Emission based sub-nanomolar silver sensing with electrospun nanofibers

In this work, the first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical silver sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric support materials. Silver sensing materials were fabricated by electrospinning technique. A fiber-optic bundle was used for measurements. Sensors were based on the change in the fluorescence signal intensity of methoxy azomethine ionophore (M-AZM). The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect silver ions are 10-100-fold higher than those of the thin film based sensors. The extraordinary sensitivities can be attributed to the high surface area of the nanofibrous membrane structures. It was found that the stability of the sensing agent in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 5 months. Our stability tests are still in progress.     

Design and realization of an ultra‐low power sensing RF energy harvesting module with its RF and DC sub‐components

Herein, design, development, and analysis of ultra‐low power sensing energy harvesting modules and their subcomponents for ISM band applications have been studied with a holistic approach in an effort to achieve a feasible and high efficient RF energy harvesting performance. The complete harvester system designed and developed here consists of a zero‐bias RF energy rectifying antenna (rectenna), DC boost converters and energy storage super‐capacitors. Compared with the counterpart energy sources, the surrounding or transmitted wireless energy has low intensity which requires designs with high efficiency. To achieve a successful harvester performance, rectifier circuits with high sensitivity Schottky diodes and proper impedance matching circuits are designed. Dedicated RF signals at various levels from nanowatts to miliwatts are applied at the input of the rectenna and the measured input power versus the scavenged DC output voltage are tabulated. Furthermore, by connecting the rectifier to a high gain antenna and using a RF signal transmitter, the wireless RF power harvesting performance at 2.4 GHz was tested up to 5 m. The performance of the rectenna is analyzed for both low‐power detection and efficiencies. Impedance matching network is implemented to reduce the reflected input RF power, DC to DC converters are evaluated for their compatibility to the rectifiers, and super‐capacitor behaviors are investigated for their charging and storage capabilities. The measured results indicate that a wide operating power range with an ultra‐low power sensing and conversion performance have been achieved by optimizing the efficiency of the Schottky rectifier as low as ?50 dBm. The system can be used for battery free applications or expanding battery life for ultra‐low power electronics, such as; RFID, LoRa, Bluetooth, ZigBee, and low power remote sensor systems.     

Board’s IQ: What makes a board smart?

The amount of investment that has been made in interactive whiteboards (IWB) in the Turkish educational system during the past several years is quite striking. This investment is part of a plan to integrate information and communication technologies (ICT) into the Turkish educational system, with the goal of increasing the qualitative and quantitative aspects of schooling. Prior to IWB investments, hundreds of thousands of computers, projectors, and printers were distributed to schools in efforts to raise a generation able to respond to the demands of the 21st century. In addition, 98% of secondary school students and 93% of primary school students were provided with Internet access via ADSL. The aim of this study is to analyze the emerging trend of smart board investment in Turkish primary and secondary schools, with consideration of problems that hinder the effective use of IWBs in classrooms as compared to previous ICT integration efforts by the Ministry of National Education. The research is designed as an evaluative case study. The required data are collected through online questionnaires, teacher and pupil interviews, and document searches from teachers and students from various Turkish primary and secondary schools. It is not surprising that the factors hindering the use of IWBs in education are similar to the inhibiting factors in previous ICT integration projects. The findings show that when the needs for in-service training, digital education materials, support, maintenance, and administration are not addressed, educational ICT is unlikely to deliver the expected results.     

An automated industrial conveyor belt system using image processing and hierarchical clustering for classifying marble slabs

