abstract: The emergence of perovskite and practical efficiency limit to silicon solar cells has opened door for perovskite and silicon based tandems with the possibility to achieve >30% efficiency. However, there are material and optical challenges that have to be overcome for the success of these tandems. In this work the aim is to understand and improve the light management issues in silicon and perovskite based tandems through comprehensive optical modeling and simulation of current state of the art tandems and by characterizing the optical properties of new top and bottom cell materials. Moreover, to propose practical solutions to mitigate some of the optical losses. Highest efficiency single-junction silicon and bottom silicon sub-cell in silicon based tandems employ monocrystalline silicon wafer textured with random pyramids. Therefore, the light trapping performance of random pyramids in silicon solar cells is established. An accurate three-dimensional height map of random pyramids is captured and ray-traced to record the angular distribution of light inside the wafer which shows random pyramids trap light as well as Lambertian scatterer. Second, the problem of front-surface reflectance common to all modules, planar solar cells and to silicon and perovskite based tandems is dealt. A nano-imprint lithography procedure is developed to fabricate polydimethylsiloxane (PDMS) scattering layer carrying random pyramids that effectively reduces the reflectance. Results show it increased the efficiency of planar semi-transparent perovskite solar cell by 10.6% relative. Next a detailed assessment of light-management in practical two-terminal perovskite/silicon and perovskite/perovskite tandems is performed to quantify reflectance, parasitic and light-trapping losses. For this first a methodology based on spectroscopic ellipsometry is developed to characterize new absorber materials employed in tandems. Characterized materials include wide-bandgap (CH3NH3I3, CsyFA1-yPb(BrxI1-x)3) and low-bandgap (Cs0.05FA0.5MA0.45(Pb0.5Sn0.5)I3) perovskites and wide-bandgap CdTe alloys (CdZnSeTe). Using this information rigorous optical modeling of two-terminal perovskite/silicon and perovskite/perovskite tandems with varying light management schemes is performed. Thus providing a guideline for further development. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2019

In this project, samples with a metal/semiconductor/metal structure were fabricated and investigated with the potential application as the interconnecting layer of a tandem solar cell in mind. Degenerately doped p-Si and n-Si were used as bottom (metal like) contacts, as Si represents one of the most common materials for the bottom cell of tandem devices. A transparent, wide bandgap semiconductor in the form of SnO₂ was investigated for the intermediate layer as it is a common choice for the selective back contact of top cells based on perovskites. However, atomic layer deposition (ALD) was used as an alternative to the typical solution based application of the SnO₂ layer. The top layer was simply chosen as a triple layer metal contact stack (Ni-Al-Ni) to provide for good contact with the SnO₂.The goal of the project was to study the electrical properties of the samples through I-V measurements and how the I-V characteristic depends on the oxide’s thickness under the possible influence of the contact areas. Three different thicknesses of the SnO2 layer were used for the p-Si sample: 50, 200 and 400 Å. For the n-Si samplesonly one thickness (400 Å) was studied. Using the diode equation, four parameterswere calculated (Jo, Rsh, Rs and n) for different measurements combing different contact configurations. The latter included measurements between the front and the back of the samples and measurements between contacts on the front with and/orwithout SnO2 layer. From the results, it was concluded that as the thickness of SnO₂ increases, the saturation current (Jo) decreases while both shunt resistance (Rsh) andseries resistance (Rs) increase. The ideality factor (n) neither depends significantly on effective area, nor on SnO2 thickness. The p-Si and n-Si samples show similar behavior in the case of 400 Å SnO2 thickness. The contact areas only appreciatively affect Jo, but it is not clear what lies behind this dependence. In all cases, the top contacts obtained major wear during measurements, reducing the number of trustworthy measurements that could be used on the smaller areas. The resistivity through the oxide layer was calculated to ρSnO₂ = 247±96 MΩ cm, which is higher than for SnO₂ deposited by other techniques, and too high for tandem cell application. Schottky barriers formed at the interfaces will typically limit the charge transport further.

