Chemistry and light - part 2: light and energy

The conversion of solar energy into more useful forms of energy, such as chemical fuels or electricity, is one of the central problems facing modern science. Progress in photochemistry and chemical synthesis has led to a point where light energy conversion by means of artificial molecular devices can be rationally attempted. In this article, a general approach towards this challenging goal is presented.

Security Authentication using Phase-Encoded Nanoparticle Structures and Polarized Light

Phase encoded nano structures such as Quick Response (QR) codes made of metallic nanoparticles are suggested to be used in security and authentication applications. We present a polarimetric optical method able to authenticate random phase encoded QR codes. The system is illuminated using polarized light and the QR code is encoded using a phase-only random mask. Using classification algorithms it is possible to validate the QR code from the examination of the polarimetric signature of the speckle pattern. We used Kolmogorov-Smirnov statistical test and Support Vector Machine algorithms to authenticate the phase encoded QR codes using polarimetric signatures.

Study of the optical properties of TeO2-PbO-TiO2 glass system

We describe the preparation and some optical properties of high refractive index TeO2-PbO-TiO2 glass system. Highly homogeneous glasses were obtained by agitating the mixture during the melting process in an alumina crucible. The characterization was done by X-ray diffraction, Raman scattering, light absorption and linear refractive index measurements. The results show a change in the glass structure as the PbO content increases: the TeO4 trigonal bipyramids characteristics of TeO2 glasses transform into TeO3 trigonal pyramids. However, the measured refractive indices are almost independent of the glass composition. We show that third-order nonlinear optical susceptibilities calculated from the measured refractive indices using Lines' theoretical model are also independent of the glass composition.

Trigger and data link system for CMS Resistive Plate Chambers at the LHC accelerator

The purpose of the work was to realize a high-speed digital data transfer system for RPC muon chambers in the CMS experiment on CERN’s new LHC accelerator. This large scale system took many years and many stages of prototyping to develop, and required the participation of tens of people. The system interfaces to Frontend Boards (FEB) at the 200,000-channel detector and to the trigger and readout electronics in the control room of the experiment. The distance between these two is about 80 metres and the speed required for the optic links was pushing the limits of available technology when the project was started. Here, as in many other aspects of the design, it was assumed that the features of readily available commercial components would develop in the course of the design work, just as they did. By choosing a high speed it was possible to multiplex the data from some the chambers into the same fibres to reduce the number of links needed. Further reduction was achieved by employing zero suppression and data compression, and a total of only 660 optical links were needed. Another requirement, which conflicted somewhat with choosing the components a late as possible was that the design needed to be radiation tolerant to an ionizing dose of 100 Gy and to a have a moderate tolerance to Single Event Effects (SEEs). This required some radiation test campaigns, and eventually led to ASICs being chosen for some of the critical parts. The system was made to be as reconfigurable as possible. The reconfiguration needs to be done from a distance as the electronics is not accessible except for some short and rare service breaks once the accelerator starts running. Therefore reconfigurable logic is extensively used, and the firmware development for the FPGAs constituted a sizable part of the work. Some special techniques needed to be used there too, to achieve the required radiation tolerance. The system has been demonstrated to work in several laboratory and beam tests, and now we are waiting to see it in action when the LHC will start running in the autumn 2008.

