Eumelanin for nature‐inspired UV‐absorption enhancement of plastics

In the human body, the black‐brown biopigment eumelanin blocks harmful ultraviolet (UV) radiation. In the plastics industry, additives are often added to polymers to increase their UV‐absorption properties. We herein report an assessment of the biopigment eumelanin as a nature‐inspired additive for plastics to enhance their UV absorption. Since eumelanin is produced by natural sources and is nontoxic, it is an interesting candidate in the field of sustainable plastic additives. In this work, the eumelanin‐containing films of commercial ethylene–vinyl acetate copolymer, a plastic used for packaging applications, were obtained by melt compounding and compression molding. The biopigment dispersion in the films was improved by means of the melanin free acid treatment. It was observed that eumelanin amounts as low as 0.8 wt% caused an increase of the UV absorption, up to one order of magnitude in the UVA range. We also evaluated the effect of eumelanin on the thermal stability and photostability of the films: the biopigment proved to be double‐edged, working both as UV‐absorption enhancer and photo‐prooxidant, as thermogravimetric analysis and infrared spectroscopy revealed. © 2019 Society of Chemical Industry     

Fatty acid composition of some pine seed oils

The fatty acid composition of seeds from seven species of the genusPinus (P. pinaster, P. griffithii, P. pinea, P. koraiensis, P. sylvestris, P. mughus, andP. nigra) was established. Pine seeds are rich in oil (31–68% by weight) and contain several unusual polymethylene-interrupted unsaturated fatty acids with acis-5 ethylenic bond. These are thecis-5,cis-9 18:2,cis-5,cis-9,cis-12 18:3,cis-5,cis-11 20:2, andcis-5,cis-11,cis-14 20:3 acids, with a trace ofcis-5,cis-9,cis-12,cis-15 18:4 acid. Their percentage relative to total fatty acids varies from a low of 3.1% (P. pinea) to a high of 30.3% (P. sylvestris), depending on the species. The majorcis-5 double bond-containing acid is generally thecis-5,cis-9,cis-12 18:3 acid (pinolenic acid). In all species, linoleic acid represents approximately one-half the total fatty acids, whereas the content of oleic acid varies in the range 14–36% inversely to the sum of fatty acids containing acis-5 ethylenic bond. The easily available seeds fromP. koraiensis appear to be a good source of pinolenic acid: their oil content isca. 65%, and pinolenic represents about 15% of total fatty acids. These values appear to be rather constant.Pinus pinaster, which is grown on several thousand acres in the southwest of France, is an interesting source ofcis-5,cis-11,cis-14 20:3 acid (7% in the oil, which isca. 35% of the dehulled seed weight), an acid sharing in common three double bonds with arachidonic acid. Apparently,P. sylvestris seed oil contains the highest level ofcis-5 double bond-containing acids among pine seed oils that have ever been analyzed.     

Component-based end-user database design for ecologists

To solve today’s ecological problems, scientists need well documented, validated, and coherent data archives. Historically, however, ecologists have collected and stored data idiosyncratically, making data integration even among close collaborators difficult. Further, effective ecology data warehouses and subsequent data mining require that individual databases be accurately described with metadata against which the data themselves have been validated. Using database technology would make documenting data sets for archiving, integration, and data mining easier, but few ecologists have expertise to use database technology and they cannot afford to hire programmers. In this paper, we identify the benefits that would accrue from ecologists’ use of modern information technology and the obstacles that prevent that use. We describe our prototype, the Canopy DataBank, through which we aim to enable individual ecologists in the forest canopy research community to be their own database programmers. The key feature that makes this possible is domain-specific database components, which we call templates. We also show how additional tools that reuse these components, such as for visualization, could provide gains in productivity and motivate the use of new technology. Finally, we suggest ways in which communities might share database components and how components might be used to foster easier data integration to solve new ecological problems.     

