Study of the Fractures in Slowly Driven Dominated Threshold Systems

Fracture mechanics plays an important role in the material science, structure design and industrial production due to the failure of materials and structures are paid high attention in human activities. For this reason, the fracture mechanics can be considered today one of the most important research fields in engineering. The attempts to predict the failure of a material are able to link different disciplines: in this dissertation, a very deep use of the statistical physics will be done in order to try to introduce the disorder of the medium into the breaking and to a give a new point of view to the fracture mechanics. In the following, we will introduce a new kind of model to evaluate the genesis of the crack: the statistical central force model. As we will see, this model tries to compute the genesis of the fracture in a medium by taking into account the presence of defects of the material that are the main cause of the differences between the critical theoretical strength of a material and the real one. This innovation introduced by this model which is difficult to find in other kinds of techniques existing today united to the fact that we try to predict the behaviour of a macro system by knowing exactly the statistical behaviour of the micro-components of the system itself (the trusses) like in complex systems happens, is the main innovation of the statistical central force model. The model consists of a truss structure in which each truss is representative of a little portion of the material. Since this model was already applied in static for a porous medium in literature, we will study it from a mathematical viewpoint and we will apply it to the study of the dynamic of a dry medium before (the applications could be for the study of the fracture in metals and composites with loads changing in time) and of a porous medium later (in order to study the fracking into soils and the fracture of the concrete). Further developments could bring us to develop the same method for the study of the spalling in the concrete because of the application of a thermal load. In the dissertation we will introduce the mathematical tools to understand this model and some simulation on generic media will be realized. This dissertation consists basically of five chapters. In chapter 1 a brief description of the state of the art will be given: we will leave from the birth of the classical elastic fracture mechanics and we will shortly talk about the fracture mechanics in a plastic field. After this we will describe two important techniques used today for the evaluation of the crack: the XFem and the Peridynamics; the first one is a numerical technique allowing the FEM to take into account the possibility to create a breaking into the material. This is done, as we will see, by adding further degrees of freedom to the finite elements. In this way a single finite element will have the possibility to “open” itself and to simulate a discontinuous field of displacements, which is the main problem concerning with FEM in calculating the fracture. The second one is a theory that postulates that each medium can be divided in particles and that each particle interacts with its own neighbours within a given horizon. From which we get the word “peri”. By this assumption it is possible to get some integro-equations that can be defined on the surfaces of the tips and of the cracks as well. In chapter 2 we will talk about the so called Fiber Bundle Model which is the basis of our statistical model. We will talk about the dry FBM that was already studied at the beginning of ’90s from a mathematical viewpoint : it consists of a bundle of fibers clamped at one edge and free to move to the other one. The model is one dimensional and it is probably one of the most naïve models to begin to study the fracture; however, despite to its simplicity, it contains an important tool: the possibility to take into account the defects of the medium by introducing the concept of variable thresholds in stress. As we will see, these thresholds will be picked up by a probability density function. Then we will apply the theory of the statistical ensembles to study one of the extensions of the FBM: the continuous fiber bundle model. This is necessary to have an idea of how the micro-components of our model, the trusses, behave in a truss structure subject to an external load. In chapter 3 we will report briefly the theory of the porous medium according to the mixture theories of De Boer. So an overview about the equations will be given and then we will discretize these equations according to the finite element technique. After this, we will briefly describe in which part of the algorithm the concept of imperfection/threshold in stress enters. We will do this for a dry medium and for a porous medium in dynamics. In chapter 4 we will report the numerical results. Some simulations in dynamics will be done both for a dry medium and for a porous medium. Furthermore we will introduce in the end a new damage law that will have a precise statistical meaning: it will be the average among all the possible realizations of the constitutive laws of our truss structure and for a big number of trusses, it will become the constitutive behaviour of our structure from which to get the damage law. And this result will take into account the disorder of the medium. In chapter 5 we will talk about a controversial argument: the Self Organized Criticality (SOC) that was sticked in previous papers to the statistical central model. We will try to understand what SOC is and if our system with our algorithm to compute the fracture gets the necessary and sufficient conditions to enter into the set of the SOC systems. At the end of our journey we will have hopefully done a first step into the description of a new numerical tool to evaluate the crack into a generic medium without needing an initial discontinuity to develop the crack itself. The next steps will be to validate this technique for existing materials and to compare it to other numerical tools like XFem or Peridynamics. After this, the future will be to extend the technique passing from trusses to 2D elements

