Cleavage Failure Research Articles

Homozygous Mutations in BTG4 Cause Zygotic Cleavage Failure and Female Infertility

Zygotic cleavage failure (ZCF) is a unique early embryonic phenotype resulting in female infertility and recurrent failure of invitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI). With this phenotype, morphologically normal oocytes can be retrieved and successfully fertilized, but they fail to undergo cleavage. Until now, whether this phenotype has a Mendelian inheritance pattern and which underlying genetic factors play a role in its development remained to be elucidated. B cell translocation gene 4 (BTG4) is a key adaptor of the CCR4-NOT deadenylase complex, which is involved in maternal mRNA decay in mice, but no human diseases caused by mutations in BTG4 have previously been reported. Here, we identified four homozygous mutations in BTG4 (GenBank: NM_017589.4) that are responsible for the phenotype of ZCF, and we found they followed a recessive inheritance pattern. Three of them-c.73C>T (p.Gln25Ter), c.1A>G (p.?), and c.475_478del (p.Ile159LeufsTer15)-resulted in complete loss of full-length BTG4 protein. For c.166G>A (p.Ala56Thr), although the protein level and distribution of mutant BTG4 was not altered in zygotes from affected individuals or in HeLa cells, the interaction between BTG4 and CNOT7 was abolished. Invivo studies further demonstrated that the process of maternal mRNA decay was disrupted in the zygotes of the affected individuals, which provides a mechanistic explanation for the phenotype of ZCF. Thus, we provide evidence that ZCF is a Mendelian phenotype resulting from mutations in BTG4. These findings contribute to our understanding of the role of BTG4 in human early embryonic development and provide a genetic marker for female infertility.

CHK2 is essential for spindle assembly and DNA repair during the first cleavage of mouse embryos

The quality of the early embryo is critical for embryonic development and implantation. Errors during cleavage lead to aneuploidy in embryos. As a cell cycle checkpoint protein, CHK2 participates in DNA replication, cell cycle arrest and spindle assembly. However, the functions of CHK2 in early development of the mouse embryo remain largely unknown. In this study, we show that CHK2 is localized on the spindle in metaphase and mainly accumulates at spindle poles in anaphase/telophase during the first cleavage of the mouse embryo. CHK2 inhibition led to cleavage failure in early embryonic development, accompanied by abnormal spindle assembly and misaligned chromosomes. Moreover, the loss of CHK2 activity increased the level of cellular DNA damage, which resulted in oxidative stress. Then, apoptosis and autophagy were found to be active in these embryos. In summary, our results suggest that CHK2 is an essential regulator of spindle assembly and DNA repair during early embryonic development in mice.

The microstructure and texture evolution of pure molybdenum sheets under various rolling reductions

Pure molybdenum sheets were prepared by powder metallurgy and unidirectional rolling process. The microstructure, texture, grain orientation, mechanical properties and fracture mechanism of sintered samples were investigated. The results show that tensile strength and microhardness of 95% rolled sheet are 1028.095 ± 19.32 MPa and 323.2 ± 11.68 HV. The main texture components of (011)〈110〉 is Goss texture with reduction in the range of 70–95%. Two grain orientations of 〈111〉 fiber & 〈100〉 fiber and 〈100〉 fiber & 〈110〉 fiber are formed in the 47% and 95% rolled molybdenum sheets, respectively. Meanwhile, the fiber structure become more refined and oriented in the rolled molybdenum sheets when the rolling reduction is >87%. Brittle characteristics show typical cleavage failure.

Aurora A inhibition disrupts chromosome condensation and spindle assembly during the first embryonic division in pigs.

