A damage constitutive model is proposed to describe the deformation and strength characteristics of intermittent jointed rocks under cyclic uniaxial compression. First, a coupled damage tensor for ...intermittent jointed rocks is derived based on the Lemaitre strain equivalence hypothesis, which combines the Weibull statistical damage model for micro-flaws and the fracture mechanics model for macro-joints. Second, a fatigue constitutive model with an internal variable (i.e., irreversible plastic strain) is proposed to reproduce the degradation behaviors in fatigue deformation and strength of rocks under cyclic loading. Finally, a damage constitutive model with a definite physical significance is constructed for the intermittent jointed rocks under cyclic uniaxial compression. Our new model comprehensively reflects the coupled damage induced by micro-flaws and macro-joints, in which the geometric parameters and the mechanical properties of intermittent joints are considered simultaneously. Moreover, this model is able to reproduce the hysteretic stress-strain curves and the cumulative fatigue plastic deformation of rock materials under cyclic loading. In addition, a compaction coefficient, which is defined as the ratio of the secant modulus to the Young's modulus, is proposed to reflect the compaction stage of rock materials during the first loading process. To validate this new model, nine cyclic uniaxial compression tests are conducted on both intact and jointed rock samples prepared with synthetic rock-like materials. A reasonable consistency is observed between the theoretical and experimental results for the cyclic stress-strain curves and the fatigue deformation modulus.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
42.
The Hydrated Electron Herbert, John M; Coons, Marc P
Annual review of physical chemistry,
05/2017, Volume:
68, Issue:
1
Journal Article
Peer reviewed
Open access
Existence of a hydrated electron as a byproduct of water radiolysis was established more than 50 years ago, yet this species continues to attract significant attention due to its role in radiation ...chemistry, including DNA damage, and because questions persist regarding its detailed structure. This work provides an overview of what is known in regards to the structure and spectroscopy of the hydrated electron, both in liquid water and in clusters
, the latter of which provide model systems for how water networks accommodate an excess electron. In clusters, the existence of both surface-bound and internally bound states of the excess electron has elicited much debate, whereas in bulk water there are questions regarding how best to understand the structure of the excess electron's spin density. The energetics of the equilibrium species
e
−
(
aq
) and its excited states, in bulk water and at the air/water interface, are also addressed.
R-loops are three-stranded structures that harbour an RNA-DNA hybrid and frequently form during transcription. R-loop misregulation is associated with DNA damage, transcription elongation defects, ...hyper-recombination and genome instability. In contrast to such 'unscheduled' R-loops, evidence is mounting that cells harness the presence of RNA-DNA hybrids in scheduled, 'regulatory' R-loops to promote DNA transactions, including transcription termination and other steps of gene regulation, telomere stability and DNA repair. R-loops formed by cellular RNAs can regulate histone post-translational modification and may be recognized by dedicated reader proteins. The two-faced nature of R-loops implies that their formation, location and timely removal must be tightly regulated. In this Perspective, we discuss the cellular processes that regulatory R-loops modulate, the regulation of R-loops and the potential differences that may exist between regulatory R-loops and unscheduled R-loops.
Full text
Available for:
FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Structural damage identification has received considerable attention during the past decades. Although several reviews have been presented, some new developments have emerged in this area, ...particularly machine learning and artificial intelligence techniques. This article reviews the progress in the area of vibration-based damage identification methods over the past 10 years. These methods are classified in terms of different damage indices and analytical/numerical techniques used with discussions of their advantages and disadvantages. The challenges and future research for vibration-based damage identification are summarised. This review aims to help researchers and practitioners in implementing existing damage detection algorithms effectively and developing more reliable and practical methods for civil engineering structures in the future.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Use of Shapely additive explanations for failure modes of RC columns and shear walls.•Importance factor for failure modes of RC columns and shear walls.•Identification of attribute contributions for ...failure mode predictions.•Explanation of the complex machine learning models.•Machine learning-based failure mode prediction models for RC columns and shear walls.
Machine learning approaches can establish the complex and non-linear relationship among input and response variables for the seismic damage assessment of structures. However, lack of explainability of complex machine learning models prevents their use in such assessment. This paper uses extensive experimental databases to suggest random forest machine learning models for failure mode predictions of reinforced concrete columns and shear walls, employs the recently developed SHapley Additive exPlanations approach to rank input variables for identification of failure modes, and explains why the machine learning model predicts a specific failure mode for a given sample or experiment. A random forest model established provides an accuracy of 84% and 86% for unknown data of columns and shear walls, respectively. The geometric variables and reinforcement indices are critical parameters that influence failure modes. The study also reveals that existing strategies of failure mode identification based solely on geometric features are not enough to properly identify failure modes.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Closed form functions of static deflection change (DC) due to damage was developed.•The static DC follows certain patterns that clearly reveal the damage location.•Linear relationship between the ...relative DC and a damage severity derivative was developed.•A new damage quantification concept named damage-severity-consistency function was proposed.•The proposed method was comprehensively validated both numerically and experimentally.
