Real-Time Cure Monitoring of Unsaturated Polyester Resin from Ultra-Violet Curing

Real time Fourier transform infrared (RTFT-IR) spectroscopy reveals the influence of the nature of the photoinitiator on the kinetics for the polymerization reaction. Real time cure monitoring was used to determine the polymerization rate of ultra-violet cured unsaturated polyester resins (UPR1:2-1:5) based on palm oil and containing styrene as a cross-linking agent in the presence of IRGACURE 184 photoinitiator. Firstly, variable types of UPR1:2-1:5 were prepared using various ratios of monoglyceride (MG) monomer to maleic anhydride which used as a source of double bond using polycondensation technique. RTFT-IR spectroscopy was used to characterize the ultra-violet curing kinetics for all the systems. This technique offered a powerful approach for monitoring changes in the chemical properties of the system during the ultra-violet curing. Pseudo first order kinetics for all UPR1:2-1:5 curable systems were determined and the rate constant values and regression coefficients were calculated. Furthermore, the thermal behaviour and morphological features for the photo-fabricated UPR1:2-1:5 systems were examined. The thermal analyses for the cured films were evaluated by TGA, DTG and DSC in nitrogen atmosphere at a heating rate of 10°C/min. All the formulations showed similar degradation pattern at 40 % and 50 % weight losses (Td = 40% and Td =50% respectively) except polymer UPR1:5 which had somewhat lower degree in the same range. In addition, the morphological properties for photo-fabricated UPR1:2,1:3,1:5 were investigated by using scanning electron microscopy.

Aquatic Toxicity of Polyethylene and Microcrystalline Cellulose Microbeads Used as Abrasives in Cosmetics

Microplastics have been part of personal care products for years, but due to microplastic pollution, many companies have replaced microplastics with natural particles, such as microcrystalline cellulose. Although natural particles are considered more environmentally friendly, their ecotoxicological profile is unknown. In this context, the aim of this study was to compare the ecotoxicity of polyethylene and microcrystalline cellulose microbeads, both extracted from a cosmetic product. The effects of the two types of particles on the aquatic macrophyte Lemna minor and the crustacean Daphnia magna, as well as the bioadhesion of the particles to Lemna minor were evaluated. The results showed no significant effects of either particle on the specific growth rate, root length, and chlorophyll content of Lemna minor. The bioadhesion of both types of particles to the plant biomass was comparable. Furthermore, no significant effects were observed on the mobility and body length of Daphnia magna. Thus, the investigated polyethylene and cellulose microbeads showed no significant toxic effects on the tested organisms. However, due to the persistence of polyethylene in the environment, the use of polyethylene microbeads in cosmetics and personal care products should be avoided. This work is licensed under a Creative Commons Attribution 4.0 International License

PLA/WOOD BIOCOMPOSITES: IMPROVING COMPOSITE STRENGTH BY CHEMICAL TREATMENT OF THE FIBERS

A resol type phenolic resin was prepared for the impregnation of wood particles used for the reinforcement of PLA. A preliminary study showed that the resin penetrates wood with rates depending on the concentration of the solution and on temperature. Treatment with a solution of 1 wt% resin resulted in a considerable increase of composite strength and decrease of water absorption. Composite strength improved as a result of increased inherent strength of the wood, but interfacial adhesion might be modified as well. When wood was treated with resin solutions of larger concentrations, the strength of the composites decreased, first slightly, then drastically to a very small value. A larger amount of resin results in a thick coating on wood with inferior mechanical properties. At large resin contents the mechanism of deformation changes; the thick coating breaks very easily leading to the catastrophic failure of the composites at very small loads

Composite absorbing potentials

The multiple scattering interferences due to the addition of several contiguous potential units are used to construct composite absorbing potentials that absorb at an arbitrary set of incident momenta or for a broad momentum interval.Comment: 9 pages, Revtex, 2 postscript figures. Accepted in Phys. Rev. Let

Parallel updating cellular automaton models of driven diffusive Frenkel-Kontorova-type systems

Three cellular automaton (CA) models of increasing complexity are introduced to model driven diffusive systems related to the generalized Frenkel-Kontorova (FK) models recently proposed by Braun [Phys.Rev.E58, 1311 (1998)]. The models are defined in terms of parallel updating rules. Simulation results are presented for these models. The features are qualitatively similar to those models defined previously in terms of sequentially updating rules. Essential features of the FK model such as phase transitions, jamming due to atoms in the immobile state, and hysteresis in the relationship between the fraction of atoms in the running state and the bias field are captured. Formulating in terms of parallel updating rules has the advantage that the models can be treated analytically by following the time evolution of the occupation on every site of the lattice. Results of this analytical approach are given for the two simpler models. The steady state properties are found by studying the stable fixed points of a closed set of dynamical equations obtained within the approximation of retaining spatial correlations only upto two nearest neighboring sites. Results are found to be in good agreement with numerical data.Comment: 26 pages, 4 eps figure

Charge Transfer via Temporary Bonds in C60+C60+C_{60} + C_{60}^+ Molecular Collisions

