An experiment was conducted to determine whether the water depth (above soil) and soil type would have any influence on the multispectral reflectances of paddy rice, and their calculated vegetation index values. The results showed that, when vegetation cover was low (below 600 grams of dry biomass per square meter), the near infrared (NIR) reflectances decreased very little with water depth. The same was true for red reflectances, but to a lesser degree. Overall the changes were not significant at 0.05 level of significance when the water depth was increased from 2.5 centimeters to 10 centimeters. When the vegetation cover became higher most NIR and red reflectances did not show a significant decrease with the increase of the water depth, and sometimes they even increased slightly up to a water depth of 6.4 cm. Nevertheless both rice cover and water depth as well as soils played an important role in the reflectance pattern in red and NIR bands. Some index values increased and some decreased depending on water depth and rice cover. Statistical analysis of the data showed that rice multispectral responses were mainly controlled by vegetation and minimally influenced by soil and water depths.

No description available.

Radio frequency (RF) lesioning and deep brain stimulation (DBS) are the two prevailing surgical treatments for movement disorders within the field of stereotactic and functional neurosurgery. For RF-lesioning, a small volume of brain tissue is coagulated and knowledge of the lesion size and growth is of great importance for the safety and outcome of the procedure. This thesis deals with adapting the laser Doppler perfusion monitoring (LDPM) technique for measurements in brain tissue during RF-lesioning. The relation between LDPM signal changes and developed lesion size was investigated. LDPM measurements were evaluated both in vitro (albumin protein solution) and in vivo in the porcine brain during RF-lesioning corresponding to a bilateral thalamotomy in man. The investigated signals from the LDPI measurements can be used for following the lesioning time course and to detect if a lesion was created, both in vitro and in the animal model. For the albumin model, both the total backscattered light intensity and the perfusion signal can be used as markers for estimating the final coagulation size, while in the animal model this conclusion was not statistical verified. Independent on surgical method, RF-lesioning or DBS, intracerebral guidance is an important aspect within stereotactic and functional neurosurgery. To increase the accuracy and precision of reaching the correct target, different methods for intracerebral guidance exist, such as microelectrode recording and impedance methods. In this thesis, the possibility of developing an optical intracerebral guidance method has been investigated. Diffuse reflectance spectroscopy served as technology and all measurements were performed stereotactically in both porcine and human brain. Measurements of white and gray matter showed large differences, with higher reflectivity for white brain matter, both in porcine and in human brain. For the human measurements during DBS-implants, large differences between white matter and functional targets were found. Additionally, differences between native and lesioned porcine brain matter were detected. Both studies support the idea of using diffuse reflectance spectroscopy for developing an intracerebral guidance method.