This paper presents a new method that can locate and quantify damage in Euler-Bernoulli beams from changes in static deflection. Using the principle of Virtual Work, for the first time, the deflection change (DC) parameter is formulated as a function of both the damage location and damage severity. Through this, the study shows that the changes in static deflection follow certain patterns that clearly reveal the damage location. Therefore, by observing a plot of the measured DC, the damage locations can be identified conveniently. Once the damage is located, its severity is estimated directly from the measured relative deflection change through a new concept named damage severity consistency (DSC) function. A constant or nearly constant DSC function indicates a high precision of the damage detection results and reflects a good quality of the measurement data. Numerical and laboratory investigations demonstrate that the method accurately locates and quantifies the damage under various scenarios in statically determinate beams. The proposed damage detection method has a clear theoretical base, does not rely on an optimization algorithm, and can be extended to other beam-type structures including statically indeterminate beams.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Radiotherapy is a major modality used to combat a wide range of cancers. Classical radiobiology principles categorize ionizing radiation (IR) as a direct cytocidal therapeutic agent against cancer; ...however, there is an emerging appreciation for additional antitumor immune responses generated by this modality. A more nuanced understanding of the immunological pathways induced by radiation could inform optimal therapeutic combinations to harness radiation-induced antitumor immunity and improve treatment outcomes of cancers refractory to current radiotherapy regimens. Here, we summarize how radiation-induced DNA damage leads to the activation of a cytosolic DNA sensing pathway mediated by cyclic GMP-AMP (cGAMP) synthase (cGAS) and stimulator of interferon genes (STING). The activation of cGAS-STING initiates innate immune signaling that facilitates adaptive immune responses to destroy cancer. In this way, cGAS-STING signaling bridges the DNA damaging capacity of IR with the activation of CD8+ cytotoxic T cell-mediated destruction of cancer-highlighting a molecular pathway radiotherapy can exploit to induce antitumor immune responses. In the context of radiotherapy, we further report on factors that enhance or inhibit cGAS-STING signaling, deleterious effects associated with cGAS-STING activation, and promising therapeutic candidates being investigated in combination with IR to bolster immune activation through engaging STING-signaling. A clearer understanding of how IR activates cGAS-STING signaling will inform immune-based treatment strategies to maximize the antitumor efficacy of radiotherapy, improving therapeutic outcomes.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Cell cycle control in cancer Matthews, Helen K; Bertoli, Cosetta; de Bruin, Robertus A M
Nature reviews. Molecular cell biology,
01/2022, Volume:
23, Issue:
1
Journal Article
Peer reviewed
Open access
Cancer is a group of diseases in which cells divide continuously and excessively. Cell division is tightly regulated by multiple evolutionarily conserved cell cycle control mechanisms, to ensure the ...production of two genetically identical cells. Cell cycle checkpoints operate as DNA surveillance mechanisms that prevent the accumulation and propagation of genetic errors during cell division. Checkpoints can delay cell cycle progression or, in response to irreparable DNA damage, induce cell cycle exit or cell death. Cancer-associated mutations that perturb cell cycle control allow continuous cell division chiefly by compromising the ability of cells to exit the cell cycle. Continuous rounds of division, however, create increased reliance on other cell cycle control mechanisms to prevent catastrophic levels of damage and maintain cell viability. New detailed insights into cell cycle control mechanisms and their role in cancer reveal how these dependencies can be best exploited in cancer treatment.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
To investigate the effects of prior cyclic loading damage in rocks on subsequent unloading failure characteristics under true-triaxial conditions, a series of complicated unloading tests ...incorporating the damage-controlled cyclic loading path and stress σ3 unloading path was conducted using a true-triaxial test system. The experimental results reveal that the prior cyclic loading damage has an impact on the strength and deformation characteristics, energy conversion and failure mode. As the number of prior cyclic loads increases, the unloading strength and Young's modulus increase firstly and then decrease, while the peak unloading strain, as well as the ratio (η) of crack damage stress to peak unloading stress, exhibits a descending trend. The energy storage capacity of rock samples is dramatically reduced as cycle number increases to 10 and enlarged slightly with a further increase in cycle number. Both shear fracture and tensile fracture appear in each rock sample under this unloading condition, as the prior cyclic loading number increases, the dominant failure mode of rock samples changes from tensile failure to mixed tensile-shear failure, then to shear failure, while the failure angle ranging from 65° to 80° deceases firstly and then turns to rise.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In Europe, floods are among the natural catastrophes that cause the largest economic damage. This article explores the potential of two distinct types of multivariate flood damage models: ...‘depth‐damage’ models and ‘rainfall‐damage’ models. We use survey data of 346 Flemish households that were victim of pluvial floods complemented with rainfall data from both rain gauges and weather radars. In the econometrical analysis, a Tobit estimation technique is used to deal with the issue of zero damage observations. The results show that in the ‘depth‐damage’ models flood depth has a significant impact on the damage. In the ‘rainfall‐damage’ models there is a significant impact of rainfall accumulation on the damage when using the gauge rainfall data as predictor, but not when using the radar rainfall data. Finally, non‐hazard indicators are found to be important for explaining pluvial flood damage in both ‘depth‐damage’ and ‘rainfall‐damage’ models.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
PDF