The human positive regulatory domain I binding factor 1 (PRDI-BF1/PRDM1) promotes differentiation of mature B cells into antibody secreting plasma cells. In contrast ectopic expression of PRDM1 in lymphoma cells can lead to inhibition of proliferation or apoptosis. However, little is currently known about the regulation of PRDM1. The first study presented demonstrates that in lymphoma cells stimulation through the B cell receptor rapidly induces endogenous PRDM1 at the level of transcription. This study provides evidence that the PRDM1 promoter is preloaded and poised for activation in the B cell lines. The transcription factor PU.1 is shown to be required for B cell receptor induced expression of PRDM1 in lymphoma cells and in PU.1 positive myeloma cells. Furthermore, activation is associated with loss of the co-repressor TLE4 from the PU.1 complex. The second study establishes the requirement for PRDM1 in Mantle cell lymphoma (MCL) response to Bortezomib. MCL, an aggressive form of B cell lymphoma, has poor disease- free survival rate. The proteasome inhibitor, Bortezomib, is approved for treatment of relapsed and refractory MCL. However, the precise mechanism of action of Bortezomib is not well understood. Bortezomib rapidly induces transcription of PRDM1 along with apoptosis in MCL cell lines and primary MCL tumor samples. Knockdown of PRDM1 inhibits Bortezomib-induced apoptosis, while ectopic expression of PRDM1 alone leads to apoptosis in MCL. MKI67 and PCNA, which are required for proliferation and survival, were identified as novel direct targets of PRDM1 in MCL. Chromatin immunoprecipitation and knockdown studies reveal specific repression of MKI67 and PCNA is mediated by PRDM1 in response to Bortezomib. Furthermore promoter studies demonstrate that PRDM1 functions through a specific site in the proximal promoter region of PCNA and through a distal upstream repression domain on the MKI67 promoter. Together these findings establish PRDM1 as a key mediator of Bortezomib activity in MCL through suppression of proliferation and survival genes. The third study presented demonstrates use of Tandem affinity purification technique followed by mass spectrometry to identify PRDM1 and Reptin52 protein interactions. The observations in this study provide preliminary evidence of novel mechanism of regulation of PRDM1 protein function.

