Characterization of Al-Si-alloys rapidly quenched from the melt

Aluminium-silicon alloys with compositions in the range 0 at% to 33.9 at % Si were rapidly quenched from the melt at cooling rates between 10⁶ and 10⁷ K sec^–1 using the melt-spinning technique. The resulting ribbons were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and X-ray diffraction methods. Metastable solid solubilities of silicon in aluminium were determined from lattice parameter and DSC data. The values found were strongly dependent on specimen thickness and a maximum of about 5 at % Si was reached for an alloy composition of 15 at % Sl (maximal equilibrium solid solubility of silicon in aluminium is 1.58 at % Si). Discrepancies between published values of metastable silicon solid solubities were related to the interpretation of the lattice parameter data. Alloy composition was shown to determine the lattice parameter of the silicon-rich phase. The crystallite sizes and the lattice distortions in the aluminium-rich and silicon-rich phases were determined by X-ray diffraction line profile analysis. From the aluminiumrich phase only strain broadening was observed whereas the silicon-rich phase gave rise to both size and strain broadening. The origin of the lattice strains was discussed. Changes in solidification behaviour are reflected in the structure parameters measured.     

Lattice changes of iron-nitrogen martensite on aging at room temperature

The aging behavior of iron-nitrogen martensite (5.5 at. pct N ≙5.8N/100Fe) at about 297 K was investigated by employing X-ray diffractometry, thereby following, in particular, the changes in the {002} and {200} line profiles. Martensitic specimens were prepared by gaseous nitriding of pure iron in a mixture of NH₃ and H₂, followed by quenching in brine and subsequently in liquid nitrogen. The aging process can be divided into two stages. First, a redistribution of nitrogen atoms in the martensite matrix occurs (aging time < about 40 hours) in three ways: segregation of nitrogen to lattice defects (about 0.07N/100Fe), transfer of a small amount of nitrogen (about 0.06N/100Fe) fromalb- toc-type octahedral interstices, and local enrichment in an ordered way of the majority of the nitrogen atoms (coherent α′’-Fe₁₆N₂ precipitates). Second, formation of incoherent α″-Fe₁₆N₂ takes place (aging time > about 40 hours). Within the range of aging times employed (up to 670 hours), the diffraction by the residual austenite did not change.     

Generation of tumor immunity by bone marrow-derived dendritic cells correlates with dendritic cell maturation stage

The mutational pattern of IgVH and IgVL genes from synovial tissue B cell hybridomas (n = 8) of patients (n = 4) with rheumatoid arthritis (RA) was analysed, which had been produced by the electrofusion technique without prior in vitro stimulation. The molecular data were correlated with immunohistopathological data and parameters of local disease activity. The IgVH genes of the B cell hybridomas belonged to the VH3 family (DP42; DP47, n = 2; DP53), the VH1 family (DP75), the VH4 family (DP71) and the VH5 family (DP73); 7/7 IgVH genes showed somatic mutations, the R/S ratio (CDR) was > 3 in 4/7 IgVH genes and the mean R/S ratio of all IgVH genes was 9.3 (CDR) and 1.0 (FR), suggesting an antigen-dependent selection. The IgVL/lambda genes belonged to the Vlambda1 family (DPL2, DPL5, DPL8nf), the Vlambda2 family (DPL11, n = 2) and to the Vlambda6 family (IGLV6S1); 6/6 IgVL genes showed somatic mutations, the R/S ratio (CDR) was > 3 in 3/6 IgVL genes and the mean R/S ratio of all IgVL was 3.0 (CDR) and 2.3 (FR), suggesting an antigen-dependent selection. The synovial tissue exhibited germinal centres in the follicles (3/4), with the unique distribution of Ki-M4+ follicular dendritic cells and Ki-67+ proliferating cells and a dominance of IgA+ plasma cells (3/3). All patients were positive for RF in serum and exhibited severe local symptoms (swelling 4/4; warmth 4/4; effusion 2/4), whereas the hybridomas were negative for RF. Since B cell hybridomas showed hypermutation and affinity selection for IgVH and IgVL/lambda genes and the patients exhibited severe local symptoms with germinal centres in synovial tissue, this study indicates that an antigen-driven process is behind the B cell expansion in the synovial tissue of clinically affected joints. These mutated B hybridomas were negative for RF, thus suggesting that antigens different from RF are also involved in the local B cell expansion and in the chronic synovitis of RA.     

