54,193 research outputs found
MICROWAVE SPECTRA AND STRUCTURE OF CFICO
No full textAuthor Institution: School of Chemistry, University of Bristol, Bristol, BS8 1TS, U.KA Chirped Pulse Fourier transform Microwave spectrometer has been used to measure the pure rotational spectrum of CFICO. This complex is generated by supersonic expansion of a gas sample containing a small percentage of CFI, and CO in argon. The rotational constant , centrifugal distortion constants, \Delta_\it{J} and \Delta_\it{JK}, and nuclear quadrupole coupling constant for iodine, (I), have been determined for each of CFICO, CFICO and CFI CO allowing determination of the distance between the two sub-units. The complex is a prolate symmetric top with symmetry
Study of the formation of interstellar CF+ from the HF + C+ →CF+ + H reaction
No full textThe detection of the carbon monofluoride cation CF+ was considered as a support of the theories of the fluorine chemistry in the interstellar medium. This molecule is formed by the reaction of HF with C+. The rates of this reaction have been estimated previously by two different groups. However, these two estimations led to different results. The main goal of this work is to study the HF + C+ reaction and determine new reactive rate coefficients. A large set of ab initio energies at the MRCI-F12/cc-pVQZ-F12 level was computed. The first reactive potential energy surface for the HF + C+ →CF+ + H reaction was developed using a reproducing kernel Hilbert space based method. The dynamics of the reaction was followed from quasi-classical trajectories. The results of such calculations showed that CF+ is produced in excited vibrational states. The rate coefficients for the HF + C+ →CF+ + H reaction from 50 K to 2000 K are reported. The impact of these new data in the astrophysical models for the determination of the interstellar conditions is also explored. © 2018 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society.Universidad Autónoma de Chil
Cf-4/Avr4-triggered hypersensitive cell death requires NRC2/3.
No full textA) Cf-4/Avr4-triggered hypersensitive cell death is lost in the nrc2/3 and nrc2/3/4 knock-out lines, but not in the nrc4 line. Representative N. benthamiana leaves infiltrated with appropriate constructs photographed 7–10 days after infiltration. The NRC CRISPR lines, nrc2/3-209.1.3.1, nrc2/3/4-210.4.3.1, and nrc4-185.1.2.1, are labelled above the leaf and the receptor/effector pair tested, Cf-4/Avr4, Prf (Pto/AvrPto), Rpi-blb2/AVRblb2 or R3a/Avr3a, are labelled on the leaf image. Cf-4/EV and EV/Avr4 were also included as negative controls. A representative leaf of the independent nrc2/3-209.3.3.1, and nrc2/3/4-210.5.5.1 CRISPR line are shown in S1B Fig) Cf-4 protein accumulation is not affected in the nrc2/3/4 lines. For the immunoblot analysis, total protein was extracted 5 days after transient expression of Cf-4-EGFP by agroinfiltration in wild-type, nrc2/3/4-210.4.3.1 and nrc2/3/4-210.5.5.1 N. benthamiana leaves. Cf-4-EGFP accumulation was detected using anti-GFP antibody. C) Quantification of hypersensitive cell death. Cell death was scored based on a 0–7 scale (S1 Fig) between 7–10 days post infiltration. The results are presented as a dot plot, where the size of each dot is proportional to the count of the number of samples with the same score within each biological replicate. The experiment was independently repeated three times. The columns correspond to the different biological replicates. Significant differences between the conditions are indicated with an asterisk (*). Details of statistical analysis are presented in S1 Fig.</p
Phosphorylation and proteome dynamics in pathogen-resistant tomato plants
No full textMicrobial plant pathogens impose a continuous threat on global food production. Similar to disease resistance in mammals, an innate immune system allows plants to recognise pathogens and swiftly activate defence. For the work described in this thesis, the interaction between tomato and the extracellular fungal pathogen Cladosporium fulvum serves as a model system to study host resistance and susceptibility in plant-pathogen interactions. Resistance to C. fulvum in tomato plants follows the gene-for-gene hypothesis, which requires the presence of a Cf resistance gene in tomato and presence of the cognate avirulence gene (Avr) in C. fulvum. Upon perception of the Avr by a tomato plant, a typical hypersensitive response (HR) is induced that renders the plant resistant to C. fulvum. In the years preceding this thesis work, most research was focussed on understanding which Avrs are produced by C. fulvum and how these Avrs are actually perceived by resistant plants (Chapter 1). The goal of the work described in this thesis is to reveal downstream signalling cascades triggered upon Avr perception. Therefore, the HR was studied by using a model system in which the Cf-4 protein of tomato and the Avr4 protein from C. fulvum were simultaneously expressed in tomato seedlings. Since the Cf-4/Avr-induced responses are