As common overexpression of Aurora A in various tumours, much attention has focused on its function in inducing cancer, and its value in cancer therapeutics, considerably less is known regarding its role in the first cleavage division of mammalian embryos. Here, we highlight an indispensable role of Aurora A during the first mitotic division progression of pig embryos just after meiosis. The expression and spatiotemporal localization of Aurora A were initially assessed in pig embryos during the first mitotic division by Western blot analysis and indirect immunofluorescent staining. Then, the potential role of Aurora A was further evaluated using a highly selective Aurora A inhibitor, MLN8054, during this mitotic progression in pig embryos. Aurora A was found to express and exhibit a specific dynamic intracellular localization pattern during the first mitotic division in pig embryos. Aurora A was diffused in the cytoplasm at the prophase stage, and then exhibited a dynamic intracellular localization which was tightly associated with the chromosome and spindle dynamics throughout subsequent mitotic phases. Inhibition of Aurora A by MLN8054 treatment led to the failure of the first cleavage, with the majority of embryos being arrested in prophase of the mitotic division. Further subcellular structure examination showed that Aurora A inhibition not only led to the failure of spindle microtubule assembly, but also resulted in severe defects in chromosome condensation, accompanied by an obvious decrease in p-TACC3(S558) expression during the prophase of the first mitosis. Together, these results illustrated that Aurora A is crucial for both spindle assembly and chromosome condensation during the first mitotic division in pig embryos, and that the regulation of Aurora A may be associated with its effects on p-TACC3(S558) expression.

Development of numerical material testing reflecting crystallographic slip and cleavage failure on ferrite-perlite steel

Development of numerical material testing reflecting crystallographic slip and cleavage failure on ferrite-perlite steel

Probabilistic and constitutive models for ductile-to-brittle transition in steels: A competition between cleavage and ductile fracture

We propose a probabilistic model coupling with the temperature dependent constitutive relationship to describe the competition between the cleavage and ductile void failure of ferritic/martensitic steels with irradiation effects. It is found that both the material deformation and failure modes exhibit significant temperature dependence. Regarding the material deformation, two regimes have been found for the ductile-to-brittle transition (DBT). At low temperature, the flow stress is controlled by the mobility of screw dislocations. The high-temperature regime is about the thermally activated jog drag of dislocations. The failure modes depend on the carbide precipitate and temperature. Cleavage micro-cracks initiate at the carbide sites at low temperature giving rise to brittle behaviors. At high temperature, void nucleation evolving from the carbide precipitate suppresses the cleavage nucleation and propagation, and leads to good ductility. It is demonstrated that the competition between the cleavage fracture and ductile void failure is the major mechanism for the DBT. Our probabilistic model successfully predicts the temperature-dependent fracture toughness and ductile-to-brittle transition temperature (DBTT). Besides temperature, irradiation has a significant effect on the DBT of steels. Upon irradiation, the steels exhibit both irradiation hardening and irradiation embrittlement, i.e., rise in yield and flow stresses, and increase on DBTT. The main reason for these irradiation effects is that the irradiation-induced hardening increases the flow stress, and the plasticity localization weakens the overall hindering effect from ductile void growth on the cleavage nucleation and propagation, promoting the development of cleavage. Our probabilistic model takes into account the cleavage nucleation-propagation process and the influence of ductile void growth simultaneously, and it gives a sound explanation for the fundamental relation between the DBTT and mechanical properties of metallic materials.

Teleost Gasdermin E Is Cleaved by Caspase 1, 3, and 7 and Induces Pyroptosis.

Pyroptosis is a newly defined gasdermin (GSDM)-dependent inflammatory type of programmed cell death. Different from mammals, which have a panel of pyroptotic GSDM members (e.g., GSDMA-E), teleosts possess only GSDME. The pyroptotic activity and regulation mechanism of teleost GSDME remain to be elucidated. In this work, we investigated the activity of the teleost Cynoglossus semilaevis (tongue sole) GSDME (CsGSDME) in association with different caspases (CASPs). We found that CsGSDME exerted pyroptotic and bactericidal activities through its N-terminal domain. Unlike human GSDME, which is exclusively cleaved by CASP3, CsGSDME was cleaved by C. semilaevis CASP (CsCASP) 1 with high efficiency and by CsCASP3 and 7 with comparatively low efficiencies, and all cleavages occurred at the 243FEVD246 site in the interdomain linker region of CsGSDME. Mutation of Phe243 to Asp/Ala and Asp246 to Ala in 243FEVD246 altered the cleavage preference of CsCASP1, 3, and 7. Treatment with loss-of-function CsCASP mutants or inhibition of CsCASP activity resulted in failure of CsGSDME cleavage. CsCASP1-cleaved CsGSDME induced pyroptosis, whereas CsCASP3/7-cleaved CsGSDME and F243 mutants induced switching of cell death from apoptosis to pyroptosis. Analysis of 54 teleost GSDME sequences revealed a conserved tetrapeptide motif that fits well to the inherent cleavage site of CASP1. Taken together, the results of our study demonstrate a hitherto, to our knowledge, unrecognized GSDME cleavage mode in teleosts that is clearly different from that in mammals, thus providing an important insight into the activation mechanism of CASP-mediated, GSDM-executed pyroptosis in teleosts.

