Symmetric and antisymmetric exchange anisotropies in quasi-one-dimensional CuSe2_2O5_5 as revealed by ESR

We present an electron spin resonance (ESR) study of single-crystalline spin chain-system CuSe$_2$O$_5$ in the frequency range between 9 GHz and 450 GHz. In a wide temperature range above the N\'{e}el temperature $T_N=17$ K we observe strong and anisotropic frequency dependence of a resonance linewidth. Although sizeable interchain interaction $J_{IC}\approx 0.1 J$ ($J$ is the intrachain interaction) is present in this system, the ESR results agree well with the Oshikawa-Affleck theory for one-dimensional $S=1/2$ Heisenberg antiferromagnet. This theory is used to extract the anisotropies present in CuSe$_2$O$_5$. We find that the symmetric anisotropic exchange $J_c=(0.04 \pm 0.01) \:J$ and the antisymmetric Dzyaloshinskii-Moriya (DM) interaction $D=(0.05\pm 0.01)\:J$ are very similar in size in this system. Staggered-field susceptibility induced by the presence of the DM interaction is witnessed in the macroscopic susceptibility anisotropy.Comment: 8 pages, 7 figures, 2 tables, published in Phys. Rev.

Oxidation of AlInAs for current blocking in a photonic crystal laser

To make an electrically pumped photonic crystal membrane laser is a challenging task. One of the problems is how to avoid short circuiting between the p- and n-doped parts of the laser diode, when the membrane thickness is limited to 200-300nm. We propose to use the oxide of AlInAs to realize a current blocking function. In this way, based on submicron selective area re-growth, we aim for electrically injected photonic crystal lasers with high output power, small threshold currents and low power consumption. Here results are presented on the oxidation of AlInAs. The results show that it is feasible to use the oxide of AlInAs for current blocking in an InP-based membrane photonic crystal laser

Overview of the EU FP7-project HISTORIC

HISTORIC aims to develop and test complex photonic integrated circuits containing a relatively large number of digital photonic elements for use in e.g. all-optical packet switching. These photonic digital units are all-optical flip-flops based on ultra compact laser diodes, such as microdisk lasers and photonic crystal lasers. These lasers are fabricated making use of the heterogeneous integration of InP membranes on top of silicon on insulator (SOI) passive optical circuits. The very small dimensions of the lasers are, at least for some approaches, possible because of the high index contrast of the InP membranes and by making use of the extreme accuracy of CMOS processing. All-optical flip-flops based on heterogeneously integrated microdisk lasers with diameter of 7.5 mu m have already been demonstrated. They operate with a CW power consumption of a few mW and can switch in 60ps with switching energies as low as 1.8 fJ. Their operation as all-optical gate has also been demonstrated. Work is also on-going to fabricate heterogeneously integrated photonic crystal lasers and all-optical flip-flops based on such lasers. A lot of attention is given to the electrical pumping of the membrane InP-based photonic crystal lasers and to the coupling to SOI wire waveguides. Optically pumped photonic crystal lasers coupled to SOI wires have been demonstrated already. The all-optical flip-flops and gates will be combined into more complex photonic integrated circuits, implementing all-optical shift registers, D flip-flops, and other all-optical switching building blocks. The possibility to integrate a large number of photonic digital units together, but also to integrate them with compact passive optical routers such as AWGs, opens new perspectives for the design of integrated optical processors or optical buffers. The project therefore also focuses on designing new architectures for such optical processing or buffer chips

Ontwikkeling signalering / vangsysteem voor schadelijke wantsen met lokstoffen en lokplanten": Onderzoek aan geurstoffen en lokplanten in laboratorium, veld en kassen

Referaat Behaarde wants, Lygus rugulipennis, en brandnetelwants, Liocoris tripustulatis, staan bekend als plagen in uiteenlopende kasgewassen waaronder paprika, komkommer, aubergine, chrysant. In het laboratorium is bepaald welke geurstoffen mogelijk bruikbaar zouden zijn om deze wantsen te monitoren met behulp van een val in combinatie met een geurstof. Tevens is een lijst van planten opgesteld, die aantrekkelijk zijn voor deze wantsen. Uit een keuzeproef met 16 plantensoorten in een kas bleek dat behaarde wants een voorkeur heeft voor kattenstaartamarant, zonnebloem, aardappel en tuinmelde boven de eerder genoemde gewassen. In een kasproef met 2000 m2 paprika werden zowel behaarde wantsen als brandnetel wantsen losgelaten gedurende 12 weken. Zowel deltavallen, als witte en blauwe signaalplaten werden opgehangen in combinatie met verschillende geurstoffen. Geen van deze combinaties van vallen en geurstoffen resulteerde in grote vangsten van de wantsen. Hoewel duizenden gekweekte wantsen werden losgelaten, trad geen schade op in het gewas.Na het loslaten vlogen wantsen niet naar het glas maar waren uren na het loslaten terug te vinden in de planten bij de loslaatpunten. Na een week waren nog enkele exemplaren op het loslaat punt aanwezig, maar in het gewas waren ze moeilijk te vinden. In de praktijk werden zowel behaarde wantsen als brandnetelwantsen verzameld in gewassen (paprika, aubergine, komkommer, gerbera) waarin schade optrad. Deze wantsen gaven op een jonge paprikaplant in een kooi geen schade. Het blijkt dat het optreden van wantsen en het al dan niet optreden van schade vragen oproept. Uit een vervolgstudie zou moeten blijken onder welke voorwaarden schade optreedt en wanneer niet. Abstract The tarnished plant bug, Lygus ruulipennis, and the coomon nettle capsid, Liocoris tripustulatis, are pests in a variety of crops in greenhouses, including sweet pepper, cucumber, eggplant and chrysantemum. Odours which were possibly attractive to the bugs were established in the laboratory.The aim was to find pheromones, which can be used in combination with a trap for monitoring the bugs.Further a list was composed of plants which are attractive for the bugs.From a choice test with 16 plant species it appeared that the tarnished plant bug us attrackted more to Amaranthus caudatus, Helianthus annuus, Sollanum tuburosum and Atriplex hortensis than to the greenhouse crops. In a greenhouse trial planted with 2000 m2 sweet pepper both tarnished plant bugs and common nettle capsids were introduced during a period of 12 weeks. Delta traps were installed and also white or blue sticky traps in combination with several lures. None of these combinations of traps and lures resulted in large catches of bugs. Although thousands of bugs were released, no symptoms were noticed in the crop. The bugs did not fly to the top of the grennhouse when they were released, but were presemt pn the plants near the releasing point for several hours. After a week some specimens were still present on the releasing point, but they were difficult to find in the crop. In commercial greenhouses both tarnished plant bugs and common nettle bugs were sampled in sweet pepper, egg plant, cucumber and gerbera were symptoms were present. These bugs did not cause any symptoms on a young sweet pepper plant in a cage. It is obvious that the occurrence of bugs and the showing or not-showing of symptoms raises questions. Further studies are necessary in order to reveal the conditions is which symptoms will occur or not

