Although photoluminescence from gallium-arsenide (GaAs) deep-centers was first observed in the 1960s, semiconductor lasers have always utilized conduction-to-valence-band transitions. Here we review recent materials studies leading to the first GaAs deep-center laser. First, we summarize well-known properties: nature of deep-center complexes, Franck-Condon effect, photoluminescence. Second, we ...

Medicinal species of mountain’s kelavs, scientifically named (kelussia odoratissmia Mozaffar.) is an endemic species in Iran. Kelussia odoratissima is a perennial species and belongs to the umbelliferae. From the ancient times, the local and nomad societies had believed that the species traditionally have anti-ache, anti-inflation and anti-cough effects. Seed and root of this species are boiled...

field capacity, fuel consumption and drive wheel slippage in massey ferguson (mf399) tractor with standard and liquid ballasted (630 kg) axle load and at 4wd mode was evaluated and compared. the tests were conducted at the experimental station, college of agriculture, shiraz university, in a field with clay loam soil at average moisture content of 18% d.b. the experiment was of a randomized com...

The regulation of quantal size through pre- rather than postsynaptic mechanisms has recently received considerable attention as a potential mechanism for plasticity. Vesicular transporters catalyze the filling of synaptic vesicles with transmitter and are thus potential substrates for such presynaptic regulation. In this issue of Neuron, Prado et al. pursue this line of investigation and show t...

Prospective data on 6905 consecutive hip fracture patients at a district general hospital were analysed to identify the risk factors for the development of deep infection post-operatively. The main outcome measure was infection beneath the fascia lata. A total of 50 patients (0.7%) had deep infection. Operations by consultants or a specialist hip fracture surgeon had half the rate of deep infec...

For n odd, a half-cycle for Zn is a cycle [a1, a2, . . . , am] of distinct elements from Zn such that (a) m = (n − 1)/2, (b) the elements ai (i = 1, 2, . . . ,m) are all distinct, and (c) the differences ai+1 − ai (i = 1, 2, . . . ,m, with am+1 = a1) are all distinct and no two of them are the negatives of one another, modulo n. Similarly, a chaplet for Zn is now newly defined to be a cycle [a1...

OBJECTIVES It is claimed that performing a "deep stop," a stop at about half of maximal diving depth (MDD), can reduce the amount of detectable precordial bubbles after the dive and may thus diminish the risk of decompression sickness. In order to ascertain whether this reduction is caused by the deep stop or by a prolonged decompression time, we wanted to test the "deep stop" theory without in...