The fundamental problem considered in this paper is the choice of materials, in this case stainless steels, for a particular industrial purpose. The choice of the appropriate material should be made ...based on the material behavior database established by experimental investigations. The mechanical behavior and mechanical properties of several stainless steels, such as ferritic, martensitic and austenitic stainless steels are investigated and analyzed in this research. Mechanical properties at room and high temperatures, creep behavior at different high temperatures and different stress levels as well as Charpy fracture impact energy were considered for several of the steels mentioned. Fracture toughness, based on the Charpy impact energy is calculated using known analytical procedure. In this sense, material properties are determined based on displayed engineering stress-strain diagrams while material creep behavior is displayed in the form of creep curves. Some of numerical values regarding the ultimate tensile strength, measured at room temperature, are given using the following order and in the following form: σm, Mat.Nr20°C. In this sense, the stress levels of the u are: 9251.4122; 7821.4034; 7261.4305; 6861.4841; 5851.4762; 6071.454120°C.
The materials for making the construction elements are selected according to the required conditions and the available material properties. In this sense mechanical properties and material behavior ...of the materials such as 42CrMo4 steel, X46Cr13 steel and X6CrNiTi18-10 steel were investigated. Mechanical properties of the mentioned materials are shown in the form of engineering stress-strain diagrams, creep behavior is presented in the form of creep curves while uniaxial fatigue of these materials are given using life diagrams. These materials differ in chemical composition, their strength properties differ within 20% while their fatigue limits are significantly different.
In this article experimentally obtained data related to material mechanical properties, material behavior at elevated temperatures and numerical modeling of material creep responses are presented. ...Tensile tests at different elevated temperatures are carried out, and for some of these temperatures one-dimensional short time creep tests for different constant stresses are made. Before presented experimental investigations the used materials were not treated. The curves representing specimen strain elongation are also presented. The materials under consideration are 56NiCrMoV7 (1.2714) and X153CrMoV12 (1.2379).
Macrophages play major roles in the onset of immune responses and inflammation by inducing a variety of cytokines such as TNF and IFN‐β. The pathogen‐associated molecular pattern, ...polyinosinic‐polycytidylic acid poly(I:C), and LPS were used to study type‐I IFN and TNF responses in human macrophages. Additionally, activation of the key signaling pathways, IFN‐regulatory factor 3 (IRF3) and NF‐κB, were studied. We found that TNF production occurred rapidly after LPS stimulation. LPS induced a strong IFN‐β mRNA response within a short time‐frame, which subsided at 8 h. The IFN‐stimulated genes (ISGs), ISG56 and IFN‐inducible protein 10, were strongly induced by LPS. These responses were associated with NF‐κB and IRF3 activation, as shown by IRF3 dimerization and by nuclear translocation assays. poly(I:C), on the other hand, induced a strong and long‐lasting (>12 h) IFN‐β mRNA and protein response, particularly when transfected, whereas only a protracted TNF response was observed when poly(I:C) was transfected. However, these responses were induced in the absence of detectable IRF3 and NF‐κB signaling. Thus, in human macrophages, poly(I:C) treatment induces a distinct cytokine response when compared with murine macrophages. Additionally, a robust IFN‐β response can be induced in the absence of detectable IRF3 activation.
Summary
We have shown previously that in listeric encephalitis of cattle and rats, nitrotyrosine was produced in microabscesses, implying that both superoxide anion (O2–) and nitric oxide (NO) are ...present and react with each other. Evidence of local synthesis of NO by macrophages was provided, but the source of O2– remained unknown. Here we have examined whether phagocytes exposed to viable and heat‐killed Listeria monocytogenes (LMΔ) produce O2– and, if so, whether this results from direct interaction of phagocytes with the bacterial surface of L. monocytogenes or whether prior opsonization is required. Using lucigenin‐enhanced chemiluminescence (LCL) for the measurement of O2–, we show that LMΔ induces an oxidative burst in human neutrophils, monocytes and monocyte‐derived macrophages (Mφ). Viability is not required, and opsonization by antibodies and/or complement does not enhance the LCL signal. As Toll‐like receptors (TLR) were shown recently to mediate an oxidative burst, TLR agonists representative for pathogen‐associated molecular patterns (PAMPs) were tested for their ability to elicit an oxidative burst. These included lipoteichoic acid (LTA), bacterial peptidoglycan (PGN), recombinant flagellin, CpG‐containing DNA and double‐stranded RNA. Only PGN and flagellin consistently elicited an LCL signal resembling that induced by LMΔ with regard to the kinetics and cell spectrum stimulated. However, flagellin was unlikely to be responsible for the LMΔ‐mediated burst, as a flagellin‐deficient mutant showed no decrease in LCL. We therefore assume that in LMΔ, core PGN acts as a PAMP and directly induces an oxidative burst in all phagocyte populations. We conclude that in cerebral lesions superoxide anion is generated locally by phagocytes recognizing bacterial PGN.
