The premature abscission of flowers and fruits limits crop yield under environmental stress. Drought-induced flower drop in tomato plants was found to be regulated by phytosulfokine (PSK), a peptide ...hormone previously known for its growth-promoting and immune-modulating activities. PSK formation in response to drought stress depends on phytaspase 2, a subtilisin-like protease of the phytaspase subtype that generates the peptide hormone by aspartate-specific processing of the PSK precursor in the tomato flower pedicel. The mature peptide acts in the abscission zone where it induces expression of cell wall hydrolases that execute the abscission process. Our results provide insight into the molecular control of abscission as regulated by proteolytic processing to generate a small plant peptide hormone.
Confocal Raman spectroscopy has emerged as a major, versatile workhorse for the non-invasive characterization of graphene. Although it is successfully used to determine the number of layers, the ...quality of edges, and the effects of strain, doping and disorder, the nature of the experimentally observed broadening of the most prominent Raman 2D line has remained unclear. Here we show that the observed 2D line width contains valuable information on strain variations in graphene on length scales far below the laser spot size, that is, on the nanometre-scale. This finding is highly relevant as it has been shown recently that such nanometre-scaled strain variations limit the carrier mobility in high-quality graphene devices. Consequently, the 2D line width is a good and easily accessible quantity for classifying the crystalline quality, nanometre-scale flatness as well as local electronic properties of graphene, all important for future scientific and industrial applications.
We present magneto-Raman spectroscopy measurements on suspended graphene to investigate the charge carrier density-dependent electron-electron interaction in the presence of Landau levels. Utilizing ...gate-tunable magnetophonon resonances, we extract the charge carrier density dependence of the Landau level transition energies and the associated effective Fermi velocity v_{F}. In contrast to the logarithmic divergence of v_{F} at zero magnetic field, we find a piecewise linear scaling of v_{F} as a function of the charge carrier density, due to a magnetic-field-induced suppression of the long-range Coulomb interaction. We quantitatively confirm our experimental findings by performing tight-binding calculations on the level of the Hartree-Fock approximation, which also allow us to estimate an excitonic binding energy of ≈6 meV contained in the experimentally extracted Landau level transitions energies.
Glucocorticoids (GCs) are widely used to treat inflammatory diseases such as multiple sclerosis (MS). They predominantly act through the GC receptor, a member of the nuclear receptor superfamily that ...controls transcription by several different mechanisms. Owing to its ubiquitous expression, there are a variety of cell types that could serve as GC targets in the pathogenesis and treatment of MS. This brings about a great diversity of mechanisms potentially involved in the modulation of neuroinflammation by GCs, including the induction of apoptosis, repression of pro‐inflammatory mediators and the expansion of myeloid‐derived suppressor cells. Nevertheless, it is not well understood which of these mechanisms are essential for therapeutic efficacy. In this review, we summarise findings made concerning the actions of GCs in MS and its animal model experimental autoimmune encephalomyelitis, and also elucidate current concepts and developments that pertain to this clinically highly relevant treatment regimen.
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•NMR experiments beyond 200,000 atm (20GPa) are reported for the first time.•The SNR is two orders of magnitude higher compared to other approaches.•The RF time resolution is suitable ...for exciting and recording broad NMR signals.•Single crystal NMR on a high-temperature superconductor (YBa2Cu3O7-δ) is shown.•An insulator-to-metal transition in AgInTe2 up to 20.2GPa was found.
Pressure-induced changes in the chemical or electronic structure of solids require pressures well into the Giga-Pascal (GPa) range due to the strong bonding. Anvil cell designs can reach such pressures, but their small and mostly inaccessible sample chamber has severely hampered NMR experiments in the past. With a new cell design that has a radio frequency (RF) micro-coil in the high pressure chamber, NMR experiments beyond 20 Giga-Pascal are reported for the first time. 1H NMR of water shows sensitivity and resolution obtained with the cells, and 63Cu NMR on a cuprate superconductor (YBa2Cu3O7-δ) demonstrates that single-crystals can be investigated, as well. 115In NMR of the ternary chalcogenide AgInTe2 discovers an insulator-metal transition with shift and relaxation measurements. The pressure cells can be mounted easily on standard NMR probes that fit commercial wide-bore magnets with regular cryostats for field- and temperature-dependent measurements ready for many applications in physics and chemistry.