We present a theoretical description of resonant charge transfer in collisions of nano-particles, specifically for $C_{60} + C_{60}^+$ collisions. We predict that transient bonds between colliding fullerenes can significantly extend the interaction time, allowing for a greater probability of charge transfer. In our model, the dumbbell-shaped $(C_{60}-C_{60})^+$ quasi-molecule, that is temporarily formed during the collision, is described as a dynamic system of 120 zero-range potentials. Using this model, we calculate the exchange interaction between colliding fullerenes and subsequently determine the corresponding charge transfer cross sections at different collision velocities. Our results have been verified with data obtained from quantum molecular dynamics simulations of the fullerene collisions. The presented theoretical model provides a description of the experimental data on the $C_{60} + C_{60}^+$ resonant charge transfer collision through the inclusion of the temporary formation of dumbbell-shaped fullerene molecules at low collision velocities.Comment: 5 pages (6 if you include citations), 3 figure

1-Methyl-3-(2-methyl­phen­yl)-3,3a,4,9b-tetra­hydro-1H-chromeno[4,3-c][1,2]oxazole-3a-carbonitrile

In the title compound, C19H18N2O2, the five-membered isoxazole ring adopts an envelope conformation and the deviation of the N atom from the mean plane of the isoxazole ring is −0.3256 (11) Å. The pyran ring adopts a half-chair conformation. The isoxazole ring forms dihedral angles of 44.07 (7) and 84.23 (7)° with the pyran and methyl­benzene rings, respectively. The mol­ecular structure is stabilized by weak C—H⋯π inter­actions

Tunable linear and quadratic optomechanical coupling for a tilted membrane within an optical cavity: theory and experiment

We present an experimental study of an optomechanical system formed by a vibrating thin semi-transparent membrane within a high-finesse optical cavity. We show that the coupling between the optical cavity modes and the vibrational modes of the membrane can be tuned by varying the membrane position and orientation. In particular we demonstrate a large quadratic dispersive optomechanical coupling in correspondence with avoided crossings between optical cavity modes weakly coupled by scattering at the membrane surface. The experimental results are well explained by a first order perturbation treatment of the cavity eigenmodes.Comment: 10 pages, 6 figure

Comparison of particle-exposure triggered pulmonary and systemic inflammation in mice fed with three different diets

<p>Abstract</p> <p>Background</p> <p>Obesity can be linked to disease risks such as diabetes and cardiovascular disorders, but recently, the adipose tissue (AT) macrophage also emerges as actively participating in inflammation and immune function, producing pro- and anti-inflammatory factors. Connections between the AT and chronic lung diseases, like emphysema and asthma and a protective role of adipocyte-derived proteins against acute lung injury were suggested.</p> <p>In this study we addressed the question, whether a diet challenge increases the inflammatory response in the alveolar and the blood compartment in response to carbon nanoparticles (CNP), as a surrogate for ambient/urban particulate air pollutants.</p> <p>Methods</p> <p>Mice were fed a high caloric carbohydrate-rich (CA) or a fat-rich (HF) diet for six weeks and were compared to mice kept on a purified low fat (LF) diet, respectively. Bronchoalveolar lavage (BAL) and blood samples were taken 24 h after intratracheal CNP instillation and checked for cellular and molecular markers of inflammation.</p> <p>Results and discussion</p> <p>The high caloric diets resulted in distinct effects when compared with LF mice, respectively: CA resulted in increased body and fat mass without affecting blood cellular immunity. Conversely, HF activated the blood system, increasing lymphocyte and neutrophil counts, and resulted in slightly increased body fat content. In contrast to higher pro-inflammatory BAL Leptin in CA and HF mice, on a cellular level, both diets did not lead to an increased pro-inflammatory basal status in the alveolar compartment per se, nor did result in differences in the particle-triggered response. However both diets resulted in a disturbance of the alveolar capillary barrier as indicated by enhanced BAL protein and lactate-dehydrogenase concentrations. Systemically, reduced serum Adiponectin in HF mice might be related to the observed white blood cell increase.</p> <p>Conclusion</p> <p>The increase in BAL pro-inflammatory factors in high caloric groups and reductions in serum concentrations of anti-inflammatory factors in HF mice, clearly show diet-specific effects, pointing towards augmented systemic inflammatory conditions. Our data suggest that extended feeding periods, leading to manifest obesity, are necessary to generate an increased susceptibility to particle-induced lung inflammation; although the diet-challenge already was efficient in driving pro-inflammatory systemic events.</p

Time-Resolved Studies of Stick-Slip Friction in Sheared Granular Layers

Sensitive and fast force measurements are performed on sheared granular layers undergoing stick-slip motion, along with simultaneous imaging. A full study has been done for spherical particles with a +-20% size distribution. Stick-slip motion due to repetitive fluidization of the layer occurs for low driving velocities. Between major slip events, slight creep occurs that is variable from one event to the next. The effects of changing the stiffness k and velocity V of the driving system are studied in detail. The stick-slip motion is almost periodic for spherical particles over a wide range of parameters, but becomes irregular when k is large and V is relatively small. At larger V, the motion becomes smoother and is affected by the inertia of the upper plate bounding the layer. Measurements of the period T and amplitude A of the relative motion are presented as a function of V. At a critical value Vc, a transition to continuous sliding motion occurs that is discontinuous for k not too large. The time dependence of the instantaneous velocity of the upper plate and the frictional force produced by the granular layer are determined within individual slipping events. The force is a multi-valued function of the instantaneous velocity, with pronounced hysteresis and a sudden drop prior to resticking. Measurements of vertical displacement reveal a small dilation of the material (about one tenth of the mean particle size in a layer 20 particles deep) associated with each slip event. Finally, optical imaging reveals that localized microscopic rearrangements precede (and follow) each slip event. The behavior of smooth particles is contrasted with that of rough particles.Comment: 20, pages, 17 figures, to appear in Phys. Rev.