inhibited at 33°C and high humidity, these Cf-4/Avr4 seedlings initiate a synchronized and reproducible HR after incubation at 33°C and a subsequent shift to 20°C, which allows studying downstream responses. To prevent pathogen proliferation in the resistant plant, defence signalling cascades need to be activated extremely fast upon pathogen recognition. Therefore, many downstream signalling cascades depend on post-translational modifications (PTMs) that allow a rapid, reversible, controlled and highly specific transduction of perceived signals. An overview of the various types of PTMs and their role in the resistance response of plants to pathogens is provided in Chapter 2. In addition, examples are provided of successful pathogens that manipulate PTMs. Protein phosphorylation seems to play an important role in the Cf-4/Avr4-triggered HR, since Avr4 perception leads to the specific activation of at least three mitogen-activated protein kinases, LeMPK1, -2 and -3, which requires phosphorylation by an upstream kinase (Chapter 3). Each of these three kinases seems to have a different role in downstream defence signalling, since the kinases were shown to have different phosphorylation specificities and therefore most likely have different downstream target substrates. Furthermore, these kinases appear to play a different role with regard to HR and full resistance to C. fulvum in tomato (Chapter 3). Since protein phosphorylation was shown to play an important role in Cf-4/Avr4-induced defence signalling, the phosphoproteome of Cf-4/Avr4 and control seedlings after HR initiation was studied using a new approach (Chapter 4). This approach led to the identification of 50 phosphoproteins, most of which have not been described in tomato before. Quantification revealed 13 phosphoproteins with an altered abundance in the Cf-4/Avr4 seedlings as compared to the control, which implies HR-induced differential phosphorylation of these proteins. Phosphorylation-mediated regulation of the activity of these proteins pointed to a swift decrease in photosynthetic activity upon HR-initiation, which was confirmed by experiments in which the actual efficiency of the photosynthesis in the Cf-4/Avr4 seedlings was determined upon induction of the HR. Furthermore, a shift from aerobic to anaerobic respiration, which possibly results from oxygen depletion caused by a massive oxidative burst consuming large amounts of oxygen, seems to take place upon initiation of the HR. Finally, differential phosphorylation of the four cytoplasmic isoforms of the Hsp90 chaperone protein was observed, suggesting that they play distinct roles during defence signalling (Chapter 4). In addition to the HR, other associated defence responses are initiated upon recognition of C. fulvum. One of these responses is the secretion of defence-related proteins into the apoplast, which is the environment where C. fulvum operates. Therefore, the dynamics of the apoplastic proteome of resistant, Cf-4-expressing plants and susceptible tomato plants lacking Cf-4, were studied after inoculation with a strain of C. fulvum that secretes Avr4 (Chapter 5). Analysis of the apoplastic proteome revealed a slow accumulation of defence proteins in the apoplast of susceptible plants, which is most likely the result of perception of general elicitors of C. fulvum by tomato. In resistant plants, the same set of proteins accumulates in the apoplast, but this occurs much faster and to higher levels. The accelerated response is caused by the Cf-4/Avr4-initiated HR that also leads to cell death. The HR, in combination with the accelerated protein secretion, renders the plants resistant to C. fulvum. In addition, in susceptible plants C. fulvum seems to specifically downregulate genes encoding cell wall proteins of which the accumulation possibly hampers nutrient and water uptake and thereby proliferation of the pathogen in the tomato apoplast. Possibly, an effector of C. fulvum targets a receptor for general elicitors, thereby suppressing transcription of these genes (Chapter 5). Most data described in this thesis have been obtained from Cf-4/Avr4 seedlings in which the HR can be inhibited by incubating the plants at 33°C. The present data suggest that this temperature-sensitivity occurs at the site of signal perception. Possibly, cytoplasmic Hsp90 stabilizes R protein complexes localized at the plasma membrane. Upon high temperature stress, an increased demand for Hsp90 occurs in the cells to stabilize unfolding proteins that play a role in basal cellular processes, which could lead to the release and subsequent degradation of R protein complexes, rendering defence signalling temperature-sensitive (Chapter 6). The temperature-sensitivity of the Cf-4/Avr4-initiated HR provides a very clean and reproducible tool to study the HR, in the absence of the fungus that produces the Avr. Furthermore, the data described in this thesis provide evidence that the Cf-4/Avr4 seedlings recover from the temperature stress before the specific