Microstructural Analysis of X38CrMov5-1 Steel Parts Manufactured by Casting and Evaluation of Possible Cleavage Failure

Microstructural characterisation has been carried out on X38CrMoV5-1 steel parts manufactured by gravity investment casting. Optimal heat treatment was applied to the parts: annealing at 780 °C (1 h) and cooling in the furnace; heating at 1020 °C (1 h), cooling in oil and double tempering at 580 °C (2 h). Hillert and Stefansson thermodynamic principles were used to calculate the fraction precipitated of V(C, N) and AlN and the percentages in solution of elements (V, Al, C, N). Calculations showed considerable V precipitation while SEM micrographs showed numerous V(C, N) precipitates of 400 nm average size. Small fraction of mixed (V, Mo)C and (V, Mo, Cr)C precipitates of approximately 5 µm was observed preferentially located close to the initial austenite grain boundaries. A small number of Al2O3 and MnS-type inclusions, with round and rectangular shapes, respectively, were also identified. Abundant pores of up to 165 µm in length and with an average size of 25 µm were located in the interdendritic regions. Comparison of the sizes and fractions of secondary phases (V(C, N), mixed precipitates), defects (pores, inclusions), and their consideration in Griffith’s equation lead to the conclusion that pores are the defects which could cause catastrophic cleavage fracture.

Stress Corrosion Cracking Resistance of Cold-Sprayed Al 6061 Deposits Using a Newly Developed Test Fixture

The stress corrosion cracking (SCC) response of Al 6061 bulk deposits produced by high-pressure cold spray (HPCS) was investigated and compared to commercial wrought Al 6061-T6 material. Representative tensile coupons were stressed to 25%, 65% and 85% of their respective yield strength and exposed to ASTM B117 salt fog for 90 days. After exposure, the samples were mechanically tested to failure, and subsequently investigated for stress corrosion cracking via optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDS). The results were compared to the wrought Al 6061-T6 properties and correlated with the observed microstructures. Wrought samples showed the initiation of stress corrosion cracking, while the cold-sprayed deposits appeared to be unaffected or affected by general corrosion only. Optical microscopy revealed evidence of stress corrosion cracking in the form of intergranular corrosion in the wrought samples, while no significant corrosion was observed in the cold-sprayed deposits. Fractography revealed wrought samples failed due to multiple mechanisms, with predominant cleavage and intergranular failure, but cold-sprayed samples only failed by ductile dimple rupture. The difference in SCC response between the differently processed materials is attributed to the documented benefits of the cold spray process, which includes maintaining fine grain structure of the feedstock powder and high density after consolidation, low oxidation, and work hardening effect.

Role of stress triaxiality on ductile versus brittle fracture in pre-cracked FCC single crystals: an atomistic study

The ductile versus brittle fracture in crystalline materials depends on the relative values of KIc and KIe as defined by well-known Rice theory, where KIc and KIe are the critical values of stress intensity factor corresponding to cleavage and dislocation emission, respectively. For KIc < KIe, the brittle fracture (or cleavage) takes place in atomically sharp pre-cracked crystal subjected to Mode I loading. For KIe < KIC, the dislocations are emitted from the crack front resulting in ductile fracture. To this end, molecular static simulations are used to explain the crystal orientation dependent fracture behaviour of FCC single crystal and its contradiction with respect to Rice theory based on stress triaxiality at the crack front. The stress triaxiality at crack front changes with crystal orientation due to transformation of stiffness tensor Cijkl. It is shown that high stress triaxiality suppressed the dislocation initiation leading to cleavage failure even for the case when KIe < KIc.

Disorders of Ventral Induction/Spectrum of Holoprosencephaly.

