Abstract
In haemoglobin the change from the low-spin (LS) hexacoordinated haem to the high spin (HS, S = 2) pentacoordinated domed deoxy-myoglobin (deoxyMb) form upon ligand detachment from the haem ...and the reverse process upon ligand binding are what ultimately drives the respiratory function. Here we probe them in the case of Myoglobin-NO (MbNO) using element- and spin-sensitive femtosecond Fe K
α
and K
β
X-ray emission spectroscopy at an X-ray free-electron laser (FEL). We find that the change from the LS (S = 1/2) MbNO to the HS haem occurs in ~800 fs, and that it proceeds via an intermediate (S = 1) spin state. We also show that upon NO recombination, the return to the planar MbNO ground state is an electronic relaxation from HS to LS taking place in ~30 ps. Thus, the entire ligand dissociation-recombination cycle in MbNO is a spin cross-over followed by a reverse spin cross-over process.
The charge-carrier dynamics of anatase TiO2 nanoparticles in an aqueous
solution were studied by femtosecond time-resolved X-ray absorption spectroscopy using an
X-ray free electron laser in ...combination with a synchronized ultraviolet femtosecond laser
(268 nm). Using an arrival time monitor for the X-ray pulses, we obtained a temporal
resolution of 170 fs. The transient X-ray absorption spectra revealed an ultrafast Ti
K-edge shift and a subsequent growth of a pre-edge structure. The edge shift occurred in
ca. 100 fs and is ascribed to reduction of Ti by localization of generated conduction band
electrons into shallow traps of self-trapped polarons or deep traps at penta-coordinate Ti
sites. Growth of the pre-edge feature and reduction of the above-edge peak intensity occur
with similar time constants of 300–400 fs, which we assign to the structural distortion
dynamics near the surface.
Purely label-free imaging to directly monitor small molecules in a biological organism is still challenging despite recent technical advancements. Time-resolved pump–probe coherent Raman scattering ...microscopy is a promising label-free approach to increase chemical specificity. However, conventional time-resolved methods involve a compromise between three conflicting requirements: high spectral resolution, low background levels, and high sensitivity. Here, we present an advanced spectral-focusing technique using asymmetric pulses produced by nonlinear chirping and demonstrate its performance in pump–probe phase-modulated stimulated Raman scattering microscopy. In addition, we report for the first time a novel frequency-scanning spectral-focusing system using tunable bandpass filters. Our concept uses the filters not only as a frequency allocation tool for the probe pulses but also as a pulse-shaping tool that provides a strong nonlinear chirp. The spectral resolution and signal-to-noise ratio are greatly improved by highly efficient time-resolved detection using asymmetric spectrally focused probe pulses. We achieve a spectral resolution of ∼25 cm−1, a reduced nonresonant background level on the order of 10−8, and a detectable concentration limit of 0.01% dimethyl sulfoxide/water solution (1.5 mM). Using this method, we demonstrate high-contrast imaging of a small-molecule drug in a tissue. These advancements will allow time-resolved coherent Raman microscopy to be used as a practical drug-imaging tool for biomedical sciences.
J-PARC E16 is an experiment to examine the origin of hadron mass through a systematic measurement of spectral changes of vector mesons in nuclei. The measurement of <inline-formula> <tex-math ...notation="LaTeX">e^{+}e^{-} </tex-math></inline-formula> pairs from the decay of vector mesons will provide the information of the partial restoration of the chiral symmetry in a normal nuclear density. To resolve a pulse pile-up and achieve good discrimination of <inline-formula> <tex-math notation="LaTeX">e^{+} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">e^{-} </tex-math></inline-formula> from the background of a reaction rate of an order of 10 MHz, the data acquisition (DAQ) system uses waveform sampling chips of APV25 and DRS4. The trigger rate and data rate are expected to be 1 kHz and 120-330 MiB/s, respectively. The DAQ system for readout of APV25 and DRS4 were developed, where events were synchronized by common trigger and tag data. The first commissioning in beam, called Run-0a, was performed in June 2020 with about 1/4 of the designed setup. The DAQ worked with a trigger rate of 300 Hz in the Run-0a and the main bottleneck was a large data size of APV25. Further optimization of the DAQ system will improve the performance.
