High peak optical power of 1ns pulse duration from laser diodes - low voltage thyristor vertical stack.

It is shown that the use of low-voltage GaAs/AlGaAs thyristors as high-speed and high-current switches in vertical stacks with semiconductor lasers ensures the efficient generation of high-power ns-duration laser pulses. The lasing and current dynamics in vertical stacks based on laser diode mini bar emitting at 1060 nm and a single as well as a double thyristor switch is studied. The possibility is demonstrated that a laser diode mini bar (with 3 laser emitters) together with a single thyristor switch can generate laser pulses with a peak power of 6 W with a duration of 950 ps and a peak current of 12 A for an operating voltage of 28 V. The use of a double thyristor switch leads to a broadening of the current pulse due to different delays in turn-on of the thyristor switches, while the peak power and duration of laser pulses increase to 8 W and 1.4 ns, respectively. It is found that the stage of low-speed turn-on of the thyristor limits the efficient generation of current and laser pulses of ns duration at low operating voltages (less than 21V). An efficient generation of current and laser pulses by low-voltage thyristors at control currents of 2-320 mA is ensured by efficient impact ionization in the region of the reverse biased p-n junction at high values of operating voltages (more than 21V).

Enhanced brain penetration of hexamethonium in complexes with derivatives of fullerene C60.

The present report describes development of hexamethonium complexes based on fullerene C60. Hexamethonium has a limited penetration into CNS and therefore can antagonize central effects of nicotine only when given at high doses. In the present studies conducted in laboratory rodents, intraperitoneal administration of hexamethonium-fullerene complexes blocked effects of nicotine (convulsions and locomotor stimulation). When compared to equimolar doses of hexamethonium, complexes of hexamethonium with derivatives of fullerene C60 were 40 times more potent indicating an enhanced ability to interact with central nicotine receptors. Thus, fullerene C60 derivatives should be explored further as potential carrier systems for polar drug delivery into CNS.

First biological images with high-energy proton microscopy.

High-energy proton microscopy provides unique capabilities in penetrating radiography including the combination of high spatial resolution and field-of-view, dynamic range of density for measurements, and reconstructing density variations to less than 1% inside volumes and in situ environments. We have recently proposed to exploit this novel proton radiography technique for image-guided stereotactic particle radiosurgery. Results of a first test for imaging biological and tissue-equivalent targets with high-energy (800 MeV) proton microscopy are presented here. Although we used a proton microscope setup at ITEP (Moscow, Russia) optimized for fast dynamic experiments in material research, we could reach a spatial resolution of 150 µm with approximately 10(10) protons per image. The potential of obtaining high-resolution online imaging of the target using a therapeutic proton beam in the GeV energy region suggests that high-energy proton microscopy may be used for image-guided proton radiosurgery.

[Treatment of abdominal aortic aneurysms in patients older than 70 years of age].

The investigation has shown that patients with the diagnosed abdominal aortic aneurysms must be operated, the age being not considered a contraindication to surgical treatment. Five years survival of the patients after resection of the abdominal aortic aneurysm and its prosthesis does not depend on the age and is higher than 70%, while the expectant management leads to rupture of the aneurysm and death of 70% of the patients. A medical algorithm has been developed allowing reduction of lethality of elderly patients with abdominal aortic aneurysms and less frequency of complications.

[Surgical treatment of atherosclerotic lesions of the terminal part of the aorta and iliac arteries].

The operations of semiclosed endarterecromy of the aortofemoral zone arteries were shown to have a number of advantages over shunting interventions with synthetic transplants. They are quick, not traumatic and have better results of long term patency. However, their application is limited by certain indications. Femoral amputations in patients with lesions of the aorta and iliac arteries independent of the age should not be recommended as a method of treatment of critical ischemia of lower extremities. Reconstructive operations on the vessels of this zone provide longer duration and better quality of life of the patients.

Excimer laser pumped by an intense, high-energy heavy-ion beam.

High-energy heavy ions are an ideal tool to generate homogeneously excited, extended volumes of nonthermal plasmas. Here, the high-energy loss (dE/dx) and absolute power deposition of heavy ions interacting with matter has been used to pump an ultraviolet laser. A pulsed 70 MeV/u 238U beam with up to 2.5 x 10(9) particles in approximately 100 ns beam bunches was stopped in a 1.2 m long laser cell filled with a 1.6 bar Ar-Kr-F2 mixture (typically 50%:49.9%:0.1%). Laser effect on the 248 nm KrF* excimer transition is clearly demonstrated.