Dendritic cells (DC) are important cells at the interface between innate and adaptive immunity. DC have a key role in antigen processing and presentation to T cells. Effector functions of DC related ...to innate immunity have not been explored extensively. We show that bovine monocyte-derived DC (mDC) express inducible nitric oxide synthase (iNOS) mRNA and protein and produce NO upon triggering with interferon-γ (IFN-γ) and heat-killed
Listeria monocytogenes (HKLM). An immunocytochemical analysis revealed that a sizeable subset (20–60%) copiously expresses iNOS (iNOS
hi) upon IFN-γ/HKLM triggering, whereas the other subset expressed low levels of iNOS (iNOS
lo). Monocyte-derived macrophages (mMϕ) are more homogeneous with regard to iNOS expression. The number of cells within the iNOS
lo mDC subset is considerably larger than the number of dead cells or cells unresponsive to IFN-γ/HKLM. The large majority of cells translocated p65 to the nucleus upon triggering by IFN-γ/HKLM. A contamination of mDC with iNOS-expressing mMϕ was excluded as follows. (i) Cell surface marker analysis suggested that mDC were relatively homogeneous, and no evidence for a contaminating subset expressing macrophage markers (e.g. high levels of CD14) was obtained. (ii) iNOS expression was stronger in iNOS
hi mDC than in mMϕ. The use of maturation-promoting stimuli revealed only subtle phenotypic differences between immature and mature DC in cattle. Nevertheless, these stimuli promoted development of considerably fewer iNOS
hi mDC upon triggering with IFN-γ/HKLM. Immunocytochemical results showed that although a significant proportion of cells expressed iNOS only or TNF only upon triggering with IFN-γ/HKLM, a significant number of cells expressed both iNOS and TNF, suggesting that TNF and iNOS producing (TIP) DC are present within bovine mDC populations obtained in vitro.
The paper at hand deals with the single layered graphene sheets. In particular, the influence of the vacancy location and the density of vacancies on the bending behavior are investigated. The ...nanomechanical model is based on the structural mechanics approach with covalent bonds modeled as beam finite elements. The used graphene sheet model is described in detail and the obtained results are presented and thoroughly discussed.
It is a requirement that parenteral medicines be tested for pyrogens (fever causing agents) using one of two animal-based tests: the rabbit pyrogen test and the bacterial endotoxin test. ...Understanding the human fever reaction has led to novel non-animal alternative tests based on in vitro activation of human monocytoid cells in response to pyrogens. Using 13 prototypic drugs, clean or contaminated with pyrogens, we have validated blindly six novel pyrogen tests in ten laboratories. Compared with the rabbit test, the new tests have a lower limit of detection and are more accurate as well as cost and time efficient. In contrast to the bacterial endotoxin test, all tests are able to detect Gram-positive pyrogens. The validation process showed that at least four of the tests meet quality criteria for pyrogen detection. These validated in vitro pyrogen tests overcome several shortcomings of animal-based pyrogen tests. Our data suggest that animal testing could be completely replaced by these evidence-based pyrogen tests and highlight their potential to further improve drug safety.
Listeria monocytogenes (LM) is a Gram-positive facultative intracellular bacterium that causes fatal meningoencephalitis in humans and ruminants. A current paradigm predicts that intracellular ...bacteria are controlled by nitric oxide (NO) whose synthesis is catalyzed by inducible nitric oxide synthase (iNOS). The ability of macrophages (MΦ) to express iNOS shows extreme interspecies variability. Here the expression of iNOS and synthesis of NO was studied in listeric encephalitis of cattle, sheep, and goats. iNOS was expressed by a subset of MΦ in cerebral microabscesses in all three species. The level of iNOS expression and the density of cells per lesion expressing iNOS was highest in cattle, intermediate in sheep, and lowest in goats. The accumulation of nitrotyrosine (NT), an indicator of local NO synthesis, was observed in lesions of cattle but not in those of small ruminants. The density of iNOS-expressing cells in lesions was inversely correlated with the number of bacteria. No species differences were observed in regard to reactive oxygen intermediate (ROI) production by stimulated granulocytes, using the flow cytometric dihydrorhodamine-123 (DHR) method indicating ROI generation. Thus, the marked species differences in iNOS expression, NT accumulation, and LM content in lesions of ruminants with listeric encephalitis are explained by different amounts of ROI produced. It suggests that variations in the ability of MΦ to synthesize NO are of pathophysiological significance in listeriosis.
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