Distributions of small molecular weight (less than 300 Da) compounds inside biological tissue have been obscure because of the lack of appropriate methods to measure them. Although fluorescence ...techniques are widely used to characterise the localisation of large biomolecules, they cannot be easily applied to the cases with small molecule compounds. We used CARS spectroscopy to detect and identify a label-free small molecule compound. To facilitate detection in aqueous environment, we utilised time-resolved and phase-sensitive techniques to reduce non-resonant background generated from water. We applied this technique to detect small molecular weight compound, taurine, inside mouse cornea tissue immersed in taurine solution as an initial model experiment. We detected a Raman peak of taurine near wavenumber 1033 cm(-1) inside cornea and successfully characterised its depth profile in the tissue. Our CARS spectra measurement can be a promising method to measure and visualise the distribution of small bio-related compounds in biological background without using any labeling, paving the way for new cell biological analysis in various disciplines.
SUMMARY
Verification of image manipulation for various alterations is an indispensable technology to protect original images. Conventional forgery detection methods using fingerprint are useful, ...since the original image is not required in detection process. However, manipulated local region can't be specified. Further, type of manipulation is not identified. In this article, a novel forgery identification method based on reversible histogram shift is proposed. Our method can detect partial and overall manipulation regions and identify manipulation type. Simulation results are shown to demonstrate the effectiveness of our method using various types of manipulated database images.
The results of room-temperature fluorescence lifetime measurements are reported for the excitation of J aggregates (Js) of pseudoisocyanine chloride (PIC-Cl) prepared in potassium polyvinyl sulfate ...(PVS) polymer thin films, their aqueous solutions, and NaCl aqueous solutions. Variations of the microscopic morphologies of the aggregates were investigated. The results show that fluorescence decay features correlated to the morphology change. The observed fluorescence lifetime and quantum efficiency of PIC J aggregates (PIC-Js) in a NaCl aqueous solution were 310 ps and 28%, respectively. The lifetime of the fibril-shaped macroaggregates prepared in PVS thin films was below the instrumental time resolution of 5 ps, and the efficiency decreased to below 3%. The results indicate that PIC-Js prepared with PVS polymers have an increased nonradiative contribution to the excitation deactivation process. In particular, macro-Js with isolated fibril-shaped structures revealed nonradiative pathway(s) that are closely associated to the specific packaging morphology of the constituent meso-Js. The possibility of a destructive effect on the formation of cavity-polaritons is also discussed.
Development of the GEM tracker for the J-PARC E16 experiment Komatsu, Yusuke; Aoki, Kazuya; Aramaki, Yoki ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2013, Letnik:
732
Journal Article
Recenzirano
The J-PARC E16 experiment has been proposed to measure the mass spectrum of ϕ mesons in nuclear matter to study the origin of QCD mass. The ϕ mesons are identified in the e+e− decay channel and the ...mass of these ϕ mesons is reconstructed using the momenta of the e+ and e− pairs. A tracking detector for this experiment is composed of a position sensitive device that employs Gas Electron Multipliers (GEMs) with a two-dimensional readout board. The ionization electrons are amplified with a triple-GEM stack. The required position resolution is 100μm up to an incidence angle of 30°.
Position resolutions and efficiencies of the tracking device are evaluated using a π− beam with a momentum of 1.0GeV/c at the J-PARC K1.1BR beam line. A position resolution of better than 100μm is obtained by calculating the center of gravity of the charges on the readout strips when tracks arrive perpendicularly at the detector plane. Timing information of charge clusters is essential to improve the position resolutions for the inclined tracks. The arrival times of the charge clusters are derived from the wave forms collected by flash ADC modules. Using the arrival times of the clusters, the obtained position resolution is better than 100μm for the track inclinations of 15° and 30°. The detection efficiency is also investigated as a function of the GEM gains, and the operational voltage is optimized.
When powder mixtures of iron, aluminum, titanium and boron were heated under pseudo hot isostatic pressure in vacuum to a temperature just above the melting point of aluminum, sudden and rapid ...temperature rise was always observed, which was due to the exothermic reactions producing FeAl and TiB
2. Metallographic investigations revealed that the products consisted of homogeneously dispersed fine hexagonal TiB
2 particles and FeAl matrix and that the products included some pores. As the concentrations of titanium and boron in the powder mixture increased, the TiB
2 particle size and porosity increased. Both the particle size and the porosity were dramatically reduced by preheating of the powder mixture, which brought about increase in Vickers hardness of the reaction products.
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