Electromechanical wavelength tuning of double-membrane photonic crystal cavities

We present a method for tuning the resonant wavelength of photonic crystal cavities (PCCs) around 1.55 um. Large tuning of the PCC mode is enabled by electromechanically controlling the separation between two parallel InGaAsP membranes. A fabrication method to avoid sticking between the membranes is discussed. Reversible red/blue shifting of the symmetric/anti-symmetric modes has been observed, which provides clear evidence of the electromechanical tuning, and a maximum shift of 10 nm with < 6 V applied bias has been obtained.Comment: 9 pages, 3 figure

Size dependent exciton g-factor in self-assembled InAs/InP quantum dots

We have studied the size dependence of the exciton g-factor in self-assembled InAs/InP quantum dots. Photoluminescence measurements on a large ensemble of these dots indicate a multimodal height distribution. Cross-sectional Scanning Tunneling Microscopy measurements have been performed and support the interpretation of the macro photoluminescence spectra. More than 160 individual quantum dots have systematically been investigated by analyzing single dot magneto-luminescence between 1200nm and 1600 nm. We demonstrate a strong dependence of the exciton g-factor on the height and diameter of the quantum dots, which eventually gives rise to a sign change of the g-factor. The observed correlation between exciton g-factor and the size of the dots is in good agreement with calculations. Moreover, we find a size dependent anisotropy splitting of the exciton emission in zero magnetic field.Comment: 15 pages, 7 figure

Presence of thiamine pyrophosphate in mammalian peroxisomes

<p>Abstract</p> <p>Background</p> <p>Thiamine pyrophosphate (TPP) is a cofactor for 2-hydroxyacyl-CoA lyase 1 (HACL1), a peroxisomal enzyme essential for the α-oxidation of phytanic acid and 2-hydroxy straight chain fatty acids. So far, HACL1 is the only known peroxisomal TPP-dependent enzyme in mammals. Little is known about the transport of metabolites and cofactors across the peroxisomal membrane and no peroxisomal thiamine or TPP carrier has been identified in mammals yet. This study was undertaken to get a better insight into these issues and to shed light on the role of TPP in peroxisomal metabolism.</p> <p>Results</p> <p>Because of the crucial role of the cofactor TPP, we reanalyzed its subcellular localization in rat liver. In addition to the known mitochondrial and cytosolic pools, we demonstrated, for the first time, that peroxisomes contain TPP (177 ± 2 pmol/mg protein). Subsequently, we verified whether TPP could be synthesized from its precursor thiamine, <it>in situ</it>, by a peroxisomal thiamine pyrophosphokinase (TPK). However, TPK activity was exclusively recovered in the cytosol.</p> <p>Conclusion</p> <p>Our results clearly indicate that mammalian peroxisomes do contain TPP but that no pyrophosphorylation of thiamine occurs in these organelles, implying that thiamine must enter the peroxisome already pyrophosphorylated. Consequently, TPP entry may depend on a specific transport system or, in a bound form, on HACL1 translocation.</p

Peroxisomal 2-Hydroxyacyl-CoA Lyase Is Involved in Endogenous Biosynthesis of Heptadecanoic Acid.

Circulating heptadecanoic acid (C17:0) is reported to be a pathology risk/prognosis biomarker and a dietary biomarker. This pathology relationship has been shown to be reliably predictive even when independent of dietary contributions, suggesting that the endogenous biosynthesis of C17:0 is related to the pathological aetiology. Little is known about C17:0 biosynthesis, which tissues contribute to the circulating levels, and how C17:0 is related to pathology. Hacl1+/- mice were mated to obtain Hacl1-/- and Hacl1+/+ control mice. At 14 weeks, they were anesthetized for tissue collection and fatty acid analysis. Compared to Hacl1+/+, C15:0 was not significantly affected in any Hacl1-/- tissues. However, the Hacl1-/- plasma and liver C17:0 levels were significantly lower: ~26% and ~22%, respectively. No significant differences were seen in the different adipose tissues. To conclude, Hacl1 plays a significant role in the liver and plasma levels of C17:0, providing evidence it can be endogenously biosynthesized via alpha-oxidation. The strong inverse association of C17:0 with pathology raises the question whether there is a direct link between α-oxidation and these diseases. Currently, there is no clear evidence, warranting further research into the role of α-oxidation in relation to metabolic diseases

The influence of human resource practices on perceived work ability and the preferred retirement age: A latent growth modelling approach

Organisations are challenged to extend working lives of older workers. However, there is little empirical evidence available on how organisations should do this. This study aims to fill this gap by testing the effect of Human Resource (HR) practices on perceived work ability and the preferred retirement age. Based on the Conversation of Resources theory, we expected that the use of HR practices has a positive effect on perceived work ability and preferred retirement age. We have conducted latent growth curve modelling to test our hypotheses amongst 12,444 employees aged 45 and older at four time points. The results indicate that developmental practices are positively related to work ability, whereas maintenance practices are negatively related to work ability and the preferred retirement age. Accommodative practices are negatively related to the intercepts of both outcomes but not to the slopes, whereas utilisation practices are not related to the outcomes at all.publishedVersio