LED lighting and seasonality effects antioxidant properties of baby leaf lettuce

We report on the application of supplementary light-emitting diode (LED) lighting within a greenhouse for cultivation of red, green and light green leaf baby lettuces (Lactuca sativa L.) grown under natural illumination and high-pressure sodium (HPS) lamps (16-h; PPFD-170 μmol m⁻² s⁻¹) during different growing season. Supplementary lighting from blue 455/470 nm and green 505/530 nm LEDs was applied (16-h; PPFD-30 μmol m⁻² s⁻¹). Our results showed that to achieve solely a positive effect is complicated, because metabolism of antioxidant properties in lettuce depended on multicomponent exposure of variety, light quality or seasonality. The general trend of a greater positive effect of supplemental LED components on the vitamin C and tocopherol contents was in order: 535 > 505 > 455 > 470 nm; on the total phenol content: 505 > 535 = 470 > 455 nm; on the DPPH free-radical scavenging capacity: 535 = 470 > 505 > 455 nm; on the total anthocyanins: 505 > 455 > 470 > 535 nm. Further investigations are needed for understanding the mechanism and interaction between antioxidants and light signal transduction pathways.     

Polyacrylamide gels with ionized functional groups in their selective recognition of trimeric molecular form of human growth hormone

Networks of polyacrylamide with ionized functional groups were studied for the possibility of imprinting of oligomeric form of human growth hormone (hGH). Trimeric molecular form of hGH was molecularly imprinted for the first time. The results show that approximately 35–40 % (w/w) of the templates (depending on polymerization conditions) could be extracted from the molecularly imprinted acrylamide polymers. Artificial gel antibodies against trimeric hGH in the form of granules of hydrogel were compared with granules of non-imprinted polymer. Investigation of the binding to imprinted polymer of the template hormone, other molecular forms of the hormone, and other proteins shows enough high selectivity of artificial gel antibodies.     

Maximum drift velocity of electrons in selectively doped InAlAs/InGaAs/InAlAs heterostructures with InAs inserts

The dependence of the electron mobility and drift velocity on the growth conditions, thickness, and doping of an InAs insert placed at the center of the quantum well in a selectively doped InAlAs/InGaAs/InAlAs heterostructure has been investigated. Record enhancement of the maximum drift velocity to (2–4) × 10⁷ cm/s in an electric field of 5 × 10³ V/cm has been obtained in a 17-nm-wide quantum well with an undoped 4-nm-thick InAs insert. In the structures with additional doping of the InAs insert, which facilitates an increase in the density of electrons in the quantum well to 4.0 × 10¹² cm^?2, the maximum drift velocity is as high as 2 × 10⁷ cm/s in an electric field of 7 × 10³ V/cm.     

Feasibility of CHP-plants with thermal stores in the German spot market

The European Energy Exchange (EEX) day ahead spot market for electricity in Germany shows significant variations in prices between peak and off-peak hours. Being able to shift electricity production from off-peak hours to peak hours improves the profit from CHP-plant operation significantly. Installing a big thermal store at a CHP-plant makes it possible to shift production of electricity and heat to hours where electricity prices are highest especially on days with low heat demand. Consequently, these conditions will have to influence the design of new CHP-plants. In this paper, the optimal size of a CHP-plant with thermal store under German spot market conditions is analyzed. As an example the possibility to install small size CHP-plant instead of only boilers at a Stadtwerke delivering 30,000 MW h-heat for district heating per year is examined using the software energyPRO. It is shown that, given the economic and technical assumptions made, a CHP-plant of 4 MW-el with a thermal store participating in the spot market will be the most feasible plant to build. A sensitivity analysis shows to which extent the optimal solution will vary by changing the key economic assumptions.     

Transport of electrons in a GaAs quantum well in high electric fields

The rates of intrasubband and intersubband scattering of electrons by polar optical and intervalley phonons are determined in relation to the electron energy and width of a deep rectangular quantum well in GaAs. The Monte Carlo method was used to calculate the field dependences of the electron’s drift velocity in quantum wells with the width of 10, 20, and 30 nm. It is shown that the drift velocity in high electric fields in a quantum well vastly exceeds the maximum drift’s saturation velocity in the bulk material.     

A novel Cr–CeO2/La2O3 nanocomposite electrodeposited in sulphate Cr(III) bath

ABSTRACT

For the first time, the Cr–CeO₂ / La₂O₃ composite has been electrochemically deposited in a sulphate Cr (III) bath with an oxalate complexing agent. XRD analysis revealed that incorporation of CeO₂/La₂O₃ particles into the Cr matrix does not change its state and the Cr matrix remains fine-crystalline (crystallites size < 1?nm). The cross-section SEM and EDS analysis confirmed the incorporation of CeO₂/La₂O₃ particles into the Cr matrix. The studies of the mechanical properties of the Cr–CeO₂/La₂O₃ composite have shown that the hardness of the composite increases over that of the Cr deposit due to CeO₂/La₂O₃ particles incorporation, while both the friction coefficient and wear rate decrease. The mechanism of CeO₂/La₂O₃ nanoparticles incorporation into the Cr matrix has been discussed.     

Effects of prior knowledge and joint attention on learning from eye movement modelling examples

Eye movement modelling examples (EMMEs) are instructional videos of a model's demonstration and explanation of a task that also show where the model is looking. EMMEs are expected to synchronize students' visual attention with the model's, leading to better learning than regular video modelling examples (MEs). However, synchronization is seldom directly tested. Moreover, recent research suggests that EMMEs might be more effective than ME for low prior knowledge learners. We therefore used a 2 × 2 between-subjects design to investigate if the effectiveness of EMMEs (EMMEs/ME) is moderated by prior knowledge (high/low, manipulated by pretraining), applying eye tracking to assess synchronization. Contrary to expectations, EMMEs did not lead to higher learning outcomes than ME, and no interaction with prior knowledge was found. Structural equation modelling shows the mechanism through which EMMEs affect learning: Seeing the model's eye movements helped learners to look faster at referenced information, which was associated with higher learning outcomes.     

Alkali-activated blends of calcined AlF3 production waste and clay

Recently, alkali-activated materials have shown great potential for use in the construction industry. The aim of this research was to study the properties of alkali-activated clay and the effect of incorporating AlF₃ production waste from a fertilizer production plant. The AlF₃ production waste, which was rich in alumina and silica, contributed to improved mechanical behaviour for all the mixtures investigated. This demonstrated the potential for use of this waste material. It was also noted that the dosage of Na₂O, Al₂O₃, and SiO₂ are significant factors that influence the binding mechanism and properties of alkali-activated clay samples. The raw materials, precursors, and alkali-activated samples were investigated by X-ray diffraction, fluorescence spectroscopy, and scanning electron microscopy. The highest compressive strength (17.50?MPa) was observed for alkali-activated clay samples containing 25% AlF₃ production waste, with an increase in compressive strength of up to 64% compared to the samples without the AlF₃ production waste. Deleterious natrite was shown to form in the samples without the production waste, which could be the reason for the lower observed mechanical properties of such samples.     

Uncertainty of measurement in spectrometric analysis: A case study

The methods of spectrometric analysis belong to a group of measurement methods that are used for their simplicity, speed of analysis, and large selectivity to solve various problems of analytes. Accuracy and reliability of any chemical analysis largely depend on the way the analyzed sample is prepared.