Dynamic Light Scattering in Biomedical Applications:feature issue introduction

The feature Issue on "Dynamic Light Scattering in Biomedical Applications" presents a compilation of research breakthroughs and technological advancements that have shaped the field of biophotonics, particularly in the non-invasive exploration of biological tissues. Highlighting the significance of dynamic light scattering (DLS) alongside techniques like laser Doppler flowmetry (LDF), diffusing wave spectroscopy (DWS), and laser speckle contrast imaging (LSCI), this issue underscores the versatile applications of these methods in capturing the intricate dynamics of microcirculatory blood flow across various tissues. Contributions explore developments in fluorescence tomography, the integration of machine learning for data processing, enhancements in microscopy for cancer detection, and novel approaches in optical biophysics, among others. Innovations featured include a high-resolution speckle contrast tomography system for deep blood flow imaging, a rapid estimation technique for real-time tissue perfusion imaging, and the use of convolutional neural networks for efficient blood flow mapping. Additionally, studies delve into the impact of skin strain on spectral reflectance, the sensitivity of cerebral blood flow measurement techniques, and the potential of photobiomodulation for enhancing brain function. This issue not only showcases the latest theoretical and experimental strides in DLS-based imaging but also anticipates the continued evolution of these modalities for groundbreaking applications in disease detection, diagnosis, and monitoring, marking a pivotal contribution to the field of biomedical optics. [Abstract copyright: © 2024 Optica Publishing Group.

Characterization of a K+-induced conformational switch in a human telomeric DNA oligonucleotide using 2-aminopurine fluorescence

Human telomeric DNA consists of tandem repeats of the DNA sequence d(GGGTTA). Oligodeoxynucletotide telomere models such as d[A(GGGTTA)(3)GGG] (Tel22) fold in a cation-dependent manner into quadruplex structures consisting of stacked G-quartets linked by d(TTA) loops. NMR has shown that in Na(+) solutions Tel22 forms a ‘basket’ topology of four antiparallel strands; in contrast, Tel22 in K(+) solutions consists of a mixture of unknown topologies. Our previous studies on the mechanism of folding of Tel22 and similar telomere analogs utilized changes in UV absorption between 270 and 325 nm that report primarily on G-quartet formation and stacking showed that quadruplex formation occurs within milliseconds upon mixing with an appropriate cation. In the current study, we assessed the dynamics and equilibria of folding of specific loops by using Tel22 derivatives in which the dA residues were serially substituted with the fluorescent reporter base, 2-aminopurine (2-AP). Tel22 folding induced by Na(+) or K(+) assessed by changes in 2-AP fluorescence consists of at least three kinetic steps with time constants spanning a range of ms to several hundred seconds. Na(+)-dependent equilibrium titrations of Tel22 folding could be approximated as a cooperative two-state process. In contrast, K(+)-dependent folding curves were biphasic, revealing that different conformational ensembles are present in 1 mM and 30 mM K(+). This conclusion was confirmed by (1)H NMR. Molecular dynamics simulations revealed a K(+) binding pocket in Tel22 located near dA1 that is specific for the so-called hybrid-1 conformation in which strand 1 is in a parallel arrangement. The possible presence of this topologically specific binding site suggests that K(+) may play an allosteric role in regulating telomere conformation and function by modulating quadruplex tertiary structure

Incommensurate and multiple-q\boldsymbol{q} magnetic misfit order in the frustrated quantum spin ladder material antlerite, Cu3_3SO4_4(OH)4_4

In frustrated magnetic systems, the competition amongst interactions can introduce extremely high degeneracy and prevent the system from readily selecting a unique ground state. In such cases, the magnetic order is often exquisitely sensitive to the balance among the interactions, allowing tuning among novel magnetically ordered phases. In antlerite, Cu$_3$SO$_4$(OH)$_4$, Cu$^{2+}$ ($S=1/2$) quantum spins populate three-leg zigzag ladders in a highly frustrated quasi-one-dimensional structural motif. We demonstrate that at zero applied field, in addition to its recently reported low-temperature phase of coupled ferromagnetic and antiferromagnetic spin chains, this mineral hosts an incommensurate helical+cycloidal state, an idle-spin state, and a multiple-$q$ phase which is the magnetic analog of misfit crystal structures. The antiferromagnetic order on the central leg is reentrant. The high tunability of the magnetism in antlerite makes it a particularly promising platform for pursuing exotic magnetic order.Comment: 18.3 pages, 16 Figures, follow-up paper to arXiv:2203.1534