Pd/GaN(0001) interface properties

This report concerns the properties of an interface formed between Pd films deposited onto the surface of (0001)-oriented n-type GaN at room temperature (RT) under ultrahigh vacuum. The surface of clean substrate and the stages of Pd-film growth were characterized in situ by X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), ultraviolet photoelectron spectroscopy (UPS), and low energy electron diffraction (LEED). As-deposited Pd films are grainy, cover the substrate surface uniformly and reproduce its topography. Electron affinity of the clean n-GaN surface amounts to 3.1 eV. The work function of the Pd-film is equal to 5.3 eV. No chemical interaction has been found at the Pd/GaN interface formed at RT. The Schottky barrier height of the Pd/GaN contact is equal to 1.60 eV.     

Modulation of CD72 by ligation of B cell receptor complex molecules on CD5+ B cells

B cells expressing CD5 also carry its ligand, CD72. As an approach to understanding the role of CD5 and CD72 on B cells, we have examined the association of CD72 with CD5 and slgM by modulation/co-modulation and capping/co-capping following ligation of these surface molecules with specific antibodies. Modulation and co-modulation were measured after 24 h, whilst capping was measured after 1 h. CD5 and slgM co-modulated each other, CD72 co-modulated with slgM and CD5, but anti-CD72 did not affect either slgM or CD5. CD5 and slgM co-capped each other, whilst CD72 failed to co-cap with either slgM or CD5. The CD5-induced co-modulation of CD72 was partially blocked by specific protein tyrosine kinase inhibitor, but not the slgM-induced co-modulation, Protein kinase C (PKC) inhibitors abrogated the anti-mu- but not the anti-CD5-triggered modulation of CD72, whereas PKC activators prevented the CD5- but not the slgM-induced 24 h modulation of CD72. None of these drugs was able to modify the anti-CD72-induced modulation of CD72. Our data suggest that CD5 is physically associated with slgM in the B cell receptor complex but not with CD72. Furthermore, from the effect of drugs on modulation, there appears to be different associations of CD72 with slgM and CD5. These two pathways differed in some respects, consistent with a co-stimulatory function of CD72 and CD5 in B cell activation.     

Yttria stabilized zirconia synthesis in supercritical CO2: Understanding of particle formation mechanisms in CO2/co-solvent systems

The increasing interest of supercritical (SC) fluids for inorganic materials synthesis recently stimulated the development of innovative synthesis processes and strategies. The supercritical CO₂ aided sol–gel process, developed for preparing various ceramic oxide powders with attractive applications in cosmetics, chromatography, catalysis or solid oxide fuel cells, usually suffer from both reproducibility problems and poor knowledge of the key parameters defining the final powder characteristics. In the present work a specific effort has been put on the understanding of reaction mechanisms and process parameters like co-solvent polarity and ageing time of the starting solution, which appeared to play a crucial role for the control of powder characteristics. Two different reaction mechanisms have been proposed to explain the formation of tetragonal yttria-doped zirconia powders by a batch process in either CO₂/pentane or CO₂/isopropanol mixtures. The first mechanism corresponds to a CO₂ anti-solvent precipitation process while the other one is based on a condensation reaction as in the conventional sol–gel process. This improved understanding in particle formation allows better control of powder characteristics and reproducibility.     

MicroRNA Profiling of B Cell Subsets from Systemic Lupus Erythematosus Patients Reveals Promising Novel Biomarkers

MicroRNAs control the differentiation and function of B cells, which are considered key elements in the pathogenesis of systemic lupus erythematosus (SLE). However, a common micro(mi)RNA signature has not emerged since published data includes patients of variable ethnic background, type of disease, and organ involvement, as well as heterogeneous cell populations. Here, we aimed at identifying a miRNA signature of purified B cells from renal and non-renal severe SLE patients of Latin American background, a population known to express severe disease. Genome-wide miRNA expression analyses were performed on naive and memory B cells and revealed two categories of miRNA signatures. The first signature represents B cell subset-specific miRNAs deregulated in SLE: 11 and six miRNAs discriminating naive and memory B cells of SLE patients from healthy controls (HC), respectively. Whether the miRNA was up or down-regulated in memory B cells as compared with naive B cells in HC, this difference was abolished in SLE patients, and vice versa. The second signature identifies six miRNAs associated with specific pathologic features affecting renal outcome, providing a further understanding for SLE pathogenesis. Overall, the present work provided promising biomarkers in molecular diagnostics for disease severity as well as potential new targets for therapeutic intervention in SLE.     

