The extension of the pump-probe approach known from UV/VIS spectroscopy to very short wavelengths together with advanced simulation techniques allows a detailed analysis of excited-state dynamics in ...organic molecules or biomolecular structures on a nanosecond to femtosecond time level. Optical pump soft X-ray probe spectroscopy is a relatively new approach to detect and characterize optically dark states in organic molecules, exciton dynamics or transient ligand-to-metal charge transfer states. In this paper, we describe two experimental setups for transient soft X-ray absorption spectroscopy based on an LPP emitting picosecond and sub-nanosecond soft X-ray pulses in the photon energy range between 50 and 1500 eV. We apply these setups for near-edge X-ray absorption fine structure (NEXAFS) investigations of thin films of a metal-free porphyrin, an aggregate forming carbocyanine and a nickel oxide molecule. NEXAFS investigations have been carried out at the carbon, nitrogen and oxygen K-edge as well as on the Ni L-edge. From time-resolved NEXAFS carbon, K-edge measurements of the metal-free porphyrin first insights into a long-lived trap state are gained. Our findings are discussed and compared with density functional theory calculations.
Pulsed production of antihydrogen Amsler, Claude; Antonello, Massimiliano; Belov, Alexander ...
Communications physics,
01/2021, Letnik:
4, Številka:
1
Journal Article
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Abstract
Antihydrogen atoms with K or sub-K temperature are a powerful tool to precisely probe the validity of fundamental physics laws and the design of highly sensitive experiments needs ...antihydrogen with controllable and well defined conditions. We present here experimental results on the production of antihydrogen in a pulsed mode in which the time when 90% of the atoms are produced is known with an uncertainty of ~250 ns. The pulsed source is generated by the charge-exchange reaction between Rydberg positronium atoms—produced via the injection of a pulsed positron beam into a nanochanneled Si target, and excited by laser pulses—and antiprotons, trapped, cooled and manipulated in electromagnetic traps. The pulsed production enables the control of the antihydrogen temperature, the tunability of the Rydberg states, their de-excitation by pulsed lasers and the manipulation through electric field gradients. The production of pulsed antihydrogen is a major landmark in the AE
$$\bar{g}$$
ḡ
IS experiment to perform direct measurements of the validity of the Weak Equivalence Principle for antimatter.
Abstract Magnetic resonance with hyperpolarized contrast agents is one of the most powerful and noninvasive imaging platforms capable for investigating in vivo metabolism. While most of the utilized ...hyperpolarized agents are based on 13 C nuclei, a milestone advance in this area is the emergence of 15 N hyperpolarized contrast agents. Currently, the reported 15 N hyperpolarized agents mainly utilize the dissolution dynamic nuclear polarization (d‐DNP) protocol. The parahydrogen enhanced 15 N probes have proven to be elusive and have been tested almost exclusively in organic solvents. Herein, we designed a reaction based reactive oxygen sensor 15 N‐boronobenzyl‐2‐styrylpyridinium ( 15 N‐BBSP) which can be hyperpolarized with para‐hydrogen. Reactive oxygen species plays a vital role as one of the essential intracellular signalling molecules. Disturbance of the H 2 O 2 level usually represents a hallmark of pathophysiological conditions. This H 2 O 2 probe exhibited rapid responsiveness toward H 2 O 2 and offered spectrally resolvable chemical shifts. We also provide strategies to bring the newly developed probe from the organic reaction solution into a biocompatible injection buffer and demonstrate the feasibility of in vivo 15 N signal detection. The present work manifests its great potential not only for reaction based reactive sensing probes but also promises to serve as a platform to develop other contrast agents.
Parahydrogen‐induced polarization (PHIP) is an emerging technique to enhance the signal of stable isotope metabolic contrast agents for Magnetic Resonance (MR). The objective of this study is to ...continue establishing 1‐13C‐pyruvate‐d3, signal‐enhanced via PHIP, as a hyperpolarized contrast agent, obtained in seconds, to monitor metabolism in human cancer. Our focus was on human pancreatic and colon tumor xenografts. 1‐13C‐vinylpyruvate‐d6 was hydrogenated using parahydrogen. Thereafter, the polarization of the protons was transferred to 13C. Following a workup procedure, the free hyperpolarized 1‐13C‐pyruvate‐d3 was obtained in clean aqueous solution. After injection into animals bearing either pancreatic or colon cancer xenografts, slice‐selective MR spectra were acquired and analyzed to determine rate constants of metabolic conversion into lactate and alanine. 1‐13C‐pyruvate‐d3 proved to follow the increased metabolic rate to lactate and alanine in the tumor xenografts.
Abstract Magnetic resonance with hyperpolarized contrast agents is one of the most powerful and noninvasive imaging platforms capable for investigating in vivo metabolism. While most of the utilized ...hyperpolarized agents are based on 13 C nuclei, a milestone advance in this area is the emergence of 15 N hyperpolarized contrast agents. Currently, the reported 15 N hyperpolarized agents mainly utilize the dissolution dynamic nuclear polarization (d‐DNP) protocol. The parahydrogen enhanced 15 N probes have proven to be elusive and have been tested almost exclusively in organic solvents. Herein, we designed a reaction based reactive oxygen sensor 15 N‐boronobenzyl‐2‐styrylpyridinium ( 15 N‐BBSP) which can be hyperpolarized with para‐hydrogen. Reactive oxygen species plays a vital role as one of the essential intracellular signalling molecules. Disturbance of the H 2 O 2 level usually represents a hallmark of pathophysiological conditions. This H 2 O 2 probe exhibited rapid responsiveness toward H 2 O 2 and offered spectrally resolvable chemical shifts. We also provide strategies to bring the newly developed probe from the organic reaction solution into a biocompatible injection buffer and demonstrate the feasibility of in vivo 15 N signal detection. The present work manifests its great potential not only for reaction based reactive sensing probes but also promises to serve as a platform to develop other contrast agents.
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