Iris zhaoana, a new name for Iris potaninii var. ionantha (I. sect. Pseudoregelia ser. Tigridiae, Iridaceae) from China: evidence from morphological and plastid DNA data

The new name Iris zhaoana is proposed to replace I. potaninii var. ionantha, which is applied to a dwarf bearded iris described from western China, usually included in I. sect. Psammiris. It is a plant occurring at high elevation and showing roots thick and grey; leaves glaucous-green, blunt to subacute and shortly mucronate at apex; flower solitary, dichromic, bluish-violet, with standards and falls similar in shape and size; falls more richly blotched with deep-violet and with whitish areas; beard of white and blue-white hairs, tipped yellow; fruits globose-ovoid to ellipsoid, shortly acuminate at apex; and seed with a comparatively prominent, large, yellow aril. These features closely relate I. zhaoana to members of I. sect. Pseudoregelia, namely to I. tigridia, with which it has sometimes been confused. Morphological and molecular data are discussed here that support recognition of the Central Asian plant at species rank and its inclusion in I. sect. Pseudoregelia ser. Tigridiae.

3. Sound waves

Sound is a small fraction of the pressure wave spectrum. In terms of wavelength, we can hear far more than we can see: while deep red light has waves about twice as long as those of deep violet, the lowest-pitched sound waves we can hear are about ten times longer than the highest. ‘Sound waves’ explains infrasound, the lower frequencies detectable by touch rather than hearing, and the audio range, describing the fundamental differences between sound power and loudness, and frequency and pitch. It also considers sound underwater. Sonar systems can be passive systems that simply detect sounds, while active sonar transmits sounds and detects those that are reflected.

Effect of QW thickness and numbers on performance characteristics of deep violet InGaN MQW lasers

The performance characteristics of deep violet indium gallium nitride (InGaN) multiquantum well (MQW) laser diodes (LDs) with an emission wavelength of around 390 nm have been investigated using the integrated system engineering technical computer aided design (ISE-TCAD) software. A comparative study on the effect of quantum well (QW) thickness and number on electrical and optical performance of deep violet In 0.082 Ga 0.918 N/GaN MQW LDs have been carried out. The simulation results showed that the highest slope efficiency and external differential quantum efficiency (DQE), as well as the lowest threshold current are obtained when the number of wells is two. The different QW thickness values of 2.2, 2.5, 2.8, 3 and 3.2 nm were compared and the best results were achieved for 2.5 nm QW thickness. The radiative recombination rate decreases with increasing QW thickness because of decreasing electron and hole carrier densities in wells. By increasing QW thickness, output power decreases and threshold current increases.