Disorders of the ventral induction give rise to a group of congenital malformations that share in common the failure of the prosencephalon cleavage and subsequent formation of midline structures, presenting with a wide spectrum of severity. This article focuses on the imaging findings of the holoprosencephaly spectrum and septo-optic dysplasia, their epidemiology, embryology, and the common clinical associated anomalies. Knowledge of the imaging features of these disorders is necessary for a correct interpretation of findings and accurate parental counseling. Diagnostic evaluation of patients should include molecular screening and genetic counseling to characterize prognosis and risk of recurrence.

The Effects of Sc Addition on the Microstructure and Mechanical Properties of Be-Al Alloy Fabricated by Induction Melting

This study investigated the alloying effects of 0.4 wt.% Sc on the microstructure, mechanical properties, and fracture behavior of a cast Be-Al alloy prepared by vacuum induction melting. The micromechanics of Sc-containing secondary-phase particles (SPs) were characterized by nanoindentation, and the fracture behavior of the alloy was investigated via tensile fractography and optical metallography. The addition of 0.4 wt.% Sc significantly modified the alloy microstructure by decreasing the secondary dendritic arm spacing (SDAS), weakening the dendritic structure of Be, and producing an equiaxed/cellular alloy microstructure with refined Be grains. Sc alloying increased the Vickers hardness by 36%, elastic modulus by 28%, yield strength by 35%, ultimate strength by 52%, but decreased the elongation from 3.6 to 2.9%. Sc-containing SPs had a higher elastic modulus, yield strength, microhardness, and a lower plasticity index than the Be and Al matrices, resulting in interface separation during the fracture process. SPs located at the Be/Al interfaces did not act as microcrack sources for the matrices, whereas highly faceted SPs within the Be grains induced microcrack formation and decreased the elongation. The failure mode of the cast Be-Al-0.4Sc alloy still involved the brittle cleavage failure of Be regions and ductile dimple failure of Al regions, which was not the case with the cast Be-Al alloy.

Mechanical characterizations of single-crystalline (Cu, Ni)6Sn5 through uniaxial micro-compression

Microelectronic industry is experiencing a major paradigm shift from the conventional two-dimensional into hierarchical three-dimensional integrated circuits (3D ICs). In 3D IC technology, through-silicon-vias and micro joints are regarded as the two vital interconnection processes to achieve higher packing density as well as heterogeneous integration. However, the miniaturization of solder joints down to micron level causes the consequence that intermetallic compounds takes up most of the volume of micro joints within a short period of time, in stark contrast to the well-known scenario at the opposite end of spectrum that soft Sn-based solders always occupies a high volume fraction of joints. Thus, intermetallics are expected to shoulder primary responsibilities of mechanical reliability in micro joints. Therefore, a full understanding about the mechanical behaviors of intermetallics at micron scale is essential for validity and reliability evaluation of 3D IC interconnections. The present study focuses on mechanical assessment of single-crystalline (Cu, Ni)6Sn5 by means of uniaxial micro-compression and nanoindentation. The anisotropic mechanical properties of hexagonal Cu6Sn5 are investigated by compression testing on single-crystalline Cu6Sn5 micropillars with different grain orientations. The jammed network of dislocation inside deformed micropillars suggests that intermittent strain bursts in stress-strain curves are relevant to dislocation-avalanche mechanism. In addition, Cu6Sn5 micropillars are found to exhibit brittle cleavage failure with most fractured pieces crushed in the same direction, and one set of preferred cleavage plane are characterized by post-mortem analysis. Moreover, the strengthening and phase-stabilizing effect of Ni element on Cu6Sn5 is also investigated by micropillar compression and X-ray diffraction, respectively.

Effect of tensile strain rate on high-temperature deformation and fracture of rolled Al-15 vol% B4C composite

Deformation behavior of a rolled Al-15 vol% B4C composite was studied at high temperatures, using single- tensile tests over a wide range of strain rates. The deformation of the composite is characterized by high apparent stress exponent, na and high activation energy, Qa, which are higher than those reported in pure Al. The analysis showed the presence of threshold stress that its value increases with decreasing the testing temperature. Using the threshold stress in the analysis, the obtained values of the true stress exponents, nt of ~ 5 and the true activation energy, Qt of 130 kJ mol−1, were similar to those reported for pure Al. TEM results of subgrain formation along with the mechanical data (nt and Qt) suggest that dislocation climb in the Al matrix is the rate controlling mechanism. The elongation (ef %) showed a maximum value at 500 °C at intermediate value of Zener-Hollomon parameter, Z. The fracture surfaces of tested samples are characterized by mixed modes of ductile (dimple formation) and brittle (cleavage) failures, which were dependent on the deformation conditions of temperature and strain rate.