Epäpuhtauksien optinen laskenta sulpusta

Työn tarkoituksena oli hakea mittausjärjestelmän raja-arvoja optiselle kamerapohjaiselle roskalaskentajärjestelmälle sekä testata roskalaskentajärjestelmän toimivuus käytännössä. Tavoitteena oli tuotteistaa kamerapohjainen roskalaskenta-analyysi palvelutuotteeksi, jota voitaisiin hyödyntää sihtien kuntokartoituksessa ja ongelmanratkaisuvälineenä. Teoriaosa koostui kahdesta kokonaisuudesta: sulpun epäpuhtauksista, roskalaskennan teoriasta ja epäpuhtauksien mittausmenetelmistä sekä markkinoinnista, tuotteistamis- ja lanseerausprosessista palvelutuotteen näkökulmasta. Kokeellisessa osassa selvitettiin kamerapohjaiseen roskalaskentaanalyysiin vaikuttavia tekijöitä: kameran tarkennus, kuvan terävyys, analysoitavan arkin väri, neliömassa ja roskapitoisuus, impregnointi, valonlähde, kuvan muokkaus, tiedostomuoto ja pikselimäärä. Kamerapohjaisen roskalaskenta-analyysin soveltuvuus käytäntöön testattiin tehdasesimerkin avulla. Havaittiin, että kamerapohjaista roskalaskenta-analyysiä voitaisiin käyttää lähes kaikille massatyypeille. Työssä määriteltiin kalibrointimenetelmä kameran tarkentamiseksi arkin tasoon sekä suljinnopeusanalyysi massatyypistä riippuvan suljinnopeuden selvitykseen. Kamerapohjaisessa roskalaskenta-analyysissä määritettiin käytettäväksi arkin neliömassana 60 g/m2, suljinaukkoa F5 ja terävyysasetusta 5. Tulokseksi saatiin, että analysoitavia arkkeja ei tarvitse impregnoida tai jälkikäsitellä. Korrelaatiota Somerville-erotustehokkuuteen ei löytynyt. Esimerkkitehtaasta selvitettiin primääriportaan roskapitoisuudet ja erotustehokkuudet. Tehdasesimerkin tulosten perusteella havaittiin happivaiheen ja D0-vaiheen olleen tehokkaimpia epäpuhtauksien poistajia.

On Transmission System Design for Wireless Broadcasting

This thesis considers aspects related to the design and standardisation of transmission systems for wireless broadcasting, comprising terrestrial and mobile reception. The purpose is to identify which factors influence the technical decisions and what issues could be better considered in the design process in order to assess different use cases, service scenarios and end-user quality. Further, the necessity of cross-layer optimisation for efficient data transmission is emphasised and means to take this into consideration are suggested. The work is mainly related terrestrial and mobile digital video broadcasting systems but many of the findings can be generalised also to other transmission systems and design processes. The work has led to three main conclusions. First, it is discovered that there are no sufficiently accurate error criteria for measuring the subjective perceived audiovisual quality that could be utilised in transmission system design. Means for designing new error criteria for mobile TV (television) services are suggested and similar work related to other services is recommended. Second, it is suggested that in addition to commercial requirements there should be technical requirements setting the frame work for the design process of a new transmission system. The technical requirements should include the assessed reception conditions, technical quality of service and service functionalities. Reception conditions comprise radio channel models, receiver types and antenna types. Technical quality of service consists of bandwidth, timeliness and reliability. Of these, the thesis focuses on radio channel models and errorcriteria (reliability) as two of the most important design challenges and provides means to optimise transmission parameters based on these. Third, the thesis argues that the most favourable development for wireless broadcasting would be a single system suitable for all scenarios of wireless broadcasting. It is claimed that there are no major technical obstacles to achieve this and that the recently published second generation digital terrestrial television broadcasting system provides a good basis. The challenges and opportunities of a universal wireless broadcasting system are discussed mainly from technical but briefly also from commercial and regulatory aspect

Gota suspensa para avaliação de aldeído total no ar interno e externo do ambiente

A sensitive and simple system was proposed for the in situ measurement of total aldehyde in outdoor or indoor ambient. The method is based on the use of a reagent drop as an useful interface to preconcentrate the sample prior to determination of total aldehyde as formaldehyde. The drop is formed at the tip of a cylindrical tube that contains two optical fibers placed on opposite sides and in contact with the reagent solution. One optical fiber carries the red light to the drop form a light emitting diode (LED). The transmitted light is measured by a second optical fiber/photodiode system. The analytical signal is read and converted into absorbance. The reagent solution of 3-methyl-2-benzothiazoline hydrazone (MBTH) forms a blue cation during reaction with formaldehyde that can be measured at 660 nm. Some aspects of kinetics reaction formation of dye were reevaluated. The formaldehyde reacts with MBTH and forms the azine in about 12 min. The oxidation of MBTH by Fe (III) and the formation of dye requires 3 min. The absorbance of the reagent drop is proportional to the sampling time and to the analyte concentration. The absorbance signal increases with increased sample gas flow until a maximum is reached then decreases until it forms a plateau. The proposed method was evaluated using both outdoor and indoor samples, and it was shown to viable provide an accurate measure of total aldehyde.

