1,726 research outputs found
DEM simulation of the mechanical properties of SiC ceramic under pre-stressing
In this paper, the method of discrete element model (DEM) simulation was used to investigate the mechanical properties of SiC ceramic materials under the action of pre-stress. Using the bonded particle model (BPM), several different numerical tests (such as UCT, TPB, SENB tests) of SiC ceramic were established. Different pre-stress values were applied on the lateral surface of the ceramic specimen during the numerical simulation process, all tests were carried out at least 5 times with different random number, and the average mechanical properties results were calculated. It was showed that the existence of pre-stress has a significant effect on the mechanical properties of materials. It can enhance the strength of materials, while the force action on material in machining process force or action force the crack’s initiation and propagation was limited
Domain Growth and Finite-Size-Scaling in the Kinetic Ising Model
This paper describes the application of finite-size scaling concepts to
domain growth in systems with a non-conserved order parameter. A finite-size
scaling ansatz for the time-dependent order parameter distribution function is
proposed, and tested with extensive Monte-Carlo simulations of domain growth in
the 2-D spin-flip kinetic Ising model. The scaling properties of the
distribution functions serve to elucidate the configurational self-similarity
that underlies the dynamic scaling picture. Moreover, it is demonstrated that
the application of finite-size-scaling techniques facilitates the accurate
determination of the bulk growth exponent even in the presence of strong
finite-size effects, the scale and character of which are graphically exposed
by the order parameter distribution function. In addition it is found that one
commonly used measure of domain size--the scaled second moment of the
magnetisation distribution--belies the full extent of these finite-size
effects.Comment: 13 pages, Latex. Figures available on request. Rep #9401
Immunomodulatory interventions in myocardial infarction and heart failure: a systematic review of clinical trials and meta-analysis of IL-1 inhibition
Following a myocardial infarction (MI), the immune system helps to repair ischaemic damage and restore tissue integrity, but excessive inflammation has been implicated in adverse cardiac remodelling and development towards heart failure (HF). Pre-clinical studies suggest that timely resolution of inflammation may help prevent HF development and progression. Therapeutic attempts to prevent excessive post-MI inflammation in patients have included pharmacological interventions ranging from broad immunosuppression to immunomodulatory approaches targeting specific cell types or factors with the aim to maintain beneficial aspects of the early post-MI immune response. These include the blockade of early initiators of inflammation including reactive oxygen species and complement, inhibition of mast cell degranulation and leucocyte infiltration, blockade of inflammatory cytokines, and inhibition of adaptive B and T-lymphocytes. Herein, we provide a systematic review on post-MI immunomodulation trials and a meta-analysis of studies targeting the inflammatory cytokine Interleukin-1. Despite an enormous effort into a significant number of clinical trials on a variety of targets, a striking heterogeneity in study population, timing and type of treatment, and highly variable endpoints limits the possibility for meaningful meta-analyses. To conclude, we highlight critical considerations for future studies including (i) the therapeutic window of opportunity, (ii) immunological effects of routine post-MI medication, (iii) stratification of the highly diverse post-MI patient population, (iv) the potential benefits of combining immunomodulatory with regenerative therapies, and at last (v) the potential side effects of immunotherapies
Scanning electron microscopy image representativeness: morphological data on nanoparticles.
A sample of a nanomaterial contains a distribution of nanoparticles of various shapes and/or sizes. A scanning electron microscopy image of such a sample often captures only a fragment of the morphological variety present in the sample. In order to quantitatively analyse the sample using scanning electron microscope digital images, and, in particular, to derive numerical representations of the sample morphology, image content has to be assessed. In this work, we present a framework for extracting morphological information contained in scanning electron microscopy images using computer vision algorithms, and for converting them into numerical particle descriptors. We explore the concept of image representativeness and provide a set of protocols for selecting optimal scanning electron microscopy images as well as determining the smallest representative image set for each of the morphological features. We demonstrate the practical aspects of our methodology by investigating tricalcium phosphate, Ca3 (PO4 )2 , and calcium hydroxyphosphate, Ca5 (PO4 )3 (OH), both naturally occurring minerals with a wide range of biomedical applications
The effect of finite-range interactions in classical transport theory
The effect of scattering with non-zero impact parameters between consituents
in relativistic heavy ion collisions is investigated. In solving the
relativistic Boltzmann equation, the characteristic range of the collision
kernel is varied from approximately one fm to zero while leaving the mean-free
path unchanged. Modifying this range is shown to significantly affect spectra
and flow observables. The finite range is shown to provide effective
viscosities, shear, bulk viscosity and heat conductivity, with the viscous
coefficients being proportional to the square of the interaction range
