Crystallographic orientation errors in mechanical exfoliation.

We evaluate the effect of mechanical exfoliation of van der Waals materials on crystallographic orientations of the resulting flakes. Flakes originating from a single crystal of graphite, whose orientation is confirmed using STM, are studied using facet orientations and electron back-scatter diffraction (EBSD). While facets exhibit a wide distribution of angles after a single round of exfoliation ([Formula: see text]), EBSD shows that the true crystallographic orientations are more narrowly distributed ([Formula: see text]), and facets have an approximately [Formula: see text] error from the true orientation. Furthermore, we find that the majority of graphite fractures are along armchair lines, and that the cleavage process results in an increase of the zigzag lines portion. Our results place values on the rotation caused by a single round of the exfoliation process, and suggest that when a 1-2 degree precision is necessary, the orientation of a flake can be gauged by the orientation of the macroscopic single crystal from which it was exfoliated.

Microarray analysis reveals influence of the sesquiterpene lactone parthenolide on gene transcription profiles in human epithelial cells.

Sesquiterpene lactones are known for their anti-inflammatory activity which has been proven in various assays on DNA, mRNA and protein level. Here we report on the change in the gene expression profile in TNF-alpha stimulated human 293 cells after treatment with parthenolide using a cDNA microarray analysis. Twenty-one of 7028 genes were found to be up- and 18 down-regulated. They encode for chemoattractants, immune system proteins, glycoproteins, metabolism, serine proteinases, and transcription factors. Confirmatory analyses were carried out using quantitative real-time RT-PCR (TaqMan). Additional studies with selected genes revealed the concentration-dependent influence of parthenolide on the expression of these genes.

Direct measurement of electrical transport through DNA molecules.

Attempts to infer DNA electron transfer from fluorescence quenching measurements on DNA strands doped with donor and acceptor molecules have spurred intense debate over the question of whether or not this important biomolecule is able to conduct electrical charges. More recently, first electrical transport measurements on micrometre-long DNA 'ropes', and also on large numbers of DNA molecules in films, have indicated that DNA behaves as a good linear conductor. Here we present measurements of electrical transport through individual 10.4-nm-long, double-stranded poly(G)-poly(C) DNA molecules connected to two metal nanoelectrodes, that indicate, by contrast, large-bandgap semiconducting behaviour. We obtain nonlinear current-voltage curves that exhibit a voltage gap at low applied bias. This is observed in air as well as in vacuum down to cryogenic temperatures. The voltage dependence of the differential conductance exhibits a peak structure, which is suggestive of the charge carrier transport being mediated by the molecular energy bands of DNA.

Oxidative stress causes rapid membrane translocation and in vivo degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase.

We have studied the turnover of an abundant chloroplast protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rbu-P2 carboxylase/oxygenase), in plants (Spirodela oligorrhiza and Triticum aestivum L.) and algae (Chlamydomonas reinhardtii and C. moewusii) induced to senesce under oxidative conditions. Rbu-P2 carboxylase/oxygenase activity and stability in vivo were found to be highly susceptible to oxidative stress, resulting in intermolecular cross-linking of large subunits by disulfide bonds within the holoenzyme, rapid and specific translocation of the soluble enzyme complex to the chloroplast membranes, and finally protein degradation. The redox state of Cys-247 in Rbu-P2 carboxylase/oxygenase large subunit seems involved in the sensitivity of the holoenzyme to oxidative inactivation and cross-linking. However, this process did not drive membrane attachment or degradation of Rbu-P2 carboxylase/oxygenase in vivo. Translocation of oxidized Rbu-P2 carboxylase/oxygenase to chloroplast membranes may be a necessary step in its turnover, particularly during leaf senescence. Thus, processes that regulate the redox state of plant cells seem closely intertwined with cellular switches shifting the leaf from growth and maturation to senescence and death.

Developmental stages of cucumber seedlings: kinetics of chlorophyll accumulation and other growth parameters.

The changes in morphology during dark germination and subsequent growth of cucumber (Cucumis sativus) seedlings in the light go through three different phases described as latent, active, and steady-state. This pattern is consistently observed for several related developmental processes. The latent period lasts about 2 days following water imbibition after which the following capabilities appear in concert: (a) root and stem elongation, (b) pigment synthesis including protochlorophyll, chlorophyll, carotenoid, and phytochrome, (c) synthesis of ribulose-1,5-bisphosphate carboxylase/oxygenase, and (d) enhancement of greening by excision. Following the active phase, which lasts for another 2 to 3 days, these processes slow to a steady-state. Inhibition of chlorphyll accumulation by SO(2) was only observed for seedlings in the steady-state phase.

Performance of the duckweed species Lemna gibba on municipal wastewater for effluent renovation and protein production.