OLED-teknologia silmänäytössä ja linssiokulaarin korvaaminen muoviprismalla

Tämä diplomityö esittelee monikäyttöisen kamerajärjestelmän, mikä on pääsääntöisesti tarkoitettu valovahvistimen perään integroitavaksi. Tarkoituksena on parantaa sotilaan pimeätoimintakykyä ja urbaanissa ympäristössä operointia. Järjestelmän yhtenä moduulina on silmänäyttö, joka perustuu itse-emittoivaan orgaaniseen LED-näyttöelementtiin ja perinteiseen okulaarioptiikkaan. Työssä tutustutaan näyttöelementin teknologiaan, sen mahdollisiin rajoituksiin sekä selvitetään optisilla mittauksilla, voitaisiinko konventionaalinen linssiokulaari korvata muovisella prismaokulaarilla. Tämä mahdollistaisi pienemmän ja kevyemmän silmänäytön kehittämisen, mikä parantaisi kamerajärjestelmän käytettävyyttä ja kilpailukykyä.

Monomer conversion of composite dental resins photoactivated by a halogen lamp and a LED: a FT-Raman spectroscopy study

Eighteen circular blocks of resins cured either by a LED or a halogen lamp (20, 40 and 60 s), had their top (T) and bottom (B) surfaces studied using a FT-Raman spectrometer. Systematic changes in the intensity of the methacrylate C=C stretching mode at 1638 cm-1 as a function of exposure duration were observed. The calculated degree of conversion (DC) ranged from 45.0% (B) to 52.0% (T) and from 49.0% (B) to 55.0% (T) for the LED and halogen lamp, respectively. LED and halogen light produced similar DC values with 40 and 60 s of irradiation.

Um fotômetro multi-led microcontrolado, portátil e de baixo custo

A microcontrolled, portable and inexpensive photometer is described. It uses six light-emitting diodes (LEDs) as radiation sources and a phototransistor as detector, as well as a microcontroller (PIC - Programmable Controller of Interruption). This device provided total autonomy to the proposed photometer, which was successfully applied to determination of Fe2+ in ferrous syrups and of seven clinical biochemical parameters. As the components are cheap (~U$30.00) and easy to find, the proposed photometer is an economical alternative for routine chemical analyses in small laboratories, for research and teaching. Being portable and microcontrolled, it allows doing field chemical analyses.

Performance Evaluation and Calibration of Machine Vision Measurement

This thesis presents the calibration and comparison of two systems, a machine vision system that uses 3 channel RGB images and a line scanning spectral system. Calibration. is the process of checking and adjusting the accuracy of a measuring instrument by comparing it with standards. For the RGB system self-calibrating methods for finding various parameters of the imaging device were developed. Color calibration was done and the colors produced by the system were compared to the known colors values of the target. Software drivers for the Sony Robot were also developed and a mechanical part to connect a camera to the robot was also designed. For the line scanning spectral system, methods for the calibrating the alignment of the system and the measurement of the dimensions of the line scanned by the system were developed. Color calibration of the spectral system is also presented.

