Fatigue Behaviour of Connectors used in Cable Harnessing through Cavity Formation Related Microstructural Degradation: A Failure Investigation Perspective

Two separately failed electrical connector pieces during a vibration test were received for failure analysis. Chemical composition, hardness values and microstructures of the each of the connector material indicate that the material of construction is a die cast aluminium-silicon type of alloy, closely matching with the standard ANSI/AA B380 alloy. Intergranular and faceted fracture features are observed and failure mechanism is found to be fatigue dominated. The connectors failed by impact fatigue arising out of the loosening of the connector assembly. This has happened by cavity formation and/or growth related microstructural degradation processes. Initial casting pores as well as microstructural degradations such as interconnected pores have developed in service and their successive growth, decohesion and interconnection of each of primary Si particles and Al-Fe-Mn precipitates (along precipitate-matrix interface) have led the initiation of the crack under fatigue loading. Brittle as-cast microstructure (as typified by the precipitate-matrix interfacial cracking), existing vibratory loading and absence of any rise in temperature in the system have assisted the initial cavity (crack) formation and/or growth. Moreover, initial fitment related looseness is an additional factor in initiating and propagating this damaging mechanism.

Zn2+-Dependent Nuclease Is Involved in Nuclear Degradation during the Programmed Cell Death of Secretory Cavity Formation in Citrus grandis ‘Tomentosa’ Fruits

Zn2+- and Ca2+-dependent nucleases exhibit activity toward dsDNA in the four classes of cation-dependent nucleases in plants. Programmed cell death (PCD) is involved in the degradation of cells during schizolysigenous secretory cavity formation in Citrus fruits. Recently, the Ca2+-dependent DNase CgCAN was proven to play a key role in nuclear DNA degradation during the PCD of secretory cavity formation in Citrus grandis ‘Tomentosa’ fruits. However, whether Zn2+-dependent nuclease plays a role in the PCD of secretory cells remains poorly understood. Here, we identified a Zn2+-dependent nuclease gene, CgENDO1, from Citrus grandis ‘Tomentosa’, the function of which was studied using Zn2+ ions cytochemical localization, DNase activity assays, in situ hybridization, and protein immunolocalization. The full-length cDNA of CgENDO1 contains an open reading frame of 906 bp that encodes a protein 301 amino acids in length with a S1/P1-like functional domain. CgENDO1 degrades linear double-stranded DNA at acidic and neutral pH. CgENDO1 is mainly expressed in the late stage of nuclear degradation of secretory cells. Further spatiotemporal expression patterns of CgENDO1 showed that CgENDO1 is initially located on the endoplasmic reticulum and then moves into intracellular vesicles and nuclei. During the late stage of nuclear degradation, it was concentrated in the area of nuclear degradation involved in nuclear DNA degradation. Our results suggest that the Zn2+-dependent nuclease CgENDO1 plays a direct role in the late degradation stage of the nuclear DNA in the PCD of secretory cavity cells of Citrus grandis ‘Tomentosa’ fruits.

Hydrophobic association and solvation of neopentane in Urea, TMAO and Urea-TMAO solution

A detailed knowledge on hydrophobic association and solvation is crucial in understanding the con-formational stability of proteins and polymers in osmolyte solutions. Using Molecular Dynamics simulations, we found the hydrophobic association using neopentane molecules is greater in mixed urea-TMAO-water solution in comparison to that in 8 M urea solution, in 4 M TMAO solution and in neat water. The neopentane association in urea solution is greater than that in TMAO solution or neat water. We find the association is even less in TMAO solution than pure water. From free ener-gy calculations, it is revealed that the neopentane sized cavity creation in mixed urea-TMAO-water is most unfavorable and that causes the highest hydrophobic association. The cavity formation in urea solution is either more unfavorable or comparable to that in TMAO solution. Importantly, it is found that the population of neopentane-neopentane contact pair and the free energy contribution for cavity formation step in TMAO solution are very sensitive towards the choice of TMAO force-fields. A careful construction of TMAO force-fields is important for studying hydrophobic associa-tion. Interestingly it is observed that the total solute-solvent dispersion interaction energy contribu-tion is always most favorable in mixed urea-TMAO-water. The magnitude of this interaction energy is greater in urea solution relative to TMAO solution for two different force-fields of TMAO, whereas the lowest value is obtained in pure water. It is revealed that the extent of the overall hy-drophobic association in osmolyte solutions is mainly governed by the cavity creation step and it nullifies the contribution comes from the solute-solvent interaction contribution.