Ned-19 inhibition of parasite growth and multiplication suggests a role for NAADP mediated signalling in the asexual development of plasmodium falciparum

BACKGROUND: Although malaria is a preventable and curable human disease, millions of people risk to be infected by the Plasmodium parasites and to develop this illness. Therefore, there is an urgent need to identify new anti-malarial drugs. Ca2+ signalling regulates different processes in the life cycle of Plasmodium falciparum, representing a suitable target for the development of new drugs. RESULTS: This study investigated for the first time the effect of a highly specific inhibitor of nicotinic acid adenine dinucleotide phosphate (NAADP)-induced Ca2+ release (Ned-19) on P. falciparum, revealing the inhibitory effect of this compound on the blood stage development of this parasite. Ned-19 inhibits both the transition of the parasite from the early to the late trophozoite stage and the ability of the late trophozoite to develop to the multinucleated schizont stage. In addition, Ned-19 affects spontaneous intracellular Ca2+ oscillations in ring and trophozoite stage parasites, suggesting that the observed inhibitory effects may be associated to regulation of intracellular Ca2+ levels. CONCLUSIONS: This study highlights the inhibitory effect of Ned-19 on progression of the asexual life cycle of P. falciparum. The observation that Ned-19 inhibits spontaneous Ca2+ oscillations suggests a potential role of NAADP in regulating Ca2+ signalling of P. falciparum

Plasma polymerization for biomedical applications: A review

Plasma polymers have long been of interest as thin film coatings on biomedical devices and products, to generate desirable surface properties for favorable bio-interfacial interactions. Plasma polymers have also been used as platforms for the covalent immobilization of bioactive molecules. More recently, additional aspects have been investigated, such as selective prevention of adhesion of microbial pathogens, either via plasma polymers per se or including antimicrobial drugs. Plasma polymers have also been investigated for the release of silver ions and small organic molecules. Complementing low-pressure plasma approaches, processes at atmospheric pressure have attracted interest recently, including for nano/biocomposite coatings. This contribution reviews the use of plasma polymers for intended biomedical applications, with a focus on more recent topic areas

Validation of colorimetric assays for hydrogen peroxide, nitrate and nitrite ions in complex plasma-treated water solutions

AbstractLiquids treated with cold plasma emerged as 'redox drugs' in biomedicine, as sources of reactive oxygen and nitrogen species targeting cellular functions, including wound healing and cancer progression. The use of cell culture media as starting liquid, however, challenges the identification of plasma‐generated chemistry, limited by the presence of many reactive species and organic compounds. Available detection methods need, therefore, to be confirmed in these liquids to avoid inaccurate results. In this research, robustness, linearity, accuracy and specificity of three colorimetric assays are investigated to detect H2O2, NO2− and NO3−, predominant plasma‐induced products. The results clearly highlight the presence of some factors affecting the detection in cell culture media like high concentrations of chlorides found interfering with the detection of NO3− in the medium

The long noncoding RNA linc-NeD125 controls the expression of medulloblastoma driver genes by microRNA sponge activity

Long noncoding RNAs (lncRNAs) are major regulators of physiological and disease-related gene expression, particularly in the central nervous system. Dysregulated lncRNA expression has been documented in several human cancers, and their tissue-specificity makes them attractive candidates as diagnostic/prognostic biomarkers and/or therapeutic agents. Here we show that linc-NeD125, which we previously characterized as a neuronal-induced lncRNA, is significantly overexpressed in Group 4 medulloblastomas (G4 MBs), the largest and least well characterized molecular MB subgroup. Mechanistically, linc-NeD125 is able to recruit the miRNA-induced silencing complex (miRISC) and to directly bind the microRNAs miR-19a-3p, miR-19b-3p and miR-106a-5p. Functionally, linc-NeD125 acts as a competing endogenous RNA (ceRNA) that, sequestering the three miRNAs, leads to de-repression of their targets CDK6, MYCN, SNCAIP, and KDM6A, which are major driver genes of G4 MB. Accordingly, linc-NeD125 downregulation reduces G4 cell proliferation. Moreover, we also provide evidence that linc-NeD125 ectopic expression in the aggressive Group 3 MB cells attenuates their proliferation, migration and invasion. This study unveils the first lncRNA-based ceRNA network in central nervous system tumours and provides a novel molecular circuit underlying the enigmatic Group 4 medulloblastoma

