Fast and rewritable colloidal assembly via field synchronized particle swapping

We report a technique to realize reconfigurable colloidal crystals by using the controlled motion of particle defects above an externally modulated magnetic substrate. The transport of particles is induced by applying a uniform rotating magnetic field to a ferrite garnet film characterized by a periodic lattice of magnetic bubbles. For filling factor larger than one colloid per bubble domain, the particle current arises from propagating defects where particles synchronously exchange their position when passing from one occupied domain to the next. The amplitude of an applied alternating magnetic field can be used to displace the excess particles via a swapping mechanism, or to mobilize the entire colloidal system at a predefined speed

Effect of random interactions in spin baths on decoherence

We study the decoherence of a central spin 1/2 induced by a spin bath with intrabath interactions. Since we are interested in the cumulative effect of interaction and disorder, we study baths comprising Ising spins with random ferro- and antiferromagnetic interactions between the spins. Using the resolvent operator method which goes beyond the standard Born-Markov master equation approach, we show that, in the weak coupling regime, the decoherence of the central spin at all times is entirely determined by the local-field distribution or equivalently, the dynamical structure factor of the Ising bath. We present analytic results for the Ising spin chain bath at arbitrary temperature for different distributions of the intrabath interaction strengths. We find clear evidence of non-Markovian behavior in the low temperature regime. We also consider baths described by Ising models on higher-dimensional lattices. We find that interactions lead to a significant reduction of the decoherence. An important feature of interacting spinbaths is the saturation of the asymptotic Markovian decay rate at high temperatures, as opposed to the conventional Ohmic boson bath.Comment: 13 page

Optimization of Short Coherent Control Pulses

The coherent control of small quantum system is considered. For a two-level system coupled to an arbitrary bath we consider a pulse of finite duration. We derive the leading and the next-leading order corrections to the evolution operator due to the non-commutation of the pulse and the bath Hamiltonian. The conditions are computed that make the leading corrections vanish. The pulse shapes optimized in this way are given for $\pi$ and $\frac{\pi}{2}$ pulses.Comment: 9 pages, 6 figures; published versio

EPR evidence for maghemitization of magnetite in a tropical soil

Electron paramagnetic spectroscopy (EPR) was used in combination with standard rock magnetic methods to study magnetic minerals in a tropical soil. The susceptibility and hysteresis measurements showed magnetite grains with a Curie temperature near 850 K as the dominant magnetic remanence carriers in the soil. A minor Ti content in the magnetite was found by energy dispersive X-ray analysis. In order to get insight into the weathering status of the magnetite, different chemical treatments, including oxalate and citrate—bicarbonate—dithionite (CBD) extraction, were applied to the soil samples. The hysteretic properties exhibited no significant differences between the untreated and the CBD or oxalate treated samples. By contrast, the comparison of the EPR spectra revealed a significant broadening of the linewidth (δB) and a shift of the g-values (geff) to lower fields after the CBD treatment. Furthermore, the spectral parameters geff and δB exhibited an angular dependence. At low temperature, the CBD treated samples showed a jump in δB between 120 and 100 K, the temperature range characteristic for the Verwey transition in magnetite. The changes in the spectral properties after the CBD treatment, which dissolves ferric oxides, were attributed to the removal of maghemite formed by the oxidation of magnetite, that is, during the maghemitization of the magnetite grain

Molecular Identification of Lactic Acid Bacteria Occurring in Must and Wine

A specifically amplified polymorphic DNA-polymerase chain reaction (SAPD-PCR), a molecularfingerprinting method based on the amplification of specific gene sequences, was applied in order to allowa rapid identification of lactic acid bacteria (LAB) occurring in must and wine. The applicability of thismethod was confirmed with isolated strains from different wine samples from the German wine growingregion Palatinate. In addition, the formation of biogenic amines by the isolated strains was studied. Morethan half of the bacterial isolates from 50 red and white wine samples were able to produce biogenic amines.General health concerns related to biogenic amines in must and wine underline the need for an identificationof these species. The majority of the isolated strains were assigned to the species Lactobacillus brevis. Themajor biogenic amines in the investigated wines which were detected by thin-layer chromatography andHPLC were tyramine, histamine and ethylamine

Laboratory evaluation of a rapid IgG4 antibody test (BLF Rapid™) for bancroftian filariasis

At the end phase of the Global Programme to Eliminate Lymphatic Filariasis, antibody testing may have a role in decision-making for bancroftian filariasis–endemic areas. This study evaluated the diagnostic performance of BLF Rapid ™ , a prototype immunochromatographic IgG4-based test using BmSXP recombinant protein, for detection of bancroftian filariasis. The test was evaluated using 258 serum samples, comprising 96 samples tested at Universiti Sains Malaysia (in-house) and 162 samples tested independently at three international laboratories in the USA and India, and two laboratories in Malaysia. The independent testing involved 99 samples from Wuchereria bancrofti microfilaria or antigen positive individuals and 63 samples from people who were healthy or had other infections. The in-house evaluation showed 100% diagnostic sensitivity and specificity. The independent evaluations showed a diagnostic sensitivity of 84–100% and 100% specificity (excluding non-lymphatic filarial infections). BLF Rapid has potential as a surveillance diagnostic tool to make “Transmission Assessment Survey”–stopping decisions and conduct post-elimination surveillance

