Localization of general and regulatory proteolysis in Bacillus subtilis cells

Protein degradation mediated by ATP-dependent proteases, such as Hsp100/Clp and related AAA+ proteins, plays an important role in cellular protein homeostasis, protein quality control and the regulation of, e.g. heat shock adaptation and other cellular differentiation processes. ClpCP with its adaptor proteins and other related proteases, such as ClpXP or ClpEP of Bacillus subtilis, are involved in general and regulatory proteolysis. To determine if proteolysis occurs at specific locations in B. subtilis cells, we analysed the subcellular distribution of the Clp system together with adaptor and general and regulatory substrate proteins, under different environmental conditions. We can demonstrate that the ATPase and the proteolytic subunit of the Clp proteases, as well as the adaptor or substrate proteins, form visible foci, representing active protease clusters localized to the polar and to the mid-cell region. These clusters could represent a compartmentalized place for protein degradation positioned at the pole close to where most of the cellular protein biosynthesis and also protein quality control are taking place, thereby spatially separating protein synthesis and degradation

Characterization of hybrid solar cells prepared from poly-thiophenes and silicon

Das Hauptaugenmerk dieser Arbeit liegt auf der Entwicklung einer Hybridsolarzelle, in der der anorganische Halbleiter Silizium, das organische Polymer und das Kontaktsystem so aufeinander abgestimmt sind, dass ihre Kombination zu einem Bauelement mit hohem Wirkungsgrad führt. Um dieses Ziel zu erreichen wurden verschiedene Maßnahmen ergriffen. Neue Polymermaterialien, abgeleitet von dem prototypischen organischen Halbleiter poly(3-hexylthiophen 2,5 diyl) (P3HT), namentlich poly(3-[3,6-dioxaheptyl]-thiophen) (P3DOT) und poly(3-[2,5,8-trioxanonyl]-thiophen) (P3TOT), wurden umfassend hinsichtlich ihrer Struktur untersucht. Poly thiophen/c-Si hybride Solarzellen, hergestellt aus diesen neuen Polymeren, erreichten Effizienzen bis zu 11 %. Die vollständigen Banddiagramme dieser Poly thiophen/c-Si Hybridgrenzflächen wurden mittels Photoelektronenspektroskopie aufgenommen. Außerdem wurde der Einfluss des Kontaktsystems auf die darunter liegenden Schichten mittels Oberflächenspannungsspektroskopie untersucht. Das Resultat dieser Messungen weißt eine Inversionslage unter der Siliziumoberfläche nach, die sich aufgrund des verwendeten semitransparenten Metallkontaktes formt. Dadurch lassen sich diese Bauteile als MIS Inversionsschicht Solarzelle kategorisieren. Um die Hybridsolarzellen weiter zu verbessern, wurde versucht den semitransparenten Metallkontakt durch Graphen zu ersetzen. Das Graphen wurde durch einen CVD-Prozess gewachsen und erreichte eine laterale Ausdehnung von bis zu 1 cm2. Der Übertrag auf die Solarzelle erfolgte mittels eines Wasser und Zerstörungsfreiem Transferprozess. Trotz dem erfolgreichen Aufbringen des Graphen limitierte ein geringer Füllfaktor aufgrund der geringen Ladungsträgerdichte im Graphen den Wirkungsgrad der Solarzelle. In einem letzten Schritt wurde das Polymer P3HT zum ersten Mal mit polykristallinen Siliziumabsorbern kombiniert. Die invertierte Zellstruktur, die hierbei zu Anwendung kam, erhöhte die Lebensdauer der Solarzelle erheblich.The scope of this thesis was the development of a hybrid solar cell based on silicon in which the inorganic semiconductor, the organic polymer and the contact system are combined in such a manner to result in a photovoltaic device with high power conversion efficiency. To reach this goal several measures were taken. New polymer materials derived from the prototypical organic semiconductor poly(3-hexylthiophene 2,5 diyl) (P3HT), namely poly(3-[3,6-dioxaheptyl]-thiophene) (P3DOT) and poly(3-[2,5,8-trioxanonyl]-thiophene) (P3TOT), were extensively characterized regarding its structural properties. Poly thiophene/c-Si hybrid solar cells fabricated from these new polymers exhibited power conversion efficiencies up to 11 %. The energy level alignment of these poly thiophene/c Si hybrid interfaces was studied using photoelectron spectroscopy. Furthermore, the influence of the contact system on the underlying wafer is investigated with surface photovoltage measurements. The measurements revealed the formation of an inversion layer beneath the silicon surface due to the semitransparent metal contact used in the devices. Therefore, these devices can be classified as MIS inversion layer solar cells. To further improve the hybrid poly thiophene/c-Si solar cells by substituting the semitransparent metal contact, graphene was implemented in the device design as a transparent front contact. The CVD grown graphene sheet had a lateral size of up to 1 cm2 and was applied onto the solar cell using a non-destructive and water-free transfer process. However, despite the successful transfer the power conversion efficiency was restricted by the low fill factor due to a low charge carrier density in the graphene. As a last step, hybrid solar cells in the combination P3HT/polycrystalline silicon absorbers on glass were fabricated for the first time. The inverted device structure used for these solar cells proved beneficial for the lifetime. These devices were stable for up to 3 months