Thesis (PhD (Physics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Silicon/silicon dioxide (Si/SiO2) interface is widely used in microelectronics as the gate between the drain and source of most metal oxide semiconductor field effect transistors (MOSFETs). The functionality, reliability and electrical properties of such transistors are strongly dependent on the quality of the Si/SiO2 structure forming the gate. Characterization of the Si/SiO2 interface is important in understanding device degradation therefore the Si/SiO2 interface is a subject of intensive investigation. Research studies of Si/SiO2 interfaces using optical methods have been reported by many groups around the world but to date many open questions still exist. The physics of photoinduced trap or defect generation processes and the subsequent trapping of charge carriers, the precise role of photoinduced interfacial electric field in altering optical properties of the Si/SiO2 interface and its role in affecting the second harmonic (SH) yield measurements are not well understood. In this work a commercial near infrared femtosecond (fs) laser source [1.55 eV, 75 ± 5 fs, 10 nJ, 80 MHz] is used to study native Si/SiO2 interfaces of free standing single crystalline Si membrane and bulk Si. Optical second harmonic (SH) generated at the Si/SiO2 interfaces of a Si membrane in reflection and for the first time in transmission is demonstrated as well as stationary, single colour, pump-probe reflectivity measurements from the Si/SiO2 interface of bulk n-type Si. The experimental setups for the second harmonic generation (SHG) and pump-probe techniques were designed and implemented, and measurements were recorded by a computer controlled data acquisition system. Free standing Si membrane samples were successfully produced at the Institut f¨ur Photonische Technologien (IPHT) in Jena, Germany from bulk Si using a chemical etching process and were characterised using the z-scan technique. The penetration depth of light with a photon energy of 1.55 eV in silicon allows transmission of the fundamental fs laser pulses through the Si membrane (∼ 10 μm in thickness) and this is exploited to generate a SH signal in transmission from the Si/SiO2 interfaces of the Si membrane. In the presence of sufficiently intense fs laser light defects are created at the interfaces and populated by multiphoton transfer of charges from Si to SiO2 where they are subsequently trapped. The transfer of charge establishes interfacial electric fields across the interfaces of the Si membrane and this enhances SHG. This phenomenon is called electric field induced second harmonic (EFISH) generation. To our knowledge, EFISH measurements from interfaces of Si membrane performed in transmission are demonstrated for the first time in the present study. The demonstration of EFISH in transmission revealed new results which allowed us to provide additional perspectives on the EFISH generation process at Si/SiO2 interfaces never reported before. The temporal response of SH signals from virgin spots were recorded at different incident laser powers for both reflection and transmission geometries. The SH responses measured in transmission were observed to be time dependent and show an increase during irradiation of the sample corresponding to EFISH process. A series of SH measurements were recorded at different laser powers to compare the magnitudes of SH yield in each detection geometry for a single Si/SiO2 interface. The magnitude of the SH yield measured in transmission was higher than expected and surpassed the SH yield measured in reflection. The expectation is based on the fact that the local intensity of the fundamental beam at the second interface where the SH in transmission is generated is low compared to the local intensity at the first interface where the SH in reflection originates. A physical model is developed to consistently interpret the experimental results obtained in this study. In this model we established the origin of EFISH signals in each detection geometry, explain the unexpected high SH signals measured in transmission and provide an analysis of the time constants extracted from SH response in transmission and reflection. In addition, we also report for the first time stationary pump-probe reflectivity measurements from bulk n-type Si(111) samples with native oxide. A strong pump beam was focused on the same spot as a weak probe beam from the same fs laser source. The change in reflectivity of the Si(111)/SiO2 system was recorded by monitoring the change in intensity of the weak reflected probe beam. The temporal evolutions of the reflectivity of the material were recorded at different pump powers. The reflectivity of the material increases over several minutes of irradiation and reaches steady-state after long time irradiation. The change in reflectivity of the material is attributed to a nonlinear process called Kerr effect, and the temporal response arises from the photoinduced interfacial electric field across the Si(111)/SiO2 interface caused by multiphoton charge transfer from bulk Si(111) to the SiO2 layer. The results reported in this study contribute to the understanding of the photoinduced interfacial electric field caused by charge carrier separation across buried solid-solid interfaces. They also reveal nonlinear optical processes such as the Kerr effect caused by charge dynamics across the interface in addition to the well known SHG process. / AFRIKAANSE OPSOMMING: Die silikon/silikon dioksied (Si/SiO2) skeidingsvlak word algemeen gebruik in mikro-elektronika as die hek tussen die put en die bron van die meeste metaaloksied halfgeleier veld-effek transistors (MOSFETs). Die werkverrigting, betroubaarheid en elektriese eienskappe van sulke transistors word grootliks bepaal deur die kwaliteit van die Si/SiO2 struktuur wat die hek vorm. Karakterisering van die Si/SiO2 skeidingsvlak is belangrik om die degradering van die transistor te verstaan en daarom is die Si/SiO2 skeidingsvlak die onderwerp van intensiewe ondersoek. Ondersoek van die Si/SiO2 skeidingsvlak deur van optiese metodes gebruik te maak is geraporteer deur verskeie internasionale groepe, maar daar bestaan tot vandag toe nog n groot aantal onbeantwoorde vrae. Die fisika van die fotogenduseerde generering van defekte en van posisies waarin ladings gevang kan word, asook die daaropvolgende vasvang van ladingsdraers, die presiese rol van die fotoge¨ınduseerde elektriese veld oor die skeidingsvlak in die verandering van die optiese eienskappe van die Si/SiO2 skeidingsvlak en die grootte van die tweede harmoniek (SH) sein word nog nie goed verstaan nie. In hierdie werk word n kommersile naby-infrarooi femtosekonde (fs) laserbron [1.55 eV, 75 ± 5 fs, 10 nJ, 80 MHz] gebruik om natuurlike Si/SiO2 skeidingsvlakke van vrystaande enkelkristallyne Si membrane en soliede Si te bestudeer. Optiese tweede harmoniek (SH) wat by die Si/SiO2 skeidingsvlakke van ’n Si membraan gegenereer word - in refleksie en vir die eerste keer in transmissie - is gedemonstreer, asook stasionˆere, een-golflengte pomp-toets refleksiemetings op die Si/SiO2 skeidingsvlak van soliede n-gedoteerde Si. Die eksperimentele opstellings vir die tweede harmoniek generering (SHG) en pomp-toets tegnieke is ontwerp en uitgevoer en metings is opgeneem deur ’n rekenaarbeheerde dataversamelingstelsel. Vrystaande Si membraan monsters is suksesvol by die Institut f¨ur Photonische Technologien (IPHT) in Jena, Duitsland vervaardig uit soliede Si deur ’n chemiese etsproses en is gekarakteriseer met behulp van die z-skanderingstegniek as deel van hierdie studie. Die diepte waartoe lig met ’n fotonenergie van 1.55 eV in silikon indring laat die transmissie van die fundamentele fs laserpulse deur die Si membraan (met ∼ 10 μm dikte) toe en dit word ontgin om ’n SH sein van die Si/SiO2 skeidingsvlakke van die Si membraan in transmissie te meet. In die teenwoordigheid van fs laserlig met voldoende intensiteit word defekte by die skeidingsvlakke geskep en bevolk deur meer-foton ladingsoordrag van die Si na die SiO2 waar die ladings daaropvolgens vasgevang word. Die oordrag van ladings skep elektriese velde oor die skeidingsvlakke van die Si membraan en dit versterk die SHG. Hierdie verskynsel word elektriese veld ge¨ınduseerde tweede harmoniek (EFISH) generering genoem. Sover ons kennis strek is die meting van EFISH seine van skeidingsvlakke van Si membrane in transmissie vir die eerste keer in hierdie studie gedemonstreer. Die demonstrasie van EFISH in transmissie het nuwe resultate opgelewer wat ons toegelaat het om bykomende perspektiewe op die EFISH genereringsproses by Si/SiO2 skeidingsvlakke te verskaf waaroor nog nooit vantevore verslag gedoen is nie. Die tydafhanklike gedrag van die SH seine van voorheen onbestraalde posisies is gemeet by verskillende drywings van die inkomende laserbundel vir beide die refleksie en transmissie geometrie¨e. Die gedrag van die SH sein in transmissie is waargeneem om tydafhanklik te wees en ’n toename te toon gedurende bestraling van die monster in ooreenstemming met EFISH prosesse. ’n Reeks van SH metings is opgeneem by verskillende laserdrywings om die groottes van die SH opbrengste in elke meetgeometrie vir ’n enkele Si/SiO2 skeidingsvlak te vergelyk. Die grootte van die SH opbrengs wat in transmissie gemeet is was ho¨er as verwag is en het die grootte van die SH opbrengs in refleksie oortref. Die verwagting is gebaseer op die feit dat die lokale intensiteit by die tweede skeidingsvlak waar SH in transmisie gegenereer word relatief laag is in vergelyking met die lokale intensiteit by die eerste skeidingsvlak waar SH in refleksie ontstaan. ’n Fisiese model is ontwikkel om die eksperimentele resultate wat in hierdie studie verkry is op ’n konsekwente wyse te interpreteer. In hierdie model het ons die oorsprong van EFISH seine in elke meetgeometrie vasgestel, die onverwagte ho¨e SH seine wat in transmissie gemeet is verklaar en ’n analise van die tydkonstantes wat uit die SH gedrag in transmissie en refleksie afgelei is gedoen. Verder rapporteer ons ook vir die eerste keer stasionˆere pomp-toets reflektiwiteitsmetings van soliede n-gedoteerde Si(111) monsters met ’n natuurlike oksied. ’n Sterk pompbundel is gefokus op dieselfde posisie as ’n swak toetsbundel van dieselfde laserbron. Die verandering in reflektiwiteit van die Si(111)/SiO2 stelsel is gemeet deur die verandering in die intensiteit van die swak weerkaatste toetsbundel te monitor. Die tydevolusie van die reflektiwiteit van die mate riaal is gemeet by verskillende pompdrywings. Die reflektiwiteit van die materiaal neem toe gedurende etlike minute van bestraling en bereik ’n stasionˆere toestand na ’n lang tyd van bestraling. Die verandering in reflektiwiteit van die materiaal word toegeskryf aan ’n nielini ˆere prosess, naamlik die Kerr effek, en die tydafhanklike gedrag ontstaan as gevolg van die fotoge¨ınduseerde elektriese veld oor die Si(111)/SiO2 skeidingsvlak wat veroorsaak word deur meer-foton ladingsoordrag van die soliede Si(111) na die SiO2 laag. Die resultate wat in hierdie studie gerapporteer word dra by tot die verstaan van die fotoge ¨ınduseerde elektriese veld oor die skeidingsvlak wat veroorsaak word deur die skeiding van ladingsdraers oor die bedekte kristal-kristal skeidingsvlak. Dit lˆe ook nie-liniˆere optiese prosesse soos die Kerr effek bloot wat veroorsaak word deur die dinamika van ladings oor die skeidingsvlak, bykomend tot die bekende SHG proses.

