On the adsorption and reactivity of element 114, flerovium.

Flerovium (Fl, element 114) is the heaviest element chemically studied so far. To date, its interaction with gold was investigated in two gas-solid chromatography experiments, which reported two different types of interaction, however, each based on the level of a few registered atoms only. Whereas noble-gas-like properties were suggested from the first experiment, the second one pointed at a volatile-metal-like character. Here, we present further experimental data on adsorption studies of Fl on silicon oxide and gold surfaces, accounting for the inhomogeneous nature of the surface, as it was used in the experiment and analyzed as part of the reported studies. We confirm that Fl is highly volatile and the least reactive member of group 14. Our experimental observations suggest that Fl exhibits lower reactivity towards Au than the volatile metal Hg, but higher reactivity than the noble gas Rn.

Observation of a correlated free four-neutron system.

A long-standing question in nuclear physics is whether chargeless nuclear systems can exist. To our knowledge, only neutron stars represent near-pure neutron systems, where neutrons are squeezed together by the gravitational force to very high densities. The experimental search for isolated multi-neutron systems has been an ongoing quest for several decades1, with a particular focus on the four-neutron system called the tetraneutron, resulting in only a few indications of its existence so far2-4, leaving the tetraneutron an elusive nuclear system for six decades. Here we report on the observation of a resonance-like structure near threshold in the four-neutron system that is consistent with a quasi-bound tetraneutron state existing for a very short time. The measured energy and width of this state provide a key benchmark for our understanding of the nuclear force. The use of an experimental approach based on a knockout reaction at large momentum transfer with a radioactive high-energy 8He beam was key.

Spectroscopy along Flerovium Decay Chains: Discovery of

A nuclear spectroscopy experiment was conducted to study α-decay chains stemming from isotopes of flerovium (element Z=114). An upgraded TASISpec decay station was placed behind the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. The fusion-evaporation reactions ^{48}Ca+^{242}Pu and ^{48}Ca+^{244}Pu provided a total of 32 flerovium-candidate decay chains, of which two and eleven were firmly assigned to ^{286}Fl and ^{288}Fl, respectively. A prompt coincidence between a 9.60(1)-MeV α particle event and a 0.36(1)-MeV conversion electron marked the first observation of an excited state in an even-even isotope of the heaviest man-made elements, namely ^{282}Cn. Spectroscopy of ^{288}Fl decay chains fixed Q_{α}=10.06(1) MeV. In one case, a Q_{α}=9.46(1)-MeV decay from ^{284}Cn into ^{280}Ds was observed, with ^{280}Ds fissioning after only 518 µs. The impact of these findings, aggregated with existing data on decay chains of ^{286,288}Fl, on the size of an anticipated shell gap at proton number Z=114 is discussed in light of predictions from two beyond-mean-field calculations, which take into account triaxial deformation.

New Short-Lived Isotope

Two short-lived isotopes ^{221}U and ^{222}U were produced as evaporation residues in the fusion reaction ^{50}Ti+^{176}Yb at the gas-filled recoil separator TASCA. An α decay with an energy of E_{α}=9.31(5) MeV and half-life T_{1/2}=4.7(7) µs was attributed to ^{222}U. The new isotope ^{221}U was identified in α-decay chains starting with E_{α}=9.71(5) MeV and T_{1/2}=0.66(14) µs leading to known daughters. Synthesis and detection of these unstable heavy nuclei and their descendants were achieved thanks to a fast data readout system. The evolution of the N=126 shell closure and its influence on the stability of uranium isotopes are discussed within the framework of α-decay reduced width.

48Ca+249Bk fusion reaction leading to element Z = 117: long-lived α-decaying 270Db and discovery of 266Lr.

The superheavy element with atomic number Z=117 was produced as an evaporation residue in the (48)Ca+(249)Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-µs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope (294)117 and its decay products. A hitherto unknown α-decay branch in (270)Db (Z = 105) was observed, which populated the new isotope (266)Lr (Z = 103). The identification of the long-lived (T(1/2) = 1.0(-0.4)(+1.9) h) α-emitter (270)Db marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an "island of stability."