An outdoor experiment was conducted in miniponds to evaluate the performance of Lemna gibba, a duckweed species, as a domestic wastewater stripper. Duckweed is one of the floating plants with a high capability of ammonia uptake and assimilation rate into valuable protein. The results indicate that under adequate operational conditions, depending mainly on the organic loading, the effluent quality meets irrigation reuse criteria and protein yield of the duckweed may reach 12 ton/ha per year, far above other conventional field crops.

Tx polyagglutination in three members of one family.

A case of acute haemolytic anaemia is described in a child. Tx polyagglutination of his red cells was observed, but no direct association with the anaemia could be proved. Polyagglutination was suspected because of irregularities in the AB0 blood grouping. Confirmation of the cryptantigen Tx was made when the patient's red cells were tested with lectins including Arachis hypogaea, Glycine soja, and Vicia cretica. Examination of family members showed Tx polyagglutination on the red cells of 2 siblings. The Tx polyagglutination was a transient phenomenon lasting 4-5.5 months, and could have been caused as the result of some unidentified bacterial or viral infection. Guidelines for transfusion therapy are suggested in patients in whom polyagglutination is recognised.

Intensified controlled fish growth in tanks implementing a multipurpose flow device.

Fish biomass (Tilapia sp.) were raised at high stocking density in 1-m(3) tanks containing 450 L of water. The water was changed continously by means of a jet flow regulator. The jet flow regulator maintained adequate dissolved oxygen (DO) and a low ammonia level, while the suspended solids were discarded. In such a system, an annual yield of above 15 kg/m(3) can be expected. The application of the jet flow regulator in aquaculture is discussed.

K22, a 'new' para-Kell antigen of high frequency.

An alloantibody is described which detects a high frequency blood group antigen absent from Ko cells but different from all the reported Kell and para-Kell antigens. The family study shows the antigen to be inherited but gives no information about its relationship to the Kell locus. It is suggested that this 'new' para-Kell antigen be called K22.

Chlorophyll determination in intact tissues using n,n-dimethylformamide.

Photosynthetic pigments from etiolated cucumber (Cucumis sativus var. Beit Alpha improved, Hazera Co., Gedera) cotyledons were extracted by direct immersion of the intact cotyledons into the solvent N,N-dimethylformamide (DMF). The solvent is especially efficient when pigment concentration is low; time and tools are saved and the loss of pigment that usually occurs in more complicated extraction procedures is prevented. The specific absorption coefficient of chlorophyll a in DMF was also determined.

PATHWAYS OF PLASTID DIFFERENTIATION IN SPIRODELA OLIGORRHIZA.

In light-grown Spirodela oligorrhiza, a duckweed, chloroplasts complete differentiation in 2·5 days. When young green fronds are transferred to the dark, their plastids undergo ultrastructural changes that are retrogressive. Prolamellar bodies appear in the intergranal spaces within 12 to 18 h, while well-developed amyloplasts can be seen after 11 days. Mature green fronds maintained in the dark for up to 3 months remain unchanged. The results are discussed in the context of monotropic and reversible pathways of plastid differentiation in higher plants.

Influences of Photoperiodism and light treatments during fruits storage on the phytochrome and on the germination of Cucumis prophetarum L. and Cucumis sativus L. seeds.

Day length, temperature, light quality and hormone treatments given to plants during the ripening of their seeds have been shown to influence the subsequent germination of these seeds. The present work demonstrates that the light conditions, SD, LD or continuous dark, red or far-red light, during storage of ripe fruits of Cucumis prophetarum and Cucumis sativum strongly influence the capacity of seeds, later removed from these fruits, to germinate in darkness.Direct measurement of phytochrome in seeds showed that the various light treatments (continuous dark, red or far-red light but not long or short days) directly affected the quantity of photoreversible phytochrome and more importantly, the percentage of active phytochrome P 730 which is critical for germination. The possible physiological implications of those results are discussed. It seems that the environment affects the dark germination of cucumber seeds through two different pathways: a phytochrome controlled and a daylength dependent mechanism.

Growth, greening, and phytochrome in etiolated spirodela (lemnaceae).

Two species of Spirodela were grown aseptically in a simple mineral medium containing sucrose. Weak red light (15 erg cm(-2) sec(-1)) enhanced dark growth of S. oligorrhiza, whereas weak far red light (15 erg cm(-2) sec(-1)) when given after the red light reduced this effect.The lag period in chlorophyll accumulation (20-24 hours) could be shortened by a brief red light illumination, at both 25 C and 0 C, 12 to 24 hr before the exposure to continuous white light. The effect of red light in shortening the lag phase was diminished when high intensity of far red light (10(3)-10(4) erg cm(-2) sec(-1)) was given simultaneously with the red light.Spectrophotometric studies showed detectable amounts of phytochrome in the plants, part of which decayed immediately during a short illumination by red light. The other relatively stable, phytochrome decayed only after prolonged illumination.