Nanocellulose-polypyrrole-coated paperboard for food packaging application

Currently, studies on packaging that improves the shelf life of perishable food while reducing the waste that is produced upon disposal are encouraged. Thus, exploration of the property improvement of paperboard (Pb) packaging is of interest since this type of packaging is biodegradable and recyclable. This work emphasizes the added value of (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidized cellulose nanofibres (TOCN) and polypyrrole (PPy) coating on such paperboard. The mechanical properties and reduced gas permeability of the coated paperboard (CPb) were significantly improved due to the dense network formed by TOCN and polypyrrole particles. These results suggest that surface coating by polypyrrole particles may be utilized for the manufacture of multilayer paperboard containers in industrial applications to reduce packaging waste generated by the often added conventional plastic. © 2018 Elsevier B.V

Self-Supervised Relative Depth Learning for Urban Scene Understanding

As an agent moves through the world, the apparent motion of scene elements is (usually) inversely proportional to their depth. It is natural for a learning agent to associate image patterns with the magnitude of their displacement over time: as the agent moves, faraway mountains don't move much; nearby trees move a lot. This natural relationship between the appearance of objects and their motion is a rich source of information about the world. In this work, we start by training a deep network, using fully automatic supervision, to predict relative scene depth from single images. The relative depth training images are automatically derived from simple videos of cars moving through a scene, using recent motion segmentation techniques, and no human-provided labels. This proxy task of predicting relative depth from a single image induces features in the network that result in large improvements in a set of downstream tasks including semantic segmentation, joint road segmentation and car detection, and monocular (absolute) depth estimation, over a network trained from scratch. The improvement on the semantic segmentation task is greater than those produced by any other automatically supervised methods. Moreover, for monocular depth estimation, our unsupervised pre-training method even outperforms supervised pre-training with ImageNet. In addition, we demonstrate benefits from learning to predict (unsupervised) relative depth in the specific videos associated with various downstream tasks. We adapt to the specific scenes in those tasks in an unsupervised manner to improve performance. In summary, for semantic segmentation, we present state-of-the-art results among methods that do not use supervised pre-training, and we even exceed the performance of supervised ImageNet pre-trained models for monocular depth estimation, achieving results that are comparable with state-of-the-art methods

Conductive nanocomposites based on TEMPO-oxidized cellulose and poly(N-3-aminopropylpyrrole-co-pyrrole)

In this paper, conductive composite films were synthetized based on oxidized cellulosic nanofibres (CNFo), 1-(2-cyanoethyl)pyrrole and pyrrole. The 1-(2-cyanoethyl)pyrrole was reduced into N-(3-aminopropyl)pyrrole before being grafted on carboxyl groups of CNFo. Oxidative polymerization of polypyrrole (Ppy) was conducted in an iron(III) chloride (FeCl3) solution, onto the N-(3-aminopropyl)pyrrole grafted. The resulting composite films were characterized by FTIR-ATR Spectroscopy, scanning electron microscopy (SEM) equipped with energy-dispersive x-ray spectroscopy (EDX), tensile strength measurement, thermogravimetric analysis (TGA), wettability and electrical conductivity measurements. The grafting of 1-(2-cyanoethyl)pyrrole played a leading role in improving these properties by increasing potential connections between chains of conducting polymer and cellulose fibres. The outcomes show that the PPy nanoparticles coating on the grafted films increase a lot of characteristics of our composite such as wettability, mechanical properties, thermal protection and more importantly the electrical conductivity which was improved by a 10E5 factor in comparison to the uncoated films. In this condition, this nanostructure could be considered in the design of high-performance electrodes for supercapacitor, battery and sensor applications. © 2016 Elsevier B.V

Power law velocity fluctuations due to inelastic collisions in numerically simulated vibrated bed of powder}

Distribution functions of relative velocities among particles in a vibrated bed of powder are studied both numerically and theoretically. In the solid phase where granular particles remain near their local stable states, the probability distribution is Gaussian. On the other hand, in the fluidized phase, where the particles can exchange their positions, the distribution clearly deviates from Gaussian. This is interpreted with two analogies; aggregation processes and soft-to-hard turbulence transition in thermal convection. The non-Gaussian distribution is well-approximated by the t-distribution which is derived theoretically by considering the effect of clustering by inelastic collisions in the former analogy.Comment: 7 pages, using REVTEX (Figures are inculded in text body) %%%Replacement due to rivision (Europhys. Lett., in press)%%

Printed microwave frequency humidity sensor operating with phase shifting scheme

This paper investigates a shifting sensing scheme combining slots, transmission lines, and printing technologies. This sensing scheme translates the electrical sensitivity of a transmission line conductor to the insertion phase as a measurement variable. A coplanar waveguide (CPW) based structure was designed, screen-printed, and tested on relative humidity (RH) conditions ranging from 22.8-75.3 %RH. For the first time, a composite material made of poly-pyrrole and TEMPO Oxidized Cellulose Nanofibers (TOCN/PPy) was integrated to the structure and studied as a humidity sensitive conductor in microwave frequencies. The measured sensitivity was 0.154°/%RH at 5.870 GHz, while insertion losses decreased by 1.26 dB. The effects of sensing layers thickness as well as trade-off considerations between phase sensitivity and signal attenuation were analyzed by simulation. © 2001-2012 IEEE

