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The CIN-TCP transcription factors promote commitment to differentiation in Arabidopsis leaf pavement cells via both auxin-dependent and independent pathways
No full textCells in organ primordia undergo active proliferation at an early stage to generate sufficient number, before exiting proliferation and entering differentiation. However, how the actively proliferating cells are developmentally reprogrammed to acquire differentiation potential during organ maturation is unclear. Here, we induced a microRNA-resistant form of TCP4 at various developmental stages of Arabidopsis leaf primordium that lacked the activity of TCP4 and its homologues and followed its effect on growth kinematics. By combining this with spatio-temporal gene expression analysis, we show that TCP4 commits leaf cells within the transition zone to exit proliferation and enter differentiation. A 24-hour pulse of TCP4 activity was sufficient to impart irreversible differentiation competence to the actively dividing cells. A combination of biochemical and genetic analyses revealed that TCP4 imparts differentiation competence by promoting auxin response as well as by directly activating HAT2, a HD-ZIP II transcription factor-encoding gene that also acts downstream to auxin response. Our study offers a molecular link between the two major organ maturation factors, CIN-like TCPs and HD-ZIP II transcription factors and explains how TCP activity restricts the cell number and final size in a leaf. Author summary Cells in a young organ primordium proliferate to generate sufficient number, before they exit division cycle and enter differentiation programme at later stages. While factors that drive cell cycle progression have been identified and studied in detail in diverse eukaryotic species, developmental factors that promote exit from division and entry into differentiation are less known, especially in the plant kingdom. Here, we show that the class II TCP proteins, notably TCP4, irreversibly reprogram the mitotic cells to exit division and acquire differentiation competence by auxin response as well as direct activation of HAT2 transcription. Our work offers a molecular link between class II TCP and HD-ZIP II genes during the cell differentiation and leaf maturation
Search for excited leptons in final states in proton-proton collisions at root s=13 TeV
No full textA search is presented for excited electrons and muons in final states at the LHC. The search is based on a data sample corresponding to an integrated luminosity of 35.9 fb(-1) of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector in 2016. This is the first search for excited leptons at = 13 TeV. The observation is consistent with the standard model background prediction, and the most stringent exclusion limits to date are set on the excited lepton mass and the compositeness scale, at 95% confidence level. Excited electrons and muons are excluded for masses below 3.9 and 3.8 TeV, respectively, under the assumption that the excited lepton mass equals the compositeness scale. The best observed limit on the compositeness scale is obtained with an excited lepton mass of around 1.0 TeV, excluding values below 25 TeV for both excited electrons and muons
Comparative analysis of thymic subpopulations during different modes of atrophy identifies the reactive oxygen species scavenger, N-acetyl cysteine, to increase the survival of thymocytes during infection-induced and lipopolysaccharide-induced thymic atrophy
No full textThe development of immunocompetent T cells entails a complex pathway of differentiation in the thymus. Thymic atrophy occurs with ageing and during conditions such as malnutrition, infections and cancer chemotherapy. The comparative changes in thymic subsets under different modes of thymic atrophy and the mechanisms involved are not well characterized. These aspects were investigated, using mice infected with Salmonella Typhimurium, injection with lipopolysaccharide (LPS), an inflammatory but non-infectious stimulus, etoposide (Eto), a drug used to treat some cancers, and dexamethasone (Dex), a steroid used in some inflammatory diseases. The effects on the major subpopulations of thymocytes based on multicolour flow cytometry studies were, first, the CD4(-)CD8(-) double-negative (DN) cells, mainly DN2-4, were reduced with infection, LPS and Eto treatment, but not with Dex. Second, the CD8(+)CD3(lo) immature single-positive cells (ISPs) were highly sensitive to infection, LPS and Eto, but not Dex. Third, treatment with LPS, Eto and Dex reduced all three subpopulations of CD4(+)CD8(+) double-positive (DP) thymocytes, i.e. DP1, DP2 and DP3, but the DP3 subset was relatively more resistant during infection. Fourth, both CD4(+) and CD8(+) single-positive (SP) thymocytes were lowered by Eto and Dex, but not during infection. Notably, LPS lowered CD4(+) SP subsets, whereas the CD8(+) SP subsets were relatively more resistant. Interestingly, the reactive oxygen species quencher, N-acetyl cysteine, greatly improved the survival of thymocytes, especially DNs, ISPs and DPs, during infection and LPS treatment. The implications of these observations for the development of potential thymopoietic drugs are discussed
