22 research outputs found
Femtosecond terahertz dynamics of cooperative transitions: from charge density waves to polariton condensates
No full textPorer M, Ménard J-M, Poellmann C, et al. Femtosecond terahertz dynamics of cooperative transitions: from charge density waves to polariton condensates. In: Ultrafast Bandgap Photonics. Proc. SPIE 9835 (98351H). SPIE-Intl Soc Optical Eng; 2016
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No full textTranscription regulation in metazoans often involves promoter-proximal pausing of RNA polymerase (Pol) II, which requires the 4-subunit negative elongation factor (NELF). Here we discern the functional architecture of human NELF through X-ray crystallography, protein crosslinking, biochemical assays, and RNA crosslinking in cells. We identify a NELF core subcomplex formed by conserved regions in subunits NELF-A and NELF-C, and resolve its crystal structure. The NELF-AC subcomplex binds single-stranded nucleic acids in vitro, and NELF-C associates with RNA in vivo. A positively charged face of NELF-AC is involved in RNA binding, whereas the opposite face of the NELF-AC subcomplex binds NELF-B. NELF-B is predicted to form a HEAT repeat fold, also binds RNA in vivo, and anchors the subunit NELF-E, which is confirmed to bind RNA in vivo. These results reveal the three-dimensional architecture and three RNA-binding faces of NELF
Synthesis and characterization of Zn-Al layered double hydroxides intercalated with 1- to 19-carbon carboxylic acid anions
No full textLayered double hydroxides (LDHs) are layered ion exchangers, with a large surface-charge density, which react easily with organic anions. Various types of organics are rapidly substituted in the interlayer space of inorganic precursor LDHs. ZnAl-LDHs were intercalated with 1- to 19-carbon monocarboxylic acid anions by anion exchange of NO -saturated LDH precursor phases in order to study the dependence of exchange reactions on synthesis parameters (temperature, pH, and interlayer anion). The carboxylic acid anion-LDHs synthesized were characterized using X-ray diffraction, infrared spectroscopy, thermal analysis, scanning electron microscopy, chemical analysis, and N adsorption. Carboxylic anion quantities in excess of the LDH anion exchange capacity easily replaced exchangeable nitrate anions at moderate pH. The intercalated LDH interlayer space depended on the alkyl chain length and orientation (inclination angle) of thecarboxylic-acid anion. The lattice parameter c ranged from 3.4 to 13.5 nm, but the a lattice parameter remained constant at 0.31 nm. Crystallographic analyses indicated a monomolecular arrangement of intercalated short-chain fatty-acid anions. At pH 10 carbons) to a more upright interlayer position
Improved oxidation behavior of Hf0.11Al0.20B0.69 in comparison to Hf0.28B0.72 magnetron sputtered thin films
No full textThe oxidation resistance of Hf0.28B0.72 and Hf0.11Al0.20B0.69 thin films was investigated comparatively at 700 degrees C for up to 8 h. Single-phase solid solution thin films were co-sputtered from HfB2 and AlB2 compound targets. After oxidation at 700 degrees C for 8 h an oxide scale thickness of 31 +/- 2 nm was formed on Hf0.11Al0.20B0.69 which corresponds to 14% of the scale thickness measured on Hf0.28B0.72. The improved oxidation resistance can be rationalized based on the chemical composition and the morphology of the formed oxide scales. On Hf0.28B0.72 the formation of a porous, O, Hf, and B-containing scale and the formation of crystalline HfO2 is observed. Whereas on Hf0.11Al0.20B0.69 a dense, primarily amorphous scale containing O, Al, B as well as approximately 3 at% of Hf forms, which reduces the oxidation kinetics significantly by passivation. Benchmarking Hf0.11Al0.20B0.69 with Ti-Al-based boride and nitride thin films with similar Al concentrations reveals superior oxidation behavior of the Hf-Al-based thin film. The incorporation of few at% of Hf in the oxide scale decelerates oxidation kinetics at 700 degrees C and leads to a reduction in oxide scale thickness of 21% and 47% compared to Ti0.12Al0.21B0.67 and Ti0.27Al0.21N0.52, respectively. Contrary to Ti-Al-based diborides, Hf0.11Al0.20B0.69 shows excellent oxidation behavior despite B-richness.An Author Correction to this article was published on 24 October 2024. Correction to: Scientific Reports https://doi.org/10.1038/s41598-024-72134-3, published online 17 September 2024</p
Sub-lethal hyperthermia promotes epithelial-to-mesenchymal-like transition of breast cancer cells: implication of the synergy between hyperthermia and chemotherapy
