Torque teno -viruksen proteiinien tuotto ja puhdistus

Torque teno -virus (TTV, TT-virus) on uusimpia löydettyjä ihmisviruksia ja se on erittäin yleinen täysin terveissäkin ihmisissä. Sitä kantaa ihmisistä yli 80 % kantajan maantieteellisestä sijainnista tai iästä riippumatta. Vielä ei osata sanoa, aiheuttaako torque teno -virus tiettyjä tauteja vai onko se osa normaaliflooraa, mikä olisi viruksista puhuttaessa täysin uutta. Helsingin yliopiston virologian laitoksella Haartman instituutissa toimiva professori Klaus Hedmanin tutkimusryhmä on kehitellyt sopivia menetelmiä TT-viruksen proteiinien tuottoon ja puhdistamiseen. Tämän opinnäytetyön tarkoituksena oli optimoida näitä menetelmiä. Proteiinien tuottoon ja puhdistukseen valittiin mukaan TTV:n genomin koodittamista kuudesta proteiinista oletettavasti kapsidiproteiinina toimiva ORF1-Arg (ORF1-proteiini, josta on poistettu arginiinirikas alue) ja ei-rakenneproteiinina toimiva ORF2/2. Proteiinit tuotettiin Sf9- ja High Five -hyönteissoluissa, ja vektorina ekspressoinnissa oli baculovirus. Puhdistukseen käytettiin agaroosigeelielektroforeesia (AGE) ja vaihtoehtoisesti histidiiniaffiniteettikromatografiaa. Proteiinien tuotossa optimoitiin solujen infektiossa käytettävän baculoviruksen määrää ja selvitettiin, että proteiineja saatiin tuotettua suunnilleen yhtä paljon sekä Sf9- että High Five -soluissa. AGE-menetelmällä saatiin puhdistettua ORF2/2-proteiinia ja menetelmää yritettiin kehitellä niin, että saataisiin puhdistuksen yhteydessä enemmän proteiineja talteen. Histidiiniaffiniteettipuhdistusta ei ollut aikaisemmin käytetty hyönteissoluissa tuotettujen TTV:n proteiinien puhdistukseen. Menetelmällä saatiin tuotettua ORF1-proteiinia, mutta puhdistusmenetelmä vaatii vielä kehittelyä. Tämän opinnäytetyön avulla saatiin menetelmien kehitystyötä eteenpäin, ja havaittiin ongelmakohtia, joihin tulee kiinnittää jatkossa huomiota. Histidiiniaffiniteettipuhdistusta ei vielä saatu toimivaksi ja AGE:n kehittelyä täytyy myös vielä jatkaa. TTV:n puhdistettuja proteiineja tullaan käyttämään apuna määritettäessä TTV:n mahdollista patogeenisuutta ja biologista merkitystä. Proteiinien avulla kehitellään laboratoriomenetelmiä TTV:n virusinfektioiden ja sairauksien löytämiseen ja diagnosointiin mm. tuottamalla proteiinien avulla spesifisiä vasta-aineita TTV:tä vastaan. Opinnäytetyössä puhdistettuja ORF2/2-proteiineja käytettiin tutkimusryhmässä TTV-spesifisen T-soluimmuniteetin tutkimiseen.

A linkage map of spring turnip rape based on RFLP and RAPD markers

Selostus: RAPD- ja RFLP-markkereista koostuva rypsin kytkentäkartta

Generating a raster map presentation of a forest resource by solving a transportation problem

Abstract

Torque vibration model of axial-flux surface-mounted permanent magnet synchronous machine