A significant part of the environmental impact of a heat pump isgenerally related to the direct emission of the refrigerant fluid during thelife time of the machine. Although the Montreal Protocol has alreadylargely secured its status as a success story by cutting the ozone deplentationrefrigerants drastically, we still have to deal with the challengesresulting from climate change.Natural refrigerants such as Propane permits to design more ecofriendlysystem without sacrificing the performance of the machine. Thethesis work is part of a European project called Next Generation of HeatPumps working with Natural fluids (NxtHPG) whose primary aim is thedevelopment of heat pumps working with Natural refrigerant that aresafe, reliable, with high efficiency and high capacity. Royal Institute oftechnology (KTH) is one of the partner of the project and responsiblefor the experimental campaign of two large propane heat pumps: an airsource heat pump (Case 1 ) and a ground source heat pump suitablefor boreholes (Case 2 ). Few cases in literature report on studies aboutlarge capacity heat pumps using propane as refrigerant.This thesis project focuses on the experimental evaluation of theCase 2 from an energy point view. The safety issues about the use of flammable refrigerant, i.e propane, are briefly reported; however theyare not considered strictly part of the thesis work since they are coveredin other phases of NxtHPG project. Experimental tests for Case 1 werenot conducted during this thesis work because of delays in the prototypedelivery from the manufacturer. However, concerns about the hydraulicloop of the test rig of both the heat pumps was identified and a newdesign was suggested and implemented.During the experimental campaign for Case 2 a significant numberof tests were performed according to a specific text matrix definedfrom the EN 14285 standard. A simple heat pump model has beenused to evaluate the overall performance of the machine from the directmeasurements. The heat pump components (compressors, condenser,evaporator, expansion valve) have been analysed in details by definingspecific analysis model for each one. The results have been comparedwith the manufacture expectation.The prototypes demonstrated to have potentially very good performance,since in the first set of tests the machine behaved as expectedby the IMST-ART software. On the other hand, a drop of the unitefficiency and capacity have been registered during the experimentalcampaign for similar working condition. Two different explanations areinvestigated to clarify the strange phenomenon. The first hypothesisconsiders minor internal damage in the compressor, as check valve leakage;consequence of the use of the compressor in a tandem layout. Itgenerates a back-flow in the non working compressor. The second explanationregards inert gas infiltration in the system. On the otherhand they are not able to explain entirely the system issues and theyneed to be confirmed by the manufacturer analysis of the open compressor.The further improvements, proposed and discussed with themanufacture companies involved, can help to solve the question markson the strange system behaviour during the future work. The nextexperimental campaign for Case 1 that will start on April 2015.The software IMST-ART, used to predict the performance of theheat pump, is demonstrated to be a fast and useful tool. The model ofthe software for propane as refrigerant and brazed plate heat exchangerpredicts adequately the experimental measurement. / Una parte significativa dell’impatto ambientale relativo a una pompadi calore è legato alle emissioni dirette di refrigerante durante ilperiodo di vita della macchina. Nonostante l’accordo di Montreal siagià stato considerato come un successo storico per il drastico taglio deirefrigeranti dannosi per lo strato di ozono, bisogna ancora fronteggiarele sfide relative al cambiamento climatico.Refrigeranti naturali, come il Propano, permettono di realizzaremacchine più ambientalmente compatibili senza però sacrificare le prestazionidella macchina stessa. Questo lavoro di tesi fa parte di unprogetto Europeo chiamato Next Generation of Heat Pumps workingwith Natural fluids (NxtHPG), in cui obiettivo primario è quello di svilupparepompe di calore che lavorano con fluidi Naturali che allo stessotempo siano sicure, affidabili, con elevata efficienza e taglia.Royal Institute of technology (KTH) è uno dei partner del progettoe anche responsabile della campagna sperimentale di due pompe dicalore a propano di grossa taglia: una pompa ad aria Case 1 e unageotermicaCase 2. Sono pochi gli esempi in letteratura che riguardanolo studio di macchine di questo tipo di grande taglia, questo costituiscela novità del lavoro.Il lavoro di tesi presentato è incentrato principalmente sulla valutazionesperimentale da un punto di vista energetico di Case 2. Leproblematiche legate alla sicurezza legate all’utilizzo di refrigeranti infiammabili,quale è il propano, sono solo citate; d’altra parte non sonoconsiderate strettamente facenti parte del lavoro di tesi in quando altrefasi del progetto NxtHPG sono incentrate su questo argomento.Misure sperimentali per Case 1 non sono state condotte durante illavoro di tesi a causa di ritardi nella consegna dei prototipi da parte dell’aziendaproduttrice. Ad ogni modo sono stati individuate problematichelegate ai circuiti idraulici dell’installazione sperimentale di entrambele pompe di calore e successivamente risolte con l’implementazione diuna nuova proposta di circuito idraulico.Durante la campagna sperimentale di Case 2, sono stati svolti undiscreto numero di misurazioni secondo una ben specifica test matrixderivata dalla normativa europea EN 14285. Un semplice modello dipompa di calore è stato utilizzato per la valutazione delle prestazionigenerali della macchina a partire dalle misurazioni dirette. I componenti della pompa di calore, quali compressore, condensatore, evaporatore,valvola di espansione, sono state analizzati separatamente definendouno specifico modello per ognuno di essi e comparato con i risultatiattesi dai produttori.Il prototipo di Case 2 dimostra avere ottime potenzialità come prestazioni,in quanto, durante il primo set di test, il comportamento dellamacchina era in linea con le previsioni del software IMST-ART. D’altraparte, durante la campagna sperimentale, si è evidenziato un fortecalo delle prestazioni nonostante le condizioni di funzionamento fosseropressoché simili. Per spiegare questa anomalia, due differenti ipotesisono state formulate. La prima assume la presenza di di deterioramentiminori nel compressore, come perdite nella valvola di non ritorno (checkvalve), conseguente ad l’utilizzo in configurazione tandem. Si genererebbeun flusso riverso di refrigerante nel compressore non funzionante.La seconda ipotesi riguarda infiltrazione di gas inerte all’interno dellamacchina. D’altra parte tali ipotesi non sono in grado di spiegareinteramente le problematicità nel sistema e hanno necessità di essereconfermate dall’analisi a compressore aperto da parte della aziendaproduttrice.Successivi perfezionamento dei prototipi sono stati proposti e discussicon le aziende produttrici coinvolte, e questo permetterebbe dirispondere ai punti di domanda riguardo lo strano comportamento delsistema. La prossima campagna sperimentale per Case 2 inizierà adAprile 2015. Il software IMST-ART, usato per predire le performancedella pompa di calore, ha dimostrato essere uno strumento veloce e utile.Il modello implementato nel software per il propano e per gli scambiatoridi calore a piatti predice adeguatamente le misure sperimentali. / Next Generation of Heat Pumps working with Natural fluids (NxtHPG)

