Evolution of deformation and breakage in sand studied using X-ray tomography

International audienceParticle breakage of a granular material can cause significant changes in its microstructure, which will govern its macroscopic behaviour; this explains why the mechanisms leading to particle breakage have been a common subject within several fields, including geomechanics. In this paper, X-ray computed micro-tomography is used, to obtain three-dimensional images of entire specimens of sand, during high-confinement triaxial compression tests. The acquired images are processed and measurements are made on breakage, local variations of porosity, volumetric strain, maximum shear strain and grading. The evolution and spatial distribution of quantified breakage and the resulting particle size distribution for the whole specimen and for specific areas are presented here for the first time and are further related to the localised shear and volumetric strains. Before peak stress is reached, compaction is the governing mechanism leading to breakage; neither compressive strains nor breakage are significantly localised and the total amount of breakage is rather low. Post peak, in areas where strains localise and breakage is present, a dilative volumetric behaviour is observed locally, as opposed to the overall compaction of the specimen. Some specimens exhibited a compaction around the shear band at the end of the test, but there was no additional breakage at that point. From the grading analysis, it is found that mainly the grains with diameter close to the mean diameter of the specimen are the ones that break, whereas the biggest grains that are present in the specimen remain intact

Stochastic Drift in Mitochondrial DNA Point Mutations: A Novel Perspective Ex Silico

The mitochondrial free radical theory of aging (mFRTA) implicates Reactive Oxygen Species (ROS)-induced mutations of mitochondrial DNA (mtDNA) as a major cause of aging. However, fifty years after its inception, several of its premises are intensely debated. Much of this uncertainty is due to the large range of values in the reported experimental data, for example on oxidative damage and mutational burden in mtDNA. This is in part due to limitations with available measurement technologies. Here we show that sample preparations in some assays necessitating high dilution of DNA (single molecule level) may introduce significant statistical variability. Adding to this complexity is the intrinsically stochastic nature of cellular processes, which manifests in cells from the same tissue harboring varying mutation load. In conjunction, these random elements make the determination of the underlying mutation dynamics extremely challenging. Our in silico stochastic study reveals the effect of coupling the experimental variability and the intrinsic stochasticity of aging process in some of the reported experimental data. We also show that the stochastic nature of a de novo point mutation generated during embryonic development is a major contributor of different mutation burdens in the individuals of mouse population. Analysis of simulation results leads to several new insights on the relevance of mutation stochasticity in the context of dividing tissues and the plausibility of ROS ”vicious cycle” hypothesis

Information and communication technology (ICT) as a tool of differentiated instruction: an informative intervention and a comparative study on educators’ views and extent of ICT Use

The differentiated instruction/differentiated classroom has been the subject of numerous studies and discussions regarding its application in today’s classrooms. Consequently, the differentiation of the teaching approach would not be unrelated to essential characteristic of our generation, namely the use of technology and its tools in any everyday activity. Nowadays, it is widely realized and accepted that both of the concepts of differentiated instruction and the educational use of Information and Communication Technology (ICT) are necessary for the modern educational practice and for that reason the present dissertation focuses on linking these two issues. The purpose of this research is to study educators’ views on the use of ICT to differentiate their instruction and explore their extent of ICT use. © 2019 International Journal of Information and Education Technology. All rights reserved

Information and communication technology (ICT) as a tool of differentiated instruction: an informative intervention and a comparative study on educators’ views and extent of ICT Use

The differentiated instruction/differentiated classroom has been the subject of numerous studies and discussions regarding its application in today’s classrooms. Consequently, the differentiation of the teaching approach would not be unrelated to essential characteristic of our generation, namely the use of technology and its tools in any everyday activity. Nowadays, it is widely realized and accepted that both of the concepts of differentiated instruction and the educational use of Information and Communication Technology (ICT) are necessary for the modern educational practice and for that reason the present dissertation focuses on linking these two issues. The purpose of this research is to study educators’ views on the use of ICT to differentiate their instruction and explore their extent of ICT use. © 2019 International Journal of Information and Education Technology. All rights reserved

Immune cell response to strenuous resistive breathing: comparison with whole body exercise and the effects of antioxidants