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5-10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range. (C) 2015 AIP Publishing LLC

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

13 págs.; 7 figs.; 8 tabs.© 2015 AIP Publishing LLC. The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5-10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range.F.F.S. and P.L.V. acknowledge the Portuguese Foundation for Science and Technology (FCT-MEC) through Grant Nos. SFRH/BPD/68979/2010 and SFRH/BSAB/105792/2014, respectively, the research Grant Nos. PTDC/FIS-ATO/1832/ 2012 and UID/FIS/00068/2013. P.L.V. also acknowledges his Visiting Research Fellow position at Flinders University, Adelaide, South Australia. The Patrimoine of the University of Liège, the Fonds National de la Recherche Scientifique, and the Fonds de la Recherche Fondamentale Collective of Belgium have also supported this research. E.L. and R.F.C.N. thank CNPq (Brazil) and the Science Without Borders Programme for opportunities to study abroad. The authors wish to acknowledge the beam time at the ISA synchrotron at Aarhus University, Denmark. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (Grant No. FP7/2007-2013) CALIPSO under Grant Agreement No. 312284. D.B.J. thanks the Australian Research Council for financial support provided through a Discovery Early Career Research Award. M.J.B. also thanks the Australian Research Council for some financial support, while M.J.B. and M.C.A.L. acknowledge the Brazilian agencies CNPq and FAPEMIG for financial support. F.B. and G.G. acknowledge partial financial support from the Spanish Ministry MINECO (Project No. FIS2012-31230) and the EU COST Action No. CM1301 (CELINA). Finally, R.F.C., M.T.do N.V., M.H.F.B., and M.A.P.L. acknowledge support from the Brazilian agency CNPq.Peer Reviewe

Studies of atomic properties of francium and rubidium.

High precision measurements of atomic properties are excellent probes for elec- troweak interaction studies at the lowest possible energy range. The extraction of standard model coupling constants relies on a unique combination of experimen- tal measurements and theoretical atomic structure calculations. It is only through stringent comparison between experimental and theoretical values of atomic prop- erties that a successful experiment can take place. Francium, with its heavy nucleus and alkali structure that makes it amenable to laser cooling and trapping, stands as an ideal test bed for such studies. Our group has successfully created, trapped and cooled several isotopes of francium, the heaviest of the alkalies, and demonstrated that precision studies of atomic properties, such as the measurement of the 8S1/2 excited state lifetime of 210Fr presented here, are feasible. Further work in our program of electroweak studies requires a better control of the electromagnetic environment observed by the sample of cold atoms as well as a lower background pressure (10-10 torr or better). We have designed and adapted to our previous setup a new &ldquo science &rdquo vacuum chamber that fulfills these requirements and the transport system that will transfer the francium atoms to the new chamber. We use this new experimental setup as well as a rubidium glass cell to perform precision studies of atomic and nuclear properties of rubidium. Spectroscopic studies of the most abundant isotopes of rubidium, 87Rb and 85Rb, are a vital component in our program. Performing measurements in rubidium allows us to do extensive and rigorous searches of systematics that can be later extrapolated to francium. We present a precision lifetime measurement of the 5D3/2 state of 87Rb and a measurement of hyperfine splittings of the 6S1/2 level of 87Rb and 85Rb. The quality of the data of the latter allows us to observe a hyperfine anomaly attributed to an isotopic difference of the magnetization distribution in the nucleus i.e. the Bohr-Weisskopf effect. The measurements we present in this work complement each other in exploring the behavior of the valence electron at different distances from the nucleus. In addition, they constitute excellent tests for the predictions of ab initio calculations using many body perturbation theory and bolster our confidence on the reliability of the experimental and theoretical tools needed for our work