Σκοπός της εργασίας είναι η μελέτη της ωριμότητας της οργανικής ύλης ορισμένων σχηματισμών της Ιόνιας Ζώνης, όπως οι αργιλικοί σχίστες του ανώτερου και κατώτερου Ιουρασικού, ο Ανώτερος Πυριτικός Ορίζοντας της Βίγλας του Κρητιδικού και οι βιτουμενιούχοι Ψαμμίτες του Τριτογενούς, χρησιμοποιώντας τεχνικές Οργανικής Πετρολογίας. Τα δείγματα συλλέχθηκαν από επιφανειακές εμφανίσεις στην Ήπειρο. Αρχικά χρησιμοποιήθηκαν οξέα (HCl-HF) για να απομακρυνθεί το μεγαλύτερο μέρος των ανθρακικών και πυριτικών ορυκτών. Το συμπύκνωμα που προέκυψε, αναμίχθηκε με ZnCl2 συγκεκριμένης πυκνότητας, ώστε να επέλθει βαρυτικός διαχωρισμός του πετρώματος σε ελαφρύ και βαρύ κλάσμα. Το οργανικό μέρος οξειδώθηκε χημικά για να υπολογιστεί η περιεκτικότητα σε Ολικό Οργανικό Άνθρακα. Στιλπνές τομές παρασκευάστηκαν με ανάμιξη του οργανικού υλικού με διάλυμα εποξικής ρητίνης και μελετήθηκαν στο ανθρακοπετρογραφικό μικροσκόπιο. Έμφαση δόθηκε στην ανακλαστικότητα βιτρινίτη και τον προσδιορισμό των maceral. Εφαρμόστηκε επίσης περιθλασιμετρία ακτίνων Χ για να προσδιοριστεί η ορυκτολογική σύσταση των πετρωμάτων. Διαπιστώθηκε ότι οι αργιλικοί σχίστες του κατώτερου Ιουρασικού περιέχουν οργανική ύλη (TOC: 4,74%), ο βαθμός ωριμότητας (Rr 0,68%) της οποίας βρίσκεται εντός του παραθύρου πετρελαίου. Ωστόσο περαιτέρω έρευνα εστιασμένη στους Κατω-Ιουρασικούς αργιλικούς σχίστες με Posidonia, με τη βοήθεια της Οργανικής Πετρολογίας και της πυρόλυσης Rock-Eval είναι αναγκαία, προκειμένου να διαπιστωθεί η ποιότητά τους ως μητρικά πετρώματα υδρογονανθράκων. / The main objective of this paper is to study by means of Organic Petrology techniques, the maturity of the dispersed organic matter from certain sedimentary formations of the Ionian Zone, such as the Bituminous Shale, the Upper Siliceous Vigla Formation and the Bituminous Sandstone. The samples were collected from outcropping sites located in the region of Epirus. Initially they were treated with acids (HCl-HF) to remove most of the carbonate and silicate minerals. Then a ZnCl2 solution was used to concentrate the organic-rich fraction. Total Organic Carbon (TOC) content was determined applying dichromate oxidation. Polished blocks were prepared from the concentrated organic matter mounted in epoxy resin and examined under the coal-petrography microscope. Emphasis was given to maceral identification and vitrinite reflectance (Rr) measurements, which provide information regarding the quality and the maturity of the organic matter respectively, with implications for the petroleum generation potential regardless the level of alteration. The TOC and Rr values (4.74% and 0.68%, respectively) confirm to the oil potential of the Lower Jurassic Posidonia Shale. Nevertheless, it is suggested that detailed and higher resolution sampling focusing on the Lower Posidonia Shale, as well as organic petrography analyses coupled with Rock-Eval pyrolysis should be carried out in order to accurately determine its quality as petroleum source rocks.

