Synergistic effects of surface grafting with heparin and addition of poly(d,l-lactide) microparticles on properties of poly(l-lactide) single crystals scaffolds

Mixtures of heparin grafted poly(l- lactide) single crystals (Hep-PLLA_sc) and poly(d ,l- lactide) (PDLLA) microparticles are used for assembling hydrophilic and cytocompatible three-dimensional tissue engineering scaffolds simply by compression molding/salt leaching technique. PLLA is grafted with heparin to promote its surface cytocompatability, while PDLLA is added to reinforce the scaffolds. PLLA_sc are aminolyzed with tetraethylenepentamine (13-atom spacer) to generate sterically accessible amino groups at the surface allowing the covalent attachment of heparin by aqueous carbodiimide chemistry. Morphological and compressive strength studies manifest the integrity and compactness of scaffolds. Toluidine blue assay assures the consistency of heparin distribution throughout the scaffolds, which is in contrary to the conventional grafting reactions by immersing the scaffold in heparin solution. The scaffolds applicability is examined by fibroblast cells seeding experiments. Contrary to pristine scaffolds, Hep-PLLA_sc scaffolds display a hydrophilic and cytocompatible interface for cell adhesion, spreading, growth, and migration. Therefore, combining presurface grafted PLLA_sc with PDLLA microparticles could offer durable scaffolds exhibiting bioactive interface and controllable spatial distribution of the grafted biomacromolecules. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47797.     

Separation of Thorium Ions Using Synthesized Zeolite–Phosphate Composite from Sulfate Solution

Radiochemistry - Zeolite modified with phosphate (Z/P) was synthesized and tested for Th4+ adsorption. The optimum adsorption conditions are as follows: pH 3.5, contact time of 30 min, 0.1 g of...     

Modeling of noise and distortion associated with ultra‐high‐speed modulation of VCSEL with slow‐light feedback

This paper presents numerical modeling on the noise properties and signal distortion associated with millimeter‐frequency modulation of vertical‐cavity surface‐emitting laser (VCSEL) under with a transverse‐coupled cavity. The study is based on a time‐delay rate equation model that takes into account the multiple round trips in the feedback cavity and the optical loss and phase delay in each round trip. Strong slow‐light feedback is found to boost the modulation bandwidth to frequencies approaching 70 GHz and induce resonance modulation due to photon–photon resonance (PPR) over passbands centered on frequencies reaching 90 GHz. We show that the relative intensity noise of the VCSEL with resonance modulation is enhanced when the noise frequency approaches the corresponding PPR frequency VCSEL. The same effect applies for the VCSEL with extended carrier‐photon resonance (CPR) at the CPR frequency. The low‐frequency part is characterized by flat (white) noise of level nearly equal to −140 dB/Hz. The second‐harmonic distortion (2HD) values are smaller than −10 dB under small‐signal modulation and increase to lower than −5 dB when the modulation index becomes 0.3. Copyright © 2015 John Wiley & Sons, Ltd.     

Friction and wear of friction composites reinforced by natural fibres

In the present work, friction material composites were proposed to be used as automotive friction materials. The composites were reinforced by agricultural fibres of corn, palm, and sugar bars. The conventional friction materials based on asbestos cause serious lung diseases and being cancerous potential. The aim of the present work is to replace them by the proposed composites because they are environmentally friendly friction material for brake lining and clutch facings. Agricultural wastes of sugar bars, corn and palms fibres were prepared to obtain fibres of length less than 5 mm. The fibre materials were mixed by carbon, barium sulfate, silica, metallic powders and phenol formaldehyde. The proposed composites were pressed in the die at 105°C temperature. The produced specimens were subjected to machining processes to obtain the cylindrical form of 8 mm diameter. Experiments were carried out using test rig designed and manufactured to measure both friction and wear. It consists of a rotating hollow flat disc made of carbon steel, with an outside diameter of 250 mm and 16 mm thickness. The experiments investigated the effect of agriculture fibre wastes (corn, sugar bars, and palms fibres) on friction coefficient and wear. Wear mechanisms of the proposed composites were characterized by scanning electronic microscopy. The tribological properties of the proposed composites materials were compared to three commercial brake linings. Based on the experimental results it was found that, addition of agriculture fibre wastes (corn, sugar bars, and palms fibres) to composites materials increased friction coefficient and decreased wear. Friction coefficient slightly increased, while wear drastically decreased with increasing fibres content. The maximum friction value (0.58) was obtained by composites containing 30 wt.% iron and 25 wt.% sugar bar fibres. The corn fibres were more compatible with aluminum powder where it gave the highest friction coefficient and relatively lower wear compared to other composites. Wear resistance of the tested composites containing bunches and aluminum represented the lowest values among composites containing corn and bunches fibres. The lowest wear values were observed for composites containing 25 wt.% corn fibres and 30 wt.% aluminum and composites containing 20–25 wt.% sugar bar fibres.     

