Charge ordering of magnetic monopoles in triangular spin ice patterns

Artificial spin ice offers the possibility to investigate a variety of dipolar orderings, spin frustrations and ground states. However, the most fascinating aspect is the realization that magnetic charge order can be established without spin order. We have investigated magnetic dipoles arranged on a honeycomb lattice as a function of applied field, using magnetic force microscopy. For the easy direction with the field parallel to one of the three dipole sublattices we observe at coercivity a maximum of spin frustration and simultaneously a maximum of charge order of magnetic monopoles with alternating charges $\pm$ 3.Comment: 7 pages, 4 figure

PAS staining of bronchoalveolar lavage cells for differential diagnosis of interstital lung disease

Bronchoalveolar lavage (BAL) is a useful diagnostic tool in interstitial lunge diseases (ILD). However, differential cell counts are often non specific and immunocytochemistry is time consuming. Staining of glyoproteins by periodic acid Schiff (PAS) reaction may help in discriminating different forms of ILD. In addition, PAS staining is easy to perform. BAL cells from patients with idiopathic pulmonary fibrosis (IPF) (n = 8), sarcoidosis (n = 9), and extrinsic allergic alveolitis (EAA) (n = 2) were investigated. Cytospins from BAL cells were made and cells were stained using Hemacolor quick stain and PAS staining. Lymphocytic alveolitis was found in sarcoidosis and EAA whereas in IPF both lymphocytes and neutrophils were increased. PAS positive cells were significantly decreased in EAA compared to IPF and sarcoidosis (25.5% ± 0.7% vs 59.8% ± 25.1% and 64.0% ± 19.7%, respectively) (P < 0.05). No significant correlation between PAS positive cells and inflammatory cells was observed. These results suggest that PAS staining of BAL cells may provide additional information in the differential diagnosis of ILD. Further studies ware warranted to evaluate PAS staining in larger numbers of BAL from patients with ILD

Seagrass workshop sea trial data report

Rep 04/11 - SiPLAB October/2011The Seagrass Workshop sea trial took place in a very shallow water area in front of STARESO (Station the recherchessous-marines et oceanographiques), Punta la Revellata, Gulf of Calvi, Corsica from 10 to 19 October 2011, in the frameworkof the Action ES0906 (Seagrass productivity: from genes to ecosystem management) supported by the FP7 Programme COST (European Cooperation in the Field of Scienti c and Technical Research). During this multidisciplinary workshop the participating groups have sampled the Posidonia oceanica eld using di erent methods in order to characterize the seagras individuals and the whole community. This report describes the data gathered by the SiPLAB/Marsensing team, which objective is to characterize the in uence of seagrass oxygen production in acoustic propagation and develop techniques to estimate oxygen production by acoustic means

CALCOM'10 Sea Trial - field calibration data report

Rep 04/10 - SiPLAB November/2010The CALCOM'10 sea trial took place in a region SSE of Vilamoura from 22nd to 24th June to support WEAM & PHITOM projects. The rst day was devoted to equipment testing and calibration. The second and third days were devoted to eld calibration and underwater communications. This report refers to eld calibration data acquired 23rd June, Day 2, and 24th June, Day 3

The search for stem cells of the epithelium in pulmonary alveoli

In recent years significant progress has been witnessed in the identification of stem cells, which have now also been identified in the lungs. The aim of this was to induce post-pneumonia alveolar regeneration to facilitate the identification of stem cells. The studies were performed on Buffalo strain rats. Pneumonia was induced in the animals by a sub-pleural injection of carragenin. On days 4, 5 and 10 of the experiment both the control and experimental animals received intraperitoneal injections of bromodeoxyuridine (BrdU). Twenty-four hours after the last BrdU injection the rats were sacrificed and samples of the lungs were taken for examination. In order to detect proliferating cells in the paraffin sections, BrdU incorporation was detected with monoclonal antibodies. In pilot experiments BrdU incorporation was demonstrated in individual alveolar cells of variable distribution and of variable intensity in the colour reaction. The results have confirmed the existence of stem cells in pulmonary alveoli but their closer characterisation requires further studies with other techniques to detect pulmonary stem cells

