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The light-harvesting apparatus of the photosynthetic bacterium Rhodobacter sphaeroides is composed of a peripheral LH2 complex which directs excitation energy to the LH1/reaction center core. The puf BA genes encoding the LH1 polypeptides have been deleted, producing a photosynthetically-competent strain which contains LH2 and reaction centers. Time-resolved absorption and fluorescence measurement
Anisotropy and isotropic transient absorption decays of a polythiophene derivative in dilute solution have been measured and compared to calculated decays on Monte Carlo simulated polymer chains to obtain knowledge about the geometrical conformation of the polymer. The polymer chain conformations are generated by a partially correlated self-avoiding random walk. Excitation migration along the isol
In this article we briefly review the molecular exciton theory and apply it to photosynthetic light harvesting systems. We derive expressions for exciton relaxation rates using perturbation theory in Hibert space representation and show how the Förster equation can be obtained from a general relaxation rate expression in case of well localized excitons. A detailed analysis of the exciton level str
We have studied excitation energy transfer in the photosynthetic antenna systems LH1 and LH2 of purple bacteria. Femtosecond pump−probe experiments are combined with computer simulations using the recently established crystal structure of these systems to assess the nature of excitation motion. We have measured the transient absorption kinetics and spectra of the LH1 and LH2 complexes in the
The excited state decay kinetics of chromatophores of the purple photosynthetic bacterium Rhodospirillum rubrum have been recorded at 77 K using picosecond absorption difference spectroscopy under strict annihilation free conditions. The kinetics are shown to be strongly detection wavelength dependent. A simultaneous kinetic modeling of these experiments together with earlier fluorescence kinetics
Using two-color pump−probe femtosecond spectroscopy, the temperature dependence of the energy transfer rate within the peripheral light-harvesting antenna (LH2) of the photosynthetic bacterium Rhodobacter sphaeroides has been measured. The energy transfer time from B800 to B850 is determined to be 0.7, 1.2, and 1.5 ps at 300, 77, and 4.2 K, respectively. These data, combined with earlier resu
Developing novel organic photovoltaic materials for organic solar cells (OSCs) requires precise characterization of their charge transfer states to optimize the photoinduced charge transfer mechanisms within the photoactive layer. The microscopic photoelectric properties of the S-shaped (DYA-I-S) and O-shaped (DYA-I-O) conformations of dimeric small molecule acceptors (DSMAs) are analyzed through
Picosecond spectrally resolved fluorescence kinetics measurements, together with model simulations of the obtained data, based on coupled rate equations, have been employed to determine the rates and the pathways of heterogeneous excitation transfer in Rhodobacter sphaeroides and Chromatium minutissimum. The presence of a directed excitation flow from the short-wavelength bacteriochlorophyll
The intensity dependence of picosecond kinetics in the light-harvesting antenna of the photosynthetic bacterium Rhodospirillum rubrum is studied at 77 K. By changing either the average excitation intensity or the pulse intensity we have been able to discriminate singlet-singlet and singlet- triplet annihilation. It is shown that the kinetics of both annihilation types are well characterized by the
Epitaxial shell is vital for enhancing the optoelectronic performance of semiconductor quantum dots (QDs), especially for the wide bandgap blue QDs, yet the shell crystal structure's impact on thermal stability and photophysical behavior remains unexplored. It is reported that the ligand-directed synthesis of ZnS shells with zinc blende (ZB) or wurtzite (WZ) structure on blue WZ CdZnS cores, where
Artificial intelligence (AI) and machine learning (ML) are rapidly permeating nearly every aspect of modern life, frompersonal devices and autonomous systems to industrial automation and environmental monitoring. The growing demandfor intelligence at the network edge is reshaping how computing hardware is conceived and built. Edge AI platforms areexpected to deliver high throughput within tight en
With the growing need to process large volumes of data, edge computing near data collection sources has become increasingly important. However, the resource constraints of edge devices require more efficient data processing techniques. Near-memory computing (NMC) presents an efficient solution, especially for data-intensive applications, by enabling processing that is both energy-efficient and har
The random k-SAT model is one of the most important and well-studied distributions over k-SAT instances. It is closely connected to statistical physics and is a benchmark for satisfiability algorithms. We show that when k=Θ(log n) , any Cutting Planes refutation for random k-SAT requires exponential length in the regime where the number of clauses guarantees that the formula is unsatisfiable with
Connections between proof complexity and circuit complexity have become major tools for obtaining lower bounds in both areas. These connections – which take the form of interpolation theorems and query-to-communication lifting theorems – translate efficient proofs into small circuits, and vice versa, allowing tools from one area to be applied to the other. Recently, the theory of TFNP has emerged
Background Selection of surgical residents is carried out in a variety of ways across the globe. In Sweden, the selection process is characterized by a lack of transparency and is conducted locally at each hospital. Recruiting suitable candidates is a matter of patient safety since patient outcome is related to surgeon characteristics and behaviors.Aim The aim of this thesis is to explore quantita
There is an urgent need for accurate and validated methods to measure plasma phosphorylated tau (p-Tau) biomarkers in Alzheimer’s disease (AD). In this study, we compared the performance of new commercially available plasma p-Tau217 assay developed by ALZpath to other established p-Tau assays in an autopsy-confirmed sample. We included 72 participants from the Arizona Study of Aging and Neurodegen
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder marked by β-amyloid (βA) accumulation, neuroinflammation, excessive synaptic pruning, and cognitive decline. Despite extensive research, effective treatments remain elusive. Here, we identify potassium channel-interacting protein 3 (KChIP3) as a key driver of AD pathology using the 5XFAD mouse model. KChIP3 levels were significan
Att placeras på HVB är en av de mest ingripande insatserna inom socialt arbete. För ungdomar innebär den ofta att tillvaron blir präglad av förändring och en känsla av att framtiden är osäker. Licentiatuppsatsen fördjupar kunskapen kring existentiella utmaningar som kan uppstå i denna process. Studien har en teoretisk utgångspunkt i existentiell filosofi och fokuserar på hur grundläggande livsvillWhen young people are placed in residential care (HVB) it is one of the mostfar-reaching interventions in social work, often involving significantdisruptions to their everyday lives, future outlook, and sense of self. Whilesuch placements frequently raise questions about meaning and freedom thesechallenges remain largely unexplored from an existential perspective in bothresearch and practice. This