Coccolithophore fluxes in the open tropical North Atlantic: influence of thermocline depth, Amazon water, and Saharan dust

Coccolithophores are calcifying phytoplankton and major contributors to both the organic and inorganic oceanic carbon pumps. Their export fluxes, species composition, and seasonal patterns were determined in two sediment trap moorings (M4 at 12 degrees N, 49 degrees W and M2 at 14 degrees N, 37 degrees W) collecting settling particles synchronously from October 2012 to November 2013 at 1200 m of water depth in the open equatorial North Atlantic. The two trap locations showed a similar seasonal pattern in total coccolith export fluxes and a predominantly tropical coccolithophore settling assemblage. Species fluxes were dominated throughout the year by lower photic zone (LPZ) taxa (Florisphaera profunda, Gladiolithus flabellatus) but also included upper photic zone (UPZ) taxa (Umbellosphaera spp., Rhabdosphaera spp., Umbilicosphaera spp., Helicosphaera spp.). The LPZ flora was most abundant during fall 2012, whereas the UPZ flora was more important during summer. In spite of these similarities, the western part of the study area produced persistently higher fluxes, averaging 241 x 10(7) +/- 76 x 10(7) coccoliths m(-2) d(-1) at station M4 compared to only 66 x 10(7) +/- 31 x 10(7) coccoliths m(-2) d(-1) at station M2. Higher fluxes at M4 were mainly produced by the LPZ species, favoured by the westward deepening of the thermocline and nutricline. Still, most UPZ species also contributed to higher fluxes, reflecting enhanced productivity in the western equatorial North Atlantic. Such was the case of two marked flux peaks of the more opportunistic species Gephyrocapsa muellerae and Emiliania huxleyi in January and April 2013 at M4, indicating a fast response to the nutrient enrichment of the UPZ, probably by wind-forced mixing. Later, increased fluxes of G. oceanica and E. huxleyi in October-November 2013 coincided with the occurrence of Amazon-River-affected surface waters. Since the spring and fall events of 2013 were also accompanied by two dust flux peaks, we propose a scenario in which atmospheric dust also provided fertilizing nutrients to this area. Enhanced surface buoyancy associated with the river plume indicates that the Amazon acted not only as a nutrient source, but also as a surface density retainer for nutrients supplied from the atmosphere. Nevertheless, lower total coccolith fluxes during these events compared to the maxima recorded in November 2012 and July 2013 indicate that transient productivity by opportunistic species was less important than "background" tropical productivity in the equatorial North Atlantic. This study illustrates how two apparently similar sites in the tropical open ocean actually differ greatly in ecological and oceanographic terms. The results presented here provide valuable insights into the processes governing the ecological dynamics and the downward export of coccolithophores in the tropical North Atlantic.Netherlands Organization for Scientific Research (NWO) [822.01.008]; European Research Council (ERC) [311152]; University of Bremen; European Union [600411]info:eu-repo/semantics/publishedVersio

Ecological study of aquatic midges and some related insects with special reference to feeding habits

Die Schweiz ist ein reiches Land. Sie verfügt über viele Millionäre. Der große Reichtum konzentriert sich auf wenige Familien und Personen. In der Schweiz leben aber auch eine halbe Million der Bevölkerung (7,5 Mio.) in Haushalten von Erwerbstätigen, die weniger als das Existenzminimum verdienen. Über 200‘000 Personen sind auf Sozialhilfe angewiesen. Bei den Vermögen und den verfügbaren Einkommen hat sich in den letzten Jahren die Kluft zwischen den obersten und untersten zehn Prozent verschärft. Die Zunahme der sozialen Ungleichheit erhöht die soziale Brisanz, was mehr zu ergründen ist. Die soziale Differenzierung dokumentiert Prozesse der Globalisierung. Sie reproduziert und spezifiziert alte soziale Ungleichheiten. Wichtig ist, dass die Soziale Arbeit das thematisiert und weiter theoretisiert

Photoionization Broadening of the 1S-2S Transition in a Beam of Atomic Hydrogen

We consider the excitation dynamics of the two-photon \sts transition in a beam of atomic hydrogen by 243 nm laser radiation. Specifically, we study the impact of ionization damping on the transition line shape, caused by the possibility of ionization of the 2S level by the same laser field. Using a Monte-Carlo simulation, we calculate the line shape of the \sts transition for the experimental geometry used in the two latest absolute frequency measurements (M. Niering {\it et al.}, PRL 84, 5496 (2000) and M. Fischer {\it et al.}, PRL 92, 230802 (2004)). The calculated line shift and line width are in excellent agreement with the experimentally observed values. From this comparison we can verify the values of the dynamic Stark shift coefficient for the \sts transition for the first time on a level of 15%. We show that the ionization modifies the velocity distribution of the metastable atoms, the line shape of the \sts transition, and has an influence on the derivation of its absolute frequency.Comment: 10 pages, 5 figure