Nuclear factor-κB(NF-κB) and p53 critically determine cancer development and progression. Defining the cross talk between these transcription factors can expand our knowledge on molecular mechanisms ...of tumorigenesis. Here, we show that induction of replicational stress activates NF-κB p65 and triggers its interaction with p53 in the nucleus. Experiments with knockout cells show that p65 and p53 are both required for enhanced NF-κ activity during S-phase checkpoint activation involving ataxiatelangiectasia mutated and checkpoint kinase-1. Accordingly, the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) also triggers formation of a transcriptionally active complex containing nuclear p65 and p53 on kB response elements. Gene expression analyses revealed that, independent of NF-κB activation in the cytosol, TNF-induced NF-κB-directed gene expression relies on p53. Hence, p53 is unexpectedly necessary for NF-κB-mediated gene expression induced by atypical and classical stimuli. Remarkably, data from gain- and loss-of function approaches argue that anti-apoptotic NF-κB p65 activity is constitutively evoked by a p53 hot-spot mutant frequently found in tumors. Our observations suggest explanations for the outstanding question why p53 mutations rather than p53 deletions arise in tumors of various origins. Oncogene (2010) 29, 2795-2806; doi: 10.1038/onc.2010.46; published online 1 March 2010 Keywords: NF-kB; p53; S-phase; hydroxyurea; TNF-a; apoptosis
Evaluators are often called upon to assess the effects of programs. To assess a program effect, evaluators need a clear understanding of how a program effect is defined. Arguably, the most widely ...used definition of a program effect is the counterfactual one. According to the counterfactual definition, a program effect is the difference between what happened after the program was implemented and what would have happened if the program had not been implemented, but everything else had been the same. Such a definition is often said to be linked to the use of quantitative methods. But the definition can be used just as effectively with qualitative methods. To demonstrate its broad applicability in both qualitative and quantitative research, I show how the counterfactual definition undergirds seven common approaches to assessing effects. It is not clear how any alternative to the counterfactual definition is as generally applicable as the counterfactual definition.
Nuclear magnetic resonance (NMR) experiments at fields up to 58 T in pulsed magnets at the Dresden High Magnetic Field Laboratory are reported. The challenge to resolve NMR shifts in these ...time-dependent fields is addressed for the first time, and it is shown that this can indeed be accomplished with high precision with an internal reference. As a result, signal averaging is possible during a single magnetic field pulse, but also for multiple pulses. Thus, even very weak signals can in principle be recorded and their shifts can be determined. In a second set of experiments, the measurement of nuclear relaxation is investigated. Using adiabatic inversion with the inherent time dependence of the magnetic field and small-angle inspection, it is shown that relaxation measurements are possible, as well. The shift experiments were performed with super(27)Al NMR on a mixture of aluminum metal and a Linde type A zeolite. For the relaxation studies, super(27)Al NMR and super(69)Ga NMR on the metals aluminum and gallium were preformed, respectively.
Optical-microphysical cirrus model Reichardt, J.; Reichardt, S.; Lin, R.-F. ...
Journal of Geophysical Research - Atmospheres,
27 November 2008, Letnik:
113, Številka:
D22
Journal Article
Recenzirano
Odprti dostop
A model is presented that permits the simulation of the optical properties of cirrus clouds as measured with depolarization Raman lidars. It comprises a one-dimensional cirrus model with explicit ...microphysics and an optical module that transforms the microphysical model output to cloud and particle optical properties. The optical model takes into account scattering by randomly oriented or horizontally aligned planar and columnar monocrystals and polycrystals. Key cloud properties such as the fraction of plate-like particles and the number of basic crystals per polycrystal are parameterized in terms of the ambient temperature, the nucleation temperature, or the mass of the particles. The optical-microphysical model is used to simulate the lidar measurement of a synoptically forced cirrostratus in a first case study. It turns out that a cirrus cloud consisting of only monocrystals in random orientation is too simple a model scenario to explain the observations. However, good agreement between simulation and observation is reached when the formation of polycrystals or the horizontal alignment of monocrystals is permitted. Moreover, the model results show that plate fraction and morphological complexity are best parameterized in terms of particle mass, or ambient temperature which indicates that the ambient conditions affect cirrus optical properties more than those during particle formation. Furthermore, the modeled profiles of particle shape and size are in excellent agreement with in situ and laboratory studies, i.e., (partly oriented) polycrystalline particles with mainly planar basic crystals in the cloud bottom layer, and monocrystals above, with the fraction of columns increasing and the shape and size of the particles changing from large thin plates and long columns to small, more isometric crystals from cloud center to top. The findings of this case study corroborate the microphysical interpretation of cirrus measurements with lidar as suggested previously.
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•NMR shift measurements in pulsed magnets (56T) are reported for the first time.•Signal averaging during single field pulse is possible.•Signal averaging across three field pulses are ...combined to improve SNR.•T1 measurements in pulsed field (58T) are reported for the first time.
Nuclear magnetic resonance (NMR) experiments at fields up to 58T in pulsed magnets at the Dresden High Magnetic Field Laboratory are reported. The challenge to resolve NMR shifts in these time-dependent fields is addressed for the first time, and it is shown that this can indeed be accomplished with high precision with an internal reference. As a result, signal averaging is possible during a single magnetic field pulse, but also for multiple pulses. Thus, even very weak signals can in principle be recorded and their shifts can be determined. In a second set of experiments, the measurement of nuclear relaxation is investigated. Using adiabatic inversion with the inherent time dependence of the magnetic field and small-angle inspection, it is shown that relaxation measurements are possible, as well. The shift experiments were performed with 27Al NMR on a mixture of aluminum metal and a Linde type A zeolite. For the relaxation studies, 27Al NMR and 69Ga NMR on the metals aluminum and gallium were preformed, respectively.
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