Gain dynamics in quickly ionized plasma for seeded operated soft x-ray lasers.

Harmonic seeded operation of a neon-like titanium plasma-based soft x-ray laser is described. The plasma amplifier is pumped with a variation of the grazing incidence technique involving a fast and localized ionization step. We discuss its effect on gain dynamics by measuring the amplifying factor as a function of the delay between pump pulse and harmonic seed. Two different regimes are pointed out, following the pumping scheme used. For one of them, a delay in the gain generation compared with the pumping laser pulse is observed.

Temporal coherence and spectral linewidth of an injection-seeded transient collisional soft x-ray laser.

The temporal coherence of an injection-seeded transient 18.9 nm molybdenum soft x-ray laser was measured using a wavefront division interferometer and compared to model simulations. The seeded laser is found to have a coherence time similar to that of the unseeded amplifier, ~1 ps, but a significantly larger degree of temporal coherence. The measured coherence time for the unseeded amplifier is only a small fraction of the pulsewidth, while in the case of the seeded laser it approaches full temporal coherence. The measurements confirm that the bandwidth of the solid target amplifiers is significantly wider than that of soft x-ray lasers that use gaseous targets, an advantage for the development of sub-picosecond soft x-ray lasers.

Fourier-limited seeded soft x-ray laser pulse.

We present what we believe to be the first measurement of the spectral properties of a soft x-ray laser seeded by a high-order harmonic beam. Using an interferometric method, the spectral profile of a seeded Ni-like krypton soft x-ray laser (32.8 nm) generated by optical field ionization has been experimentally determined, and the shortest possible pulse duration has been deduced. The source exhibits a Voigt spectral profile with an FWHM of 3.1+/-0.3 mA, leading to a Fourier-transform pulse duration of 4.7 ps. This value is comparable with the upper limit of the soft x-ray pulse duration determined by experimentally investigating the gain dynamics, from which we conclude that the source has reached the Fourier limit. The measured bandwidth is in good agreement with the predictions of a radiative transfer code, including gain line narrowing and saturation rebroadening.

Dynamical description of transient x-ray lasers seeded with high-order harmonic radiation through Maxwell-Bloch numerical simulations.

The Maxwell-Bloch code COLAX has been upgraded to use detailed hydrodynamical and collisional-radiative simulations of a soft x-ray laser plasma with traveling-wave pumping. The seeding of short pulses of high-order harmonics of the pump laser into the x-ray laser medium has been simulated. The amplification is shown to be a dynamic, two-stage process: the atomic dipoles of the lasing ions are first coherently excited by the short pulse, and subsequently generate a radiation wake which is amplified along its path through the plasma, with consequences on the experimentally recorded spectra.

Optimization toward a high-average-brightness soft-x-ray laser pumped at grazing incidence.

We report the near-field imaging characterization of a 10 Hz Ni-like 18.9 nm molybdenum soft-x-ray laser pumped in a grazing incidence pumping (GRIP) geometry with a table-top laser driver. We investigate the effect of varying the GRIP angle on the spatial behavior of the soft-x-ray laser source. After multiparameter optimization, we were able to find conditions to generate routinely a high-repetition-rate soft-x-ray laser with an energy level of up to 3 microJ/pulse and to 6x10(17) photons/s/mm2/mrad2/(0.1% bandwidth) average brightness and 1x10(28) photons/s/mm2/mrad2/(0.1% bandwidth) peak brightness.

Quantitative study of 10 Hz operation of a soft x-ray laser-energy stability and target considerations.

A soft x-ray laser from Ni-like Mo, pumped in grazing incidence (GRIP), is analyzed with regard to high repetition rate operation. Reliable lasing is obtained, but with significant energy fluctuations attributed mainly to beam pointing jitter from the pump laser. Two modes of operation are compared: continuously moving target and stationary target. With a moving target the soft X-ray output is constant on average, whereas the repeated use of the same target position leads to a pulse energy which increases for several tens of shots. This effect might be caused by improved guiding of the pump laser in the formed groove and the removal, through laser ablation, of the oxide layer on the target surface.

Demonstration of a Ni-like Kr optical-field-ionization collisional soft x-ray laser at 32.8 nm.

