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Multiphoton spectroscopy of doubly excited, bound, and autoionizing states of strontium

We present a theory attempting an interpretation of existing data on three- and four-photon ionization of Sr in the wavelength range 557-575 nm and at 532 nm. Two-photon resonances with bound excited states and three-photon resonances with doubly excited autoionizing states are studied. ac Stark shifts and broadening of resonances, as well as singlet-triplet transitions, are shown to yield interes

Multiple-harmonic generation in rare gases at high laser intensity

We present experimental measurements of vacuum ultraviolet light emission processes in a 15-Torr rare-gas medium exposed to a strong 1064-nm laser field. Apart from a small number of lines which correspond to discrete transitions, and a broad continuum emission, we essentially observe the odd harmonics of the laser field, up to very high order. At a 3×1013 W cm-2 laser intensity, the highest-order

Calculations of high-order harmonic-generation processes in xenon at 1064 nm

We perform detailed calculations of harmonic conversion in a 15-Torr jet of xenon into which a 1064-nm-wavelength 36-ps-pulse-width laser has been tightly focused, so that the peak intensity ranges from 5×1012 to 5×1013 W cm-2. The single-atom emission rates are obtained by integrating the time-dependent Schrödinger equation. We employ an improved atomic model which includes excitation and ionizat

Theory of high-harmonic generation by low-frequency laser fields

We present a simple, analytic, and fully quantum theory of high-harmonic generation by low-frequency laser fields. The theory recovers the classical interpretation of Kulander et al. in Proceedings of the SILAP III Works hop, edited by B. Piraux (Plenum, New York, 1993) and Corkum [Phys. Rev. Lett. 71, 1994 (1993)] and clearly explains why the single-atom harmonic-generation spectra fall off at an

Optical determination of the characteristics of a pulsed-gas jet

A pulsed-gas jet with interesting properties has been developed. A typical pressure obtained at the output of this pulsed-gas jet is 25 Torr for a backing pressure of 150 Torr. At a repetition rate of 10 Hz, the background pressure stays below 1.5×10-4 Torr. Laser-induced fluoresence measurements permit one to determine the pressure and the divergence of the gas jet accurately.

Insulin inhibits glucagon release by SGLT2-induced stimulation of somatostatin secretion

Hypoglycaemia (low plasma glucose) is a serious and potentially fatal complication of insulin-treated diabetes. In healthy individuals, hypoglycaemia triggers glucagon secretion, which restores normal plasma glucose levels by stimulation of hepatic glucose production. This counterregulatory mechanism is impaired in diabetes. Here we show in mice that therapeutic concentrations of insulin inhibit g

Self-compression of ultrashort pulses in filaments

We report the self-compression of linearly and circularly polarized light pulses down to the few-cycle regime by self-guided beam propagation of intense 38-fs pulses in different gases with uniform density and with a pressure gradient.

Digital in-line holography with a single high-order harmonic pulse

In this paper, we review the optimization and characterization of a high-order harmonic generation (HHG) source for application in coherence imaging, and the use of this light source in a digital in-line holography setup. The high-order harmonic beam is generated by focusing a powerful infrared beam into an Ar gas cell. The length of the cell and the focusing parameters are optimized to maximize t

Multiple-harmonic conversion of 1064 nm radiation in rare gases

The authors report the observation of very-high-order odd harmonics of Nd:YAG laser radiation in rare gases at an intensity of about 1013 W cm-2. Harmonic light as high as the 33rd harmonic in the XUV range (32.2 nm) is generated in argon. The key point is that the harmonic intensity falls slowly beyond the fifth harmonic as the order increases. Finally, a UV continuum, beginning at 350 nm and ext

High-order harmonic generation in rare gases : a new source in photoionization spectroscopy

We demonstrate that we can use the extreme ultraviolet radiation produced by high order harmonic generation to perform photoionization experiments. With harmonics from the 11th to the 69th of a 140 fs Cr:LiSAF laser operating at 825 nm, we measure the relative photoionization cross sections of xenon, krypton, argon and neon over the range 10 to 110 eV. With narrow bandwidth harmonics produced by a

Lifetime measurements of the e1II, v = 0 and v = 1 states of12C16O, 13C16O, and13C18O

In a laboratory investigation using tunable picosecond lasers in a pump-probe configuration, lifetimes of the E 1u, v = 0 and v = 1 states of CO are experimentally determined. For E 'D, v = 1, the lifetime is found to vary significantly for the isotopomers. Combining the data with existing oscillator strengths, predissociation probabilities within the range of 93.6%-98.6% result for 12C16O, 13C16O

Monitoring real-time hormone release kinetics via high-content 3-D imaging of compensatory endocytosis

High-content real-time imaging of hormone secretion in tissues or cell populations is a challenging task, which is unlikely to be resolved directly, despite immense translational value. We approach this problem indirectly, using compensatory endocytosis, a process that closely follows exocytosis in the cell, as a surrogate read-out for secretion. The tissue is immobilized in an open-air perifusion

Adrenaline Stimulates Glucagon Secretion by Tpc2-Dependent Ca2+ Mobilization From Acidic Stores in Pancreatic α-Cells

Adrenaline is a powerful stimulus of glucagon secretion. It acts by activation of β-adrenergic receptors, but the downstream mechanisms have only been partially elucidated. Here, we have examined the effects of adrenaline in mouse and human α-cells by a combination of electrophysiology, imaging of Ca2+ and PKA activity, and hormone release measurements. We found that stimulation of glucagon secret

Attosecond pulse trains generated in a filament

We present temporal characterization of attosecond pulse trains generated during selfguided propagation of intense pulses in a long gas target. Spectral phase jumps are observed, affecting the temporal shape of the attosecond pulse train.

Femtosecond pulses as probe of the atomic structure under strong irradiation

Huge dynamic Stark shifts of atomic energy levels in xenon induced by high-intensity laser light have been measured by a new method based upon multiphoton ionization by a tunable femtosecond laser source. Stark-induced multiphoton resonances appear as identifiable structures in the photoelectron energy spectra. The change in the structures positions, when the photon energy is tuned, is directly re

Increased vimentin in human α- and β-cells in type 2 diabetes

Type 2 diabetes (T2DM) is associated with pancreatic islet dysfunction. Loss of β-cell identity has been implicated via dedifferentiation or conversion to other pancreatic endocrine cell types. How these transitions contribute to the onset and progression of T2DM in vivo is unknown. The aims of this study were to determine the degree of epithelial-to-mesenchymal transition occurring in α and β cel

Genetic variation in caveolin-1 correlates with long-term pancreas transplant function

Pancreas transplantation is a successful treatment for a selected group of people with type 1 diabetes. Continued insulin production can decrease over time and identifying predictors of long-term graft function is key to improving survival. The aim of this study was to screen subjects for variation in the Caveolin-1 gene (Cav1), previously shown to correlate with long-term kidney transplant functi