Mechanical and antibacterial properties of a nanocellulose-polypyrrole multilayer composite

In this study, a composite film based on TEMPO-oxidized cellulose nanofibers (TOCN), polyvinyl alcohol (PVA) and polypyrrole (PPy) was synthesized in situ by a chemical polymerization, resulting in the induced absorption of PPy on the surface of the TOCN. The composite films were investigated with scanning electron microscopy, thermogravimetric analysis, contact angle measurements, mechanical tests, and evaluation of antibacterial properties. The developed composite has nearly identical Young modulus (3.4 GPa), elongation (2.6%) and tensile stress (about 51 MPa) to TOCN even if PPy, which as poor properties by itself, was incorporated. From the energy-dispersive X-ray spectroscopy (EDX) results, it was shown that PPy is mainly located on the composite surface. Results confirmed by an increase from 54.5 to 83° in contact angle, an increased heat protection (Thermogravimetric analysis) and a decrease in surface energy. The nanocomposites were also evaluated for antibacterial activity against bacteria occasionally found in food: Gram-positive Bacillus subtilis (B. subtilis) and Gram-negative bacteria Escherichia coli (E. coli). The results indicate that the nanocomposites are effective against all of the bacteria studied as shown by the decrease of 5.2 log colony forming units (CFU) for B. subtilis and 6.5 log CFU for E. coli. Resulting in the total destruction of the studied bacteria. The perfect match between the resulting inhibition zone and the composite surface area has demonstrated that our composite was contact active with a slight leaching of PPy. Our composite was successful as an active packaging on meat (liver) as bacteria were killed by contact, thereby preventing the spread of possible diseases. While it has not been tested on bacteria found in medicine, TOCN/PVA-PPy film may be able to act as an active sterile packaging for surgical instruments. © 2016 Elsevier B.V

Numerical model for granular compaction under vertical tapping

A simple numerical model is used to simulate the effect of vertical taps on a packing of monodisperse hard spheres. Our results are in agreement with an experimantal work done in Chicago and with other previous models, especially concerning the dynamics of the compaction, the influence of the excitation strength on the compaction efficiency, and some ageing effects. The principal asset of the model is that it allows a local analysis of the packings. Vertical and transverse density profiles are used as well as size and volume distributions of the pores. An interesting result concerns the appearance of a vertical gradient in the density profiles during compaction. Furthermore, the volume distribution of the pores suggests that the smallest pores, ranging in size between a tetrahedral and an octahedral site, are not strongly affected by the tapping process, in contrast to the largest pores which are more sensitive to the compaction of the packing.Comment: 8 pages, 15 figures (eps), to be published in Phys. Rev. E. Some corrections have been made, especially in paragraph IV

Polypyrrole/nanocellulose composite for food preservation: barrier and antioxidant characterization

When food cannot be consumed immediately after production, food packaging must create a protective atmosphere around the food product. The packaging must improve the shelf life of perishable foods and protect the food from dirt, dust, oxygen, light, pathogenic microorganisms, and moisture by acting as an effective barrier to moisture, gases (CO2 and O2) or even by possessing antimicrobial properties. However, extending the shelf life and enhancing food quality while reducing packaging waste is encouraged. The exploration of new bio-based packaging materials, such as TEMPO-oxidize nanofibrillated cellulose (TOCN), has increased due to its biodegradable and renewable character. This work emphasizes the antioxidant activity and high barrier properties against the diffusion of oxygen, carbon dioxide and water vapor from a nanocomposite based on polypyrrole (PPy) and TOCN, as well as its biodegradability for food packaging applications. The preparation, characterization and application of the nanocomposite in food packaging are discussed. © 2017 Elsevier Lt

Diffusion as mixing mechanism in granular materials

We present several numerical results on granular mixtures. In particular, we examine the efficiency of diffusion as a mixing mechanism in these systems. The collisions are inelastic and to compensate the energy loss, we thermalize the grains by adding a random force. Starting with a segregated system, we show that uniform agitation (heating) leads to a uniform mixture of grains of different sizes. We define a characteristic mixing time, $\tau_{mix}$, and study theoretically and numerically its dependence on other parameters like the density. We examine a model for bidisperse systems for which we can calculate some physical quantities. We also examine the effect of a temperature gradient and demonstrate the appearance of an expected segregation.Comment: 15 eps figures, include

Energy Dissipation and Trapping of Particles Moving on a Rough Surface

We report an experimental, numerical and theoretical study of the motion of a ball on a rough inclined surface. The control parameters are $D$, the diameter of the ball, $\theta$, the inclination angle of the rough surface and $E_{ki}$, the initial kinetic energy. When the angle of inclination is larger than some critical value, $\theta>\theta_{T}$, the ball moves at a constant average velocity which is independent of the initial conditions. For an angle $\theta < \theta_{T}$, the balls are trapped after moving a certain distance. The dependence of the travelled distances on $E_{ki}$, $D$ and $\theta$. is analysed. The existence of two kinds of mechanisms of dissipation is thus brought to light. We find that for high initial velocities the friction force is constant. As the velocity decreases below a certain threshold the friction becomes viscous.Comment: 8 pages RevTeX, 12 Postscript figure