Necessary and sufficient conditions for componentwise stability of interval matrix systems

In the asymptotic stability (AS) analysis of interval matrix systems, some results are available that operate only as sufficient conditions, based on a unique test matrix, adequately built from the interval matrix. Our note reveals the complete role of this test matrix for fully characterizing the componentwise asymptotic stability (CWAS) of interval matrix systems. CWAS is a special type of AS which ensures the flow invariance of certain time-dependent sets with respect to the state-space trajectories. Hence, the sufficient conditions for AS get a new and deeper meaning by their reformulation as necessary and sufficient conditions with respect to the stronger property of CWAS.     

Modeling task systems using parameterized partial orders

Inspired by work on model-based design of printers, the notion of a parametrized partial order (PPO) has recently been introduced. PPOs are a simple extension of partial orders, expressive enough to compactly represent large task graphs with finite repetitive behavior. We present a translation of a subclass of PPOs to timed automata and prove that the transition system induced by the Uppaal models is isomorphic to the configuration structure of the original PPO. Moreover, we introduce real-time task systems (RTTSs), a general model for real-time embedded systems that we have used to describe the data paths of realistic printer designs. In an RTTS, tasks are represented as PPOs and the pace of a task instance may vary, depending on the resources that are allocated to it. We describe a translation of a subclass of RTTSs to Uppaal, and establish, for an even smaller subclass, bisimulation equivalence between the timed configuration semantics of an RTTS and the transition system induced by the corresponding Uppaal translation. Lastly, we report on a series of experiments which demonstrates that the resulting Uppaal models are more tractable than handcrafted models of the same systems used in earlier case studies.     

Identification and spectral properties of PAHs in carbonaceous material produced by laser pyrolysis

Carbonaceous materials have been prepared by laser-induced pyrolysis of a mixture of hydrocarbons (C₂H₂, C₂H₄, and benzene) under different conditions. We have investigated the soluble and insoluble part of the condensed carbon powders with several techniques, such as UV/VIS and IR spectroscopy, mass spectroscopy, gas chromatography combined with mass and IR spectrometry and high-performance liquid chromatography (HPLC) in order to obtain information on the total content and composition of the extracted soluble part and on the influence of the soluble component on the spectroscopic properties of the condensed carbon nanopowder. It has been found that the extract contains more than 64 different polycyclic aromatic hydrocarbons (PAHs). The most abundant PAH molecules are those containing 3–5 rings. The total amount of aromatic soluble components depends on the temperature in the condensation zone whereas the ratio between high- and low-mass PAHs is influenced by both, the temperature and the precursor gases. IR spectroscopic investigations of the extract have shown partial hydrogenation of PAHs leading to the formation of CH₂ groups, at the edge of PAH molecules. The IR spectral properties of the carbonaceous materials and of the PAHs are influenced by the adsorption process.     

Sample-based cameras for feed forward reflection rendering

This paper presents sample-based cameras for rendering high quality reflections on convex reflectors at interactive rates. The method supports change of view, moving objects and reflectors, higher order reflections, view-dependent lighting of reflected objects, and reflector surface properties. In order to render reflections with the feed forward graphics pipeline, one has to project reflected vertices. A sample-based camera is a collection of BSP trees of pinhole cameras that jointly approximate the projection function. It is constructed from the reflected rays defined by the desired view and the scene reflectors. A scene point is projected by invoking only the cameras that contain it in their frustums. Reflections are rendered by projecting the scene geometry and then rasterizing in hardware     

Carbon nanopowders from the continuous-wave CO2 laser-induced pyrolysis of ethylene

Carbon nanopowders were obtained by the laser pyrolysis of ethylene. The high-temperature gradients and very rapid reaction times characteristic of the process lead to the formation of very fine powders. Carbon powders obtained in runs with different laser power values (400–900 W), pressures (250–950 mbar), and gas flows (100–300 sccm) were characterised by transmission electron microscopy (TEM), including high-resolution mode (HREM), electron energy loss spectroscopy (EELS), X-ray diffraction (XRD) and Raman spectroscopy. The carbon particles were found to be approximately spherical in shape, with diameters around 45 nm, which may coalesce into larger agglomerates. The particles were found to be made up of layers forming a turbostratic structure. The experimental parameters influence the soot morphology and particle microstructure. Increasing the laser power and gas pressure leads to less coalescence and increased order. Structural parameters are presented for particles produced under different conditions.     

Protective Role of Melatonin and Its Metabolites in Skin Aging

The skin, being the largest organ in the human body, is exposed to the environment and suffers from both intrinsic and extrinsic aging factors. The skin aging process is characterized by several clinical features such as wrinkling, loss of elasticity, and rough-textured appearance. This complex process is accompanied with phenotypic and functional changes in cutaneous and immune cells, as well as structural and functional disturbances in extracellular matrix components such as collagens and elastin. Because skin health is considered one of the principal factors representing overall “well-being” and the perception of “health” in humans, several anti-aging strategies have recently been developed. Thus, while the fundamental mechanisms regarding skin aging are known, new substances should be considered for introduction into dermatological treatments. Herein, we describe melatonin and its metabolites as potential “aging neutralizers”. Melatonin, an evolutionarily ancient derivative of serotonin with hormonal properties, is the main neuroendocrine secretory product of the pineal gland. It regulates circadian rhythmicity and also exerts anti-oxidative, anti-inflammatory, immunomodulatory, and anti-tumor capacities. The intention of this review is to summarize changes within skin aging, research advances on the molecular mechanisms leading to these changes, and the impact of the melatoninergic anti-oxidative system controlled by melatonin and its metabolites, targeting the prevention or reversal of skin aging.     

Polyester/lignosulfonate blends with enhanced properties

The compatibility of poly(ethylene terephthalate) and its copolymer containing isophthalate units with epoxy-modified lignin has been studied. The following methods have been used: DSC, thermogravimetry, IR spectroscopy, contact angle measurements and dielectric properties determination. The optimum compatibility ratios and the necessity of a partial crosslinking with 4,4′-diaminodiphenylmethane to obtain a stable morphology have been established.     

In Vitro Studies Regarding the Safety of Chitosan and Hyaluronic Acid-Based Nanohydrogels Containing Contrast Agents for Magnetic Resonance Imaging

The aim of this study was to investigate the biocompatibility of contrast agents, such as gadolinium 1, 4, 7, 10 tetraazacyclo-dodecane tetraacetic acid (GdDOTA) and gadolinium dioctyl terephthalate (GdDOTP), encapsulated in a polymeric matrix containing chitosan and hyaluronic acid using RAW264.7 murine macrophages and human blood samples. The cell viability and cytotoxicity were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays, while cell cycle analysis was determined in RAW264.7 cells using flow cytometry. The mitochondrial membrane potential (MMP), hemolytic index, complement activation, and thrombogenic potential of gadolinium (Gd) containing nanohydrogels were measured by fluorometric and spectrophotometric methods. Taken together, our results demonstrate the good bio- and hemocompatibility of chitosan-based nanohydrogels with the RAW264.7 cell line and human blood cells, suggesting that these could be used as injectable formulations for the magnetic resonance imaging diagnostic of lymph nodes.