Lattice dynamics localization in low-angle twisted bilayer graphene

A low twist angle between the two stacked crystal networks in bilayer graphene enables self-organized lattice reconstruction with the formation of a periodic domain. This superlattice modulates the vibrational and electronic structures, imposing new rules for electron-phonon coupling and the eventual observation of strong correlation and superconductivity. Direct optical images of the crystal superlattice in reconstructed twisted bilayer graphene are reported here, generated by the inelastic scattering of light in a nano-Raman spectroscope. The observation of the crystallographic structure with visible light is made possible due to lattice dynamics localization, the images resembling spectral variations caused by the presence of strain solitons and topological points. The results are rationalized by a nearly-free-phonon model and electronic calculations that highlight the relevance of solitons and topological points, particularly pronounced for structures with small twist angles. We anticipate our discovery to play a role in understanding Jahn-Teller effects and electronic Cooper pairing, among many other important phonon-related effects, and it may be useful for characterizing devices in the most prominent platform for the field of twistronics.Comment: 9 pages, 8 figure

Interaction and uptake of exosomes by ovarian cancer cells

<p>Abstract</p> <p>Background</p> <p>Exosomes consist of membrane vesicles that are secreted by several cell types, including tumors and have been found in biological fluids. Exosomes interact with other cells and may serve as vehicles for the transfer of protein and RNA among cells.</p> <p>Methods</p> <p>SKOV3 exosomes were labelled with carboxyfluoresceine diacetate succinimidyl-ester and collected by ultracentrifugation. Uptake of these vesicles, under different conditions, by the same cells from where they originated was monitored by immunofluorescence microscopy and flow cytometry analysis. Lectin analysis was performed to investigate the glycosylation properties of proteins from exosomes and cellular extracts.</p> <p>Results</p> <p>In this work, the ovarian carcinoma SKOV3 cell line has been shown to internalize exosomes from the same cells via several endocytic pathways that were strongly inhibited at 4°C, indicating their energy dependence. Partial colocalization with the endosome marker EEA1 and inhibition by chlorpromazine suggested the involvement of clathrin-dependent endocytosis. Furthermore, uptake inhibition in the presence of 5-ethyl-N-isopropyl amiloride, cytochalasin D and methyl-beta-cyclodextrin suggested the involvement of additional endocytic pathways. The uptake required proteins from the exosomes and from the cells since it was inhibited after proteinase K treatments. The exosomes were found to be enriched in specific mannose- and sialic acid-containing glycoproteins. Sialic acid removal caused a small but non-significant increase in uptake. Furthermore, the monosaccharides D-galactose, α-L-fucose, α-D-mannose, D-N-acetylglucosamine and the disaccharide β-lactose reduced exosomes uptake to a comparable extent as the control D-glucose.</p> <p>Conclusions</p> <p>In conclusion, exosomes are internalized by ovarian tumor cells via various endocytic pathways and proteins from exosomes and cells are required for uptake. On the other hand, exosomes are enriched in specific glycoproteins that may constitute exosome markers. This work contributes to the knowledge about the properties and dynamics of exosomes in cancer.</p

High Levels of Exosomes Expressing CD63 and Caveolin-1 in Plasma of Melanoma Patients

BACKGROUND: Metastatic melanoma is an untreatable cancer lacking reliable and non-invasive markers of disease progression. Exosomes are small vesicles secreted by normal as well as tumor cells. Human tumor-derived exosomes are involved in malignant progression and we evaluated the presence of exosomes in plasma of melanoma patients as a potential tool for cancer screening and follow-up. METHODOLOGY/PRINCIPAL FINDINGS: We designed an in-house sandwich ELISA (Exotest) to capture and quantify exosomes in plasma based on expression of housekeeping proteins (CD63 and Rab-5b) and a tumor-associated marker (caveolin-1). Western blot and flow cytometry analysis of exosomes were used to confirm the Exotest-based findings. The Exotest allowed sensitive detection and quantification of exosomes purified from human tumor cell culture supernatants and plasma from SCID mice engrafted with human melanoma. Plasma levels of exosomes in melanoma-engrafted SCID mice correlated to tumor size. We evaluated the levels of plasma exosomes expressing CD63 and caveolin-1 in melanoma patients (n = 90) and healthy donors (n = 58). Consistently, plasma exosomes expressing CD63 (504+/-315) or caveolin-1 (619+/-310) were significantly increased in melanoma patients as compared to healthy donors (223+/-125 and 228+/-102, respectively). While the Exotest for CD63+ plasma exosomes had limited sensitivity (43%) the Exotest for detection of caveolin-1+ plasma exosomes showed a higher sensitivity (68%). Moreover, caveolin-1+ plasma exosomes were significantly increased with respect to CD63+ exosomes in the patients group. CONCLUSIONS/SIGNIFICANCE: We describe a new non-invasive assay allowing detection and quantification of human exosomes in plasma of melanoma patients. Our results suggest that the Exotest for detection of plasma exosomes carrying tumor-associated antigens may represent a novel tool for clinical management of cancer patients