Andreas Asimakos,1,2,* Dimitrios Toumpanakis,1,2,* Maria-Helena Karatza,3 Spyridoula Vasileiou,3 Paraskevi Katsaounou,1,2 Zafeiria Mastora,1,2 Theodoros Vassilakopoulos1,2,4 1GP Livanos and M Simou Laboratories, Thorax Foundation, 2Critical Care Department and Pulmonary Unit, Evangelismos Hospital, Medical School, National and Kapodistrian University of Athens, 3Flow Cytometry Unit, Hematology Clinic Evangelismos Hospital, 43rd Department of Critical Care Medicine, Evgenideion Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece *These authors contributed equally to this work Background/hypothesis: Whole body exercise (WBE) changes lymphocyte subset percentages in peripheral blood. Resistive breathing, a hallmark of diseases of airway obstruction, is a form of exercise for the inspiratory muscles. Strenuous muscle contractions induce oxidative stress that may mediate immune alterations following exercise. We hypothesized that inspiratory resistive breathing (IRB) alters peripheral blood lymphocyte subsets and that oxidative stress mediates lymphocyte subpopulation alterations following both WBE and IRB.Patients and methods: Six healthy nonathletes performed two WBE and two IRB sessions for 45 minutes at 70% of VO2 maximum and 70% of maximum inspiratory pressure (Pimax), respectively, before and after the administration of antioxidants (vitamins E, A, and C for 75 days, allopurinol for 30 days, and N-acetylcysteine for 3 days). Blood was drawn at baseline, at the end of each session, and 2 hours into recovery. Lymphocyte subsets were determined by flow cytometry.Results: Before antioxidant supplementation at both WBE end and IRB end, the natural killer cell percentage increased, the T helper cell (CD3+ CD4+) percentage was reduced, and the CD4/CD8 ratio was depressed, a response which was abolished by antioxidants only after IRB. Furthermore, at IRB end, antioxidants promoted CD8+ CD38+ and blunted cytotoxic T-cell percentage increase. CD8+ CD45RA+ cell percentage changes were blunted after antioxidant supplementation in both WBE and IRB.Conclusion: We conclude that IRB produces (as WBE) changes in peripheral blood lymphocyte subsets and that oxidative stress is a major stimulus predominantly for IRB-induced lymphocyte subset alterations. Keywords: resistive breathing, exercise, antioxidants, lymphocyt

Immune cell response to strenuous resistive breathing: Comparison with whole body exercise and the effects of antioxidants

Background/hypothesis: Whole body exercise (WBE) changes lymphocyte subset percentages in peripheral blood. Resistive breathing, a hallmark of diseases of airway obstruction, is a form of exercise for the inspiratory muscles. Strenuous muscle contractions induce oxidative stress that may mediate immune alterations following exercise. We hypothesized that inspiratory resistive breathing (IRB) alters peripheral blood lymphocyte subsets and that oxidative stress mediates lymphocyte subpopulation alterations following both WBE and IRB. Patients and methods: Six healthy nonathletes performed two WBE and two IRB sessions for 45 minutes at 70% of VO2 maximum and 70% of maximum inspiratory pressure (Pimax), respectively, before and after the administration of antioxidants (vitamins E, A, and C for 75 days, allopurinol for 30 days, and N-acetylcysteine for 3 days). Blood was drawn at baseline, at the end of each session, and 2 hours into recovery. Lymphocyte subsets were determined by flow cytometry. Results: Before antioxidant supplementation at both WBE end and IRB end, the natural killer cell percentage increased, the T helper cell (CD3+ CD4+) percentage was reduced, and the CD4/CD8 ratio was depressed, a response which was abolished by antioxidants only after IRB. Furthermore, at IRB end, antioxidants promoted CD8+ CD38+ and blunted cytotoxic T-cell percentage increase. CD8+ CD45RA+ cell percentage changes were blunted after antioxidant supplementation in both WBE and IRB. Conclusion: We conclude that IRB produces (as WBE) changes in peripheral blood lymphocyte subsets and that oxidative stress is a major stimulus predominantly for IRB-induced lymphocyte subset alterations. © 2018 Asimakos et al

Relationship of BAL and lung tissue CD4+ and CD8+ T lymphocytes, and their ratio in idiopathic pulmonary fibrosis

