192815 research outputs found
Sort by
Unraveling the triplet energy transfer pathways in bacteriochlorophyll b -based photosynthetic complexes: insights from sub-nanosecond time-resolved absorption spectroscopy of Blastochloris viridis
No full textPhotosynthetic bacteria provide an excellent model for investigating the primary processes of photosynthesis due to their relatively simple photochemical systems and ease of biochemical sample preparation. While light-harvesting (LH) complexes containing bacteriochlorophyll (Bchl) a have been extensively studied, much less is known about Bchl b-based pigment–protein complexes. The purple photosynthetic bacterium Blastochloris (Blc.) viridis is unusual in possessing only an LH1–reaction center (RC) core complex. Its LH1 complex incorporates Bchl b dimers along with two distinct carotenoids—1,2-dihydroneurosporene and 1,2-dihydrolycopene. Unlike Bchl a-containing systems, this complex features a remarkably red-shifted Qy absorption band located at 1010 nm, enabling efficient LH in the near-infrared region. Beyond their role in energy transfer, carotenoids in LH1–RC complexes serve as crucial photoprotective agents, mitigating oxidative stress by quenching triplet states that could otherwise generate harmful reactive oxygen species. However, the triplet energy transfer and quenching reactions in Bchl b-containing systems remain largely unexplored. In this study, we employed sub-nanosecond time-resolved absorption spectroscopy to investigate the excitation energy transfer dynamics and photoprotective mechanisms in the purified LH1–RC and RC complexes of Blc. viridis. Our findings reveal previously uncharacterized triplet–triplet energy transfer processes from Bchl b to carotenoids. These results not only advance our understanding of Bchl b-based light-harvesting systems but also provide key insights for the development of artificial photosynthetic platforms optimized for near-infrared light utilization
Excitation energy transfer dynamics from carotenoid to bacteriochlorophyll a in the LH2 complex of Rhodobacter sphaeroides: insights from reconstitution experiments with carotenoids and B800 bacteriochlorophyll a
Get PDFCarotenoids are crucial for photosynthesis, playing key roles in light harvesting and photoprotection. In this study, spheroidene and bacteriochlorophyll a (Bchl a) were reconstituted into the chromatophores of the carotenoidless mutant Rhodobacter sphaeroides R26.1, resulting in the preparation of high-quality LH2 complexes. Global and target analyses of transient absorption data revealed that incorporating B800 Bchl a significantly enhances excitation energy transfer (EET) efficiency from carotenoids to Bchl a. EET predominantly occurs from the carotenoid S2 state, with additional pathways from the S1 state observed in native LH2. Unique relaxation dynamics were identified, including the generation of the carotenoid S* state in reconstituted LH2 with both spheroidene and B800 Bchl a and the formation of the carotenoid T1 state in reconstituted LH2. These findings underscore the critical influence of pigment composition and spatial organization on energy transfer mechanisms. They provide valuable insights into the molecular interplay that governs excitation energy transfer in photosynthetic light-harvesting systems
Applications of machine learning in gravitational-wave research with current interferometric detectors
Get PDFThis article provides an overview of the current state of machine learning in gravitational-wave research with interferometric detectors. Such applications are often still in their early days, but have reached sufficient popularity to warrant an assessment of their impact across various domains, including detector studies, noise and signal simulations, and the detection and interpretation of astrophysical signals. In detector studies, machine learning could be useful to optimize instruments like LIGO, Virgo, KAGRA, and future detectors. Algorithms could predict and help in mitigating environmental disturbances in real time, ensuring detectors operate at peak performance. Furthermore, machine-learning tools for characterizing and cleaning data after it is taken have already become crucial tools for achieving the best sensitivity of the LIGO–Virgo–KAGRA network. In data analysis, machine learning has already been applied as an alternative to traditional methods for signal detection, source localization, noise reduction, and parameter estimation. For some signal types, it can already yield improved efficiency and robustness, though in many other areas traditional methods remain dominant. As the field evolves, the role of machine learning in advancing gravitational-wave research is expected to become increasingly prominent. This report highlights recent advancements, challenges, and perspectives for the current detector generation, with a brief outlook to the next generation of gravitational-wave detectors
