the pathogenesis of inflammatory bowel disease and suggest a novel mechanism by which ASB3 increases the risk of colitis. Our results suggest that future inhibition of ASB3 in intestinal epithelial cells may be a novel clinical strategy.
Small molecule communication of
Legionella
: the ins and outs of autoinducer and nitric oxide signaling
Authors: Michaelis Sarah , Gomez-Valero Laura , Chen Tong , Schmid Camille , Buchrieser Carmen , Hilbi Hubert
Published: August 2024

Legionella pneumophila
is a Gram-negative environmental bacterium, which survives in planktonic form, colonizes biofilms, and infects protozoa. Upon inhalation of
Legionella
-contaminated aerosols, the opportunistic pathogen replicates within and destroys alveolar macrophages, thereby causing a severe pneumonia termed Legionnaires’ disease. Gram-negative bacteria employ low molecular weight organic compounds as well as the inorganic gas nitric oxide (NO) for cell-cell communication.
L. pneumophila
produces, secretes, and detects the α-hydroxyketone compound
Legionella
autoinducer-1 (LAI-1, 3-hydroxypentadecane-4-one). LAI-1 is secreted by
L. pneumophila
in outer membrane vesicles and not only promotes communication among bacteria but also triggers responses from eukaryotic cells.
L. pneumophila
detects NO through three different receptors, and signaling through the volatile molecule translates into fluctuations of the intracellular second messenger cyclic-di-guanylate monophosphate. The LAI-1 and NO signaling pathways are linked
via
the pleiotropic transcription factor LvbR. In this review, we summarize current knowledge about inter-bacterial and inter-kingdom signaling through LAI-1 and NO by
Legionella
species.
Complete genome sequences of
Escherichia coli
KA0011 clinical isolate used as a quality control strain of carbapenem susceptibility testing in Japan
Authors: Nomoto Ryohei , Nakanishi Noriko , Komatsu Shoko , Matsui Mari , Suzuki Satowa
Published: August 2024

Escherichia coli
KA0011 had stable minimum inhibitory concentration values around the breakpoint range of meropenem and imipenem, making it suitable for use as a quality control strain for antimicrobial susceptibility testing. Here, we report the complete genomic sequence of KA0011.
Draft genomes of
Klebsiella aerogenes
,
Klebsiella huaxiensis
, and
Klebsiella michiganensis
isolates from the urinary tract
Authors: Kula Alex , Arman Muna , Appleberry Helen , Wolfe Alan J. , Putonti Catherine
Published: August 2024

Several
Klebsiella
spp. can be the cause of urinary tract infections. Here we present the draft genome assemblies for four urinary isolates of three
Klebsiella
spp.:
Klebsiella aerogenes
UMB7541,
Klebsiella michiganensis
UMB11142 and UMB11423, and
Klebsiella huaxiensis
UMB11391 to further explore the genetic diversity of
Klebsiella
in the urinary tract.