Polarization discontinuity driven two dimensional electron gas at A(2)Mo(3)O(8)/B2Mo3O8 (A, B: Zn, Mg, Cd) interfaces
No full textWe propose a novel heterostructure system consisting of compounds with chemical formula A(2)Mo(3)O(8) (A, B: Zn, Mg, Cd) that can host a two-dimensional electron/hole gas (2DEG/2DHG). The formation of a 2DEG/2DHG in these heterostructures, which have a low interfacial strain, is driven by a polarization discontinuity at the interface. The sheet carrier densities and charge localization in these heterostructures are comparable to other well-known heterostructures that host 2DEG opening up the possibility of a wide variety of applications. Published under license by AIP Publishing
High-power, cascaded random Raman fiber laser with near complete conversion over wide wavelength and power tuning
No full textCascaded Raman fiber lasers based on random distributed feedback (RDFB) are proven to be wavelength agile, enabling high powers outside rare-earth doped emission windows. In these systems, by simply adjusting the input pump power and wavelength, high-power lasers can be achieved at any wavelength within the transmission window of optical fibers. However, there are two primary limitations associated with these systems, which in turn limits further power scaling and applicability. Firstly, the degree of wavelength conversion or spectral purity (percentage of output power in the desired wavelength band) that can be achieved is limited. This is attributed to intensity noise transfer of input pump source to Raman Stokes orders, which causes incomplete power transfer reducing the spectral purity. Secondly, the output power range over which the high degree of wavelength conversion is maintained is limited. This is due to unwanted Raman conversion to the next Stokes order with increasing power. Here, we demonstrate a high-power, cascaded Raman fiber laser with near complete wavelength conversion over a wide wavelength and power range. We achieve this by culmination of two recent developments in this field. We utilize our recently proposed filtered feedback mechanism to terminate Raman conversion at arbitrary. wavelengths, and we use the recently demonstrated technique (by J Dong and associates) of low-intensity noise pump sources (Fiber ASE sources) to achieve high-purity Raman conversion. Pump-limited output powers >34W and wavelength conversions >97% (highest till date) were achieved over a broad - 1.1 mu m to 1.5 mu m tuning range. In addition, high spectral purity (>90%) was maintained over a broad output power range (>15%), indicating the robustness of this laser against input power variations. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen
Fine-Scale Tracking of Ambient Temperature and Movement Reveals Shuttling Behavior of Elephants to Water
No full textMovement strategies of animals have been well studied as a function of ecological drivers (e.g., forage selection and avoiding predation) rather than physiological requirements (e.g., thermoregulation). Thermal stress is a major concern for large mammals, especially for savanna elephants (Loxodonta africana), which have amongst the greatest challenge for heat dissipation in hot and arid environments. Therefore, elephants must make decisions about where and how fast to move to reduce thermal stress. We tracked 14 herds of elephant in Kruger National Park (KNP), South Africa, for 2 years, using GPS collars with inbuilt temperature sensors to examine the influence of temperature on movement strategies, particularly when accessing water. We first confirmed that collar-mounted temperature loggers captured hourly variation in relative ambient temperatures across the landscape, and, thus, could be used to predict elephant movement strategies at fine spatio-temporal scales. We found that elephants moved slower in more densely wooded areas, but, unexpectedly, moved faster at higher temperatures, especially in the wet season compared to the dry season. Notably, this speed of movement was highest when elephants were approaching and leaving water sources. Visits to water showed a periodic shuttling pattern, with a peak return rate of 10-30 h, wherein elephants were closest to water during the hotter times of the day, and spent longer at water sources in the dry season compared to the wet season. When elephants left water, they showed low fidelity to the same water source, and traveled farther in the dry season than in the wet season. In KNP, where water is easily accessible, and the risk of poaching is low, we found that elephants use short, high-speed bursts of movement to get to water at hotter times of day. This strategy not only provides the benefit of predation risk avoidance, but also allows them to use water to thermoregulate. We demonstrate that ambient temperature is an important predictor of movement and water use across the landscape, with elephants responding facultatively to a ``landscape of thermal stress.'