Test of lepton flavor universality with Bs0→ϕℓ+ℓ− decays
Get PDFLepton flavor universality in rare b → s transitions is tested for the first time using B0
s meson decays. The
measurements are performed using pp collision data collected by the LHCb experiment between 2011 and
2018, corresponding to a total integrated luminosity of 9 fb−1. Branching fraction ratios between the
B0
s → ϕeþe− and B0
s → ϕμþμ− decays are measured in three regions of dilepton mass squared, q2, with
0.1 < q2 < 1.1, 1.1 < q2 < 6.0, and 15 < q2 < 19 GeV2=c4. The results agree with the standard model
expectation of lepton flavor universality
Search for resonance-enhanced CP and angular asymmetries in the Λc+ → pμ+μ− decay at LHCb
Get PDFThe first measurement of the CP asymmetry of the decay rate (ACP) and the CP average (ΣAFB) and CP asymmetry (ΔAFB) of the forward-backward asymmetry in the muon system of Λc+→pμ+μ− decays is reported. The measurement is performed using a data sample of proton-proton collisions, recorded by the LHCb experiment from 2016 to 2018 at a center-of-mass energy of 13 TeV, which corresponds to an integrated luminosity of 5.4 fb−1. The asymmetries are measured in two regions of dimuon mass near the ϕ-meson mass peak. The dimuon-mass integrated results are ACP=(−1.1±4.0±0.5)%, ΣAFB=(3.9±4.0±0.6)%, ΔAFB=(3.1±4.0±0.4)%, where the first uncertainty is statistical and the second systematic. The results are consistent with the conservation of CP symmetry and the Standard Model expectations
Measurements of ψ(2S) and χc1(3872) production within fully reconstructed jets
Get PDFThis paper presents the first measurement of
ψ(2S) and χc1(3872) meson production within fully reconstructed jets. Each quarkonium state (tag) is reconstructed
via its decay to the J/ψ(→μ+μ−)π+π− final state in the
forward region using proton-proton collision data collected
by the LHCb experiment at the center-of-mass-energy of
13TeV in 2016, corresponding to an integrated luminosity
of 1.64 fb−1. The fragmentation function, presented as the
ratio of the quarkonium-tag transverse momentum to the full
jet transverse momentum (pT(tag)/pT(jet)), is measured differentially in pT(jet) and pT(tag) bins. The distributions are
separated into promptly produced quarkonia from protonproton collisions and quarkonia produced from displaced
b-hadron decays. While the displaced quarkonia fragmentation functions are in general well described by parton-shower
predictions, the prompt quarkonium distributions differ significantly from fixed-order non-relativistic QCD (NRQCD)
predictions followed by a QCD parton shower
A Neuroscientific Perspective on Understanding and Managing Stress
No full textThis guest post provides an overview of the biology of stress and describes ways students can manage stress
Supporting Student Wellbeing and Learning with Yoga: Research Proposal
Get PDFYoga is adaptable for all abilities and backgrounds, fostering inclusivity. It also supports neurodiverse students and those with anxiety or physical challenges. It is a form of embodied learning that encourages self-awareness, mindfulness, and reflection-skills that enhance academic and personal growth. This study aims to provide evidence for the integration of yoga into university curricula as a sustainable strategy for improving student health and resilience
The quantum Bruhat graph for SLˆ2 and double affine Demazure products
Get PDFWe investigate the Demazure product in a double affine setting. A recent preprint by Muthiah and Puskás gives a conjectural way to define this in terms of the q = 0 specialisation of these Hecke algebras. We instead take a different approach generalising work by Felix Schremmer, who gave an equivalent formula for the (single) affine Demazure product in terms of the quantum Bruhat graph. We focus on typê SL2 , where we prove that the quantum Bruhat graph of this type satisfies some nice properties, which allows us to construct a well-defined associative Demazure product for the double affine Weyl semigroup WT (for level greater than one). We give results regarding the Demazure product and Muthiah and Orr’s length function for WT , and we verify that our proposal matches specific examples computed by Muthiah and Puskás using the Kac-Moody affine Hecke algebra
Data sources:
Access Repository Dashboard
Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