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The fortification of military and civilian infrastructures against explosive events has garnered heightened consideration among structural engineers, owing to the surge in subversive detonations and inadvertent blasts witnessed in recent times. Notable examples include the Beirut port explosion in 2020 and the Kabul airport attack in 2021, which underscore the critical need for enhanced protective measures in structural design. In the domain of structural engineering, safeguarding slender structural elements, notably slabs, emerges as a pivotal concern. Slabs, integral constituents within architectural constructs, bear significant responsibility in upholding structural integrity and providing support. Nonetheless, their slender configuration exposes them to heightened vulnerability in the face of detonations, particularly those initiated by direct contact. In contrast to sturdier structural components like columns or walls, slabs exhibit diminished mass and intrinsic resilience, rendering them predisposed to deformation, fracturing, and ultimate failure when subjected to explosive forces. This research employs an Integrated Eulerian Lagrangian formulation within the framework of the FEM, utilizing the dynamic computational tool Abaqus/Explicit. Its objective is to scrutinize the behavior and efficacy of a mono-reinforced one-way concrete slab when subjected to a central contact explosion. The computational model undergoes validation through comparison with experimental findings readily available in the public domain. Subsequently, the validated model is applied to explore the response of the slab in two distinct scenarios: in the initial configuration, the TNT charge is positioned on the upper surface, designated as the compression face, while in an alternate configuration, it is situated on the lower surface, known as the tension face. The damages incurred by the slab for the two distinct blast scenarios are compared to gain better insight into the structural response under differing blast conditions. Results showed that the placement of TNT explosives at the lower surface (tension face) of the slab (Scenario: II) led to increased upward deformation and tensile stress in reinforcement bars compared to Scenario I. Specifically, Scenario II exhibited a 1.27-fold increase in deformation and heightened stress intensity, indicating greater severity in terms of damage and structural failure potential.

Originally rooted in military engineering, blast engineering has transitioned across centuries, from ancient fortifications to modern civil structures and nuclear facilities. Emerging from its historical association with warfare, particularly evident in World War II advancements, the field now encompasses a broader scope, addressing the challenges of protecting civilian infrastructure against blasts, both accidental and intentional. This evolution reflects a continuum of expertise, from ancient defenses to contemporary simulations and materials, ensuring resilience in the face of evolving threats. Slabs serve as indispensable structural elements in construction, crucial for dispersing loads and furnishing essential support as floors, ceilings, or roofs. Their primary function is to ensure structural stability by uniformly distributing weight onto columns and walls, while simultaneously furnishing level surfaces for various activities and augmenting architectural appeal. Nevertheless, owing to their extensive horizontal orientation and substantial surface area, slabs are exceptionally susceptible to explosions, particularly those initiated by direct contact, owing to the rapid fluctuations in pressure and impulse loading they undergo. This research initiative is dedicated to probing the anti-blast capabilities inherent in slabs through an innovative paradigm. The methodology entails the integration of vertical short bars, colloquially referred to as studs, to interconnect the compression and tension layer bars of the slab. These studs are purposed as supplementary reinforcement to bolster the structural robustness and fortitude of the slab against blast-induced forces. By introducing this pioneering design component, the authors endeavour to scrutinize the efficacy of the slab's performance when subjected to a touch-off explosion. The investigation juxtaposes the performance of these fortified slabs against two alternative scenarios: slabs lacking studs bridging the compression and tension layers, and slabs reinforced solely on the tension side—an arrangement corroborated by extant experimental study. The findings reveal that incorporating vertical studs significantly strengthens structural integrity, reduces deformation and stress, and improves energy dissipation and damage response under blast loads. This enhancement is attributed to enhanced shear resistance, increased ductility, and superior load transfer, ultimately reducing damage and enhancing resilience.

The significance of Low-Velocity Drop Weight Impact (LDWI) testing cannot be overstated, as it plays a crucial role in assessing the impact resistance of structural components across various sectors, including aerospace, automotive, construction, and defense. Low-velocity impacts are evident across a spectrum of circumstances, spanning from occurrences in nature to mishaps within industrial settings. Instances encompass boulders striking rooftops amidst landslides, plummeting rocks posing threats to infrastructure within mountainous terrain, and industrial mishaps entailing collisions among equipment or machinery. The response of structures to rapid loading induced by LDWI is of utmost importance, necessitating precise and dependable testing methodologies. For researchers and professionals engaged in LDWI testing, a deep comprehension of essential equipment is essential to ensure the accuracy and reliability of experimental outcomes. Central to this endeavor is the drop weight apparatus, comprising components such as a descending weight, an impactor, and a guiding mechanism, which are pivotal in regulating impact parameters like velocity and trajectory. This research offers a thorough examination of the fundamental equipment necessary for LDWI analysis and delineates the procedures for conducting such assessments on structural elements like slabs. By amalgamating insights from diverse scholarly sources, the authors present a comprehensive overview of indispensable apparatus and assessment techniques. This exposition serves as a valuable asset for both researchers and practitioners, furnishing guidance in equipment selection, procedural comprehension, and precise interpretation of experimental results. The assimilation of this knowledge enriches the proficiency and effectiveness of LDWI testing efforts, thereby facilitating informed decision-making in material selection, structural design, and optimization of impact resistance across a wide array of engineering applications.