Influence of moisture content on the specific methanogenic activity of dry mesophilic municipal solid waste digestate

The objective of this study was to evaluate the influence of moisture content on the specific methanogenic activity (SMA) of a fresh dry mesophilic digestate from a municipal solid waste digester plant. For this purpose, SMA tests were performed under mesophilic conditions in 500 mL glass bottles of volume used as batch reactors, during a period of 20–25 days. Cellulose, propionate and acetate were used as substrates (5 g_COD kg^?1 digestate) at four different moisture contents, ranging from 65 to 82%. The moisture content strongly influenced the specific methanogenic activity. The highest SMA values were observed at a moisture content of 82% (11.1, 7.8 and 6.0 mg_COD g_VS^?1 d^?1 for cellulose, propionate and acetate spikes, respectively). SMA and moisture content were found to be linearly linked. Dry digestion at low water content is thus detrimental to the biological activity, probably due to physical limitations. Copyright © 2011 Society of Chemical Industry     

Impact of the injection‐level‐dependent lifetime on Voc,FF, ideality m,J02, and the dim light response in a commercial PERC cell

The injection‐level‐dependent (ILD) lifetime of the silicon wafer impacts many characteristics of the final photovoltaic cell. While efficiency is commonly understood to be impacted by the silicon bulk lifetime (at the maximum power point injection level), this work demonstrates the wide ranging impacts of ILD lifetime on the V_oc, the fill factor (FF), the diode ideality factor m, and the dim light response. Instead of a two‐diode model, we utilize a boundary + ILD bulk lifetime model to analyze a commercial passivated emitter rear contact (PERC) cell featuring an AlO_x dielectric rear passivation. The ILD lifetime is directly measured and used to calculate the bulk recombination current across injection levels. With this boundary + ILD lifetime model, we demonstrate the role of the ILD lifetime on many cell parameters in this PERC cell. For most high efficiency commercial p‐type monocrystalline solar cells, the typically lower bulk lifetime at the maximum power point versus the lifetime at the open circuit point reduces the measured FF and pseudo‐FF. This work illustrates that for a commercial PERC cell with AlO_x rear passivation, the ILD lifetime is the primary mechanism behind reduced FF, ideality factors greater than 1, and the source of the J₀₂ term in the two‐diode model. The crucial implications of this work are not only to better understand commercial PERC cell loss mechanisms but also to encourage a focus on different metrics in cell diagnostics. One such metric is the V_oc at 0.1 or 0.05 suns. Copyright © 2016 John Wiley & Sons, Ltd.     

On the LTI properties of adaptive feedforward systems with tapdelay-line regressors

It is shown that an adaptive system whose regressor is formed by tap delay-line (TDL) filtering of a multitone sinusoidal signal is representable as a parallel connection of a linear time-invariant (LTI) block and a linear time-varying (LTV) block. A norm-bound (induced 2-norm) is computed explicitly on the LTV block and is shown to decrease as N^-1, where N is the number of taps. Hence, the adaptive system becomes LTI in the limit as the number of taps goes to infinity. In the more realistic case where the number of taps N is finite, the new “LTI plus norm-bounded perturbation” representation renders, for the first time, the adaptive system analyzable by standard robust control methods     

An algorithm for state-space frequency domain identificationwithout windowing distortions

An algorithm is presented for identifying state-space models from frequency-domain data. The main advantage of this approach is that it avoids windowing distortions associated with other frequency-domain methods. Other advantages are that an arbitrary frequency weighting can be introduced to shape the estimation error, and the system order can be overspecified. The numerical properties are demonstrated on real physical data taken on a complex flexible structure, leading to the successful identification of a multivariable (four-input/three-output) 100-state model over a bandwidth of 100 Hertz. The results indicate that the algorithm would be useful in applications requiring the accurate identification of high-order systems over wide bandwidths     

Proprietes magnetiques de l'oxyde de vanadium V3O7

Magnetic susceptibility and magnetization measurements on V₃O₇ from 4,2 to 600 K characterize a paramagnetic behaviour above 18 K : the samples follow a Curie-Weiss law with a Curie constant in good agreement with a spin only value $\text{S}\text{=}\text{1}\text{2}$ per V⁴⁺. At lower temperature the magnetic ordering may be attributed to a metamagnetic behaviour resulting from the layer type structure.     

K-pulse techniques for short-pulse radiation from dipole arrays

An investigation of K-pulse techniques to transmit short-time duration pulses from dipole arrays is presented. The array is analyzed from a radiation standpoint using the singularity expansion method. The analysis also makes use of the method of moments to express the array's radiation in terms of the terminal voltages and pole singularities. Following a numerical search in the complex frequency plane (from which the dominant singularities of the array are located), the time-domain waveform of the approximated K-pulse voltage is constructed. Calculated plots of the far-zone radiated electric field resulting from applying these voltages at the array terminals are presented, and their energy concentrations are compared to those of the optimum solutions