Enhanced stability of P3HT poly crystalline Si thin film hybrid solar cells

Hybrid solar cells have been fabricated from solution processing of poly 3 hexylthiophen 2,5 diyl onto planar poly crystalline thin film silicon poly Si absorbers on glass. The poly Si layers were prepared by laser crystallization. Methyl passivation of the poly Si surface by a one step grafting process via methyl Grignard enabled open circuit voltages of up to 552mV and an overall power conversion efficiency of 6.6 for this device type. The solar cell exhibited significant advantages compared to the wafer based counterparts. The inverted device structure of the thin film cell lead to an enhancement of the quantum efficiency since the back side contacted cell had less light absorption and reflection losses due to the gold layer which was used as front contact for the c Si based hybrid solar cell. As a result, a photo current of 24.3 mA cm2 was obtained for a 10mm thin poly Si layer on glass. Furthermore, the inverted device structure showed a pronounced increase in stability due to the much thicker gold back contact that reduces the diffusion of water and oxygen toward the polymer layer. After 3 months in ambient air, this type of solar cell operated with 86 of its initial efficienc

Polythiophenes as emitter layers for crystalline silicon solar cells Parasitic absorption, interface passivation, and open circuit voltage

We investigated the influence of the emitter amorphous Si, a Si, or polythiophene derivatives poly 3 hexylthiophene , P3HT, and poly 3 [3,6 dioxaheptyl] thiophene , P3DOT and the interface passivation intrinsic a Si or SiOX and methyl groups or SiOX on the c Si based 1 amp; 8201; amp; 8201;1 amp; 8201;cm2 planar hybrid heterojunction solar cell parameters. We observed higher short circuit currents for the P3HT or P3DOT c Si solar cells than those obtained for a Si c Si devices, independent of the interface passivation. The obtained VOC of 659 amp; 8201;mV for the P3DOT SiOX c Si heterojunction solar cell with hydrophilic 3,6 dioxaheptyl side chains is among the highest reported for c Si polythiophene devices. The maximum power conversion efficiency, PCE, was 11 for the P3DOT SiOX c Si heterojunction solar cell. Additionally, our wafer lifetime measurements reveal a field effect passivation in the wafer induced by the polythiophenes when deposited on c S

Infrared spectroscopic ellipsometry of micrometer sized SiO2 line gratings

For the design and process control of periodic nano structured surfaces spectroscopic ellipsometry is already established in the UV VIS spectral regime. The objective of this work is to show the feasibility of spectroscopic ellipsometry in the infrared, exemplarily, on micrometer sized SiO2 line gratings grown on silicon wafers. The grating period ranges from 10 to about 34 amp; 956;m. The IR ellipsometric spectra of the gratings exhibit complex changes with structure variations. Especially in the spectral range of the oxide stretching modes, the presence of a Rayleigh singularity can lead to pronounced changes of the spectrum with the sample geometry. The IR ellipsometric spectra of the gratings are well reproducible by calculations with the RCWA method Rigorous Coupled Wave Analysis . Therefore, infrared spectroscopic ellipsometry allows the quantitative characterization and process control of micrometer sized structure

The new and recurrent FLT3 juxtamembrane deletion mutation shows a dominant negative effect on the wild-type FLT3 receptor

In acute myeloid leukemia (AML), the Fms-like tyrosine kinase 3 (FLT3) is one of the most frequently mutated genes. Recently, a new and recurrent juxtamembrane deletion mutation (p.Q569Vfs*2) resulting in a truncated receptor was identified. The mutated receptor is expressed on the cell surface and still binds its ligand but loses the ability to activate ERK signaling. FLT3 p.Q569fs-expressing Ba/F3 cells show no proliferation after ligand stimulation. Furthermore, coexpressed with the FLT3 wild-type (WT) receptor, the truncated receptor suppresses stimulation and activation of the WT receptor. Thus, FLT3 p.Q569Vfs*2, to our knowledge, is the first FLT3 mutation with a dominant negative effect on the WT receptor

Side chain engineering of poly thiophene and its impact on crystalline silicon based hybrid solar cells

The influence of ether groups in the side chain of spin coated regioregular polythiophene derivatives on the polymer layer formation and the hybrid solar cell properties were investigated using electrical, optical, and X ray diffraction experiments. The polymer layers are of high crystallinity but the polymer with 3 ether groups in the side chain P3TOT did not show any vibrational fine structure in the UV Vis spectrum. The presence of ether groups in the side chains leads to better adhesion resulting in thinner and more homogeneous polymer layers. This, in turn, enhances the electronic properties of the planar hybrid solar cell. We find that the power conversion efficiency increases with the number of ether groups in the side chains, and a maximum power conversion efficiency of 9.6 is achieved even in simple planar structures. amp; 8195