Spectroscopy of element 115 decay chains.

A high-resolution α, x-ray, and γ-ray coincidence spectroscopy experiment was conducted at the GSI Helmholtzzentrum für Schwerionenforschung. Thirty correlated α-decay chains were detected following the fusion-evaporation reaction 48Ca + 243Am. The observations are consistent with previous assignments of similar decay chains to originate from element Z=115. For the first time, precise spectroscopy allows the derivation of excitation schemes of isotopes along the decay chains starting with elements Z>112. Comprehensive Monte Carlo simulations accompany the data analysis. Nuclear structure models provide a first level interpretation.

InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids.

Growing InGaN quantum dots (QDs) at the apex of hexagonal GaN pyramids is an elegant approach to achieve a deterministic positioning of QDs. Despite similar synthesis procedures by metal organic chemical vapor deposition, the optical properties of the QDs reported in the literature vary drastically. The QDs tend to exhibit either narrow or broad emission lines in the micro-photoluminescence spectra. By coupled microstructural and optical investigations, the QDs giving rise to narrow emission lines were concluded to nucleate in association with a (0001) facet at the apex of the GaN pyramid.

Hemodialysis dialyzers contribute to contamination of air microemboli that bypass the alarm system in the air trap.

BACKGROUND: Previous studies have shown that micrometer-sized air bubbles are introduced into the patient during hemodialysis. The aim of this study was to investigate, in vitro, the influence of dialysis filters on the generation of air bubbles. METHODS: Three different kind of dialyzers were tested: one high-flux FX80 dry filter (Fresenius Medical Care AG&Co. KGaA, Bad Homburg, Germany), one low-flux F8HPS dry filter (Fresenius Medical Care AG&Co. KGaA, Bad Homburg, Germany) and a wet-stored APS-18u filter (Asahi Kasei Medical, Tokyo, Japan). The F8HPS was tested with pump flow ranging between 100 to 400 ml/min. The three filters were compared using a constant pump flow of 300 ml/min. Measurements were performed using an ultrasound Doppler instrument. RESULTS: In 90% of the series, bubbles were measured after the outlet line of the air trap without triggering an alarm. There were significantly more bubbles downstream than upstream of the filters F8HPS and FX80, while there was a significant reduction using the APS-18u. There was no reduction in the number of bubbles after passage through the air trap versus before the air trap (after the dialyzer). Increased priming volume reduced the extent of bubbles in the system. CONCLUSIONS: Data indicate that the air trap does not prevent air microemboli from entering the venous outlet part of the dialysis tubing (entry to the patient). More extended priming of the dialysis circuit may reduce the extent of microemboli that originate from dialysis filters. A wet filter may be favorable instead of dry-steam sterilized filters.

Electrical current leakage during hemodialysis may increase blood-membrane interaction.

UNLABELLED: During hemodialysis blood - membrane interaction causes complement activation. During dialysis there may be an electrical current leakage to the dialyzer, especially if there is a broken ground or a defect in another electrical device coupled to the patient. This study investigated whether an electric current of 1.5 mA DC could alter blood membrane interaction as measured by changes in C3d in the blood. Such a high current leakage could occur because there is no protection in the dialysis machine (Class 1B) against auxiliary current leakage. Such a current could come from a defective external device in contact with the patient during hemodialysis. MATERIALS: A dialysis machine (Fresenius 2008C) with a filled blood-line system containing about 350 ml whole blood from each of 8 different donors was used in vitro. Each of the eight test-runs also contained 1000 U added heparin. The dialysis procedure was performed using hemophan membranes (GFS + 12, Gambro) with bicarbonate and potassium 3.0 (D210, Gambro) as dialysate. Two electric poles were placed in the blood line, before and after the dialyzer (connected in parallel) and the ground was placed at entry and exit of the dialysate fluid coming from the machine to the dialysis filter. C3d was measured before the start of "dialysis" and at 15, 30, 45 and 60 min, during dialysis. Thereafter the 1.5 mA current was switched on and additional samples were drawn at 75 and 90 min. The mean C3d values were calculated. Paired non-parametric statistical analyses were performed. RESULTS: There was a significant and continuous increase in C3d as compared to the "predialysis" level. The increase during 0 to 30 minutes was greater than that from 30 to 60 minutes (p=0.018); the increase in C3d during 60 to 90 min, was greater than that from 30 to 60 min (p=0.018) and there was no difference between the 0 to 30 and the 60 to 90 min increases. CONCLUSIONS: A current, used in this study, was able to induce a blood membrane interaction during in vitro dialysis. Even a weaker current leakage might have such adverse effects and similar interactions seem possible during regular dialysis depending on the extent of the leakage.