Treatment of constraint in BS 7910:2013, ISO 27306 and DNVGL-RP-F108

Annex N of BS 7910:2013 (‘Guide to methods for assessing the acceptability of flaws in metallic structures’) describes two procedures for allowing for constraint effects in fracture assessment. One (Procedure I) is based on modifying the Failure Assessment Line (FAL) to account for constraint, the other (Procedure II) on modifying the failure assessment point. They are intended to be used in conjunction with the main fracture assessment procedures (Clause 7) ‘to estimate any increase in reserve factors likely to arise under conditions of low constraint.’ This paper addresses the origins of Annex N and illustrates its application to the assessment of a pair of plain steel wide plate specimens containing through-thickness cracks, which failed by brittle cleavage. It is shown that the expected advantages of the method (reduction in excessive conservatism without jeopardising safety) may be offset by a need to define the fracture toughness of the specimens in a more conservative manner and/or by carrying out many more tests than is currently considered acceptable.Annex N is also compared with DNVGL-RP-F108 (‘Assessment of flaws in pipeline and riser girth welds’) and ISO 27306 (‘Method of constraint loss correction of CTOD fracture toughness for fracture assessment of steel components’). The former is a very particular form of Procedure II of Annex N and is routinely applied to the assessment of pipeline girth welds operating on the upper shelf. The latter is restricted to cleavage failure and a rather limited range of applicability in terms of flaw size (unless additional numerical modelling is carried out). Annex N is concluded to be the most versatile method, since in principle it can be used throughout the ductile/brittle transition curve and for a wide range of structures and flaw sizes.

Identification of a conserved DNA sulfur recognition domain by characterizing the phosphorothioate-specific endonuclease SprMcrA from Streptomyces pristinaespiralis.

Streptomyces species have been valuable models for understanding the phenomenon of DNA phosphorothioation in which sulfur replaces a non-bridging oxygen in the phosphate backbone of DNA. We previously reported that the restriction endonuclease ScoMcrA from Streptomyces coelicolor cleaves phosphorothioate DNA and Dcm-methylated DNA at sites 16-28 nucleotides away from the modification sites. However, cleavage of modified DNA by ScoMcrA is always incomplete and accompanied by severe promiscuous activity on unmodified DNA. These features complicate the studies of recognition and cleavage of phosphorothioate DNA. For these reasons, we here characterized SprMcrA from Streptomyces pristinaespiralis, a much smaller homolog of ScoMcrA with a rare HRH motif, a variant of the HNH motif that forms the catalytic center of these endonucleases. The sulfur-binding domain of SprMcrA and its phosphorothioation recognition site were determined. Compared to ScoMcrA, SprMcrA has higher specificity in discerning phosphorothioate DNA from unmodified DNA, and this enzyme generally cuts both strands at a distance of 11-14 nucleotides from the 5' side of the recognition site. The HRH/HNH motif has its own sequence specificity in DNA hydrolysis, leading to failure of cleavage at some phosphorothioated sites. An R248N mutation of the central residue in HRH resulted in 30-fold enhancement in cleavage activity of phosphorothioate DNA and altered the cleavage efficiency at some sites, whereas mutation of both His residues abolished restriction activity. This is the first report of a recognition domain for phosphorothioate DNA and phosphorothioate-dependent and sequence-specific restriction activity.

The MADS-box Transcription Factor PsMAD1 Is Involved in Zoosporogenesis and Pathogenesis of Phytophthora sojae.