In order that the radius and thus ununiform structure of the teeth and otherelectrical and magnetic parts of the machine may be taken into consideration the calculation of an axial flux permanent magnet machine is, conventionally, doneby means of 3D FEM-methods. This calculation procedure, however, requires a lotof time and computer recourses. This study proves that also analytical methods can be applied to perform the calculation successfully. The procedure of the analytical calculation can be summarized into following steps: first the magnet is divided into slices, which makes the calculation for each section individually, and then the parts are submitted to calculation of the final results. It is obvious that using this method can save a lot of designing and calculating time. Thecalculation program is designed to model the magnetic and electrical circuits of surface mounted axial flux permanent magnet synchronous machines in such a way, that it takes into account possible magnetic saturation of the iron parts. Theresult of the calculation is the torque of the motor including the vibrations. The motor geometry and the materials and either the torque or pole angle are defined and the motor can be fed with an arbitrary shape and amplitude of three-phase currents. There are no limits for the size and number of the pole pairs nor for many other factors. The calculation steps and the number of different sections of the magnet are selectable, but the calculation time is strongly depending on this. The results are compared to the measurements of real prototypes. The permanent magnet creates part of the flux in the magnetic circuit. The form and amplitude of the flux density in the air-gap depends on the geometry and material of the magnetic circuit, on the length of the air-gap and remanence flux density of the magnet. Slotting is taken into account by using the Carter factor in the slot opening area. The calculation is simple and fast if the shape of the magnetis a square and has no skew in relation to the stator slots. With a more complicated magnet shape the calculation has to be done in several sections. It is clear that according to the increasing number of sections also the result will become more accurate. In a radial flux motor all sections of the magnets create force with a same radius. In the case of an axial flux motor, each radial section creates force with a different radius and the torque is the sum of these. The magnetic circuit of the motor, consisting of the stator iron, rotor iron, air-gap, magnet and the slot, is modelled with a reluctance net, which considers the saturation of the iron. This means, that several iterations, in which the permeability is updated, has to be done in order to get final results. The motor torque is calculated using the instantaneous linkage flux and stator currents. Flux linkage is called the part of the flux that is created by the permanent magnets and the stator currents passing through the coils in stator teeth. The angle between this flux and the phase currents define the torque created by the magnetic circuit. Due to the winding structure of the stator and in order to limit the leakage flux the slot openings of the stator are normally not made of ferromagnetic material even though, in some cases, semimagnetic slot wedges are used. In the slot opening faces the flux enters the iron almost normally (tangentially with respect to the rotor flux) creating tangential forces in the rotor. This phenomenon iscalled cogging. The flux in the slot opening area on the different sides of theopening and in the different slot openings is not equal and so these forces do not compensate each other. In the calculation it is assumed that the flux entering the left side of the opening is the component left from the geometrical centre of the slot. This torque component together with the torque component calculated using the Lorenz force make the total torque of the motor. It is easy to assume that when all the magnet edges, where the derivative component of the magnet flux density is at its highest, enter the slot openings at the same time, this will have as a result a considerable cogging torque. To reduce the cogging torquethe magnet edges can be shaped so that they are not parallel to the stator slots, which is the common way to solve the problem. In doing so, the edge may be spread along the whole slot pitch and thus also the high derivative component willbe spread to occur equally along the rotation. Besides forming the magnets theymay also be placed somewhat asymmetric on the rotor surface. The asymmetric distribution can be made in many different ways. All the magnets may have a different deflection of the symmetrical centre point or they can be for example shiftedin pairs. There are some factors that limit the deflection. The first is that the magnets cannot overlap. The magnet shape and the relative width compared to the pole define the deflection in this case. The other factor is that a shifting of the poles limits the maximum torque of the motor. If the edges of adjacent magnets are very close to each other the leakage flux from one pole to the other increases reducing thus the air-gap magnetization. The asymmetric model needs some assumptions and simplifications in order to limit the size of the model and calculation time. The reluctance net is made for symmetric distribution. If the magnets are distributed asymmetrically the flux in the different pole pairs will not be exactly the same. Therefore, the assumption that the flux flows from the edges of the model to the next pole pairs, in the calculation model from one edgeto the other, is not correct. If it were wished for that this fact should be considered in multi-pole pair machines, this would mean that all the poles, in other words the whole machine, should be modelled in reluctance net. The error resulting from this wrong assumption is, nevertheless, irrelevant.

