Time-resolved XUV-IR photoion mass spectroscopy of naphthalene conducted with broadband, as well as with wavelength-selected narrowband XUV pulses reveals a rising probability of fragmentation ...characterized by a lifetime of \(92\pm4\)~fs. This lifetime is independent of the XUV excitation wavelength and is the same for all low appearance energy fragments recorded in the experiment. Analysis of the experimental data in conjunction with a statistical multi-state vibronic model suggests that the experimental signals track vibrational energy redistribution on the potential energy surface of the ground state cation. In particular, populations of the out-of-plane ring twist and the out-of-plane wave bending modes could be responsible for opening new IR absorption channels leading to enhanced fragmentation.
Transient absorption is a very powerful observable in attosecond experiments on atoms, molecules and solids and is frequently used in experiments employing phase-locked few-cycle infrared and XUV ...laser pulses derived from high harmonic generation. We show numerically and analytically that in non-centrosymmetric systems, such as many polyatomic molecules, which-way interference enabled by the lack of parity conservation leads to new spectral absorption features, which directly reveal the laser electric field. The extension of Attosecond Transient Absorption Spectroscopy (ATAS) to such targets hence becomes sensitive to global and local inversion symmetry. We anticipate that ATAS will find new applications in non-centrosymmetric systems, in which the carrier-to-envelope phase of the infrared pulse becomes a relevant parameter and in which the orientation of the sample and the electronic symmetry of the molecule can be addressed.
Rauch D, Bohnemann L, Kurtz C, et al. Vascular response to gadolinium-containing contrast media in an ex vivo rabbit arterial model. Invest Radiol 2001;36:589–596.
RATIONALE AND OBJECTIVES. To assess ...the influence of gadolinium-containing magnetic resonance contrast agents on contractility of the arterial vessel wall.
METHODS.Bilateral segments of rabbit carotid arteries were mounted in flow chambers, surrounded by aerated (95% O2, 5% CO2) Krebs’ solution, and perfused at a constant rate by separated and aerated Krebs’ solution. Therefore, changes in pressure of the circulating Krebs’ solution indicated alterations of vessel wall contractility. Viability of the artery was tested by 124 mmol/L KCl, 3 × 10 mol/L phenylephrine, and 10 mol/L acetylcholine. After a washout phase, gadopentate (n = 10) or gadoteridol (n = 10) was added to the perfusate of one carotid artery in increments of 0.1, 0.3, and 0.6 mmol/L. Concentrations up to 0.9 mmol/L and 1.2 mmol/L were tested, respectively. The contralateral artery served as a control. To assess potential relaxing effects of the media, vessels were brought into a contracted status with 3 × 10 mol/L phenylephrine and then received gadolinium chelates.
RESULTS.Potassium chloride and phenylephrine increased and acetylcholine decreased the pressure, indicating vasoconstriction and vasodilatation, respectively. After gadopentate and gadoteridol infusion, no statistically significant pressure changes could be detected, ruling out any vasoconstrictor or vasodilator effect.
CONCLUSIONS.Gadopentetate and gadoteridol in doses of up to 1.2 mmol/L did not alter vessel wall tone. The impact of contrast media on blood pressure, as has been shown in some clinical trials, probably is not due to direct changes in arterial wall tone.
Refraction is a well-known optical phenomenon that alters the direction of light waves propagating through matter. Microscopes, lenses and prisms based on refraction are indispensable tools for ...controlling the properties of light beams at visible, infrared, ultraviolet and X-ray wavelengths. The large absorption of extreme-ultraviolet (XUV) radiation in matter, however, hinders the development of refractive lenses and prisms in this spectral region. Here, we demonstrate control over the refraction of XUV radiation by using a gas jet with a density gradient across the XUV beam profile. A gas phase prism is demonstrated that leads to a frequency-dependent deflection of the XUV beam. The strong deflection in the vicinity of atomic resonances is further used to develop a deformable XUV refractive lens, with low absorption and a focal length that can be tuned by varying the gas pressure. Our results provide novel opportunities in XUV science and open a route towards the transfer of refraction-based techniques including microscopy and nanofocusing, which are well established in other spectral regions, to the XUV domain.
This classification is based on the results of a retrospective study with 86 patients treated arthroscopically for osteochondritis dissecans (OD) of the ankle joint. Radiography, magnetic resonance ...imaging (MRI) and the findings from arthroscopy were combined for a new classification (six stages) of OD. Additionally, 17 patients of a prospective study based on preoperative and postoperative findings were used to validate this classification. The classification stages have been developed taking into account localization, extent of the necrotic area of subchondral bone and cartilage, edema or perifocal alterations, and especially the uptake of gadolinium (Magnevist, i.v.) in MRI examination. Furthermore, a therapy strategy has been suggested based on arthroscopic results, imaging modalities, and patient age.