Sex pheromones and reproductive isolation in four european small ermine moths

Reproductive isolation among four sympatric small ermine moths (Yponomeuta) is analyzed in terms of niches in the sexual communication channel. Potential pheromone components were identified from pheromone gland secretions ofY. evonymellus,Y. cagnagellus,Y. padelius, andY. vigintipunctatus by gas chromatography with flame ionization and electroantennographic detection and tested for behavioral activity in the field. The species were found to share (Z)-11-tetradecenyl acetate (Z11-14: OAc) in combination with varying proportions of theE isomer as primary sex pheromone components.Y. cagnagellus differs from the rest of the species by having only a small amount (1.5%) ofE isomer relative toZ isomer in its pheromone. The closely relatedY. padelius has a three-component pheromone including large amounts (ca. 400%) of (Z)-11-hexadecenyl acetate (Z11–16:OAc) in addition toZ11–14: OAc (100%) andE11–14: OAc (34%).Z11–16: OAc appears to reduce trap catches ofY. evonymellus andY. vigintipunctatus when added to the pheromone. Although these species are the two most distantly related European small ermine moths, they seem to share the same sex pheromone, i.e.,Z11–14OAc (+20%E) and (Z)-11-tetradecenol. Our interpretation is that this might have been the sex pheromone of the ancestor of today'sYponomeuta species.1 Lepidoptera: Yponomeutidae Latr.     

Differences in attraction to semiochemicals present in sympatric pine shoot beetles,Tomicus minor andT. piniperda

The chemical ecology of host- and mate-finding in the pine shoot beetles,Tomicus minor andT. piniperda, was studied in southern Sweden. Beetles were collected in the field from defined attack phases on Scots pine. Using gas chromatography-mass spectroscopy, a number of oxygen-containing monoterpenes, e.g., 3-carene-10-ol, myrtenol,trans-verbenol, and verbenone, were identified from hindgut extracts of both sexes of both species. Compared toT. minor,T. piniperda contained additional compounds and in larger amounts. The amounts were highest in both species at the time when the beetles had bored into contact with the resin-producing xylem-phloem tissue. The synthesis of (1S,6R)-3-carene-10-ol by photooxidatipn of (+)-(1S,6R)-3-carene is described. In comparative electroantennogram (EAG) measurements on males and females of both species, the most active of the tested compounds wastrans-verbenol. Laboratory bioassays of walking beetles showed thatT. piniperda was attracted to uninfestèd pine logs.T. minor was more strongly attracted to pine logs infested with females than to uninfested pine logs, indicating a female-produced aggregation pheromone. Field tests confirmed thatT. piniperda was strongly attracted to pine logs. The attraction ofT. minor to logs was significant only when logs were combined with racemictrans-verbenol and (1S,6R)-3-carene-10-ol.T. minor was also attracted to a combination of these monoterpene alcohols alone. We suggest that host and mate location inT. piniperda is achieved by means of a kairomone composed of host monoterpenes, whileT. minor utilizes a primitive pheromone synergized by host odors. Evolution of host colonization strategies of the two beetles are discussed.Coleoptera: Scolytidae.This study was made within the project Odour signals for control of pest insects.     

Pulsed Odors from Maize or Spinach Elicit Orientation in European Corn Borer Neonate Larvae

Lepidoptera larvae are capable of orienting towards or away from plants by using odors as cues but whether this attraction is innate or secondarily acquired remains unknown. We tested the hypothesis that European corn borer (ECB) neonate larvae express an innate attraction towards odors released from maize, and avoidance towards odors from spinach. Neonate larvae were placed on a locomotion compensator within a constant stream of humidified air that was loaded intermittently with airborne odors drawn from potted plants. The odor stream was delivered continuously or pulsed (1 to 10 sec pulses) at 40 ml/min. ECB larvae oriented toward maize odors pulsed at 2 to 6 sec but walked away from maize odors delivered at lower frequencies (9 and 10 sec pulses or to continuous ones). They consistently walked away from spinach odors, irrespective of the pulsing regime except at 1 sec pulses that did not elicit orientation. We further explored odor intensity on orientation towards maize odors by adjusting the odor stream intensity. At higher intensity (60 ml/min), the direction reversal started at the 6 sec half period, while at lower intensity (20 ml/min), it showed up only for the continuous stimulus. ECB larvae exhibit a striking ability to lock on to a direction, which they maintained despite gaps of up to 10 sec in the odor stream. Our results demonstrate that ECB neonate larvae express innate orientation preferences towards natural odors from plants. These reactions correlate well with the biological value of these plants for ECB: maize generally is accepted by ECB larvae and adults, while spinach represents a poor host because it produces (non-volatile) phytoecdysteroids that are toxic and deterrent.