Patient psychological and information needs when the diagnosis is diabetes

Both aromatase and 5 alpha-reductase activities were found by whole-cell assay in osteoblast-like cells, MG-63 and HOS. Aromatase activity was measured by the [3H] water release method, and the formation of 5 alpha-androstanedione from androstenedione was expressed as 5 alpha-reductase activity. When CGS16949A, an inhibitor of aromatase, was added to the incubation medium at a concentration of 2 x 10(-9) M, sufficient to completely inhibit placental aromatase activity, only 63% to 68% inhibitions were observed. When progesterone, a competitive inhibitor of 5 alpha-reductase, was added at a concentration of 10(-5) M, 28% to 40% inhibitions were recorded. Because the release of [3H] from [1 beta-3H] androstenedione into water by 5 alpha-reductase is reported, results from the present study suggest that the measurement of aromatase activity in osteoblasts by the [2H] water release method may overestimate aromatase activity owing to the inclusion of 5 alpha-reductase activity. The results also suggest that osteoblast cells may play an important role in bone metabolism by transforming androgens into estrogens and more biologically active androgen derivatives.     

Multimode analysis of relative intensity noise associated with intensity modulation of semiconductor lasers

This paper analyzes the relative intensity noise (RIN) associated with intensity modulation (IM) of multilongitudinal mode semiconductor lasers. We considered two states of operation; namely, stable single-mode and multimode hopping that correspond to weak and strong asymmetric gain suppression. The former is typically considered by AlGaAs lasers, whereas the latter is considered by InGaAsP lasers. We introduce comparison of the influence of the modulation parameters on both the total and modal RIN between both lasers. We show that the IM response and 2HD display a peak at the relaxation frequency. The multimode hopping in the InGaAsP laser induces levels of signal distortion much higher than those in the AlGaAs laser in the regime of low modulation frequencies. Under weak modulation, the total and modal RINs of both the lasers vary little from those of the non-modulated lasers. The deep modulation releases the multimode hopping phenomenon in the InGaAsP laser and suppresses the mode-hopping peak in the RIN spectrum.     

Impact of mechanical cutting on the channel roughness

The impact of mechanical cutting for weed control along vegetated irrigation canals in terms of Manning's n, is discussed. Flow resistance was measured in channels completely infested by submerged macrophytes. Next, a path was cut along one or both canal banks by mechanical means and the measurement of flow resistance was repeated. The experiments and measurements carried out during only one seasson are described. A series of relationships between the flow resistance and a cross-section of areas both free from vegetation and with vegetation density, respectively, were found. Clearly, the elucidation of such relationships will be useful in assessing the frictional effects of submerged macrophyte growths in relation to the design and management of irrigation and drainage channels.     

A tutorial on using genetic algorithms for the design of network topology

The design of network topology is an important part of network design, since network topology is directly associated with network operational behavior, capacity, reliability, and cost. This paper is a tutorial paper concerned with illustrating how the optimization capabilities of genetic algorithms can be used to design suitable network topologies considering basic topology problems. Simple genetic algorithms have been developed for the topology problem of mesh networks, considering single node and single link failure tolerance. The algorithms are based on criteria of two important measures: minimizing the length of communication links; and minimizing traffic flow through these links for given traffic loads. The first measure contributes to minimizing the cost of cabling, while the second measure contributes to minimizing the cost of link capacity. The work provides a useful approach and tools to network students and professionals concerned with the topology design of backbone networks. The developed software is made available on the Internet. Copyright © 2006 John Wiley & Sons, Ltd.