Cf-4/Avr4-triggered HR is initiated. The possibility to separate the events directly associated with the HR from the full resistance response of the plant to the invading fungus, provides new insight into the complexity of plant defence responses and their specific suppression upon successful colonization by C. fulvum (Chapter 6). Comparison of the defence response to other processes that occur in the cell underlines that resistance and HR execution cannot be seen as an independent and separate process in resistant plants that have recognized a pathogen. On the contrary, signalling cascades seem to depend on similar components and on cascades that possibly converge, eventually leading to a similar response (Chapter 6). Finally, an up to date model for the Cf-4/Avr4-triggered HR and resistance is proposed, based on data that have been published before and the results obtained with the research described in this thesis (Chapter 6). <br/
3D Thermal Network Supported by CF Felt for Improving the Thermal Performance of CF/C/Epoxy Composites
No full textThe heat generated by a high-power device will seriously affect the operating efficiency and service life of electronic devices, which greatly limits the development of the microelectronic industry. Carbon fiber (CF) materials with excellent thermal conductivity have been favored by scientific researchers. In this paper, CF/carbon felt (CF/C felt) was fabricated by CF and phenolic resin using the “airflow network method”, “needle-punching method” and “graphitization process method”. Then, the CF/C/Epoxy composites (CF/C/EP) were prepared by the CF/C felt and epoxy resin using the “liquid phase impregnation method” and “compression molding method”. The results show that the CF/C felt has a 3D network structure, which is very conducive to improving the thermal conductivity of the CF/C/EP composite. The thermal conductivity of the CF/C/EP composite reaches 3.39 W/mK with 31.2 wt% CF/C, which is about 17 times of that of pure epoxy
Climate-related variations in atmospheric Sb and Tl in the EPICA Dome C ice (East Antarctica) during the past 800,000 years
No full textA record of antimony (Sb) and thallium (Tl) from the European Project for Ice Coring in Antarctica (EPICA) Dome C Antarctic ice core provides the characteristics of climate-related natural changes in concentrations and fluxes of these toxic elements over the time period back to Marine Isotope Stage 20.2, similar to 800kyrB.P. A strong variability in concentrations and fluxes are observed for both elements, with considerably higher values during glacial maxima and lower values during intermediate and warm periods. Rock and soil dust accounts for, on average, 58% of Sb and 76% of Tl in ice during glacial maxima. This contribution remains significant during warm periods, accounting for 21% for Sb and 27% for Tl. The contribution from volcanoes appears to be very important particularly for Tl when climatic conditions become warmer, with an estimated volcanic contribution of 72% for Tl during interglacials. The sea-salt contribution is significant for Sb, particularly during intermediate climatic periods, with an average contribution of 17%. This sea-salt contribution is most likely caused by greater production of sea salt from highly saline frost flowers and relatively more efficient transport of Sb-enriched sea-ice salt from source areas on the East Antarctic Plateau. Our ice core data, along with snow data recently reported from the Antarctic snow layers at Dome Fuji, shows that the present-day Sb flux (6.6ng/m(2)/yr) is approximately double the highest natural level (2.8ng/m(2)/yr) during glacial maxima throughout the last successive eight glacial/interglacial cycles. This result indicates that human activity has induced the greatest perturbation of the atmospheric cycle of Sb ever experienced over a period of similar to 800 kyr in the most remote area on Earth
Synthesis of bifluorene-based molecular materials: effect of C-9 spirocyclohexane functionalization and end-group tailoring
No full textThe preparation and properties of the first spirocyclohexane-functionalized bifluorene-based mono-dispersed molecular materials is described. The obtained compounds were characterized by H-1 NMR, C-13[H-1] NMR, IR, DSC, UV-vis and photoluminescence both in solution and in the solid state. The molecules show emissions ranging from the blue to the blue-green region, and higher glass transition temperatures and spectral stability with respect to the analogous compounds containing 9,9,9',9'-tetrahexyl-[2,2']-bifluorene core. The materials were used as active layers in electroluminescent devices with ITO/PEDOT-PSS/SB1-4/Ca/Al and ITO/PEDOT-PSS/SB1-4/BCP/Ca/Al configurations. (c) 2008 Elsevier Ltd. All rights reserved
First detection of CF
No full textContext. CF+ has been established as a valuable diagnostic tool for investigating photodissociation regions (PDRs) and fluorine abundances in the Milky Way. However, its role in extragalactic environments remains largely uncharted.
