9,213 research outputs found
Designed-in security for cyber-physical systems
An expert from academia, one from a cyber-physical system (CPS) provider, and one from an end asset owner and user offer their different perspectives on the meaning and challenges of 'designed-in security.' The academic highlights foundational issues and talks about emerging technology that can help us design and implement secure software in CPSs. The vendor's view includes components of the academic view but emphasizes the secure system development process and the standards that the system must satisfy. The user issues a call to action and offers ideas that will ensure progress
Cryptic blues: mechanism in sight!
Several plant responses are mediated by blue-light as also UV-A radiation. Until a few years ago, the identity of the blue/UV-A sensing photoreceptors was equivocal. In the past few years, however, the molecular genetic analysis of Arabidopsis mutants has greatly aided in the identification and characterization of blue/UV-A sensing cryptochrome 1 (cry1), cryptochrome 2 (cry2) and phototropin (JK224/ nph1). The cry1 and cry2 receptors, like DNA photolyases, are dual chromophore proteins and may harbour both a flavin (FAD) and a pterin for primarily regulating hypocotyl growth inhibition, cotyledon expansion and flowering time, besides sensing light for entraining endogenous clocks. In contrast, JK224/nph1 anchors another flavin, FMN, and regulates phototropism. In addition to flavins and pterin, evidence is mounting in favour of a carotenoid, zeaxanthin, for regulating blue-light-induced stomatal opening. There is little information on the signalling components acting downstream to blue sensory receptors, but nph1 has an intrinsic kinase domain that on photoexcitation initiates a phosphorelay through interaction with phosphoproteins like NPH3. Although the primary mechanism of action of cry1 and cry2 is unknown, their localization in the nucleus and protein-protein interaction with phytochromes indicates that they may directly regulate changes in gene expression. The occurrence of cryptochromes in both plants and animals indicates their ubiquitous nature and a prominent role in regulating diverse responses
Floral induction in a photoperiodically insensitive duckweed, Lemna paucicostata LP6
The effects of 20 amino acids and two amides were studied on the flowering of a photoperiodically insensitive duckweed, Lemna paucicostata LP6. Alanine, asparagine, aspartate, cystine, glutamate, glutamine, glycine, lysine, methionine, proline, serine, and threonine induced flowering under a photoperiodic regime of 16 hours light and 8 hours darkness. Among these, glutamate and aspartate were found to be the most effective for flower induction. These acids could initiate flowering even at 5×10-7 molar level, though maximal flowering (about 80%) was obtained at 10-5 molar. Change in the photoperiodic schedule or the pH of the nutrient medium did not influence glutamate- or aspartate-induced flowering. The low concentrations at which glutamate and aspartate are effective suggests that they may have a regulatory role rather than simply acting as metabolites
A photonic crystal cavity-optical fiber tip nanoparticle sensor for biomedical applications
We present a sensor capable of detecting solution-based nanoparticles using
an optical fiber tip functionalized with a photonic crystal cavity. When sensor
tips are retracted from a nanoparticle solution after being submerged, we find
that a combination of convective fluid forces and optically-induced trapping
cause an aggregation of nanoparticles to form directly on cavity surfaces. A
simple readout of quantum dot photoluminescence coupled to the optical fiber
shows that nanoparticle presence and concentration can be detected through
modified cavity properties. Our sensor can detect both gold and iron oxide
nanoparticles and can be utilized for molecular sensing applications in
biomedicine.Comment: 13 pages, 5 figure
Inelastic X-ray scattering in correlated (Mott) insulators
We calculate the inelastic light scattering from X-rays, which allows the
photon to transfer both energy and momentum to the strongly correlated charge
excitations. We find that the charge transfer peak and the low energy peak both
broaden and disperse through the Brillouin zone similar to what is seen in
experiments in materials like Ca_2 Cu O_2 Cl_2.Comment: 5 pages Revtex4, 6 figure
Searching for Galactic White Dwarf Binaries in Mock LISA Data using an F-Statistic Template Bank
We describe an F-statistic search for continuous gravitational waves from
galactic white-dwarf binaries in simulated LISA Data. Our search method employs
a hierarchical template-grid based exploration of the parameter space. In the
first stage, candidate sources are identified in searches using different
simulated laser signal combinations (known as TDI variables). Since each source
generates a primary maximum near its true "Doppler parameters" (intrinsic
frequency and sky position) as well as numerous secondary maxima of the
F-statistic in Doppler parameter space, a search for multiple sources needs to
distinguish between true signals and secondary maxima associated with other,
"louder" signals. Our method does this by applying a coincidence test to reject
candidates which are not found at nearby parameter space positions in searches
using each of the three TDI variables. For signals surviving the coincidence
test, we perform a fully coherent search over a refined parameter grid to
provide an accurate parameter estimation for the final candidates. Suitably
tuned, the pipeline is able to extract 1989 true signals with only 5 false
alarms. The use of the rigid adiabatic approximation allows recovery of signal
parameters with errors comparable to statistical expectations, although there
is still some systematic excess with respect to statistical errors expected
from Gaussian noise. An experimental iterative pipeline with seven rounds of
signal subtraction and re-analysis of the residuals allows us to increase the
number of signals recovered to a total of 3419 with 29 false alarms.Comment: 29 pages, 11 figures; submitted to Classical and Quantum Gravit
Phytochrome modulation of calcium fluxes in wheat (Triticum aestivum L.) protoplasts
Employing the metallochromic dye murexide and by monitoring the uptake of radiolabelled calcium, photoreversible calcium fluxes were measured in wheat leaf protoplast suspensions. Results obtained by both methods were identical - red light promoted and subsequent far-red irradiation reversed an influx of Ca++ ions into the protoplasts. These findings imply phytochrome regulation of Ca++ fluxes across the plasma membrane. The influx of Ca++ stimulated by 2 min red irradiation could be maintained in total darkness for the initial 16-18 min after illumination, after which a 6-8 min efflux process was triggered and the basal Ca++ level restored. Verapamil, a calcium channel blocker, inhibited the red-promoted influx, whereas the far-red mediated efflux could be checked by the use of the ATPase inhibitor vanadate, and also by the calmodulin antagonist chlorpromazine, thus suggesting a role of ion channels and pumps in phytochrome-controlled Ca++ fluxes. The possible involvement of phosphoinositides in phytochrome-modulated calcium fluxes was also investigated
Apomixis: an enigma with potential applications
Apomixis has been the focus of research in plant sciences
in recent years with lot of scope for crop improvement.
It results in clonal progeny without fertilization, having
maternal genetic constitution. The impact of introducing
apomixis in crop plants could be significant mainly for
its use in fixation of hybrid vigour. Because of epigenetic
barriers, introgression of apomixis from a close
relative to a sexual crop plant by conventional plant
breeding methods could not generate expected results.
Recent developments in plant molecular biology and
biotechnology can help in developing potential strategies.
This article summarizes various aspects of apomixis
research that are being followed in India and abroad
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