Hybrid permeable metal-base transistor with large common-emitter current gain and low operational voltage

We demonstrate the suitability of N,N'-diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB), an organic semiconductor widely used in organic light-emitting diodes (OLEDs), for high-gain, low operational voltage nanostructured vertical-architecture transistors, which operate as permeable-base transistors. By introducing vanadium oxide (V2O5) between the injecting metal and NPB layer at the transistor emitter, we reduced the emitter operational voltage. The addition of two Ca layers, leading to a Ca/Ag/Ca base, allowed to obtain a large value of common-emitter current gain, but still retaining the permeable-base transistor character. This kind of vertical devices produced by simple technologies offer attractive new possibilities due to the large variety of available molecular semiconductors, opening the possibility of incorporating new functionalities in silicon-based devices.     

Enhanced photocurrent generation with quantum dots containing multilayers on gold

Quantum dots (QD) immobilised on electrodes show a light-triggered current depending on the applied potential. In this study it is investigated whether multiple layers of QD can be formed on electrodes and used for an enhanced photocurrent generation. Therefore multilayers of QD and the redox protein cytochrome c (cyt c) are constructed verified by quartz crystal microbalance (QCM) measurements. The voltammetric investigation of these multilayer assemblies shows no enhancement of the redox signal from cyt c in contrast to multilayers of cyt c and polyelectrolytes or gold nanoparticles. But photocurrent measurements reveal a slight enhancement of the signal which is depending on the number of deposited QD layers. In a second step QD multilayers with a positively charged polyelectrolyte are built up verified by QCM. Chronoamperometric investigations reveal an increase of the photocurrent which is proportional to the number of deposited layers. This indicates an efficient electron transfer between the QD layers. At an electrode with 5 bilayers (QD and polyallylamine) the light-induced current is increased about 5 times compared to a monolayer.     

Fatigue of selected GRP composite components and joints with damage evaluation

The paper summarises the most important results of selected experimental programmes on static and fatigue strength of heavy loaded components and joints made of glass reinforced plastic (GRP) composites, having been recently performed in fatigue laboratory of the SVÚM a.s. research and testing institute. Components like GRP trailer leaf springs, springs for railway freight vehicles are addressed, along with heavy loaded joints like stud connections in rotor blade roots at different loading and environmental conditions. It was confirmed during the different kind of tests that fatigue damage accumulation can be well monitored particularly when there are no defects or imperfections in the material. Then the damage curve usually had the typical three-stages sigmoidal shape. In case of fatigue tests of stud joints, where damage was located into the bonded area inside the specimen, temperature changes were considerably more sensitive than displacement and detailed temperature monitoring indicated weak areas in the full scale model specimens. Sudden break was mostly characteristic for defect material with insufficient wet out or with different bubbles and voids. After a more detailed analysis of fatigue tests, some further links like connections between total fatigue life and initial stiffness or initial temperature increase gradient were indicated.     

The Effects of Nanomaterials as Endocrine Disruptors

In recent years, nanoparticles have been increasingly used in several industrial, consumer and medical applications because of their unique physico-chemical properties. However, in vitro and in vivo studies have demonstrated that these properties are also closely associated with detrimental health effects. There is a serious lack of information on the potential nanoparticle hazard to human health, particularly on their possible toxic effects on the endocrine system. This topic is of primary importance since the disruption of endocrine functions is associated with severe adverse effects on human health. Consequently, in order to gather information on the hazardous effects of nanoparticles on endocrine organs, we reviewed the data available in the literature regarding the endocrine effects of in vitro and in vivo exposure to different types of nanoparticles. Our aim was to understand the potential endocrine disrupting risks posed by nanoparticles, to assess their underlying mechanisms of action and identify areas in which further investigation is needed in order to obtain a deeper understanding of the role of nanoparticles as endocrine disruptors. Current data support the notion that different types of nanoparticles are capable of altering the normal and physiological activity of the endocrine system. However, a critical evaluation of these findings suggests the need to interpret these results with caution since information on potential endocrine interactions and the toxicity of nanoparticles is quite limited.     

An evaluation tool for research of user behavior in a realistic mobile environment

User behavior is significantly influenced by the surrounding environment. Especially complex and dynamically changing environments (like mobile environment) are represented by a wide variety of extraneous variables, which influence the user behavior in an unpredictable and mostly uncontrolled way. For researchers, it is challenging to measure and analyze the user behavior in such environments. We introduce a complex tool—the IVE tool—which provides a unique way of context visualization and synchronization of measured data of various kinds. Thanks to this tool it is possible to efficiently evaluate data acquired during complex usability tests in a mobile environment. The functionality of this tool is demonstrated on the use case “Navigation of visually impaired users in the building with support of a navigation system called NaviTerier.” During the experiment, we focused on collection and analysis of data that may show user stress and which may influence his/her ability to navigate. We analyzed objective data like Galvanic Skin Response parameter (GSR), Heart Rate Variability parameters (HRV) and audio video recordings and also subjective data like the user’s subjective stress feeling and observation of the user’s behavior.     

Compact cw Terahertz Spectrometer Pumped at 1.5 μm Wavelength

A compact and low-cost continuous wave terahertz spectrometer operating at an optical wavelength of 1.5 μm is presented. The spectrometer employs high power distributed feedback (DFB) laser diodes in integrated “butterfly” packages. No further optical amplification of the beating signal is required. An integrated photodiode antenna with an output power of 5 μW at 500 GHz is used as efficient terahertz emitter. Employing low-temperature grown (LT-) InGaAs/InAlAs photoconductive receivers as coherent detectors, SNR values of the terahertz power up to 75 dB are attained at an integration time of 300 ms. Accurate characterization of the thermal tuning behavior of the DFBs and precise thermal control yield an absolute accuracy of 1 GHz and a resolution of better than 5 MHz, without any on-line monitoring of the optical frequency. Due to the high frequency resolution no delay line is needed to vary the terahertz phase.     

Integrative Approaches for Mechanical Mold Design in Injection Molding

The injection mold faces a number of different loads during the injection molding process for plastic parts. The effect on the mechanical behavior of the mold, inserts, and adjacent processes can be complex and may cause bad final parts. By using an integrative simulation approach it is possible to take the process influence into account when calculating the solid body behavior of the mold in a structural simulation. A newly developed approach at IKV uses the advantages of the integrative approach and extends it by an automatic back coupling of deformation results during the filling simulation. This way the interaction of the melt flow and the deformation of inserts or mold components can be considered during the filling phase.