Intergranular films at Au-sapphire interfaces

The existence of nanometer-thick amorphous equilibrium films at metal-ceramic interfaces has been experimentally verified for the Au–Al₂O₃ system. The films were formed using a novel experimental approach, in which thin sputtered films of Au were dewetted on a sapphire substrate which was previously partially wetted with drops of anorthite glass (CaO–2SiO₂–Al₂O₃). High-resolution transmission electron microscopy and qualitative analytical transmission electron microscopy were used to confirm the existence of the amorphous films. In addition, positive and relatively large Hamaker constants were calculated for the Au-film-Al₂O₃ interface, which indicates the existence of an attractive van der Waals force which stabilizes the film, similar to equilibrium films at grain boundaries in ceramics. A ∼ 1 nm thick surface film was also detected on the (0001) surface of sapphire substrates partially wetted by anorthite glass. The refractive index required to stabilize the surface films, via a positive Hamaker constant, is explored.     

Molecular cloning, sequencing, and expression of the 36 kDa protein present in pars planitis. Sequence homology with yeast nucleopore complex protein

PURPOSE: Patients with active pars planitis have increased levels of a 36 kDa protein (p-36) in their circulation. The current studies were undertaken to determine the primary structure of this protein. METHODS: A degenerate oligonucleotide probe based on the amino terminal sequence of p-36 was used to identify a clone from a human spleen cDNA library. The cDNA insert was subcloned into the EcoR1 site of pUC-19, and both strands were sequenced. Southern blot analysis was used to study the genomic hybridization pattern. p-36 cDNA was subcloned in a pSG5 expression vector, and the construct was used to transfect COS-7 cells. RESULTS: The cDNA sequence contained an open reading frame of 966 base pairs encoding a protein of 322 amino acids, an untranslated region of 322 base pairs, and 2693 base pairs at the 5' and 3' ends, respectively. The deduced amino acid sequence showed 96.8% identity with the carboxy-terminal region of a yeast nucleopore complex protein, nup 100. Southern blot analysis of human genomic DNA revealed a simple hybridization pattern. Transfection of p-36 cDNA in COS-7 cells resulted in the presence of p-36 mRNA and expression of protein. CONCLUSIONS: The 36 kDa protein (p-36) detected at increased levels in the blood of patients with active pars planitis was cloned from a human spleen cDNA library. Its deduced amino acid sequence is homologous with the carboxy-terminal region of a nucleopore complex protein. Thus, we refer to this protein as nup36.     

Pu(V)O2+ adsorption and reduction by synthetic magnetite (Fe3O4)

Changes in aqueous- and solid-phase Pu oxidation state were monitored over time in magnetite (Fe3O4) suspensions containing 239Pu(V)-amended 0.01 M NaCl. Oxidation state distribution was determined by leaching of Pu into an aqueous phase followed by an ultrafiltration/solvent extraction technique. The capability of the technique to measure Pu oxidation state distribution was verified using 230Th(IV), 237Np(V), and 233U(VI) as oxidation state analogues. Reduction of Pu(V) was observed at all pH values (pH 3 to 8) and magnetite concentrations (10 to 100 m2 L(-1)). In the pH range 5 to 8, adsorption was a rate-limiting step, and reduction was mediated by the solid phase; at pH 3 reduction occurred in the aqueous phase. The overall reaction (describing both adsorption and reduction of Pu(V)) was found to be approximately first order with respect to the magnetite concentration and of order -0.34+/-0.02 with respect to the hydrogen ion concentration. Assuming first order dependence with respect to Pu, the overall reaction rate constant was calculated as k(rxn) = 4.79+/-0.62 x 10(-8) (m(-2) L)0.99(mol(-1) L)-0.34(s(-1)). The Pu(IV) solid-phase species became more stable over time.     

Helicase activity is only partially required for Schizosaccharomyces pombe Rqh1p function

The RecQ-related family of DNA helicases is required for the maintenance of genomic stability in organisms ranging from bacteria to humans. In humans, mutation of three RecQ-related helicases, BLM, WRN and RecQL4, cause the cancer-prone and premature ageing diseases of Bloom syndrome, Werner's syndrome and Rothmund-Thompson syndrome, respectively. In the fission yeast Schizosaccharomyces pombe, disruption of the rqh1(+) gene, which encodes the single Sz. pombe RecQ-related helicase, causes cells to display reduced viability and elevated levels of chromosome loss. After S-phase arrest or DNA damage, cells lacking rqh1(+) function display elevated levels of homologous recombination and defective chromosome segregation. Here we show that, like other RecQ family members, the Rqh1p protein displays 3' to 5' DNA helicase activity. Interestingly, however, unlike other RecQ family members, the helicase activity of Rqh1p is only partially required for its function in recovery from S-phase arrest or DNA damage. We also report that high cellular levels of Rqh1p result in lethal chromosome segregation defects, while more moderate levels of Rqh1p cause significantly elevated rates of chromosome loss. This suggests that careful regulation of RecQ-like protein levels in eukaryotic cells is vital for maintaining genome stability.     

Carnivore Attractant or Plant Elicitor? Multifunctional Roles of Methyl Salicylate Lures in Tomato Defense

Synthetic plant volatile lures attract natural enemies, but may have non-target effects due to the multifunctional nature of volatile signals. For example, methyl salicylate (MeSA) is used to attract predators, yet also serves as a signaling hormone involved in plant pathogen defense. We investigated the consequences of deploying MeSA lures to attract predators for tomato (Solanum lycopersicum) defense against herbivores. To understand the spatial distribution of the lure’s effect, we exposed tomatoes in the field to MeSA along a linear distance gradient and induced defenses by simulating feeding by hornworm caterpillars in a fully crossed factorial design (+/? MeSA, +/? herbivory). Subsequently, we analyzed activity of several defensive proteins (protease inhibitors, polyphenol oxidase, peroxidase), development of hornworm larvae (Manduca sexta), growth of fungal pathogens (Cladosporium and Alternaria), and attractiveness to herbivores and predators. Overall, MeSA-exposed plants were more resistant to both insects and pathogens. Secondary pathogen infection was reduced by 25% in MeSA exposed plants, possibly due to elevated polyphenol oxidase activity. Interestingly, we found that lures affected plant pathogen defenses equivalently across all distances (up to 4 m away) indicating that horizontal diffusion of a synthetic volatile may be greater than previously assumed. While thrips avoided colonizing hornworm– damaged tomato plants, this induced resistance was not observed upon pre-exposure to MeSA, suggesting that MeSA suppresses the repellant effect induced by herbivory. Thus, using MeSA lures in biological control may inadvertently protect crops from pathogens, but has mixed effects on plant resistance to insect herbivores.     

Ion Electrodiffusion Governs Silk Electrogelation

Silk electrogelation involves the transition of an aqueous silk fibroin solution to a gel state (E-gel) in the presence of an electric current. The process is based on local pH changes as a result of water electrolysis - generating H(+) and OH(-) ions at the (+) and (-) electrodes, respectively. Silk fibroin has a pI=4.2 and when local pH相似文献