No description available.

Identifying a peptide on the basis of a scan from a mass spectrometer is an important yet highly challenging problem. To identify peptides, we present a Bayesian approach which uses prior information about the average relative abundances of bond cleavages and the prior probability of any particular amino acid sequence. The scoring function proposed is composed of two overall distance measures, which measure how close an observed spectrum is to a theoretical scan for a peptide. Our use of our scoring function, which approximates a likelihood, has connections to the generalization presented by Bissiri and co-workers of the Bayesian framework. A Markov chain Monte Carlo algorithm is employed to simulate candidate choices from the posterior distribution of the peptide sequence. The true peptide is estimated as the peptide with the largest posterior density.

The agricultural sector is the backbone which supports the livelihoods and the economic development of nations across the globe. In consequence, the need for robust and continuous monitoring of agricultural crops is primordial to face the interlinked challenges of growth rate population, food security and climate change. Synthetic Aperture Radar (SAR) sensors have the powerful imaging capability of operating at almost all weather conditions, independent of day and night illumination. By penetrating through clouds and into the vegetation canopy, the incident radar signal interacts with the structural and dielectric properties of the vegetation and soil, thus providing critical information of the crop state, such as height, biomass, crop yield or leaf structure, which can help devise sustainable agricultural management practices. This is achieved by means of the Polarimetric SAR Interferometry (PolInSAR) technique, which by coherently combining interferometric SAR acquisitions at different polarization states allows for the retrieval of biophysical parameters of the vegetation. In this framework, this thesis focuses on the development of crop monitoring techniques that properly exploit satellite-based PolInSAR data. All the known InSAR and PolInSAR methodologies for this purpose have been analysed. The sensitivity of these data provided by the TanDEM-X bistatic system to both the physical parameters of the scene (height and structure of the plants, moisture and roughness of the soil) and the sensor configuration (polarization modes and observation geometry) is evaluated. The effect of different simplifications made in the physical model of the scene on the crop estimates is assessed. The interferometric sensitivity requirements to monitor a crop scenario are more demanding than others, such as forests. Steep incidences associated with the largest spatial baselines provided by the available data set lead to the most accurate estimates under all the different model assumptions. Shallower incidences, on the other hand, generally yield important errors due to their characteristic shorter spatial baselines. Through the methodologies proposed in this thesis, PolInSAR data have shown potential to refine current methods for the quantitative estimation of crop parameters. Results encourage to continue further research towards the objective of achieving operational crop monitoring applications. / Work supported by the Spanish Ministry of Science and Innovation, the State Agency of Research (AEI) and the European Funds for Regional Development (EFRD) under Project TEC2017-85244-C2-1-P. Noelia Romero-Puig received a grant from the Generalitat Valenciana and the European Social Fund (ESF) [ACIF/2018/204].

