Stable operation of a synchronously pumped colliding-pulse mode-locked ring dye laser

Pulses of 100-fsec duration are obtained by synchronous pumping of a colliding-pulse ring dye laser with a mode-locked Ar+-ion laser. Stable operation of the synchronously pumped colliding-pulse mode-locked laser over hours was obtained by a suitable choice of the distance between the gain and the absorber in combination with an appro-priate pump-pulse sequence. Passive mode locking of a ring dye laser by the inter-action of two counterpropagating pulses in a thin sat-urable absorber (colliding-pulse mode locking) yields femtosecond laser pulses. ' In these lasers the gain medium (Rhodamine 6G) is pumped by a cw Ar+-ion laser. The saturable absorber (DODCI, 3,3-diethyl-oxadicarbocyanine iodide) synchronizes two counter-propagating pulses meeting in the absorber jet stream. The colliding pulses form a transient grating, which synchronizes and stabilizes the pulses.2 In order to ensure equal amplification for both counterpropagatin

Tail amputation for treatment of osteomyelitis of the first and second coccygeal vertebrae in a cow

Diseases of the tail are common in cattle (3, 4). Infection or necrosis of the tail tip, injury of the coccygeal vertebrae resulting in tail paralysis (8, 12) as well as fracture or luxation of the coccygeal vertebrae(6) are some of the most common disorders. Congenital defects, diskospondylitis and tumours of the tail occur occasionally (5, 8). Tail fractures or luxations are usually the result of trauma, such as falls, excessive traction on the tail when moving a downer cow, excessive traction on a calf during assisted delivery, and mounting by other cows or heavy bulls (3, 13). Clinical signs depend on the severity of nerve damage and the location of the fracture. Fractures involving the second (S2), third and fourth sacral (S3 and S4) segments may affect the pudendal nerve, pelvic nerves and the tail nerve resulting in paralysis of the urinary bladder, anus and tail. Tail paralysis without other neurological deficits indicates damage to the coccygeal nerve (7). Diseases of the tail may be treated conservatively or by amputation cranial to the affected area. Tail amputation in cattle is a very controversial subject because in some countries, it is carried out prophylactically for management reasons without any medical indication (1, 9, 11). Prophylactic tail amputation is done 7–8 cm below the vulva in calves and 5–6 cm below the vulva in heifers and mature cows. The present case report describes complete amputation of the tail at the level of the sacrum in a cow with osteomye - litis of the first (C1) and second coccygeal (C2) vertebrae

Femtosecond spectroscopy of the first events of the photochemical cycle in bacteriorhodopsin

The first steps in the photochemistry of bacteriorhodopsin (BR) are investigated with light pulses of 160 fs duration. Four samples are studied: (i) the purple membrane, (ii) deuterated purple membrane, (iii) BR trimers and (iv) BR monomers. In all samples the first intermediate J is formed within 430±50 fs. No isotope effect is observed in the formation of J upon deuteration, in contrast to previous reports with much higher excitation energies. Thus proton movement to or from the retinal Schiff's base is not relevant during the first step. Comparing the data for trimeric and monomeric BR suggests an upper limit of 50 fs for the transfer of excitation energy from the excitonically coupled trimer to a single retinal chromophore