Influence of Zn doping profiles on excitation dependence of photoluminescence intensity in InGaAsP heterostructures

It is known that the Zn doping profile in strained multi-quantum-well (MQW) InGaAsP lasers strongly affects the electro-optical characteristics of these devices and their temperature sensitivity. A systematic investigation of the excitation dependence of the active layer photoluminescence (PL) intensity from compressively strained InGaAsP MQW pin laser material with different Zn doping profiles is described. When the pn junction lies within the active region, the excitation dependence of the PL intensity is superlinear at low excitation and linear at higher excitation. As the Zn profile is set back from the heterointerface creating a displaced pn junction from the active region, the excitation dependence is superlinear and linear at 300 K but becomes linear for all excitation powers at 77 K. The implications of these observations are discussed

On the sense of taste in two Malagasy Primates (Microcebus murinus and Eulemur mongoz)

The relationship between phylogeny and taste is of growing interest. In this study we present recordings from the chorda tympani proper (CT) nerve of two lemuriforme primates, the lesser mouse lemur (Microcebus murinus) and the mongoose lemur (Eulemur mongoz), to an array of taste stimuli which included the sweeteners acesulfame-K, alitame, aspartame, D-glucose, dulcin, monellin, neohesperidin dihydrochalcone (NHDHC), saccharin, sodium superaspartame, stevioside, sucralose (TGS), sucrose, suosan, thaumatin and xylitol, as well as the non-sweet stimuli NaC1, citric acid, tannin and quinine hydrochloride. In M.murinus the effects of the taste modifiers gymnemic acid and miraculin on the CT response were recorded. Conditioned taste aversion (CTA) experiments in M.murinus and two-bottle preference (TBP) tests in E.mongoz were also conducted. We found that all of the above tastants except thaumatin elicited a CT response in both species. The CTA technique showed that M.murinus generalized from sucrose to monellin but not to thaumatin. The intake of aspartame, ranging in concentration from 0.1 to 30 mM was measured in E.mongoz with TBP tests. At no concentration did we see a preference, but there was a significant rejection of 10 and 30 mM aspartame (P←0.025). Miraculin had no effects on the CT response to acids, and gymnemic acid did not selectively suppress the CT response to sucrose or that of any other sweeteners. The absence of ability to taste thaumatin in these species supports the dichotomy between catarrhine and non-catarrhine species. The difference in results with thaumatin and monellin indicate that their sweet moieties are not identical. It also points to a phylogenetic difference in taste within the prosimian group. Further, the results with aspartame indicate that the perception of sweetness from aspartame is limited to catarrhine species. Finally, neither miraculin nor gymnemic acid exhibit the same taste modifying effects in lemuriformes as they do in hominoidea. Thus the results with gymnemic acid and miraculin corroborate those obtained earlier in other prosimian

Dominated Splitting and Pesin's Entropy Formula

Let $M$ be a compact manifold and $f:\,M\to M$ be a $C^1$ diffeomorphism on $M$. If $\mu$ is an $f$-invariant probability measure which is absolutely continuous relative to Lebesgue measure and for $\mu$ $a.\,\,e.\,\,x\in M,$ there is a dominated splitting $T_{orb(x)}M=E\oplus F$ on its orbit $orb(x)$, then we give an estimation through Lyapunov characteristic exponents from below in Pesin's entropy formula, i.e., the metric entropy $h_\mu(f)$ satisfies $$h_{\mu}(f)\geq\int \chi(x)d\mu,$$ where $\chi(x)=\sum_{i=1}^{dim\,F(x)}\lambda_i(x)$ and $\lambda_1(x)\geq\lambda_2(x)\geq...\geq\lambda_{dim\,M}(x)$ are the Lyapunov exponents at $x$ with respect to $\mu.$ Consequently, by using a dichotomy for generic volume-preserving diffeomorphism we show that Pesin's entropy formula holds for generic volume-preserving diffeomorphisms, which generalizes a result of Tahzibi in dimension 2

Quantum ergodicity of C* dynamical systems

This paper contains a very simple and general proof that eigenfunctions of quantizations of classically ergodic systems become uniformly distributed in phase space. This ergodicity property of eigenfunctions f is shown to follow from a convexity inequality for the invariant states (Af,f). This proof of ergodicity of eigenfunctions simplifies previous proofs (due to A.I. Shnirelman, Colin de Verdiere and the author) and extends the result to the much more general framework of C* dynamical systems.Comment: Only very minor differences with the published versio