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Search Results: 1 - 10 of 224040 matches for " R. Merlin "
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An Exactly Solvable Model of an Avalanche-Type Measuring Device: Macroscopic Distinctiveness and Wavefunction Collapse
R. Merlin
Physics , 2005,
Abstract: A quantum many-body model is presented with features similar to those of certain particle detectors. The energy spectrum contains a single metastable 'ready'-state and macroscopically-distinct 'pointer' states. Measurements do not pose paradoxes or require interventions outside the field theory formalism. Transitions into classical-like states can be triggered by a single particle with help of the thermal bath. Schroedinger cat states are associated with superpositions of inequivalent vacua, thus relating wavefunction collapse to the dynamics of symmetry breaking in phase transformations.
Comment on "Perfect imaging with positive refraction in three dimensions"
R. Merlin
Physics , 2010, DOI: 10.1103/PhysRevA.82.057801
Abstract: Leonhard and Philbin [Phys. Rev. A 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit.
Imaging with an Almost Perfect Lens
R. Merlin
Physics , 2003,
Abstract: The problem of imaging for a nearly-perfect lens, namely, a slab of a left-handed material with refractive index n = -(1-sigma)^1/2 is solved analytically for |sigma| << 1. The electromagnetic field behavior is determined largely by singularities arising from the excitation of surface polaritons with wavevector q -->oo. Depending on the sign of sigma, the near field is either odd or even with respect to the lens middle plane. Images exhibit an anomalous interference pattern with length scale determined by the width of the slab. Consistent with recent studies by Smith et al. [Appl. Phys. Lett. 82, 1506 (2003)] and G'omez-Santos [Phys. Rev. Lett. 90, 077401 (2003)], the resolution depends logarithmically on |sigma|.
Near-Field Focusing Plates and Their Design
A. Grbic,R. Merlin
Physics , 2007, DOI: 10.1109/TAP.2008.929436
Abstract: This paper describes the design of near-field focusing plates, which are grating-like structures that can focus electromagnetic radiation to spots or lines of arbitrarily small subwavelength dimension. A general procedure is outlined for designing a near-field plate given a desired image, and its implementation at microwave frequencies is discussed. Full-wave (method of moments) simulations clearly demonstrate the near-field plate's ability to overcome the diffraction limit. Finally, it is shown that the performance of near-field plates is weakly affected by losses.
Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons
J. K. Wahlstrand,R. Merlin
Physics , 2003, DOI: 10.1103/PhysRevB.68.054301
Abstract: We report on the generation of coherent phonon polaritons in ZnTe, GaP and LiTaO$_{3}$ using ultrafast optical pulses. These polaritons are coupled modes consisting of mostly far-infrared radiation and a small phonon component, which are excited through nonlinear optical processes involving the Raman and the second-order susceptibilities (difference frequency generation). We probe their associated hybrid vibrational-electric field, in the THz range, by electro-optic sampling methods. The measured field patterns agree very well with calculations for the field due to a distribution of dipoles that follows the shape and moves with the group velocity of the optical pulses. For a tightly focused pulse, the pattern is identical to that of classical Cherenkov radiation by a moving dipole. Results for other shapes and, in particular, for the planar and transient-grating geometries, are accounted for by a convolution of the Cherenkov field due to a point dipole with the function describing the slowly-varying intensity of the pulse. Hence, polariton fields resulting from pulses of arbitrary shape can be described quantitatively in terms of expressions for the Cherenkov radiation emitted by an extended source. Using the Cherenkov approach, we recover the phase-matching conditions that lead to the selection of specific polariton wavevectors in the planar and transient grating geometry as well as the Cherenkov angle itself. The formalism can be easily extended to media exhibiting dispersion in the THz range. Calculations and experimental data for point-like and planar sources reveal significant differences between the so-called superluminal and subluminal cases where the group velocity of the optical pulses is, respectively, above and below the highest phase velocity in the infrared.
R. Johnsi Rani,C. Merlin Rose
International Research Journal of Pharmacy , 2012,
Abstract: One of the unique properties of living organisms is growth. Growth is a complex phenomenon and represents the end result of metabolic pathways bringing about an overall irreversible change. Growth is the final morphological expression of various metabolic activities taking place in the plant. Salt stress influences all these metabolic activities and hence influences growth also. Salt stress is caused by concentrations greater than the required for optimum growth of a typical crop plant. If excessive amounts of salt enter into the plant, salt will eventually rise to toxic levels and reduce the photosynthetic leaf area of the plant that cannot sustain growth. Because of the importance of wheat in Indian Agricultural Economy and in order to understand the processes that give rise to tolerance of salt and to identify the salt stress proteins into salt stress effect on plant growth was studied using different salt solutions like copper sulphate, cadmium chloride and zinc sulphate with different concentrations like 200μM, 150 μM and100 μM.