Currently thin film solar cells have efficiencies in the range of 16-18%. Higher efficiencies of 20% or more can be achieved by two junction solar cells in which two p-n junctions are connected in series one on top of the other in a tandem structure. The ideal bandgaps for optimum efficiency in a tandem structure are about 1eV for the top cell and 1.7 eV for the bottom cell. Copper Indium Gallium di-Selenide (CIGS) with a bandgap of 1 eV is a suitable candidate for the bottom cell and Cadmium Zinc Telluride (CZT) with a tunable bandgap of 1.44-2.26 eV is a suitable candidate for the top cell. This work involves characterization of cadmium zinc telluride films and solar cells prepared by close spaced sublimation. CZT is deposited by co-sublimation of CdTe and ZnTe. The process has been investigated on various wide bandgap semiconductor materials including cadmium sulphide, cadmium oxide and zinc selenide. Different post deposition heat treatments were carried out to determine their effect on film and device properties. Characterization of the CZT devices was done using XRD, EDS, SIMS, J-V and spectral response measurements. CZT (Eg~1.7 eV) /CdS exhibited best performance when compared to the other window layers investigated. The best device exhibited Voc=640mV, FF=40% and Jsc=4.5 mA/cm2. The theoretical performance of CZT based solar cells were investigated using SCAPS. The effect of bulk and interface defects on the device parameters were studied.

abstract: Silicon photovoltaics is the dominant contribution to the global solar energy production. As increasing conversion efficiency has become one of the most important factors to lower the cost of photovoltaic systems, the idea of making a multijunction solar cell based on a silicon bottom cell has attracted broad interest. Here the potential of using dilute nitride GaNPAs alloys for a lattice-matched 3-terminal 2-junction Si-based tandem solar cell through multiscale modeling is investigated. To calculate the electronic band structure of dilute nitride alloys with relatively low computational cost, the sp^3 d^5 s^* s_N tight-binding model is chosen, as it has been demonstrated to obtain quantitatively correct trends for the lowest conduction band near Γ, L, and X for dilute-N GaNAs. A genetic algorithm is used to optimize the sp^3 d^5 s^* tight-binding model for pure GaP and GaAs for their optical properties. Then the optimized sp^3 d^5 s^* s_N parametrizations are obtained for GaNP and GaNAs by fitting to experimental bandgap values. After that, a virtual crystal approach gives the Hamiltonian for GaNPAs alloys. From their tight-binding Hamiltonian, the first-order optical response functions of dilute nitride GaNAs, GaNP, and GaNPAs are calculated. As the N mole fraction varies, the calculated critical optical features vary with the correct trends, and agree well with experiment. The calculated optical properties are then used as input for the solar device simulations based on Silvaco ATLAS. For device simulation, a bottom cell model is first constructed to generate performance results that agree well with a demonstrated high-efficiency Si heterojunction interdigitated back contact (IBC) solar cell reported by Kaneka. The front a-Si/c-Si interface is then replaced by a GaP/Si interface for the investigation of the sensitivity of the GaP/Si interface to interface defects in terms of degradation of the IBC cell performance, where we find that an electric field that induces strong band bending can significantly mitigate the impact of the interfacial traps. Finally, a lattice-matched 3-terminal 2-junction tandem model is built for performance simulation by stacking a dilute nitride GaNP(As) cell on the Si IBC cell connected through a GaP/Si interface. The two subcells operate quasi-independently. In this 3-terminal tandem model, traps at the GaP/Si interface still significantly impact the performance of the Si subcell, but their effects on the GaNP subcell are relatively small. Assuming the interfacial traps are well passivated, the tandem efficiency surpasses that of a single-junction Si cell, with values close to 33% based on realistic parameters. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2019

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18161号 / 医博第3881号 / 新制||医||1003(附属図書館) / 31019 / 京都大学大学院医学研究科医学専攻 / (主査)教授 伊達 洋至, 教授 杉田 昌彦, 教授 中山 健夫 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM