244 research outputs found
Extraction of tidal channel networks from airborne scanning laser altimetry and aerial photography
The study of the morphodynamics of tidal channel networks is important because of their role in tidal propagation and the evolution of salt-marshes and tidal flats. Channel dimensions range from tens of metres wide and metres deep near the low water mark to only 20-30cm wide and 20cm deep for the smallest channels on the marshes. The conventional method of measuring the networks is cumbersome, involving manual digitising of aerial photographs. This paper describes a semi-automatic knowledge-based network extraction method that is being implemented to work using airborne scanning laser altimetry (and later aerial photography). The channels exhibit a width variation of several orders of magnitude, making an approach based on multi-scale line detection difficult. The processing therefore uses multi-scale edge detection to detect channel edges, then associates adjacent anti-parallel edges together to form channels using a distance-with-destination transform. Breaks in the networks are repaired by extending channel ends in the direction of their ends to join with nearby channels, using domain knowledge that flow paths should proceed downhill and that any network fragment should be joined to a nearby fragment so as to connect eventually to the open sea
Photoemission studies of the near Fermi level spectral weight shifts in FeSe1-xTex superconductor
Our valence band photoelectron spectroscopic studies show a temperature
dependent spectral weight transfer near the Fermi level in the Fe-based
superconductor FeSe1-xTex. Using theoretical band structure calculations we
have shown that the weight transfer is due to the temperature induced changes
in the Fe(Se,Te)4 tetrahedra. These structural changes lead to shifts in the
electron occupancy from the xz/yz and x2-y2 orbitals to the 3z2-r2 orbitals
indicating a temperature induced crossover from a metallic state to an Orbital
Selective Mott (OSM) Phase. Our study presents the observation of a temperature
induced crossover to a low temperature OSM phase in the family of Fe
chalcogenides.Comment: 10 pages, 4 figure
Evolution of Sonar Survey Systems for Sea Floor Studies
Approximately 71% of our planet is covered with oceans. It is also known
that oceans are the last frontiers for the mankind’s survival and therefore it
becomes pertinent that they are studied in great details. It has been found
that the exploration of the oceans can be done more precisely using
acoustics as one of the methods, as the acoustic waves can propagate over
large distances and also using a broad spectrum of frequencies various
issues of the ocean studies can be addressed more effectively than many of
the other methods, both in terms resolution (using high frequency
components) of measuring parameters and over large ranges (using low to
very low frequency components). Currently with the technological
advancement and improved computing algorithms, we have state of art
systems for ocean exploration, which can provide information about the
sea floor, sub-surface including ocean floor classification. These could be
projected in 2-D and 3-D visualization to a great accuracy. Also available
are acoustical methods wherein one can obtain an extremely important
information about water column properties (both in terms of bioinformation
and physical properties), and has great importance as this
water column is the medium for transmission of all kind of
energies(acoustic for short, medium and long ranges and some time light
source for exploration over a very short distance) that are used for
exploration on the oceans. It will therefore be interesting to understand the
progress of underwater acoustics from its very primitive stage, where
acoustic transmission through water medium was used for first time to the
present day highly complex but very advanced acoustic sea-floor
surveying systems. It will also be interesting to know, with a very old
maritime history of using seas for transportation, as to what were the
methods used by early time seafarers to understand depths of the oceans
they were sailing. It has taken almost a century in developing an acoustic
system to arrive at the present day advancement. An attempt has been
made to present a perspective of evolution and advancement in underwater
acoustics and related electronic, material and computational advancement,
starting from the early attempts to the modern day acoustic equipments
Investigation of correlation effects in FeSe and FeTe by LDA + U method
Correlation effects are observed strong in Iron chalcogenides superconductors
by experimental and theoretical investigations. We present a comparative study
of the influence of Coulomb interaction and Hund's coupling in the electronic
structure of FeSe and FeTe. The calculation is based on density functional
theory (DFT) with local density approximation(LDA+U) framework employed in
TB-LMTO ASA code. We found the correlation effects were orbital selective due
to the strength of interorbital hybridization among different Fe-3d orbitals
mediated via chalcogen (Se/Te-p) orbitals is different in both the compounds,
however Coulomb interaction is screened significantly by Te-p bands in FeTe.
Similarly the orbital section is different in both the compounds because of the
difference in the chalcogen height
The role of endoplasmic reticulum stress response in pollen development and heat stress tolerance
Endoplasmic reticulum (ER) stress is defined by a protracted disruption in protein folding and accumulation of unfolded or misfolded proteins in the ER. This accumulation of unfolded proteins can result from excessive demands on the protein folding machinery triggered by environmental and cellular stresses such as nutrient deficiencies, oxidative stress, pathogens, and heat. The cell responds to ER stress by activating a protective pathway termed unfolded protein response (UPR), which comprises cellular mechanisms targeted to maintain cellular homeostasis by increasing the ER’s protein folding capacity. The UPR is especially significant for plants as being sessile requires them to adapt to multiple environmental stresses. While multiple stresses trigger the UPR at the vegetative stage, it appears to be active constitutively in the anthers of unstressed plants. Transcriptome analysis reveals significant upregulation of ER stress-related transcripts in diploid meiocytes and haploid microspores. Interestingly, several ER stress-related genes are specifically upregulated in the sperm cells. The analysis of gene knockout mutants in Arabidopsis has revealed that defects in ER stress response lead to the failure of normal pollen development and enhanced susceptibility of male gametophyte to heat stress conditions. In this mini-review, we provide an overview of the role of ER stress and UPR in pollen development and its protective roles in maintaining male fertility under heat stress conditions
RNA-seq highlights molecular events associated with impaired pollen-pistil interactions following short-term heat stress in Brassica napus
The global climate change is leading to increased frequency of heatwaves with crops getting exposed to extreme temperature events. Such temperature spikes during the reproductive stage of plant development can harm crop fertility and productivity. Here we report the response of short-term heat stress events on the pollen and pistil tissues in a commercially grown cultivar of Brassica napus. Our data reveals that short-term temperature spikes not only affect pollen fitness but also impair the ability of the pistil to support pollen germination and pollen tube growth and that the heat stress sensitivity of pistil can have severe consequences for seed set and yield. Comparative transcriptome profiling of non-stressed and heat-stressed (40°C for 30 min) pollen and pistil (stigma + style) highlighted the underlying cellular mechanisms involved in heat stress response in these reproductive tissues. In pollen, cell wall organization and cellular transport-related genes possibly regulate pollen fitness under heat stress while the heat stress-induced repression of transcription factor encoding transcripts is a feature of the pistil response. Overall, high temperature altered the expression of genes involved in protein processing, regulation of transcription, pollen-pistil interactions, and misregulation of cellular organization, transport, and metabolism. Our results show that short episodes of high-temperature exposure in B. napus modulate key regulatory pathways disrupted reproductive processes, ultimately translating to yield loss. Further investigations on the genes and networks identified in the present study pave a way toward genetic improvement of the thermotolerance and reproductive performance of B. napus varieties
Rapid transcriptional reprogramming associated with heat stress-induced unfolded protein response in developing Brassica napus anthers
Climate change associated increases in the frequency and intensity of extreme temperature events negatively impact agricultural productivity and global food security. During the reproductive phase of a plant’s life cycle, such high temperatures hinder pollen development, preventing fertilization, and seed formation. At the molecular level, heat stress-induced accumulation of misfolded proteins activates a signaling pathway called unfolded protein response (UPR) in the endoplasmic reticulum (ER) and the cytoplasm to enhance the protein folding capacity of the cell. Here, we report transcriptional responses of Brassica napus anthers exposed to high temperature for 5, 15, and 30 min to decipher the rapid transcriptional reprogramming associated with the unfolded protein response. Functional classification of the upregulated transcripts highlighted rapid activation of the ER-UPR signaling pathway mediated by ER membrane-anchored transcription factor within 5 min of heat stress exposure. KEGG pathway enrichment analysis also identified “Protein processing in ER” as the most significantly enriched pathway, indicating that the unfolded protein response (UPR) is an immediate heat stress-responsive pathway during B. napus anther development. Five minutes of heat stress also led to robust induction of the cytosolic HSF-HSP heat response network. Our results present a perspective of the rapid and massive transcriptional reprogramming during heat stress in pollen development and highlight the need for investigating the nature and function of very early stress-responsive networks in plant cells. Research focusing on very early molecular responses of plant cells to external stresses has the potential to reveal new stress-responsive gene networks that can be explored further for developing climate change resilient crops
Biological parts for engineering abiotic stress tolerance in plants
It is vital to ramp up crop production dramatically by 2050 due to the increasing global population and demand for food. However, with the climate change projections showing that droughts and heatwaves becoming common in much of the globe, there is a severe threat of a sharp decline in crop yields. Thus, developing crop varieties with inbuilt genetic tolerance to environmental stresses is urgently needed. Selective breeding based on genetic diversity is not keeping up with the growing demand for food and feed. However, the emergence of contemporary plant genetic engineering, genome-editing, and synthetic biology offer precise tools for developing crops that can sustain productivity under stress conditions. Here, we summarize the systems biology-level understanding of regulatory pathways involved in perception, signalling, and protective processes activated in response to unfavourable environmental conditions. The potential role of noncoding RNAs in the regulation of abiotic stress responses has also been highlighted. Further, examples of imparting abiotic stress tolerance by genetic engineering are discussed. Additionally, we provide perspectives on the rational design of abiotic stress tolerance through synthetic biology and list various bioparts that can be used to design synthetic gene circuits whose stress-protective functions can be switched on/off in response to environmental cues
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