84 research outputs found
Oscillation-free method for semilinear diffusion equations under noisy initial conditions
Noise in initial conditions from measurement errors can create unwanted
oscillations which propagate in numerical solutions. We present a technique of
prohibiting such oscillation errors when solving initial-boundary-value
problems of semilinear diffusion equations. Symmetric Strang splitting is
applied to the equation for solving the linear diffusion and nonlinear
remainder separately. An oscillation-free scheme is developed for overcoming
any oscillatory behavior when numerically solving the linear diffusion portion.
To demonstrate the ills of stable oscillations, we compare our method using a
weighted implicit Euler scheme to the Crank-Nicolson method. The
oscillation-free feature and stability of our method are analyzed through a
local linearization. The accuracy of our oscillation-free method is proved and
its usefulness is further verified through solving a Fisher-type equation where
oscillation-free solutions are successfully produced in spite of random errors
in the initial conditions.Comment: 19 pages, 9 figure
A Density Matrix Renormalization Group Method Study of Optical Properties of Porphines and Metalloporphines
The symmetrized Density-Matrix-Renormalization-Group (DMRG) method is used to
study linear and nonlinear optical properties of Free base porphine and
metallo-porphine. Long-range interacting model, namely, Pariser-Parr-Pople
(PPP) model is employed to capture the quantum many body effect in these
systems. The non-linear optical coefficients are computed within correction
vector method. The computed singlet and triplet low-lying excited state
energies and their charge densities are in excellent agreement with
experimental as well as many other theoretical results. The rearrangement of
the charge density at carbon and nitrogen sites, on excitation, is discussed.
From our bond order calculation, we conclude that porphine is well described by
the 18-annulenic structure in the ground state and the molecule expands upon
excitation. We have modelled the regular metalloporphine by taking an effective
electric field due to the metal ion and computed the excitation spectrum.
Metalloporphines have symmetry and hence have more degenerate excited
states. The ground state of Metalloporphines show 20-annulenic structure, as
the charge on the metal ion increases. The linear polarizability seems to
increase with the charge initially and then saturates. The same trend is
observed in third order polarizability coefficients.Comment: 13 pages, 6 figure
Electromagnetically induced transparency in cold 85Rb atoms trapped in the ground hyperfine F = 2 state
We report electromagnetically induced transparency (EIT) in cold 85Rb atoms,
trapped in the lower hyperfine level F = 2, of the ground state 5
(Tiwari V B \textit{et al} 2008 {\it Phys. Rev.} A {\bf 78} 063421). Two steady
state -type systems of hyperfine energy levels are investigated using
probe transitions into the levels F = 2 and F = 3 of the
excited state 5 in the presence of coupling transitions F = 3
F = 2 and F = 3 F = 3, respectively. The
effects of uncoupled magnetic sublevel transitions and coupling field's Rabi
frequency on the EIT signal from these systems are studied using a simple
theoretical model.Comment: 12 pages, 7 figure
Role of ambient air on photoluminescence and electrical conductivity of assembly of ZnO Nanoparticles
Effect of ambient gases on photoluminescence (PL) and electrical conductivity
of films prepared using ZnO nanoparticles (NPs) have been investigated. It is
observed that NPs of size below 20 nm kept inside a chamber exhibit complete
reduction in their visible PL when oxygen partial pressure of the surrounding
gases is decreased by evacuation. However the visible PL from ZnO NPs is
insensitive to other major gases present in the ambient air. The rate of change
of PL intensity with pressure is inversely proportional to the ambient air
pressure and increases when particle size decreases due to the enhanced surface
to volume ratio. On the other hand an assembly of ZnO NPs behaves as a complete
insulator in the presence of dry air and its major components like N2, O2 and
CO2. Electrical conduction having resistivity ~102 - 103 {\Omega}m is observed
in the presence of humid air. The depletion layer formed at the NP surface
after acquiring donor electrons of ZnO by the adsorbed oxygen, has been found
to control the visible PL and increases the contact potential barrier between
the NPs which in turn enhances the resistance of the film.Comment: arXiv admin note: significant text overlap with arXiv:1008.249
Like Sign Dilepton Signature for Gluino Production at LHC with or without R Conservation
The isolated like sign dilepton signature for gluino production is
investigated at the LHC energy for the conserving as well as the and
violating SUSY models over a wide range of the parameter space. One gets
viable signals for gluino masses of 300 and 600 GeV for both conserving and
violating models, while it is less promising for the violating case.
For a 1000 GeV gluino, the violating signal should still be viable; but the
conserving signal becomes too small at least for the low luminosity option
of LHC.Comment: (e-mail: [email protected]) Latex: No. of pages 21, no. of figures
6 - available on reques
Maintaining Diversity of Integrated Rice and Fish Production Confers Adaptability of Food Systems to Global Change
Rice and fish are preferred foods, critical for healthy and nutritious diets, and provide the foundations of local and national economies across Asia. Although transformations, or "revolutions," in agriculture and aquaculture over the past half-century have primarily relied upon intensified monoculture to increase rice and fish production, agroecological approaches that support biodiversity and utilize natural processes are particularly relevant for achieving a transformation toward food systems with more inclusive, nutrition-sensitive, and ecologically sound outcomes. Rice and fish production are frequently integrated within the same physical, temporal, and social spaces, with substantial variation amongst the types of production practice and their extent. In Cambodia, rice field fisheries that strongly rely upon natural processes persist in up to 80% of rice farmland, whereas more input and infrastructure dependent rice-shrimp culture is expanding within the rice farmland of Vietnam. We demonstrate how a diverse suite of integrated production practices contribute to sustainable and nutrition-sensitive food systems policy, research, and practice. We first develop a typology of integrated production practices illustrating the nature and degree of: (a) fish stocking, (b) water management, (c) use of synthetic inputs, and (d) institutions that control access to fish. Second, we summarize recent research and innovations that have improved the performance of each type of practice. Third, we synthesize data on the prevalence, outcomes, and trajectories of these practices in four South and Southeast Asian countries that rely heavily on fish and rice for food and nutrition security. Focusing on changes since the food systems transformation brought about by the Green Revolution, we illustrate how integrated production practices continue to serve a variety of objectives to varying degrees: food and nutrition security, rural livelihood diversification and income improvement, and biodiversity conservation. Five shifts to support contemporary food system transformations [i.e., disaggregating (1) production practices and (2) objectives, (3) utilizing diverse metrics, (4) valuing emergent, place-based innovation, (5) building adaptive capacity] would accelerate progress toward Sustainable Development Goal 2, specifically through ensuring ecosystem maintenance, sustainable food production, and resilient agricultural practices with the capacity to adapt to global change.This work was undertaken as part of the CGIAR
Research Program on Fish Agri-Food Systems (FISH) led
by WorldFish with contribution from the CGIAR Research
program on Water Land and Ecosystems (WLE) led by the
International Water Management Institute. Both these programs
are supported by contributors to the CGIAR Trust Fund.
Additional funding support for this work was provided by
the Australian Government and the Australian Centre for
International Agricultural Research grant work was provided by
the Australian Centre for International Research through the
Development of Rice Fish Systems in the Ayeyarwady Delta,
Myanmar (ACIAR project FIS/2016/135). The support through
the United States Agency for International Development under
Cooperative Agreement No. AID-OAA-L-14-00006 and KAES
contribution number 20-317-J and grant number AID-442-IO12-00001 are duly acknowledged. Photo credits: Anon., Finn
Thilsted, Anon., Anon., Todd Brown (Figure 1)
Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties
Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure
- …