Aims. Our objective is to explore the significance of CF+ in the Large Magellanic Cloud (LMC) and assess its utility as a probe for examining C+ and fluorine abundances in external galaxies.
Methods. We performed pointed CF+ observations toward an active star-forming region, N113 in the LMC, using the Atacama Pathfinder EXperiment 12 m submillimeter telescope.
Results. We report the first discovery of CF+ in the LMC through the successful detection of the CF+ (2→1) and (3→2) lines. The excitation models indicate that CF+ emission originates from dense PDRs characterized by an H2 number density of (0.5–7.9) × 104 cm−3 in N113. Our observations provide the first constraint on the fluorine abundance in molecular clouds in the LMC, ≲1.7 × 10−9. This value is about an order of magnitude lower than those previously measured toward red giants in the LMC, indicative of fluorine deficiency in the molecular gas. The estimated column density ratio between C+ and CF+ appears to be lower than the anticipated equilibrium ratio derived from the fluorine abundance in red giants. Both phenomena can be explained by the deficiency of CF+ caused by the freeze-out of its primary chemical precursor, HF, onto dust grains.
Conclusions. The deficiency of CF+ within molecular clouds suggests that the measurements presented in this work serve exclusively as conservative estimates, establishing lower bounds for both the fluorine abundance and C+ column densities in external galaxies
Effects of SiC content on the mechanical and thermophysical properties of 3D C<sub>f</sub>/SiC–Al composites
No full text3D Cf/SiC–Al composites were achieved through the pressure infiltration of liquid Al–Si alloy into porous 3D Cf/SiC preform, which was produced by different cycles of precursor infiltration and pyrolysis. The effect of silicon carbide volume fraction on the microstructure, anisotropic mechanical response, and thermophysical characteristics of the 3D Cf/SiC–Al composites was investigated. The results demonstrated that the initial microstructure of 3D Cf/SiC can be retained, and the obtained Cf/SiC–Al composites presented remarkable anisotropy characteristics. As the silicon carbide ceramics content increased from 12.5 vol% to 41.8 vol%, the thermal conductivity and thermal expansion coefficient of 3D Cf/SiC–Al composites decreased, whereas the bending strength initially increased and then decreased in the Z-direction. The bending strength perpendicular (Z) to the carbon cloth layer of 3D Cf/SiC–Al composites was higher than that of parallel (X–Y) to the carbon cloth layer. However, a significant anisotropy in the thermal conductivity values was the opposite. The 3D Cf/SiC–Al composite with 1ow ceramic content (17 vol%) had a higher thermal conductivity in the X–Y direction (64 W m−1 K−1) than in the Z-direction (34 W m−1 K−1). The thermal expansion coefficient of all the 3D Cf/SiC–Al composites along the X–Y direction also decreased initially and then increased in the range of 100–450 °C, which presents low expansion characteristics.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.QN/Groeblacher La
Hepatosplenic sarcoidosis: contrast-enhanced ultrasound findings and implications for clinical practice.
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