Purification and properties of cowpea mosaic virus RNA replicase

This thesis concerns the partial purification and properties of an RNA-dependent RNA polymerase (RNA replicase) produced upon infection of Vigna unguiculata plants with Cowpea Mosaic Virus (CPMV). The enzyme is believed to be coded, at least in part, by the virus genome and to be responsible for the replication of the virus RNA.In chapter 1 we describe the scope of the investigations and the motives underlying this thesis.In chapter 2 a literature review is presented of the RNA replicases of viruses containing a single-stranded RNA genome of the plus type. With respect to the prokaryote virus RNA replicases, studies are described on the structure and properties of QB replicase, with special emphasis on the role the individual subunits of the enzyme are playing in the different stages of RNA synthesis. Reviewing the research on animal and plant virus RNA replicases had to be limited necessarily to a description of the isolation and properties of several crude enzyme preparations, since no purified replicases have been obtained and little progress is made with their purification.In chapter 3 we describe the detection of an RNA-dependent RNA polymerase activity which is present in Vigna unguiculata leaves infected with CPMV but not in uninfected leaves. It is shown, that this RNA polymerase activity, which is designated as CPMV replicase and is associated with a membrane fraction, becomes detectable one day after infection and then continues to increase until the fourth day. This membrane-bound replicase activity was found to require Mg 2+ -ions and all four ribonucleoside triphosphates and to be resistant to DNase and actinomycin D. Analysis of the in vitro synthesized RNA products by sucrose gradient centrifugation and treatment with RNases revealed, that the majority consisted of double-stranded RNA species sedimenting at 17S and 20S, probably representing the replicative forms of both virus RNAs. A minor part consists of two single-stranded RNA species, similar in sedimentation rate (26S and 34S) to the virion RNAs. From these results we concluded, that we were dealing with a bound replicase complex most likely representing the replicase involved in virus replication in vivo. Having the final purification of CPMV replicase in view, we were then faced with the solubilization of the enzyme required to continue the purification.In chapter 4 we describe a very gentle and easy method to release the replicase from the membranes without employing detergent. The method consists of a washing procedure involving a Mg 2+ -deficient buffer, and provides several advantages in comparison with other solubilization procedures. Firstly, the solubilized replicase is highly stable, thus facilitating the further purification. Secondly, the release of the replicase from the membranes is rather selective. The majority of proteins is retained in the membrane pellet and the specific activity of the solubilized replicase is increased about 2-3 fold with respect to the membrane-bound replicase. Thirdly, more than 80% of the replicase activity is detached from the membranes. The solubilized replicase can be further purified and freed of endogenous template RNA by DEAE-BioGel. column chromatography to provide a highly stable enzyme dependent on template.In chapter 5 we describe several properties of the DEAE-purified replicase preparation. Replicase activity is not inhibited by a- amanitin, rifampicin, cordycepin, actinomycin D, DNase and orthophosphate but is completely suppressed by pyrophosphate and RNase A plus RNase T 1 . The in vitro RNA synthesis is shown to proceed for at least 15 hours under the following optimal conditions: 8 mM Mg(OAc) 2 or 12 mM MgCl 2 ; 60 mM (NH 4 ) 2 SO 4 , up to 100 mM K(OAc), but KCl as low as possible; pH 8.2; 30 to 34°C; all four ribonucleoside triphosphates present and 5-10 μg of CPMV RNA as template per 15 μg of protein.Having established the optimal conditions for RNA synthesis, we have studied the template specificity using a variety of viral, nonviral and synthetic template RNAs. It is shown that the replicase readily accepts natural RNAs as templates but is unable to efficiently synthesize RNA complementary to the synthetic ribopolymers poly(C), poly(G) and poly(U); poly(A) is able to direct the incorporation of 3 H-UMP, but only at a high concentration (400 μg/ml) and inefficiently with respect to CPMV RNA. Several possibilities to account for the lack of template specificity displayed by CPMV replicase and many other eukaryote replicases, are discussed. It is argued that template specificity does not have to be an intrinsic property of, and a prerequisite for, eukaryote virus RNA replicases to function properly in vivo, taking into account the specific location of the replication process in the cell and the occurrence of host RNA molecules as ribonucleoprotein particles. Moreover, the loss of essential protein factor(s), the possible requirement for primer(s) and the use of non-specific reaction conditions are considered.Initial studies have been carried out on the binding of CM replicase to 32 P-CPMV RNA and, in addition on the size and nature of the in vitro synthesized RNA products. The binding experiments using a nitrocellulose filter technique to detect RNA-protein complexes, demonstrate that the DEAE-purified replicase, but not a corresponding protein preparation isolated from healthy leaves, binds to CM RNA. This binding can be abolished by synthetic poly(A) and poly(U) but not by poly(C), suggesting that the poly(A) on the CM RNA genome comprises a potential part of the replicase binding site. However, further experiments are needed to substantiate this hypothesis.The bulk of the in vitro synthesized RNA was found to consist of 16S RNA and a rather small amount of faster sedimenting RNA (20S-38S), the latter representing single-stranded RNA molecules still attached to their parental template strand. Although about 60% of the RNA products appears to be sensitive to treatment with RNase A plus RNase T 1 , no free, full-length size virus RNA molecules were formed, due to the presence of RNase(s) contaminating the replicase preparation.In chapter 6 we show that the DEAE-purified replicase can be purified further by glycerol gradient centrifugation. This step affords the removal of some proteins predominating in all earlier stages. A final purification of about 150-200 fold relative to the crude extract is achieved. From analysis by polyacrylamide gel electrophoresis of the replicase purified by glycerol gradient centrifugation and of a corresponding protein preparation from mock-infected leaves, we conclude that the replicase still needs additional purification steps to allow its identification. However, the stability of the enzyme seems to offer good prospects to achieve this aim.<p/

A Correlation between the Emission Intensity of Self-Assembled Germanium Islands and the Quality Factor of Silicon Photonic Crystal Nanocavities

We present a comparative micro-photoluminescence study of the emission intensity of self-assembled germanium islands coupled to the resonator mode of two-dimensional silicon photonic crystal defect nanocavities. The emission intensity is investigated for cavity modes of L3 and Hexapole cavities with different cavity quality factors. For each of these cavities many nominally identical samples are probed to obtain reliable statistics. As the quality factor increases we observe a clear decrease in the average mode emission intensity recorded under comparable optical pumping conditions. This clear experimentally observed trend is compared with simulations based on a dissipative master equation approach that describes a cavity weakly coupled to an ensemble of emitters. We obtain evidence that reabsorption of photons emitted into the cavity mode is responsible for the observed trend. In combination with the observation of cavity linewidth broadening in power dependent measurements, we conclude that free carrier absorption is the limiting effect for the cavity mediated light enhancement under conditions of strong pumping.Comment: 8 pages, 5 figure