The site-specific management of alfalfa has not been well-evaluated, despite the economic importance of this crop. The objectives of this work were to i) characterize the effects of soil moisture deficits on alfalfa and alfalfa yield components and ii) evaluate the use of canopy reflectance patterns in measuring treatment-induced differences in alfalfa yield. A randomized complete block design with five replicates of subsurface drip irrigation (SDI) and rainfed treatments of alfalfa was established at the University of Kentucky Animal Research Center in 2003. Potassium, as KCl, was broadcast on split-plots on 1 October 2004 at 0, 112, 336, and 448 kg K2O ha-1. In the drought year of 2005, five harvests (H1 - H5) were taken from each split-plot and from four locations within each SDI and rainfed plot. One day prior to each harvest, canopy reflectance was recorded in each plot. Alfalfa yield, yield components, and leaf area index (LAI) were determined. In 2005, dry matter yields in two harvests and for the seasonal total were increased (Pandlt;0.05) by SDI, but SDI did not affect crown density. Herbage yield was strongly associated with yield components but yields were most accurately estimated from LAI. Canopy reflectance within blue (450 nm), red (660 nm) and NIR bands were related to LAI, yield components, and yield of alfalfa and exhibited low variance (cv andlt; 15%) within narrow ( 0.125 Mg ha-1) yield ranges. Red-based Normalized Difference Vegetation Indices (NDVIs) and Wide Dynamic Range Vegetation Indices (WDRVIs) were better than blue-based VIs for the estimation of LAI, yield components, and yield. Decreasing the influence of NIR reflectance in VIs by use of a scalar (0.1, 0.05, or 0.01) expanded the range of WDRVI-alfalfa yield functions. These results indicate that VIs may be used to estimate LAI and dry matter yield of alfalfa within VI-specific boundaries.