Surface Chemistry of Almandine Garnet

Almandine garnet is used commonly in abrasive blasting processes to prepare metallic surfaces for painting. However, there is evidence that the process leads to significant amounts of abrasive embedded in the “cleaned” surface, and hence the surface chemistry of garnet will affect the binding of any coatings subsequently applied. In addition, in marine environments seawater aerosol droplets are expected to impact the exposed surface prior to coating application, depositing both water and dissolved inorganic ions. In this work, we provide indepth analysis of the chemistry of the almandine garnet surface using angle-resolved X-ray photoelectron spectroscopy (XPS) and note a correlation for several elemental oxides between literature values of the binding energy of the surface oxygen 1s XPS peak and the basicity of the hydroxyl group that forms on the surface. We also consider the adsorption to almandine garnet powder of seawater-relevant inorganic ions (sodium, magnesium, and calcium): Binding constants have been determined using titration measurements, solution-depletion isotherms, and numerical modeling, with calcium observed to bind more strongly than magnesium. The relevance of Langmuir-type fits to constant-pH adsorption isotherms is discussed. By contrast, sodium either binds very weakly or is effectively inert toward the garnet surface under the experimental conditions. The complex adsorption behavior observed emphasizes the necessity of using multiple techniques to characterize mineral surfaces

Induction of adrenal scavenger receptor BI and increased high density lipoprotein-cholesteryl ether uptake by in vivo inhibition of hepatic lipase

Hepatic lipase (HL) and scavenger receptor type B class I (SR-BI) have both been implicated in high density lipoprotein (HDL)-cholesteryl ester uptake in cholesterol-utilizing tissues. Inactivation of HL by gene-directed targeting in mice results in up-regulation of SR-BI expression in adrenal gland (Wang, N., Weng, W., Breslow, J. L., and Tall, A. R. (1996) J. Biol. Chem. 271, 21001-21004). The net effect on HDL-cholesteryl ester uptake is not known. We determined the impact of acute in vivo inhibition of rat adrenal HL activity by antibodies on SR-BI expression and on human and rat HDL-[3H]cholesteryl ether (CEth) uptake in the adrenal gland. Rat HDL was isolated from rats in which HL activity had been inhibited for 1 h. The rats were studied under basal conditions (not ACTH-treated) and after previous treatment with ACTH for 6 days (ACTH-treated). Intravenous injection of anti-HL resulted in 70% lowering of adrenal HL activity in both conditions which were maintained for at least 8 h. In not ACTH-treated rats, inhibition of adrenal HL increased adrenal SR-BI mRNA (5.2-fold) and mass (1. 6-fold) within 4 h. HL inhibition resulted in 41% and 14% more adrenal accumulation of human HDL-[3H]CEth during 4 and 24 h, respectively. The adrenal uptake of rat HDL-[3H]CEth increased by 68%, 4 h after the antibody injection. ACTH treatment increased total adrenal HL activity from 3.7 +/- 0.5 milliunits to 34.0 +/- 17. 2 milliunits, as well as adrenal SR-BI mRNA from 2.9 +/- 0.7 arbitrary units (A.U.) to 86.8 +/- 41.1 A.U. and SR-BI mass from 7.7 +/- 1.8 A.U. to 63.16 +/- 46.7 A.U. The human HDL-[3H]CEth uptake by adrenals was also significantly increased from 0.58 +/- 0.11% of injected dose to 7.24 +/- 1.58% of injected dose. Inhibition of adrenal HL activity did not result in further induction of SR-BI expression and did not affect human HDL-[3H]CEth uptake. These findings indicate that SR-BI expression may be influenced by changes in HL activity. HL activity is not needed for the SR-BI-mediated HDL-cholester