We report the first experimental demonstration of a Ni-like optical-field ionization collisional soft x-ray laser. The amplifying medium is generated by focusing a circularly polarized 760 mJ, 30 fs, 10-Hz Ti:sapphire laser beam in a few mm cell filled with krypton. We have measured a gain coefficient of 78 cm(-1) on the 3d(9)4d 1S0-3d(9)4p(1)P1 transition at 32.8 nm, which is here amplified for the first time. This radiation source represents the shortest wavelength optical-field ionization collisional soft x-ray laser ever produced. The influence of the gas pressure and the pumping energy on the lasing output are also presented.

Saturated amplification of a collisionally pumped optical-field-ionization soft X-ray laser at 41.8 nm.

We report the first saturated amplification of an optical-field-ionization soft x-ray laser. The amplifying medium is generated by focusing a circularly polarized 330-mJ, 35-fs, 10-Hz Ti:sapphire laser system in a few-mm cell filled with xenon. A gain of 67 cm(-1) on the 4d(9)5p-4d(9)5d transition at 41.8 nm in Pd-like xenon and a gain-length product of 15 have been inferred at saturation. This source delivers about 5 x 10(9) photons per pulse. The influence of the pumping energy and the laser polarization on the lasing output are also presented.

Hemoperitoneum in patients receiving hemodialysis.

Acute abdominal pain in chronic hemodialysis patients has well-known causes, including acute pancreatitis, mesenteric arterial insufficiency, or complicated duodenal ulcer. Others, such as hemoperitoneum, are far less common. Although hemoperitoneum occurs in patients receiving peritoneal dialysis, dialysis is seldom if ever the direct cause of the bleeding. Hemoperitoneum is often related to menses or ovulation, particularly to ovarian cyst rupture; therefore, it is more common in young women. In most cases, no specific treatment is required. Hemoperitoneum is rarely considered as the cause of acute abdominal pain in chronic hemodialysis patients. In this report of hemoperitoneum confirmed by emergency laparotomy in 3 women, bleeding was not related to gynecologic origin. All of the women were younger than age 50 and undergoing long-term hemodialysis. All patients had a history of acute abdominal pain associated with shock. The cause of bleeding was always an organ lesion: hepatic amyloidosis with suspected portal hypertension or sclerosing peritonitis and acute hemorrhagic pancreatitis. Coagulation abnormalities and the use of anticoagulants during hemodialysis sessions may have been aggravating factors in all three patients. Hemoperitoneum is difficult to diagnose, particularly in the minor forms, and consequently its incidence may be underestimated. Therefore, it should be considered whenever a chronic hemodialysis patient presents with persistent acute abdominal pain.

[Rotavirus infection associated with adult thrombotic microangiopathy]. / Infection à Rotavirus associée à la survenue d'une microangiopathie thrombotique de l'adulte.

BACKGROUND: A preceding viral syndrome is classically cited as a triggering factor for thrombotic microangiopathy although only anecdotal reports of the causal agent have been documented. CASE REPORT: An 84-year-old woman developed thrombotic microangiopathy secondary to diarrhea. An exhaustive etiological work-up documented the presence of Rotavirus alone in the fecal matter. The clinical course was favorable after 9 plasma exchanges using frozen fresh plasma and was associated with disappearance of the Rotavirus. DISCUSSION: Enterohemorrhagic Escherichia coli is the most commonly identified infectious agent causing thrombotic microangiopathy. A small number of cases caused by viral agents (particularly retroviruses) have also been documented. To our knowledge, this is the first case attributable to a Rotavirus. In our case, the presence of the Rotavirus in the fecal matter and the favorable clinical course when the virus disappeared would be in favor of its causal role in the pathogenesis of thrombotic micorangiopathy.

Combined idiopathic retroperitoneal and mediastinal fibrosis with pericardial involvement.

We report the case of a 54-year-old woman with renal failure related to bilateral hydronephrosis. Clinical and radiologic findings were consistent with retroperitoneal fibrosis associated with pleuro-pericardial involvement. These features matched criteria for combined idiopathic retroperitoneal fibrosis and idiopathic mediastinal fibrosis. There are few reported cases of pericardial involvement in this combined disorder. In our observation, nuclear-magnetic resonance was the radiologic procedure of choice for aortic exploration. The responsibility of therapeutic agents (beta-adrenoreceptor-blocking drugs and ergotamine) and therapeutic options for the sclerosing disease are also discussed. Bilateral ureteral stents and corticosteroids produced favorable outcome without recurrence one year after treatment was stopped.