Anatomy and histology of the thymus of American mink genotypes Standard, Sapphire, Lavander in the early postnatal period of ontogenesis

Data are presented on the thymus structure of American Mink of the Standard, Sapphire, Lavender colouring genotypes in the early postnatal period from birth to 180 days. The thymus is known to be a fully formed organ at birth. The anatomical structure of the thymus and its topography are not determined by genotype. At 45 days of age, the changes are manifested by an increase in the thymic lobule area and the brain matter therein, a decrease in the cortex area; the most intense growth of the thymus due to the rise in the number of lobules is noted. The thymus of mink at 45 to 90 days of age is characterised by an equalisation between the genotypes, increasing cortical area values to about the level of newborn mink with a corresponding increase in the cortical-brain index. The thymus of minks at the age of 90 to 180 days retains the typical morphological structure. Still, the signs of age involutive processes are seen – reduction of the lobule area, enlargement of the medulla, changes in the form of the organ (lobule fusion), increased signs of fat transformation thymus. Hassall’s corpuscles were found in the medulla in all periods of investigation. The number of Hassall’s bodies and their morphology depends on the functional activity of the thymus. In newborns, unicellular, young and juvenile forms predominate. In 45-day-old minks, young and immature forms predominate. In 90-day-old female and male Standard burros, young and quite often unicellular bodies are visualised, while mature and juvenile records are less common. In mink of the coloured genotypes, immature and youthful Hassall’s corpuscles are predominant. By 180 days, the number of mature and young corpuscles with signs of central cell destruction with detritus accumulation and cavity formation increases.

Elevated Natural Killer Cell-Mediated Cytotoxicity Is Associated with Cavity Formation in Pulmonary Tuberculosis Patients

Cavitation is a major pathological feature of pulmonary tuberculosis (TB). The study is aimed at investigating the mechanism of natural killer (NK) cells participating the cavity formation during Mycobacterium tuberculosis (MTB) infection. Human peripheral blood samples were donated by pulmonary TB patients with cavity or not. Real-time quantitative PCR and enzyme-linked immunosorbent assay were performed to analyze the expression of cytokines secreted by NK cells. And the cytotoxicity of NK cells was compared between two groups. Our data showed that NK cells were more abundant in cohorts of cavity. Increased abundance of granzyme A and granzyme B was observed in culture supernatants of NK cells isolated from cavitary TB patients, which also resulted in a higher level of nonviable MTB-infected monocytes. Our data firstly demonstrates that NK cells participate in cavity formation in pulmonary TB patients. The elevated level and increased cytotoxicity of NK cells accelerate the cavitary formulation.

A hydro-osmotic coarsening theory of biological cavity formation

Fluid-filled biological cavities are ubiquitous, but their collective dynamics has remained largely unexplored from a physical perspective. Based on experimental observations in early embryos, we propose a model where a cavity forms through the coarsening of myriad of pressurized micrometric lumens, that interact by ion and fluid exchanges through the intercellular space. Performing extensive numerical simulations, we find that hydraulic fluxes lead to a self-similar coarsening of lumens in time, characterized by a robust dynamic scaling exponent. The collective dynamics is primarily controlled by hydraulic fluxes, which stem from lumen pressures differences and are dampened by water permeation through the membrane. Passive osmotic heterogeneities play, on the contrary, a minor role on cavity formation but active ion pumping can largely modify the coarsening dynamics: it prevents the lumen network from a collective collapse and gives rise to a novel coalescence-dominated regime exhibiting a distinct scaling law. Interestingly, we prove numerically that spatially biasing ion pumping may be sufficient to position the cavity, suggesting a novel mode of symmetry breaking to control tissue patterning. Providing generic testable predictions, our model forms a comprehensive theoretical basis for hydro-osmotic interaction between biological cavities, that shall find wide applications in embryo and tissue morphogenesis.