Stimulation of Brain AMP-activated Protein Kinase Attenuates Inflammation and Acute Lung Injury in Sepsis
Sepsis and septic shock are enormous public health problems with astronomical financial repercussions on health systems worldwide. The central nervous system (CNS) is closely intertwined in the septic process but the underlying mechanism is still obscure. AMP-activated protein kinase (AMPK) is a ubiquitous energy sensor enzyme and plays a key role in regulation of energy homeostasis and cell survival. In this study, we hypothesized that activation of AMPK in the brain would attenuate inflammatory responses in sepsis, particularly in the lungs. Adult C57BL/6 male mice were treated with 5-aminoimidazole-4-carboxamide riboneucleotide (AICAR, 20 ng), an AMPK activator, or vehicle (normal saline) by intracerebro-ventricular (ICV) injection, followed by cecal ligation and puncture (CLP) at 30 min post-ICV. The septic mice treated with AICAR exhibited elevated phosphorylation of AMPKalpha in the brain along with reduced serum levels of aspartate aminotransferase, tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6), compared to the vehicle. Similarly, the expressions of TNF-alpha, IL-1beta, keratinocyte-derived chemokine and macrophage inflammatory protein-2 as well as myeloperoxidase activity in the lungs of AICAR-treated mice were significantly reduced. Moreover, histological findings in the lungs showed improvement of morphologic features and reduction of apoptosis with AICAR treatment. We further found that the beneficial effects of AICAR on septic mice were diminished in AMPKalpha2 deficient mice, showing that AMPK mediates these effects. In conclusion, our findings reveal a new functional role of activating AMPK in the CNS to attenuate inflammatory responses and acute lung injury in sepsis
Blocking cold-inducible RNA-binding protein protects liver from ischemia-reperfusion injury
Cold-inducible RNA-binding protein (CIRP) is a nuclear protein that has been recently identified as a novel inflammatory mediator in hemorrhagic shock and sepsis. We hypothesized that CIRP acts as a potent inflammatory mediator in hepatic ischemia-reperfusion (I/R), and thus blocking CIRP protects against I/R-induced liver injury. Male C57BL/6 mice were subjected to 70% hepatic ischemia by microvascular clamping of the hilum of the left and median liver lobes for 60 min, followed by reperfusion. Anti-CIRP antibody (1 mg/kg body weight) or vehicle (normal saline) in 0.2 mL was injected via the internal jugular vein at the beginning of the reperfusion. Blood and liver tissues were collected 24 h after I/R for various measurements, and a 10-day survival study was performed. Cold-inducible RNA-binding protein released into the circulation was significantly increased 24 h after hepatic I/R. Anti-CIRP antibody treatment markedly reduced hepatocellular damage markers and significantly improved the liver microarchitecture. Anti-CIRP also reduced the systemic and local inflammation demonstrated by attenuation in both serum and hepatic levels of interleukin 6. The expression of neutrophil-attracting chemokine as well as liver neutrophil infiltration was reduced by anti-CIRP treatment. Anti-CIRP also dramatically decreased the amount of apoptosis and nitrosative stress, evidenced by decrease in TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining and inducible nitric oxide synthase and cyclooxygenase 2 levels, respectively. Finally, the 10-day survival rate was increased from 37.5% in the vehicle group to 75% in the anti-CIRP treatment group. Thus, targeting CIRP offers potential therapeutic implications in the treatment of hepatic I/R injury
Regge Trajectories for Mesons in the Holographic Dual of Large-N_c QCD
We discuss Regge trajectories of dynamical mesons in large-N_c QCD, using the
supergravity background describing N_c D4-branes compactified on a thermal
circle. The flavor degrees of freedom arise from the addition of N_f<<N_c D6
probe branes. Our work provides a string theoretical derivation, via the
gauge/string correspondence, of a phenomenological model describing the meson
as rotating point-like massive particles connected by a flux string. The
massive endpoints induce nonlinearities for the Regge trajectory. For light
quarks the Regge trajectories of mesons are essentially linear. For massive
quarks our trajectories qualitatively capture the nonlinearity detected in
lattice calculations.Comment: 21 pages, 4 figures. v2: typos corrected, references and
acknowledgments adde
Termination of the Phase of Quintessence by Gravitational Back-Reaction
We study the effects of gravitational back-reaction in models of
Quintessence. The effective energy-momentum tensor with which cosmological
fluctuations back-react on the background metric will in some cases lead to a
termination of the phase of acceleration. The fluctuations we make use of are
the perturbations in our present Universe. Their amplitude is normalized by
recent measurements of anisotropies in the cosmic microwave background, their
slope is taken to be either scale-invariant, or characterized by a slightly
blue tilt. In the latter case, we find that the back-reaction effect of
fluctuations whose present wavelength is smaller than the Hubble radius but
which are stretched beyond the Hubble radius by the accelerated expansion
during the era of Quintessence domination can become large. Since the
back-reaction effects of these modes oppose the acceleration, back-reaction
will lead to a truncation of the period of Quintessence domination. This result
impacts on the recent discussions of the potential incompatibility between
string theory and Quintessence.Comment: 7 pages a few clarifying comments adde
Facile and ultraclean graphene-on-glass nanopores by controlled electrochemical etching
Supramolecular & Biomaterials Chemistr
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