Background: Surgical biopsy specimens have shown that T lymphocytes (TLs) infiltrate lung parenchyma in patients with idiopathic pulmonary fibrosis (IPF) and might play a pathogenetic role. BAL, a far less invasive technique, has also been used for the investigation of IPF pathogenesis. However, controversy exists whether the BAL fluid cellular profile reflects the cellular composition of the lung parenchyma. Study objective: To compare infiltrating TLs subpopulations (CD4+, CD8+, and CD4+/CD8+ ratio) in lung tissue and BAL fluid. Patients and methods: Immunohistochemistry was performed according to the streptavidin-biotin method on the surgical biopsy specimens of 12 untreated patients with IPF. The number of CD3+, CD4+, and CD8+ TLs was determined by observer-interactive computerized image analysis (SAMBA microscopic image processor; Meylan, France). In BAL fluid, the same TLs subpopulations were evaluated by flow cytometry. Results: In lung tissue, CD3+ TLs accounted for a mean (± SEM) of 28.8 ± 7% of total cells, CD4+ TLs accounted for 14.5 ± 4% of total cells (50.1 ± 4% of CD3+ TLs), and CD8+ TLs accounted for 13.8 ± 4% of total cells (47.4 ± 4% of CD3+ TLs). In BAL fluid, lymphocytes accounted for 9.8 ± 2.5% of total cells, CD4+ TLs accounted for 51.8 ± 4% of CD3+ TLs, and CD8+ TLs accounted for 42.2 ± 4% of CD3+ TLs. Tissue CD4+ and CD8+ TLs (expressed as a percentage of CD3+ TLs) correlated significantly with the number of CD4+ and CD8+ TLs in BAL fluid (r = 0.846 and p = 0.001 vs r = 0.692 and p = 0.013, respectively). A significant positive correlation was also found between the mean CD4+/CD8+ ratio found in tissue and BAL fluid (1.05 ± 0.21 and 1.5 ± 0.27, respectively; r = 0.832; p = 0.01). Conclusion: The results suggest that in patients with IPF, the TL subpopulations in BAL fluid reflect the pattern of lymphocytic infiltration in pulmonary parenchyma

CD8+T lymphocytes in bronchoalveolar lavage in idiopathic pulmonary fibrosis

Background. Recently it was shown that in Idiopathic Pulmonary Fibrosis (IPF) tissue infiltrating CD8+ T lymphocytes (TLs) are associated with breathlessness and physiological indices of disease severity, as well as that CD8+ TLs recovered by bronchoalveolar lavage (BAL) relate to those infiltrating lung tissue. Since BAL is a far less invasive technique than tissue biopsy to study mechanisms in IPF we further investigated the usefulness offered by this means by studying the relationship between BAL macrophages, neutrophils, eosinophils, CD3+, CD4+, CD8+, CD8+/38+ TLs and CD4+/CD8+ ratio with breathlessness and physiological indices. Patients and methods. 27 IPF patients, 63 ± 9 years of age were examined. Cell counts were expressed as percentages of total cells and TLs were evaluated by flow cytometry. FEV 1, FVC, TLC, RV, DLCO, PaO2, and PaCO2 were measured in all. Breathlessness was assessed by the Medical Research Council (MRC) chronic dyspnoea scale. Results. CD8+ TLs correlated positively (rs = 0.46, p = 0.02), while CD4+/CD8+ ratio negatively (rs = -0.54, p = 0.006) with the MRC grade. CD 8+ TLs correlated negatively with RV (rs = -0.50, p = 0.017). CD8+/38+ TLs were negatively related to the FEV1 and FVC (rs = -0.53, p = 0.03 and rs = -0.59, p = 0.02, respectively). Neutrophils correlated positively with the MRC grade (r s = 0.42, p = 0.03), and negatively with the DLCO (rs = -0.54, p = 0.005), PaO2 (rs = -0.44, p = 0.03), and PaCO2 (rs = -0.52, p = 0.01). Conclusion. BAL CD 8+ TLs associations with physiological and clinical indices seem to indicate their implication in IPF pathogenesis, confirming our previous tissue study. © 2007 Papiris et al; licensee BioMed Central Ltd