Lab-Scale Performance Evaluation of Vertical Flow Reed Beds for the Treatment of Chlorobenzene Contaminated Groundwater  [PDF]
Gerard Merlin, Nathalie Cottin
Journal of Environmental Protection (JEP) , 2012, DOI: 10.4236/jep.2012.328099
Abstract: Chlorinated Benzenes (CBs) that were released into the environment contaminate groundwater at many existing and former industrial sites. A research program was initiated to investigate the ecoremediation of CBs contaminated groundwater using subsurface flow constructed wetlands. Four lab-scale experiments were performed to evaluate re- moval efficiency with different operation conditions. The first experiment was achieved with two different solid-state materials: a peat and a lava stone (pozzolana). In order to stimulate biological activity, organic matter coming from an aged Vertical Flow Constructed Wetlands (VFCW) was added to the media. Mass balance was determined to assess the fate of these pollutants in this system. The biofiltres of the second experiment were constructed with the same materials but bioaugmentation was realized by adding organic matter of VFCW or by bacteria inoculums. Peat and pozzolana biofiltres planted with Phragmites australis constituted the third experiment to evaluate the effect of plants. Bioaugmen- tation was constituted by the addition of OM coming from aged VFCW. Compost mixed with pozzolana was the solid-state material of the fourth experiment. Columns were made of two stages. The first stage was unplanted and the second stage was planted with Phragmites. Peat has been replaced by compost, a renewable material. Lab-scale biofil- tres remove CBs with an efficiency of 70% - 99%, depending on studied media and conditions. Greater efficiency was observed with bioaugmented media. Volatilization was very low (<0.2%) and the detection of chlorides in water indi- cated the occurrence of biodegradation. The experiments have shown that organic solid-state materials (compost or peat) are useful for groundwater remediation, with higher treatment efficiency than pozzolana material. Bioaugmentation increased biological activity. Clogging of biofiltres have been observed and can be reduced by the presence of plants or by a resting period of 14 - 21 days (requiring alternative feedings on several filters).
Energy and Emergy Analysis to Evaluate Sustainability of Small Wastewater Treatment Plants: Application to a Constructed Wetland and a Sequencing Batch Reactor  [PDF]
Gerard Merlin, Thierry Lissolo
Journal of Water Resource and Protection (JWARP) , 2010, DOI: 10.4236/jwarp.2010.212120
Abstract: The aim of this study is to assess the sustainability of two wastewater treatment systems by energy and emergy analyses. The first system is a Sequencing Batch Reactor (SBR) which is a concrete and electricity dependent intensive process. The second is a constructed wetland, usually considered as an extensive process. The two studied facilities have similar treatment capacity and removal efficiencies. This study sheds new light on the comparison of wastewater treatment plants. We defined a new unit, the “Functional Efficiency Index” (or FEI) to describe the energetic efficiency of the facilities, expressed in kJ per year and per kg of removed COD. The energy analysis showed that, after its construction, the constructed wetland system uses only renewable energy, in marked contrast to the SBR, totally dependent on electricity which is considered here as a non renewable. The emergy analysis showed no significant differences between the two processes, but energy and emergy indices are in favour of the constructed wetland process and thus confirm its sustainability.
Theoretical Investigation of Structural, Electronic, and Mechanical Properties of Two Dimensional C, Si, Ge, Sn  [PDF]
Rita John, Benita Merlin
Crystal Structure Theory and Applications (CSTA) , 2016, DOI: 10.4236/csta.2016.5304
Abstract: In this article, we investigate the predictions of the first principles on structural stability, electronic and mechanical properties of 2D nanostructures: graphene, silicene, germanene and stenane. The electronic band structure and density of states in all these 2D materials are found to be generic in nature. A small band gap is generated in all the reported materials other than graphene. The linearity at the Dirac cone changes to quadratic, from graphene to stenane and a perfect semimetalicity is exhibited only by graphene. All other 2D structures tend to become semiconductors with an infinitesimal band gap. Bonding characteristics are revealed by density of states histogram, charge density contour, and Mulliken population analysis. Among all 2D materials graphene exhibits exotic mechanical properties. Analysis by born stability criteria and the calculation of formation enthalpies envisages the structural stability of all the structures in the 2D form. The calculated second order elastic stiffness tensor is used to determine the moduli of elasticity in turn to explore the mechanical properties of all these structures for the prolific use in engineering science. Graphene is found to be the strongest material but brittle in nature. Germanene and stenane exhibit ductile nature and hence could be easily incorporated with the existing technology in the semiconductor industry on substrates.
Prediction of Ultimate Bearing Capacity of Cohesionless Soils Using Soft Computing Techniques
S. Adarsh,R. Dhanya,G. Krishna,R. Merlin
ISRN Artificial Intelligence , 2012, DOI: 10.5402/2012/628496
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