The structural response of masonry/concrete structures depends upon the load-carrying mechanism and subsequently deformations produced by loads carried. In masonry/concrete structures, identification of the stress/strain imposing stress conditions and strain hardening/softening makes the structural response more complicated. Elastic damage models or elastic-plastic constitutive laws are inadequate to simulate masonry/concrete response under high strain-rate loadings. Further, irreversible or plastic strain cannot be realized using the elastic damage model. Several constitutive damage models are available in the literature. In this article, a concise explanation of the functioning of different material models in the Abaqus software package has been provided. These models include concrete damage plasticity for concrete and masonry, traction separation constitutive laws for brick-mortar interface, Hashin's criteria for CFRP, Johnson-Cook plasticity for steel, and crushable foam plasticity hardening for metallic foams. Researchers frequently utilize these models for numerical simulations and modeling of infrastructural elements and their respective materials when subjected to various structural loads. Besides, this paper presents a discourse on problem-solving methods and a comparison between explicit and implicit analysis. The research provides valuable input to researchers and practitioners in the field of structural engineering for an in-depth understanding of the functioning of Abaqus' pre-existing material models.

Mycobacterium tuberculosis (M. tb) is one of the most successful human pathogens, causing a severe and widespread infectious disease. The frequent emergence of multidrug-resistant (MDR) strains has exacerbated this public health crisis, particularly in underdeveloped regions. M. tb employs a sophisticated array of virulence factors to subvert host immune responses, both innate and adaptive. It utilizes the early secretory antigenic target (ESAT6) secretion system 1 (ESX-1) type VII secretion system (T7SS) and cell wall lipids to disrupt phagosomal integrity, inhibiting phagosome maturation, and fusion with lysosomes. Although host cells activate mechanisms such as ubiquitin (Ub), Ub-ligase, and cyclic GMP-AMP synthase-stimulator of interferon genes 1 (CGAS-STING1)-mediated autophagy to inhibit M. tb survival within macrophages, the pathogen counteracts these defenses with its own virulence factors, thereby inhibiting autophagy and dampening host-directed responses. T7SSs are critical for transporting proteins across the complex mycobacterial cell envelope, performing essential functions, including metabolite uptake, immune evasion, and conjugation. T7SS substrates fall into two main families: ESAT-6 system proteins, which are found in both Firmicutes and Actinobacteria, and proline-glutamic acid (PE) and proline-proline-glutamic acid (PPE) proteins, which are unique to mycobacteria. Recent studies have highlighted the significance of T7SSs in mycobacterial growth, virulence, and pathogenesis. Understanding the mechanisms governing T7SSs could pave the way for novel therapeutic strategies to combat mycobacterial diseases, including tuberculosis (TB). T7SS of M. tb plays a critical role in the bacterium's virulence, pathogenesis, and survival within host cells. T7SS mediates the secretion of PE-PPE proteins and ESX substrates, which are pivotal in various cellular processes. These include damaging the phagosome, inducing ubiquitination, autophagy, and promoting the release dsDNA. Furthermore, T7SS activates key immune responses such as inflammasome formation, CGAS-STING1 signaling, and type I IFN production, while stimulating the secretion of proinflammatory cytokines. It also contributes to inflammation, necroptosis, pyroptosis, and facilitates the dissemination of M. tb to neighboring cells. In addition to promoting immune responses, T7SS is involved in nutrient acquisition and inhibits host cell defense mechanisms. It prevents phagosome-lysosome fusion, impairs phagosome repair mechanisms, and inhibits phagosome maturation, enabling M. tb to survive within macrophages. Targeting multiple stages of the T7SS pathway offers potential therapeutic strategies to inhibit its function, thereby reducing M. tb replication, virulence, and pathogenicity, as highlighted in the accompanying figure through cross-marks. These insights provide promising avenues for the development of interventions aimed at disrupting the T7SS and mitigating M. tb infection. AR = autophagy receptors (SQSTM1/p62, NBR1, CALCOCO2, TAX1BP1, OPTN, TRIM16, and TRIM32). HIGHLIGHTS: Emergence of MDR strains exacerbates the TB health crisis. M. tb uses T7SS to disrupt host immune responses. Pathogen counters autophagy, dampening host defense mechanisms. T7SSs critical for protein transport and immune evasion. Understanding T7SSs may lead to new TB therapies. [ABSTRACT FROM AUTHOR]

Mycobacterium tuberculosis (M. tb) is a significant intracellular pathogen responsible for numerous infectious disease‐related deaths worldwide. It uses ESX‐1 T7SS to damage phagosomes and to enter the cytosol of host cells after phagocytosis. During infection, M. tb and host mitochondria release dsDNA, which activates the CGAS‐STING1 pathway. This pathway leads to the production of type I interferons and proinflammatory cytokines and activates autophagy, which targets and degrades bacteria within autophagosomes. However, the role of type I IFNs in immunity against M. tb is controversial. While previous research has suggested a protective role, recent findings from cgas‐sting1 knockout mouse studies have contradicted this. Additionally, a study using knockout mice and non‐human primate models uncovered a new mechanism by which neutrophils recruited to lung infections form neutrophil extracellular traps. Activating plasmacytoid dendritic cells causes them to produce type I IFNs, which interfere with the function of interstitial macrophages and increase the likelihood of tuberculosis. Notably, M. tb uses its virulence proteins to disrupt the CGAS‐STING1 signaling pathway leading to enhanced pathogenesis. Investigating the CGAS‐STING1 pathway can help develop new ways to fight tuberculosis. [ABSTRACT FROM AUTHOR]