Recent Advances in Linear and Nonlinear Optics

Sight is the dominant sense of mankind to apprehend the world at the earth scale and beyond the frontiers of the infinite, from the nanometer to the incommensurable. Primarily based on sunlight and natural and artificial light sources, optics has been the major companion of spectroscopy since scientific observation began. The invention of the laser in the early sixties has boosted optical spectroscopy through the intrinsic or specific symmetry electronic properties of materials at the multiscale (birefringence, nonlinear and photonic crystals), revealed by the ability to monitor light polarization inside or on the surface of designed objects. This Special Issue of Symmetry features articles and reviews that are of tremendous interest to scientists who study linear and nonlinear optics, all oriented around the common axis of symmetry. Contributions transverse the entire breadth of this field, including those concerning polarization and anisotropy within colloids of chromophores and metal/semiconducting nanoparticles probed by UV-visible and fluorescence spectroscopies; microscopic structures of liquid–liquid, liquid–gas, and liquid–solid interfaces; surface- and symmetry-specific optical techniques and simulations, including second-harmonic and sum-frequency generations, and surface-enhanced and coherent anti-Stokes Raman spectroscopies; orientation and chirality of bio-molecular interfaces; symmetry breaking in photochemistry; symmetric multipolar molecules; reversible electronic energy transfer within supramolecular systems; plasmonics; and light polarization effects in materials

Structural and optical studies of condensed gases under extreme conditions

Dense solidified gases are sources of rich physical and chemical phenomena and model objects to be widely used in theoretical calculations. The focus of this thesis has been the structural and optical properties of simple gases and gas mixtures under extreme conditions. Three simple dense gas systems, methane (CH₄), Xe-Ar mixture and nitrogen-trifluoride (NF₃) have been studied and characterized using high pressure and high temperature techniques in combination with Raman spectroscopy and x-ray diffraction in diamond anvil cells (DACs). CH₄ is one of the major constituents of the Uranus and Neptune interiors, and large amounts of it are also present in the deep Earth. As the simplest hydrocarbon, CH₄ presents a rich variety of crystal structures at low temperature and pressure regime. However, despite being widely studied, phase relations between numerous CH₄ phases are poorly understood even at relatively low pressure. In this thesis, by combining Raman spectroscopy and in-situ high-pressure, high-temperature resistive heating techniques, we demonstrate the complexity of the phase diagram of CH₄ up to 45 GPa and 1400 K. Changes in the frequencies and Raman profiles of the ν₁ and ν₃ vibrational modes of CH₄ molecule were used to detect phase transitions and construct boundaries between individual phases in the phase diagram. A triple point between fluid, phases I, and phase alone the melting curve was found and precisely located in the studied P-T range. The melting curve changes its slope above the triple point. Moreover, previously reported sluggish transitions from phase A to phase B was found to be controlled by kinetics. These results represent a significant revision of the existing phase diagram of CH₄. The second system under investigation is the binary mixture of xenon and argon. The simple closed-shell electronic configurations make rare gases and their mixtures an ideal system for comparing experiment with theory. Rare gases are archetypal van der Waals systems. Previously, no binary compound of Xe and Ar were known. We have explored rare gas solids Xe-Ar₂ system up to pressure of 60 GPa with combined Raman spectroscopy, x-ray diffraction and first-principles density functional theory (DFT) calculations. A novel van der Waals compound XeAr₂ has been observed at 3.5 GPa. We find that pressure stabilizes the formation of this stoichiometric, solid van der Waals compound of composition XeAr₂. Synchrotron x-ray diffraction shows that this compound adopts a MgZn₂-type crystal structure, which is in a Laves phase. Our DFT calculation of the formation enthalpy indicates that XeAr₂ stays stable to at least 80 GPa. The last condensed gas solid presented here is nitrogen-trifluoride (NF₃). Since first synthesized by molten salt electrolysis, NF₃ has attracted wide interests, ranging from fundamental study to industrial applications. However, structures and phase relations on NF₃ under high pressure remains unknown. In the contributing work, NF₃ has been studied by synchrotron x-ray diffraction and Raman spectroscopy combined with DFT calculation. At 300 K, NF₃ solidifies at 3.5 GPa into the orthorhombic structure (Pnma). Phase diagram of NF₃ has been studied by Raman spectroscopy, two solid phases have been observed between 77 and 300 K up to 120 GPa. Our DFT calculations suggests NF₃ remains stable to at least 150 GPa

Organic photosensitizers for light-driven hydrogen evolution: synthesis, characterization and application

This work utilizes organic chromophores, namely perylene dyes and BODIPYs, as light-active component in light-driven hydrogen evolution