Direct torque control of permanent magnet synchronous machines - analysis and implementation

Thedirect torque control (DTC) has become an accepted vector control method besidethe current vector control. The DTC was first applied to asynchronous machines,and has later been applied also to synchronous machines. This thesis analyses the application of the DTC to permanent magnet synchronous machines (PMSM). In order to take the full advantage of the DTC, the PMSM has to be properly dimensioned. Therefore the effect of the motor parameters is analysed taking the control principle into account. Based on the analysis, a parameter selection procedure is presented. The analysis and the selection procedure utilize nonlinear optimization methods. The key element of a direct torque controlled drive is the estimation of the stator flux linkage. Different estimation methods - a combination of current and voltage models and improved integration methods - are analysed. The effect of an incorrect measured rotor angle in the current model is analysed andan error detection and compensation method is presented. The dynamic performance of an earlier presented sensorless flux estimation method is made better by improving the dynamic performance of the low-pass filter used and by adapting the correction of the flux linkage to torque changes. A method for the estimation ofthe initial angle of the rotor is presented. The method is based on measuring the inductance of the machine in several directions and fitting the measurements into a model. The model is nonlinear with respect to the rotor angle and therefore a nonlinear least squares optimization method is needed in the procedure. A commonly used current vector control scheme is the minimum current control. In the DTC the stator flux linkage reference is usually kept constant. Achieving the minimum current requires the control of the reference. An on-line method to perform the minimization of the current by controlling the stator flux linkage reference is presented. Also, the control of the reference above the base speed is considered. A new estimation flux linkage is introduced for the estimation of the parameters of the machine model. In order to utilize the flux linkage estimates in off-line parameter estimation, the integration methods are improved. An adaptive correction is used in the same way as in the estimation of the controller stator flux linkage. The presented parameter estimation methods are then used in aself-commissioning scheme. The proposed methods are tested with a laboratory drive, which consists of a commercial inverter hardware with a modified software and several prototype PMSMs.

Analysis of torque and speed ripple producing non-idealities of frequency converters in electric drives

Electric motors driven by adjustable-frequency converters may produce periodic excitation forces that can cause torque and speed ripple. Interaction with the driven mechanical system may cause undesirable vibrations that affect the system performance and lifetime. Direct drives in sensitive applications, such as elevators or paper machines, emphasize the importance of smooth torque production. This thesis analyses the non-idealities of frequencyconverters that produce speed and torque ripple in electric drives. The origin of low order harmonics in speed and torque is examined. It is shown how different current measurement error types affect the torque. As the application environment, direct torque control (DTC) method is applied to permanent magnet synchronous machines (PMSM). A simulation model to analyse the effect of the frequency converter non-idealities on the performance of the electric drives is created. Themodel enables to identify potential problems causing torque vibrations and possibly damaging oscillations in electrically driven machine systems. The model is capable of coupling with separate simulation software of complex mechanical loads. Furthermore, the simulation model of the frequency converter's control algorithm can be applied to control a real frequency converter. A commercial frequencyconverter with standard software, a permanent magnet axial flux synchronous motor and a DC motor as the load are used to detect the effect of current measurement errors on load torque. A method to reduce the speed and torque ripple by compensating the current measurement errors is introduced. The method is based on analysing the amplitude of a selected harmonic component of speed as a function oftime and selecting a suitable compensation alternative for the current error. The speed can be either measured or estimated, so the compensation method is applicable also for speed sensorless drives. The proposed compensation method is tested with a laboratory drive, which consists of commercial frequency converter hardware with self-made software and a prototype PMSM. The speed and torque rippleof the test drive are reduced by applying the compensation method. In addition to the direct torque controlled PMSM drives, the compensation method can also beapplied to other motor types and control methods.

Asia... lijknat widh een flygande Häst, hwilken Poëterne kalla Pegasum - [Kartta - kartan - the map]

Stockholm 1595, Andreas Gutterwitz