Transcriptional regulation is critical for plant pathogen development and virulence. MADS-box transcription factors belong to a highly conserved transcriptional regulator family in eukaryotic organisms that are involved in various important biological processes. Only one predicted MADS-box gene, PsMAD1, was identified in Phytophthora sojae, which was highly expressed during the sporangia and infection stages. To investigate its function, we generated PsMAD1 knockout mutants using the CRISPR/Cas9 system. Compared with the wild-type strain, the mutants showed no changes in vegetative growth, oospore production, or no differences in sensitivity to various abiotic stresses. Although sporangia production was normal, no zoospore release was detected in PsMAD1 mutants. Microscopy analyses revealed failure of cleavage of the cytoplasm into uninucleate zoospores in the mutants. In addition, the mutants showed reduced virulence in soybean. RNA-seq data indicated that PsMAD1 may regulate many zoospore development and infection associated genes. Thus, PsMAD1 may be a major regulator of P. sojae involved in zoosporogenesis and pathogenesis.

Study into the effect of strengthening phase amount in aluminum-based dispersion-hardened composite on failure process regularities

The paper presents the results obtained when studying static tensile strength of aluminum-based cast dispersion-hardened composites with a different content of the Al2O3strengthening phase. The investigated materials are manufactured using a fundamentally different technology for the production of cast dispersion-hardened aluminum composites based on the process of burning out the aluminum melt when interacting with oxygen or an oxygen-nitrogen mixture. The fractographic patterns of static failure surfaces are stidued on samples failed at maximum stress values. It is found that samples with the low Al2O3content have a purely viscous failure pattern consisting mainly of a single fibrous zone. The fracture pattern shows a radial area with a solid phase doubled, while a tripled Al2O3content causes viscous failure by the separation and shear mechanism alternated with brittle cleavage failure signs. The fracture profile diagrams of samples containing 10 % and 30 % of solid phase inclusions reveal no sharp relief differences, but demonstrate a completely different failure pattern. However, in both cases profile diagrams feature no any abrupt jumps in the relief or extreme profile values, so it is possible to assert that failure processes are stable. This is not true for the 20 % Al2O3sample failure showing a rather significant one-time drop. Optical microscopy reveals features of changes in the failure surface relief and the difference in the location and number of fracture origins in the studied samples.

Modeling of failure mode switching and shear band propagation using the correspondence framework of peridynamics

This study presents an approach to model dynamic failure mode switching and shear band propagation using the correspondence framework of state-based peridynamics. To effectively model spontaneous shear-band-to-crack switching phenomenon, which is of intrinsic complexity, a combined peridynamic nonlocal and classical local damage model for failure prediction is proposed. The concept of bond failure, often employed in the bond-based peridynamic modeling of brittle materials, is extended to the state-based peridynamics to model cleavage failure in elasto-viscoplastic materials so that the directional and progressive nature of damage can be readily handled. The classical constitutive relation for viscous fluid is adapted for use in non-ordinary state-based peridynamics to model stress collapsing state in shear bands. To show the effectiveness of the proposed approach, a comprehensive numerical study of a pre-notched plate subjected to asymmetric impact loading is conducted, including the phenomenon of shear-band-to-crack switching under an intermediate impact velocity and ductile failure under high impact velocity. A zero-energy mode suppression with an upper bound to avoid over-correction is introduced. By using the proposed modeling approach, dynamic failure mode switching and shear band propagation path are accurately captured.

Forces and Heat Variation Laws of Pine Materials Processing and Microcosmic Characteristics of Surface Damage

Pinus massoniana material was processed on a shaper in which a quartz three-component dynamometer and forward-looking infrared (FLIR) system were used to measure the cutting forces and cutting zone temperature, respectively. In addition, a high-speed camera and the FLIR systems were used to capture the chip formation process. Cutting forces and cutting zone temperature were measured under the cutting conditions of three different rake angles (25°, 40°, and 50°) and four different cutting depths (0.1 mm, 0.2 mm, 0.3 mm, and 0.5 mm), while feed speed was kept constant. Analysis of the experimental data and chip formation process showed that the cutting forces and cutting zone temperature of pine material were both decreased by increases of rake angle and increased by increases of cutting depth. Cutting forces were decreased under the cutting conditions of 0.3 mm cutting depth and rake angles of 40° and 50° due to the cleavage failure parallel to pine grain. The cutting temperature was not decreased under that cutting condition. The microcosmic characteristics of surface damage were mainly fiber burrs and fiber traces.