31,961 research outputs found
Critical comments on the constancy of the speed of light
Criticisms on the theory of the constancy of the speed of light are answered. It is shown that the new theory is not logically inconsistent for the reasons expressed
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Quantifying the reliability of four global datasets for drought monitoring over a semiarid region
Drought is one of the most relevant natural disasters, especially in arid regions such as Iran. One of the requirements to access reliable drought monitoring is long-term and continuous high-resolution precipitation data. Different climatic and global databases are being developed and made available in real time or near real time by different agencies and centers; however, for this purpose, these databases must be evaluated regionally and in different local climates. In this paper, a near real-time global climate model, a data assimilation system, and two gridded gauge-based datasets over Iran are evaluated. The ground truth data include 50 gauges from the period of 1980 to 2010. Drought analysis was carried out by means of the Standard Precipitation Index (SPI) at 2-, 3-, 6-, and 12-month timescales. Although the results show spatial variations, overall the two gauge-based datasets perform better than the models. In addition, the results are more reliable for the western portion of the Zagros Range and the eastern region of the country. The analysis of the onsets of the 6-month moderate drought with at least 3 months’ persistence indicates that all datasets have a better performance over the western portion of the Zagros Range, but display poor performance over the coast of the Caspian Sea. Base on the results of this study, the Modern-Era Retrospective Analysis for Research and Applications (MERRA) dataset is a preferred alternative for drought analysis in the region when gauge-based datasets are not available
Speed of light as measured by two terrestrial stable clocks
Despite the recent criticism within the special theory of relativity, there exists an arrangement of stable clocks rotating with the earth which predicts diurnal variations of the one-way speed of light, as suggested previously
Quantum gravity at a TeV and the renormalization of Newton's constant
We examine whether renormalization effects can cause Newton¿s constant to change dramatically with energy, perhaps even reducing the scale of quantum gravity to the TeV region without the introduction of extra dimensions. We examine a model that realizes this possibility and describe experimental signatures from the production of small black holes
Invisible Higgs boson, continuous mass fields and unHiggs mechanism
We explore the consequences of an electroweak symmetry breaking sector which
exhibits approximately scale invariant dynamics -- i.e., nontrivial fixed point
behavior, as in unparticle models. One can think of an unHiggs as a composite
Higgs boson with a continuous mass distribution. We find it convenient to
represent the unHiggs in terms of a Kallen-Lehmann spectral function, from
which it is simple to verify the generation of gauge boson and fermion masses,
and unitarization of WW scattering. We show that a spectral function with broad
support, which corresponds to approximate fixed point behavior over an extended
range of energy, can lead to an effectively invisible Higgs particle, whose
decays at LEP or LHC could be obscured by background.Comment: 8 page
Analysis of the Relationship Between Microstructure and Elastic Properties of the Cell Wall
A three-dimensional analysis of the relationship between the microstructure and the anisotropic elastic properties of the cell wall was made, using the theory of composite materials. In particular, the influence of the orientation of microfibrils in each layer, crossed helical structure, thickness of layers, and the spacing between the rectangular reinforced microfibrils to such properties were explored; spacing between microfibrils in each wall layer was found to be critical, and presence of crossed helices in the Sa layer and the S2 micro-fibril angles was found significant in relation to elastic properties. Numerical data of all elastic constants of the cell wall were evaluated for five hypothetical models that included the fibers of earlywood, latewood, and compression wood. Theoretical data of the axial Young's modulus of the wood fibers were compared with those values obtained from static tension tests and sonic tests by other investigators. The inadequacy of the technique used in the static tension tests of wood fibers was discussed, and a proper approach for such analysis was suggested
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