Martin Jaanus

Digital Microfluidic Sampler for a Portable Capillary Electropherograph

A new sample introduction/analysis approach was developed by combining a digital microfluidic (DMF) device with a portable capillary electrophoresis (CE) analyzer based on short separation capillary and contactless conductivity detection. The DMF sample injection was performed by transporting sample and buffer droplets in succession under the CE capillary inlet end allowing the capillary to be immersed into the sample/buffer droplet, and CE separation was performed by applying a high voltage between the (grounded) buffer droplet and CE outlet reservoir. Electrowetting on dielectric (EWOD) phenomenon was used for droplets actuation. With the use of the DMF sampler, CE separation of a mixture of vitamins was achieved. A droplet evaporation process with simultaneous concentration of sample in the droplet was monitored. It was found that the concentration process closely followed the theoretically predicted function.

Fraction collection in capillary electrophoresis for various stand-alone mass spectrometers.

A procedure for collecting fractions during capillary electrophoresis for their analysis using various stand-alone instruments is described. The results of a systematic study of the optimization and application of capillary electrophoresis (CE) in conjunction with a reverse-phase high-performance liquid chromatography electrospray ionization quadrupole time of flight-tandem mass spectrometry (RP-HPLC-ESI-Q-TOF-MS/MS) and inductively-coupled mass spectrometry (ICP-MS) to the analysis of the seed extract of the Japanese Pagoda Tree (Sophora japonica) are presented. The off-line coupling of CE to the matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) for the proteins mixture was applied. The cathode end of the capillary was placed inside a stainless steel needle using a coaxial liquid-sheath-flow configuration. The optimization of experimental parameters resulted in an efficient methodology for MS analysis of fractions. Several components contained in the extract of S. japonica were identified, some not previously known. It was demonstrated that low sensitivity, which is a real problem in off-line CE-MS analysis, could be tolerated because of a more flexible optimization of the CE separation conditions and the choice of independent stand-alone instruments for analysis of separated fractions. The estimated limit of detection for CE-RP-HPLC-ESI-Q-TOF-MS was 50 microM of polyphenols and for CE-ICP-MS, 1-100 microg/l.

Home Lab Kits for Introductory Course in Electrical Engineering

Design, implementation, and experience of application of HomeLabKits are described. HomeLabkit is a small box containing everything needed to perform labs in a courses related to introduction into electrical engineering. In addition to the kit, a student needs a computer with Internet connection only. Both power supply and data processing is performed over USB-connection. The paper describes content of kit, the labs for which the kit has been designed, software functions and experience of application during one and half year (3 semesters). The different categories of students have used the kit and also different modes of usage were tested. Very positive results have lead us to the decision to base labs on HomeLabKits only.

Digital microfluidics platform for interfacing solid-liquid extraction column with portable capillary electropherograph for analysis of soil amino acids.

In this work, the concept of a field‐portable analyzer is proposed that operates with milliliter amounts of solvents and samples. The need to develop such an analyzer is not only driven by specific extraterrestrial analysis but also, for example, by forensics applications where the amount of liquid that can be taken to the field is severely limited. The prototype of the proposed analyzer consists of a solid–liquid extractor, the output of which is connected to the micropump, which delivers droplets of extracts to digital microfluidic platform (DMFP). In this way, world‐to‐chip interfacing is established. Further, the sample droplets are transported to CE capillary inlet port, separated and detected via a contactless conductivity detector. Working buffers and other solvents needed to perform CE analysis are also delivered as droplets to the DMFP and transported through the CE capillary. The performance of the analyzer is demonstrated by analysis of amino acids in sand matrices. The recovery of the spiked amino acids from the inert sand sample was from 34 to 51% with analysis LOD from 0.2 to 0.6 ppm and migration time RSD from 0.2 to 6.0%.

New concepts of automatic answer evaluation in competence based learning

This paper introduces current work with automatic evaluation that has been done to enable algorithms generating proper feedback according to the mistakes students have made. Learning environment using novel competence based approach has been used to implement those concepts and over the years data from different development steps has been collected that can be used to verify the benefits to students results of offered algorithm that mimics step-by-step student answering process.

Student forgetting model: Practical experience

This paper describes student memory model applied during one semester for control of learning activities in Electrical Engineering introductory course. All assignments include tasks of 128 levels of difficulty; transitions between them are controlled by a state machine. For any level achieved by a student in one session, exponential forgetting function is applied. Two different time constants are used for theoretical tests and lab experiments. Recalculation of level, time constant, and floor is applied after any successive session. Students accepted that model quickly and analysis of results showed that it really helped to implement ldquorepetitio est mater studiorumrdquo. In the paper we describe the model in more details and provide analysis of collected data.

Competence-based approach to learning

This paper describes competence based approach to complete learning process. The learning process is fully web-based and can be completed without attending campus. It consists of small exercises and lab experiments. Automatic evaluation by stimulating student answering process is explained. Labs are supported by HomeLabKit, small box that contains everything needed to perform lab tasks and can be lent from university. After two years of using competence-based learning in real learning, a lot of information has been collected that can now be analyzed.

Two-Dimensional Knowledge Model for Learning Control and Competence Mapping

The paper presents two-dimensional model for knowledge representation with volume as one variable and ability as another one. This makes possible describing current state of learner’s abilities and integration for higher level parameters e.g. grading related to course or other entities. Both values are related to atomized knowledge elements (competences) with volume interpreted as credit units and ability levels are formed during learning with application of forgetting. This model makes possible characterization (grading) of knowledge based on real abilities independently of predeclared courses and for ‘drop-outs’. So, on that bases one can obtain grade for some course if proper knowledge has been obtained in different courses and schools even when courses had not passed. Also this model helps to build connections between courses as using courses in the role of prerequisites becomes less usable. Not wasting knowledge obtained in MOOCs is another example with high drop-out levels where classical passed-failed model does not work.

Implementation of the robot arm in the interactive learning environment

While the robotics is becoming the more important branch of technology and industry, the teaching of industrial robotics has remained rather limited and expensive due to high cost of the industrial equipment and workrooms. Those drawbacks may be overcome by using the reduced size educational robot arm and the remote control of it via the interactive e-learning environment. The present paper describes the technical solutions that were designed and realized in order to give the possibility to students to learn the basics of industrial robot programming via the interactive environment.

Progress in development of the resonant tunneling diodes as promising compact sources at the THz gap bottom

In recent years remarkable progress has been made in filling the “terahertz gap” of compact sources from the “optical” side using quantum cascade lasers and difference frequency generation systems. On the “electronic” side the range up to 0.5 THz is covered by several devices like Gunn diodes, IMPATT diodes and HEMT transistors. However for the most difficult central range 0.5–2 THz, which includes frequencies for detection of explosives and several airborne threats, along with the popular semi-compact Schottky diodes based frequency multiplier systems, the resonant tunneling diodes (RTD) as micrometer-size range ultrafast electronic devices able to operate at room temperature may offer a real solution for the design of compact portable equipment. It has been predicted that frequency limit for operation of the RTDs may extend up to 3 THz if the problem of the low, microwatt-range output power could be solved. Over the last 10 years remarkable progress has been achieved in increasing the output power of RTDs by almost 2 orders of magnitude, and in extending the operation frequencies from earlier 0.7 THz range to the values near 2 THz, thus making RTDs competitive with the Schottky diode based multipliers. The chapter compares the RTDs with other compact THz sources and discusses the design approaches that have yielded remarkable increase of power and frequency of RTDs.