Plasma Treated Water Solutions in Cancer Treatments: The Contrasting Role of RNS

Abstract: Plasma Treated Water Solutions (PTWS) recently emerged as a novel tool for the generation of Reactive Oxygen and Nitrogen Species (ROS and RNS) in liquids. The presence of ROS with a strong oxidative power, like hydrogen peroxide (H2O2), has been proposed as the main effector for the cancer‐killing properties of PTWS. A protective role has been postulated for RNS, with nitric oxide (NO) being involved in the activation of antioxidant responses and cell survival. However, recent evidences proved that NO‐derivatives in proper mixtures with ROS in PTWS could enhance rather than reduce the selectivity of PTWS‐induced cancer cell death through the inhibition of specific antioxidant cancer defenses. In this paper we discuss the formation of RNS in different liquids with a Dielectric Barrier Discharge (DBD), to show that NO is absent in PTWS of complex composition like plasma treated (PT)‐cell culture media used for in vitro experiments, as well as its supposed protective role. Nitrite anions (NO2‐) instead, present in our PTWS, were found to improve the selective death of Saos2 cancer cells compared to EA.hy926 cells by decreasing the cytotoxic threshold of H2O2 to non‐toxic values for the endothelial cell line

Plasma activated water and airborne ultrasound treatments for enhanced germination and growth of soybean

The effect of two novel technologies, also in combination, on germination and growth of soybeans has been investigated. On one side, ultrasound treatment of the seeds increased water uptake without altering the morphology and the wettability of the seed coat, but also induced slight chemical modifications of the outer part of the seed. Plasma-activated water (PAW), obtained from treating water with non-thermal atmospheric-pressure plasma in air, increased the rate of germination and subsequent plant growth. Different combinations of these two technologies were tested in order to study their interaction and to identify an optimum treatment process. Industrial relevance A great urgency in crop management is to enhance sustainability. The aim is to achieve a cheap and eco-friendly production process reducing the wide current use of energy, irrigation water, chemicals and pesticides. Soybeans is a legume whose worldwide production is increasing in the last years therefore a higher efficiency and sustainability in its cultivation is obviously very appealing. Cold plasma and Ultrasound technologies are well-known in the industrial scenario and their applications in crop production are recently drawing attention; the potential of combining these two powerful techniques is clearly very promising

Substrate reduction therapy with Miglustat in pediatric patients with GM1 type 2 gangliosidosis delays neurological involvement: A multicenter experience

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A Multicenter Retrospective Survey regarding Diabetic Ketoacidosis Management in Italian Children with Type 1 Diabetes

We conducted a retrospective survey in pediatric centers belonging to the Italian Society for Pediatric Diabetology and Endocrinology. The following data were collected for all new-onset diabetes patients aged 0-18 years: DKA (pH < 7.30), severe DKA (pH < 7.1), DKA in preschool children, DKA treatment according to ISPAD protocol, type of rehydrating solution used, bicarbonates use, and amount of insulin infused. Records (n = 2453) of children with newly diagnosed diabetes were collected from 68/77 centers (87%), 39 of which are tertiary referral centers, the majority of whom (n = 1536, 89.4%) were diagnosed in the tertiary referral centers. DKA was observed in 38.5% and severe DKA in 10.3%. Considering preschool children, DKA was observed in 72%, and severe DKA in 16.7%. Cerebral edema following DKA treatment was observed in 5 (0.5%). DKA treatment according to ISPAD guidelines was adopted in 68% of the centers. In the first 2 hours, rehydration was started with normal saline in all centers, but with different amount. Bicarbonate was quite never been used. Insulin was infused starting from third hour at the rate of 0.05-0.1 U/kg/h in 72% of centers. Despite prevention campaign, DKA is still observed in Italian children at onset, with significant variability in DKA treatment, underlying the need to share guidelines among centers