A Quaternary ZnCdSeTe Nanotip Photodetector

The authors report the growth of needle-like high density quaternary Zn0.87Cd0.13Se0.98Te0.02nanotips on oxidized Si(100) substrate. It was found that average length and average diameter of the nanotips were 1.3 μm and 91 nm, respectively. It was also found that the as-grown ZnCdSeTe nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. Furthermore, it was found that the operation speeds of the fabricated ZnCdSeTe nanotip photodetector were fast with turn-on and turn-off time constants both less than 2 s

Anatomical Specializations for Nocturnality in a Critically Endangered Parrot, the Kakapo (Strigops habroptilus)

The shift from a diurnal to nocturnal lifestyle in vertebrates is generally associated with either enhanced visual sensitivity or a decreased reliance on vision. Within birds, most studies have focused on differences in the visual system across all birds with respect to nocturnality-diurnality. The critically endangered Kakapo (Strigops habroptilus), a parrot endemic to New Zealand, is an example of a species that has evolved a nocturnal lifestyle in an otherwise diurnal lineage, but nothing is known about its' visual system. Here, we provide a detailed morphological analysis of the orbits, brain, eye, and retina of the Kakapo and comparisons with other birds. Morphometric analyses revealed that the Kakapo's orbits are significantly more convergent than other parrots, suggesting an increased binocular overlap in the visual field. The Kakapo exhibits an eye shape that is consistent with other nocturnal birds, including owls and nightjars, but is also within the range of the diurnal parrots. With respect to the brain, the Kakapo has a significantly smaller optic nerve and tectofugal visual pathway. Specifically, the optic tectum, nucleus rotundus and entopallium were significantly reduced in relative size compared to other parrots. There was no apparent reduction to the thalamofugal visual pathway. Finally, the retinal morphology of the Kakapo is similar to that of both diurnal and nocturnal birds, suggesting a retina that is specialised for a crepuscular niche. Overall, this suggests that the Kakapo has enhanced light sensitivity, poor visual acuity and a larger binocular field than other parrots. We conclude that the Kakapo possesses a visual system unlike that of either strictly nocturnal or diurnal birds and therefore does not adhere to the traditional view of the evolution of nocturnality in birds

Human malarial disease: a consequence of inflammatory cytokine release

Malaria causes an acute systemic human disease that bears many similarities, both clinically and mechanistically, to those caused by bacteria, rickettsia, and viruses. Over the past few decades, a literature has emerged that argues for most of the pathology seen in all of these infectious diseases being explained by activation of the inflammatory system, with the balance between the pro and anti-inflammatory cytokines being tipped towards the onset of systemic inflammation. Although not often expressed in energy terms, there is, when reduced to biochemical essentials, wide agreement that infection with falciparum malaria is often fatal because mitochondria are unable to generate enough ATP to maintain normal cellular function. Most, however, would contend that this largely occurs because sequestered parasitized red cells prevent sufficient oxygen getting to where it is needed. This review considers the evidence that an equally or more important way ATP deficency arises in malaria, as well as these other infectious diseases, is an inability of mitochondria, through the effects of inflammatory cytokines on their function, to utilise available oxygen. This activity of these cytokines, plus their capacity to control the pathways through which oxygen supply to mitochondria are restricted (particularly through directing sequestration and driving anaemia), combine to make falciparum malaria primarily an inflammatory cytokine-driven disease

FEMTOSECOND WAVE MIXING EXPERIMENTS IN ZNCDSE/ZNSE QUANTUM-WELLS

Extreme high order nonlinear diffracted signals are found in ZnCdSe/ZnSe quantum wells in two beam, self-diffraction geometry. Diffracted signals of all observed orders are shown to originate predominantly from excitonic resonances. Using four-wave mixing, an individual of hole-longitudinal optical phonon scattering between the heavy and the light hole states is found, and exciton-phonon interaction is studied

FEMTOSECOND 4-WAVE-MIXING STUDIES OF EXCITON LOCALIZATION AND EXCITON-EXCITON INTERACTION IN ZNSE/ZNXCD1-XSE QUANTUM-WELLS

Femtosecond degenerate four-wave-mixing experiments are performed in the two-beam self-diffracted geometry in two inhomogeneously broadened ZnSe/ZnxCd1???xSe multiple-quantum-well samples at the excitonic resonances at 10 K. A large change in the dephasing time across the linewidth of one sample is observed, whereas it is nearly constant in the other, implying a different degree of localization in these two samples. Exciton-exciton interaction rates are determined across the linewidth, and it is shown that the exciton-exciton interaction rate is much less for excitons that are strongly localized compared to those that are extended

FEMTOSECOND COHERENT SPECTROSCOPY OF BULK ZNSE AND ZNCDSE/ZNSE QUANTUM-WELLS

Femtosecond two beam, self-diffraction experiments are performed in ZnSe and ZnCdSe/ZnSe quantum wells. Degenerate wave mixing signals from the third to the thirteenth order are easily visible to the naked eye, implying that nonlinear effects in this system may already be in the nonperturbative regime. Spectrally resolved data indicate that the nonlinearities originate entirely from the excitonic resonance. In addition, the existence of four-wave mixing signals in bulk ZnSe at negative time delay suggests that exciton-exciton interaction plays an important role. Exciton-phonon interaction rates are deduced as a function of temperature in ZnSe and ZnCdSe/ZnSe quantum wells