Although there are many industrial machines used in marble industry, classification of marble slabs in terms of quality is generally performed by human experts. Due to economic losses of this rather subjective process, automatic and computerized methods are needed in order to obtain reproducible and objective results in classification. With the aim of remedying this insufficiency in marble industry, a new electro-mechanical system, which automatically classifies marble slabs while they are on a conveyor belt and groups them with the help of a control mechanism, is proposed. The developed system is composed of two parts: the software part acquires digital images of marble slabs, extracts several features using these images, and finally performs the classification using clustering methods. The hardware part is composed of a conveyor belt, a serial port communication system, pneumatic pistons, a programmable logic controller (PLC), and its control circuits, all employed together for grouping the marble slabs mechanically. Although similar studies exist, this paper proposes three novelties over the existing systems. Firstly, a new hierarchical clustering approach is introduced for quality classification without requiring a training set. Secondly, a new feature set based on morphological properties of marble surface images is proposed. Finally, an electro-mechanical system is designed for accomplishing the task of sorting out the classified marble slabs. In the literature, only a system with a labeling mechanism has been presented. Our system, on the other hand, comes with a complete conveyor belt acting as an element that links the production line with the proposed system. This allows the possibility of embedding the proposed system into the production line of a marble factory. It has been observed that although the performance of the developed system is not as high as neural network based systems that use training, it could still be employed in industry when there is no available training set of samples. With this advantage, it provides an increase in the quality control standards of marble slab classification, since marbles are classified with an objective and uniform-through-time criterion.     

Solvent extraction of bacteriocins from model solutions and fermentation broths

A novel method for the extraction and purification of bacteriocins (small peptides with antimicrobial properties) from fermentation broths is described. Model solutions of nisin were prepared from Nisaplin®, a commercial whey‐based powder containing about 2.5% nisin and sold as a food preservative. These model solutions and fermentation broths from a culture of nisin‐producing Lactococcus lactis subsp lactis were cross‐flow filtered and stirred with toluene to obtain a white suspension in the toluene layer, which was back extracted with 10 mmol dm⁻³ HCl. Yields of the order of 90% for a single stage extraction were obtained followed by similar yields on back extraction. Yields dropped with decreasing pH, going through a minimum at pH 2. In larger scale experiments (11 dm³) at pH 6, a gel layer was formed which, on centrifugation and drying, gave a white solid containing about 50% nisin, the remainder being water and salt. Further process development would almost certainly bring this figure closer to the small‐scale value. The phase transfer technique was also applied to solutions containing variacin and carnocin (produced by Micrococcus varians and Carnobacterium piscicola, respectively). The mechanism of bacteriocin extraction probably involves concentration of the peptides, which are surface active, at the interface until their solubility is exceeded and they form reverse submicelles, which aggregate into reverse micelles to give a gel. © 2000 Society of Chemical Industry     

A Thienothiophene-Based Cation Treatment Allows Semitransparent Perovskite Solar Cells with Improved Efficiency and Stability

Perovskite surface treatment with additives has been reported to improve charge extraction, stability, and/or surface passivation. In this study, treatment of a 3D perovskite ((FAPbI₃)_1−x(MAPbBr₃)_x) layer with a thienothiophene-based organic cation (TTMAI), synthesized in this work, is investigated. Detailed analyses reveal that a 2D (n = 1) or quasi-2D layer does not form on the PbI₂-rich surface 3D perovskite. TTMAI-treated 3D perovskite solar cells (PSCs) fabricated in this study show improved fill factors, providing an increase in their power conversion efficiencies (PCEs) from 17% to over 20%. It is demonstrated that the enhancement is due to better hole extraction by drift-diffusion simulations. Furthermore, thanks to the hydrophobic nature of the TTMAI, PSC maintains 82% of its initial PCE under 15% humidity for over 380 h (the reference retains 38%). Additionally, semitransparent cells are demonstrated reaching 17.9% PCE with treated 3D perovskite, which is one of the highest reported efficiencies for double cationic 3D perovskites. Moreover, the semitransparent 3D PSC (TTMAI-treated) maintains 87% of its initial efficiency for six weeks (>1000 h) when kept in the dark at room temperature. These results clearly show that this study fills a critical void in perovskite research where highly efficient and stable semitransparent perovskite solar cells are scarce.     