Pleiotrophin as a central nervous system neuromodulator, evidences from the hippocampus

Pleiotrophin (PTN) is a secreted growth factor, and also a cytokine, associated with the extracellular matrix, which has recently starting to attract attention as a significant neuromodulator with multiple neuronal functions during development. PTN is expressed in several tissues, where its signals are generally related with cell proliferation, growth, and differentiation by acting through different receptors. In Central Nervous System (CNS), PTN exerts post-developmental neurotrophic and -protective effects, and additionally has been involved in neurodegenerative diseases and neural disorders. Studies in Drosophila shed light on some aspects of the different levels of regulatory control of PTN invertebrate homologs. Specifically in hippocampus, recent evidence from PTN Knock-out (KO) mice involves PTN functioning in learning and memory. In this paper, we summarize, discuss, and contrast the most recent advances and results that lead to proposing a PTN as a neuromodulatory molecule in the CNS, particularly in hippocampus.

Study of a vapor-compression air-conditioning system for jetliners

Most modern passenger aeroplanes use air cycle cooling. A high-speed air cycle is a reliable and light option, but not very efficient. This thesis presents research work done to design a novel vapour cooling cycle for aeroplanes. Due to advancements in high-speed permanent magnet motors, the vapour cycle is seen as a competitive option for the air cycle in aeroplanes. The aerospace industry places tighter demands on the weight, reliability and environmental effects of the machinery than those met by conventional chillers, and thus modifications to conventional design are needed. The thesis is divided into four parts: the initial screening of the working fluid, 1-D design and performance values of the compressor, 1-D off-design value predictions of the compressor and the 3-D design of the compressor. The R245fa was selected as the working fluid based the study. The off-design range of the compressor was predicted to be wide and suitable for the application. The air-conditioning system developed is considerably smaller than previous designs using centrifugal compressors.

Pleiotrophin as a central nervous system neuromodulator, evidences from the hippocampus

Pleiotrophin (PTN) is a secreted growth factor, and also a cytokine, associated with the extracellular matrix, which has recently starting to attract attention as a significant neuromodulator with multiple neuronal functions during development. PTN is expressed in several tissues, where its signals are generally related with cell proliferation, growth, and differentiation by acting through different receptors. In Central Nervous System (CNS), PTN exerts post-developmental neurotrophic and -protective effects, and additionally has been involved in neurodegenerative diseases and neural disorders. Studies in Drosophila shed light on some aspects of the different levels of regulatory control of PTN invertebrate homologs. Specifically in hippocampus, recent evidence from PTN Knock-out (KO) mice involves PTN functioning in learning and memory. In this paper, we summarize, discuss, and contrast the most recent advances and results that lead to proposing a PTN as a neuromodulatory molecule in the CNS, particularly in hippocampus.

Energiatehokas toimisto - LED -teknologia

Tässä työssä käsitellään toimistorakennusten energiankulutusta ja nykyisiä toimistojen valaistusratkaisuja. Työssä perehdytään LED-valaistusteknologiaan sekä energiatehokkaaseen toimistovalaistukseen. Energiatehokkaan valaistuksen osalta käsitellään toimistovalaistuksen vaatimuksia, valaistuksen ohjausta ja luonnonvalon vaikutusta energiankulutukseen. Tutkimuskohteena oli Helsingin yliopiston tiloissa sijaitsevat neljä toimistohuonetta, joista kahden valaistusjärjestelmä uusittiin ja kahden jätettiin entiselleen vertailun vuoksi. Tutkimuksessa kartoitettiin toimistohuoneiden nykyistä energiankulutusta ja etsittiin keinoja sen tehostamiseen valaistuksen osalta. Tässä työssä tutkittiin erityisesti LED-valaisimien ja valaistuksen ohjauksen hyödynnettävyyttä toimistotiloissa. Toimistotilojen elinkaarikustannuslaskelmilla pyrittiin toteamaan valaistusjärjestelmien taloudellinen kannattavuus 30 vuoden tarkastelujaksolla. Tutkimuksessa tehtiin käyttäjäkysely toimistohuoneissa työskenteleville henkilöille ennen ja jälkeen muutoksen. Kyselyn perusteella voitiin todeta uusitun valaistusjärjestelmän hyödyt ja puutteet käyttäjän näkökulmasta.