Growth optimization and device integration of narrow-bandgap graphene nanoribbons

The electronic, optical and magnetic properties of graphene nanoribbons (GNRs) can be engineered by controlling their edge structure and width with atomic precision through bottom-up fabrication based on molecular precursors. This approach offers a unique platform for all-carbon electronic devices but requires careful optimization of the growth conditions to match structural requirements for successful device integration, with GNR length being the most critical parameter. In this work, we study the growth, characterization, and device integration of 5-atom wide armchair GNRs (5-AGNRs), which are expected to have an optimal band gap as active material in switching devices. 5-AGNRs are obtained via on-surface synthesis under ultra-high vacuum conditions from Br- and I-substituted precursors. We show that the use of I-substituted precursors and the optimization of the initial precursor coverage quintupled the average 5-AGNR length. This significant length increase allowed us to integrate 5-AGNRs into devices and to realize the first field-effect transistor based on narrow bandgap AGNRs that shows switching behavior at room temperature. Our study highlights that optimized growth protocols can successfully bridge between the sub-nanometer scale, where atomic precision is needed to control the electronic properties, and the scale of tens of nanometers relevant for successful device integration of GNRs

Wpływ sposobu uprawy roli i zagospodarowania resztek pożniwnych oraz aplikacji biostymulatora na plonowanie pszenicy ozimej w narastającej monokulturze

The field experiment on agricultural practices in winter wheat in short-term monoculture was carried out over the years 2011/2012 and 2012/2013 in Chemce (52o61’N; 18o44’E). The experimental factors included: A – tillage systems (variants with post-harvest tillage with a grubber or without and with the use of manure and sow ploughing and single ploughing, as well as direct sowing), B – method of managing postharvest residues (four variants with the use of straw and effective microorganisms or without), C – application of a biostimulant Asahi SL (two levels). The aim of the study was determination of the effect of these factors on the yield components and grain yield of winter wheat cultivated in the 2nd and 3rd year of monoculture. The best tillage system for winter wheat yield, irrespective of the duration of monoculture and the course of weather conditions over the years of research, was grubbing the stubble field with a previous application of manure and conducting sow ploughing. Under conditions unfavorable for winter plant yield with a freezing snowless winter, double grubbing and direct sowing was also a good tillage method, leaving a large amount of post-harvest residues on the field surface. Fertilization with straw, especially with a simultaneous use of effective microorganisms, appeared to be relevant under unfavorable habitat conditions. In the year with a beneficial course of weather conditions this treatment generally did not increase the grain yield. Biostimulant Asahi SL caused increase in the quantity of yield components and grain yield in winter wheat, irrespective of the duration of monoculture or of weather conditions over the years of research.Doświadczenie polowe nad agrotechniką pszenicy ozimej w krótkotrwałej monokulturze wykonano w latach 2011/2012 i 2012/2013 w Chełmcach (52o61’ N; 18o44’ E). Czynnikami doświadczenia były: A – sposób uprawy roli (warianty z uprawą pożniwną gruberem lub bez i stosowaniem obornika oraz orką siewną i razówką, a także siew bezpośredni), B – sposób zagospodarowania resztek pożniwnych (cztery warianty ze stosowaniem słomy i efektywnych mikroorganizmów lub bez), C – aplikacja biostymulatora Asahi SL (dwa poziomy). Celem badań było określenie wpływu tych czynników na elementy plonowania i plon ziarna pszenicy ozimej uprawianej w 2. i 3. roku monokultury. Najlepszym sposobem uprawy roli dla plonowania pszenicy ozimej, niezależnie od długości okresu monokultury oraz przebiegu warunków pogodowych w latach badań, było gruberowanie ścierniska poprzedzone stosowaniem obornika i wykonanie orki siewnej. W warunkach niesprzyjających plonowaniu roślin ozimych z mroźną, bezśnieżną zimą dobrymi sposobami uprawy roli było także dwukrotne gruberowanie oraz siew bezpośredni, pozostawiające dużą ilość resztek pożniwnych na powierzchni pola. Nawożenie słomą, zwłaszcza z jednoczesnym stosowaniem efektywnych mikroorganizmów, okazało się zasadne w niekorzystnych warunkach siedliskowych. W roku o korzystnym przebiegu pogody zabieg ten na ogół nie zwiększał plonu ziarna. Biostymulator Asahi SL spowodował wzrost wielkości elementów plonowania i plonu ziarna pszenicy ozimej niezależnie od długości okresu monokultury i warunków pogodowych w latach badań