4-Aminophenyl boronic acid modified gold platforms for influenza diagnosis

As a potential pandemic threat to human health, there has been an urgent need for rapid, sensitive, simpler and less expensive detection method for the highly pathogenic influenza A virus. For this purpose, Quartz Crystal Microbalance (QCM) and Surface Plasmon Resonance (SPR) sensors have been developed for the recognition of hemagglutinin (HA) which is a major protein of influenza A virus. 4-Aminophenyl boronic acid (4-APBA) has been synthesized and used as a new ligand for binding of sialic acid (SA) via boronic acid–sugar interaction. SA has an important role in binding of HA. QCM and SPR sensor surfaces have been modified with thiol groups and then 4-APBA and SA have been immobilized on sensor surfaces, respectively. Sensor surfaces have been screened with AFM and used for the determination of HA from aqueous solution. The selective recognition of the QCM and SPR sensors toward Concanavalin A has been reported in this work. Also, the binding capacity and detection limits of QCM and SPR sensors have been calculated and detection limits were found to be 4.7 × 10^? 2 μM, (0.26 μg ml^? 1) and 1.28 × 10^? 1 μM, (0.72 μg ml^? 1) in the 95% confidence interval, respectively.     

Conformational changes during protein adsorption. FT-IR spectroscopic imaging of adsorbed fibrinogen layers

The influence of hydrophobicity of the substrate surface on structural changes during protein adsorption was investigated. Plasma fibrinogen was chosen to model this effect as it is the most important protein in the body that adsorbs to foreign surfaces. Only conformations of adsorbed fibrinogen similar to that of the protein in solution do not activate the process of blood coagulation. Small spots on the substrate surface with conformational changes within the adsorbed protein are already sufficient to deteriorate biocompatibility. Mid-infrared hyperspectral imaging permits the identification of coagulated spots down to a few micrometers in size. The spectra of the FT-IR images that were assessed to be of suitable quality were clustered by a fuzzy c-means algorithm. The determination of the appropriate number of clusters was based on cluster variance. Subsequent evaluation of the centroid spectra of each cluster showed that their amide I band was separated into contributions from different structural units, with the alpha-helix content always being dominant. Significant differences between hydrophobic and hydrophilic surfaces were observed for turn and sheet contributions. Lower sheet/turn ratios appear to indicate inferior biocompatibility. Spots on hydrophilic surfaces could be identified, which exhibit structural changes similar to those on hydrophobic surfaces.     

Characterization and differentiation of gel-like elastomers and compact silicones in order to realize a sensorial rating

Sensorial tests on silicones tackiness perception with naïve consumers show that the stickiness sensation can be disturbed by the sensation of finger penetration into the sample. Indeed a frequent report is that a non-expert people cannot perceive whether tackiness sensation is related to the material adhesion properties or whether it is related to the finger penetration. The samples are both elastomers silicones but some are gel-like elastomers and others are compact silicones. We use an experimental device to realize indentation tests in order to try to differentiate mechanically the two silicones. The apparatus developed in the laboratory allows to characterize and to study the adhesion properties of materials. The analysis of the results should allow to investigate which parameter can influence the sensorial analysis of tackiness.     

Phase stability,microstructure and high-temperature properties of NbSi<Subscript>2</Subscript>- and TaSi<Subscript>2</Subscript>-oxide conducting ceramic composites

NbSi₂- and TaSi₂-based electroconductive ceramic composites with the addition of 40–70 vol% Al₂O₃ and ZrO₂ particles were fabricated by high-temperature sintering (1400–1600 °C) under argon. Their phase stability, microstructural evolution, oxidation kinetics and electrical properties were studied at high temperatures. The densification of the composites was improved by increasing the oxide phase content and sintering temperature. The interaction of the starting metal disilicides with residual oxygen sources resulted in the formation of the hexagonal-structured 5–3 metal silicide (Nb₅Si₃ and Ta₅Si₃) phases. The increasing sintering temperature and volume percentage of the oxide phase reduced the pest oxidation, particularly for the silicide–alumina composites, which exhibited lower oxidation-induced mass changes than their dense monolithic metal silicides. Depending on the silicide–oxide volume percentage, their electrical conductivities ranged from 5.3 to 111.3 S/cm at 900 °C. Their phase stability, reduced oxidation rates and high electrical conductivities at high temperatures show promise for future high-temperature applications in advanced sensing.