Soluble organic semiconductors have attracted interest due to their potential in making flexible and cheap electronics. Though their use is being implemented in electronics today, the conduction mechanism is still under investigation. In order to study the charge transport, this study examines the position, voltage, and frequency dependence of charge induced changes in far infrared absorption in soluble organic semiconductors in thin-film transistor structures. Measurements are compared to a simple model of a one-dimensional conductor which gives insight into the charge distribution and timing in devices. Main results of the study are dynamic measurements of charge taken by varying the frequency of the applied gate voltage while observing signal at one position within the transistor; mobility values obtained from a comparison to the one-dimensional model compare well with standard current-voltage measurements. Two small molecule soluble organic semiconductors were studied: 6,13 bis(triisopropylsilylethynyl)-pentacene and fluorinated 5,11 bis(triethylsilylethynyl) anthradithiophene.

Soils darken upon wetting due to changes in the scattering properties of the individual soil particles. The objective of this research was to develop a procedure to map the distribution of wet soils using the radiance measurements acquired by a spaceborne imaging scanner. The soil-mapping procedure was designed for use in the regional exploration for ground water resources. The soil-mapping procedure was based upon the detection of reflectance changes in a comparison of Landsat 5 Thematic Mapper (TM) scenes acquired before and after a rain. The Stronghold watershed, which is situated on the western slopes of the Dragoon Mountains, Cochise County, Arizona, was chosen as the test site for the soil-mapping procedure. TM scenes depicting the watershed on 7 June 1985 and 14 November 1985 were used in the change-detection analysis. The region was dry at the time of the June overpass, the November overpass occurred two days after a rain. The recovery of reflectance from radiance requires knowledge of 1) the orientation of the surface relative to the sun and the satellite, 2) the exoatmospheric solar irradiance, 3) the atmospheric optical depth, and 4) the atmospheric path radiance. The orientation of the surface elements were defined through the use of a digital elevation model of the Stronghold watershed. The solar irradiance and atmospheric optical depth were obtained from the literature; the atmospheric path radiance was estimated from shadowed areas depicted in the images. Temporal changes in reflectance were detected by subtracting the November reflectance estimates from those recovered from the June radiance measurements. Changes significant at the 0.05 level were identified through use of the Student-t test. The identical significance level was used to identify temporal changes in the Perpendicular Vegetation Index, or PVI. A surface element was classified as an anomaly if there was a significant temporal change in reflectance with no attendant change in PVI. Field checks of the anomalies proved that wet soils could be mapped via the remote detection of changes in their reflectance. The majority of the false anomalies could be attributed to the disparity between the spatial resolutions of the radiance measurements and the topographic data.

No description available.

No description available.