[Intestinal complications of thrombotic microangiopathy in the adult. 4 cases and review of the literature]. / Complications intestinales de la microangiopathie thrombotique de l'adulte. Quatre observations et revue de la littérature.

We report four cases of adult thrombotic microangiopathy associating diarrhea with severe ischemic colitis. In one case, the intestinal complications was severe and diffuse ischemic colitis, in two cases an inaugural colonic perforation requiring colectomy and in the last case a massive mesenteric infarct. In three cases, histologic examination showed vessel occlusion with microthrombi. Despite treatment with plasma exchange and plasma infusion, death ensued in two cases. Principally described in childhood thrombotic microangiopathy, intestinal complications occur exceptionally in adult thrombotic microangiopathy and are associated with a poor prognosis. Inaugural ischemic colitis revealing an adult thrombotic microangiopathy is also uncommon and thrombotic microangiopathy could be evoked in all patients presenting acute ischemic colitis.

[Association of acute pericarditis and acute renal insufficiency: causes and prognosis]. / Association d'une péricardite aiguë à une insuffisance rénale aiguë: causes et pronostic. 11 observations.

OBJECTIVE: To assess the etiologic diagnoses and outcome of acute pericardial effusion associated to acute renal renal failure. PATIENTS AND METHODS: A retrospective study from 1978 to 1996 in a 10 bed medical/surgical intensive care unit included 11 patients who have an acute pericardial effusion associated with an acute renal failure. RESULTS: Etiological diagnoses were systemic lupus with extracapillary glomerulonephritis (n = 2), systemic fibrosis with obstructive renal failure (n = 2), anticoagulation accident with hemodynamic renal failure (n = 2), lung adenocarcinoma (n = 2), adenocarcinoma of undetermined origin (n = 1), systemic polyarteritis nodosa (n = 1), and Wegener granulomatosis (n = 1). Intensive care unit deaths was 4, including 2 cases of neoplasic origin. DISCUSSION: Despite infection or malignancy being claimed as the leading causes of acute pericardial effusion, when associated to acute renal failure other etiologic diagnoses, such connectivite tissue disease or vasculitis, must be evoked that prompt specific treatment and could prevent unfavorable evolution. Neoplasic causes were characterised by receiving pericardial effusion and a high mortality rate.

[Vitiligo in multiple autoimmune syndrome: a retrospective study of 11 cases and a review of the literature]. / Le vitiligo au cours des syndromes auto-immuns multiples: étude rétrospective de 11 observations et revue de la littérature.

PURPOSE: The occurrence in the same patient of three or more autoimmune diseases defines multiple autoimmune disease. Multiple autoimmune disease is an unusual condition in which dermatological autoimmune diseases and especially vitiligo have an important place. METHODS: We examined retrospectively 11 cases of multiple autoimmune diseases associating vitiligo. We studied the clinical characteristics of vitiligo and those of the associated autoimmune disorders. RESULTS: Type III multiple autoimmune disease was diagnosed in all the 11 cases observed. Autoimmune vitiligo was the first autoimmune disorder observed in seven cases and was bilateral, symmetrical and acrofacial in eight cases. Autoimmune thyroid disorder was associated in ten cases. Our data confirms the important association between vitiligo and thyroid autoimmune disorders. CONCLUSION: The predominant female ratio and the acrofacial topography of skin lesions could predict association with others autoimmune disorders in patients with vitiligo.

High-resolution x-ray imaging of extended lasing plasmas.

An x-ray imaging system with a bent focusing crystal was used for time-resolved one-dimensional imaging of a long plasma column of highly ionized aluminum. This scheme uses a focusing geometry with a spherically bent crystal and a slit on the Rowland circle. Alternative schemes of x-ray monochromatic imaging are briefly discussed. The homogeneity of the up to 40-mm-long laser-generated plasma column was studied with a temporal resolution of 100 ps. The potential spatial resolution of the instrument is 90 microm or better. Monochromatic images taken on the resonance He alpha line of Al XII characterize the homogeneity of a plasma generated to study a recombination x-ray laser scheme, giving an amplified spontaneous emission in Al XI.