Image reconstruction from undersampled confocal microscopy data using multiresolution based maximum entropy regularization
No full textWe consider the problem of reconstructing 2D images from randomly under-sampled confocal microscopy samples. The well known and widely celebrated total variation regularization, which is the l(1) norm of derivatives, turns out to be unsuitable for this problem; it is unable to handle both noise and under-sampling together. This issue is linked with the notion of phase transition phenomenon observed in compressive sensing research, which is essentially the break-down of total variation methods, when sampling density gets lower than certain threshold. The severity of this breakdown is determined by the so-called mutual incoherence between the derivative operators and measurement operator. In our problem, the mutual incoherence is low, and hence the total variation regularization gives serious artifacts in the presence of noise even when the sampling density is not very low. There has been very few attempts in developing regularization methods that perform better than total variation regularization for this problem. We develop a multi-resolution based regularization method that is adaptive to image structure. In our approach, the desired reconstruction is formulated as a series of coarse-to-fine multi-resolution reconstructions; for reconstruction at each level, the regularization is constructed to be adaptive to the image structure, where the information for adaption is obtained from the reconstruction obtained at coarser resolution level. This adaptation is achieved by using maximum entropy principle, where the required adaptive regularization is determined as the maximizer of entropy subject to the information extracted from the coarse reconstruction as constraints. We also utilize the directionally adaptive second order derivatives for constructing the regularization with directions guided by the given coarse reconstruction, which leads to an improved suppression of artifacts. We demonstrate the superiority of the proposed regularization method over existing ones using several reconstruction examples
Fabrication and Characterization of Toughened Nanocomposites Based on TiO2 Nanowire-Epoxy System
No full textTiO2(B) nanowires (TiO2(B)-NWs) were synthesized and characterized by X-ray diffraction, and Scanning Electron Microscopy (SEM) micrographs and the influence of different morphologies of TiO2 nanostructures on the mechanical performance of epoxy nanocomposites were thoroughly investigated. Transmission Optical Micrograph images of TiO2(B)-NW/epoxy nanosuspension reveals an excellent dispersion of TiO2(B)-NWs in the epoxy matrix. Tensile strength (similar to 26%), tensile modulus (similar to 16%), and fracture toughness (similar to 136%) improved remarkably for TiO2(B)-NWs modified epoxy composites. The mechanism that paved way to the enhancement in the fracture toughness of the TiO2(B)-NW/epoxy nanocomposites was evaluated. SEM micrographs disclose that the phenomena of shear yielding, crack deflection and crack bridging are responsible for the improved fracture toughness of TiO2(B)-NW/epoxy composite. Moreover, the analysis of visco-elastic properties revealed a very high modulus and improved T-g for the TiO2(B)-NW/epoxy composites when compared with neat epoxy owing to better filler/matrix interfacial interaction between TiO2(B)-NWs and epoxy matrix. This was further confirmed by quantitative analysis of the constrained region and by the evaluation of the interaction parameter B. TGA study shows that the thermal stability of composites are not compromised by the incorporation of TiO2 nanofillers. The obtained results can be considered as beneficial in the manufacture of components with higher strength-to-weight ratios for such uses as windmill blades or aircraft components. POLYM. COMPOS., 40:2629-2638, 2019. (c) 2018 Society of Plastics Engineer
A Performance Comparison Between beta-Ga2O3 and GaN HEMTs
No full textWe report on the quantitative estimates of various metrics of performance for beta-Ga2O3-based high electron mobility transistors (HEMTs) for RF and power applications and compare them with III-nitride devices. Device parameters such as electron velocity and current density are estimated based on an optical phonon model reported earlier. 2-D simulation using an appropriate velocity-field relationshipwas employed to study the device characteristics and to assess the RF performance. It is found that despite a lower cutoff frequency, beta-Ga2O0 HEMTs are likely to provide higher RF output power compared to GaN HEMTs in the low-frequency regime. However, the thermal resistance (TR) and the channel temperature of beta-Ga2O3 HEMTs are expected to be significantly higher than those of GaN HEMTs which will pose serious limitations on heat dissipation. beta-Ga2O3 modulation doped field effect transistor on extremely thinned substrates will have similar TR s as compared to GaN devices on GaN substrates. The cutoff frequency was found to drop by 50% as the power dissipation increases from 1 to 7 W/mm. On the other hand, for estimates of dc power switching performance, we estimate the net losses as a function of device periphery and find that similar to 8x-10x lower electron mobility in Ga2O3 devices compared to that in AlGaN/GaN HEMTs will limit its dc switching as well as its ON-state performance in terms of efficiency, loss, and current carrying capability although the blocking voltage can be much higher than in GaN