No full textThermotherapy has demonstrated a potential to be an effective non-surgical technique to treat breast cancer. Despite its advantages, including low toxicity and high repeatability, thermotherapy is typically required to be applied in combination with other treatments since the residual tumor cells that survive after hyperthermal treatment often cause recurrence. In this study, we confirmed that breast cancer cells tolerate temperature of up to 47 °C by synthesizing a large amount of heat shock proteins. Further changes in the molecular properties of the heat-exposed cells were investigated using western blotting, quantitative reverse transcription polymerase chain reaction, and immunocytochemistry. We found that low-temperature hyperthermia promoted epithelial-to-mesenchymal-like transition (EMT), as observed by the increased mesenchymal marker expression levels while decreasing epithelial markers. Moreover, cell morphology changed from cobblestone-like to a more spindle-like appearance, in addition to significantly enhanced cell motility upon heat treatment. These results all support that sub-lethal hyperthermal stress induces EMT. In addition, we examined changes in the chemo-sensitivity of the heat-treated cells. Addition of a chemo-drugs caused increased cytotoxicity of the heat-treated cells compared to the cells that were not co-treated with heat. Our study demonstrates that thermotherapy alone may cause undesirable EMT, which could be well overcome through a synergistic effect when applied with chemotherapy
Use of 29 Si and 27 Al MAS NMR to study thermal activation of kaolinites from Brazilian Amazon kaolin wastes
No full textThe study of thermal activation of kaolinite at various temperatures to produce highly reactive metakaolinite from Brazilian Amazon kaolin wastes was studied using 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR). The wastes used in the current study came from the Capim and Jari regions in northern Brazil. The mineralogical and chemical characterizations of Jari kaolin (KJ) waste were performed by XRD, FTIR, DTA–TGA, SEM and chemical analyses. The results indicate that the Jari and Capim kaolins (KC) wastes are composed primarily of kaolinite and that KJ is composed of a typical kaolinite with a low degree of structural order. The ideal temperature to produce highly reactive metakaolinite is 600 °C for KJ and 700 °C for KC, suggesting that the degree of structural order of kaolinite has a definite influence on its dehydroxylation temperature. These results were confirmed when zeolite NaA was synthesized from metakaolins produced at temperatures used in this work
Caracterização química e mineralógica de birnessita natural da Mina do Azul (Província Mineral de Carajás, Brasil) e seu análogo sintético (K-OL-1) obtido pelo método sol-gel
No full textResumo O presente trabalho descreve um estudo comparativo das propriedades química e mineralógica de birnessita natural (BIR-AZ) proveniente da mina do Azul (Província Mineral de Carajás, Brasil) e seu análogo sintético obtido pelo método sol-gel (K-OL-SG). As caracterizações foram realizadas por difração de raios X, espectroscopia FT-Raman, análise térmica (TG-DTA), microscopia eletrônica de varredura e análise química. Os resultados confirmam a presença das fases lamelares com sistema monoclínico, grupo espacial C2/m e com os seguintes parâmetros de cela unitária: BIR-AZ, a = 5,148 Å; b=2,843 Å, c=7,175 Å e β = 100,75º; K-OL-SG, a = 5,150 Å; b = 2,846 Å, c = 7,214 Å e β = 101,29º. Birnessita possui estabilidade térmica próxima a 600 ºC, enquanto seu análogo sintético acima de 900 ºC. Bandas obtidas por espectroscopia Raman foram observadas a 635, 570 e 410 cm-1 e atribuídas às deformações Mn-O e K-O na estrutura lamelar. O estudo da morfologia dos produtos revela que birnessita se apresenta como folhas tabulares de 1 a 5 µm, enquanto que o composto sintético possui morfologia em glóbulos (< 1 μm) dispostos aleatoriamente
Microcavity design for low threshold polariton condensation with ultrashort optical pulse excitation
No full textWe present a microcavity structure with a shifted photonic stop-band to enable efficient non-resonant injection of a polariton condensate with spectrally broad femtosecond pulses. The concept is demonstrated theoretically and confirmed experimentally for a planar GaAs/AlGaAs multilayer heterostructure pumped with ultrashort near-infrared pulses while photoluminescence is collected to monitor the optically injected polariton density. As the excitation wavelength is scanned, a regime of polariton condensation can be reached in our structure at a consistently lower fluence threshold than in a state-of-the-art conventional microcavity. Our microcavity design improves the polariton injection efficiency by a factor of 4, as compared to a conventional microcavity design, when broad excitation pulses are centered at a wavelength of lambda = 740 nm. Most remarkably, this improvement factor reaches 270 when the excitation wavelength is centered at 750 nm. (c) 2015 AIP Publishing LLC