The gene encoding for MC56 determinant (drug-sensitivity marker) is located on the short arm of human chromosome 11.

A panel of mouse x human B- and T-cell hybrids was analyzed for the expression of MC56 determinant which marks the drug-sensitive state of CEM cells. Karyotypic and phenotypic analyses of the tested clones showed that the expression of MC56 determinant correlated to the presence of human chromosome 11 and segregated concordantly to the epitopes recognized by monoclonal antibodies in the CD44 cluster. By using a particular class of interspecific rodent x human-cell hybrids in which the human genome counterpart is represented in the different clones only by human chromosome 11 or its fragments, we showed that the gene encoding for MC56 determinant is located on the region p13-pter of the short arm of chromosome 11. Therefore, the hypothesized homology between the drug-sensitivity marker MC56 and the CD44 determinant is supported also by gene mapping studies.

The gene for human lymphocyte homing receptor is located on chromosome 11.

The mouse monoclonal antibody Hermes-3 recognizes the human lymphocyte homing receptor. A panel of mouse-human T lymphocyte hybrids, carrying all mouse chromosomes and a limited number of human chromosomes, was analyzed for expression of human homing receptor by indirect immunofluorescence and immunoprecipitation of radiolabeled cell lysates with Hermes-3 antibody. Karyotypic analysis of the tested clones showed that the expression of human homing receptor correlated to the presence of human chromosome 11 in all but one clone. However, concanavalin A induced a weak to moderate expression of the homing receptor in this clone, but not in a chromosome 11- clone. Another clone, heterogeneous for the expression of homing receptor, was separated into a Hermes-3+ and a Hermes-3- fraction with a fluorescence-activated cell sorter. Karyotypic analysis performed after sorting showed human chromosome 11 to segregate with the Hermes-3 antigen. To confirm these data we correlated the expression of two chromosome 11-coded antigens, Trop-4 and Leu-7, with the expression of the homing receptor. In our hybrid clones these three antigens were expressed concordantly. The gene coding for the human lymphocyte homing receptor recognized by Hermes-3 is thus assigned to chromosome 11.

Gene for human CD59 (likely Ly-6 homologue) is located on the short arm of chromosome 11.

The CD59 (MEM-43) antigen, which probably is a human homologue of mouse Ly-6 antigens, is a broadly expressed Mr 18,000-25,000 human leucocyte surface glycoprotein recognized by monoclonal antibody MEM-43. Ten mouse-human T-lymphocyte hybrids, carrying all mouse chromosomes and a limited number of human chromosomes, were analyzed for expression of CD59 by indirect immunofluorescence and immunoblotting with MEM-43 antibody. Karyotypic analysis of the tested clones showed that the presence of human chromosome 11 correlated with the expression of CD59 in all clones tested. Three other human chromosome 11-encoded antigens, 4F2 (Trop-4), Leu 7 (HNK-1, CD57), and lymphocyte homing receptor, were expressed concordantly with CD59. A more exact localization of the gene for CD59 was obtained by the study of Chinese hamster-human cell hybrids containing short or long arm deletions of human chromosome 11. CD59 segregated with hybrids containing part of the short arm of human chromosome 11, but not with the hybrids containing the long arm. Based on these studies we assign the gene for CD59 to region p14-p13 of the short arm of chromosome 11.