34 research outputs found
ANALYSIS OF TIME-DELAYED NON-LINEAR EQUATIONS USING HF FUNCTIONS
The paper deals with the analysis of non-linear time delayed differential equations solved using HF functions. The analysis is first performed on Mackey-Glass Equation, which is a standard model for quantitative characterization of chaotic dynamics. The procedure is then performed on a generalized Human respiratory control model, where for different simulation parameters the analysis of Cheyne-Stokes Breathing is done. Both models are simulated in MATLAB. The graphs thus generated are used to provide suitable conclusions
Colossal electroresistance in ferromagnetic insulating state of single crystal NdPbMnO
Colossal electroresistance (CER) has been observed in the ferromagnetic
insulating (FMI) state of a manganite. Notably, the CER in the FMI state occurs
in the absence of magnetoresistance (MR). Measurements of electroresistance
(ER) and current induced resistivity switching have been performed in the
ferromagnetic insulating state of a single crystal manganite of composition
NdPbMnO (NPMO30). The sample has a paramagnetic to
ferromagnetic (Curie) transition temperature, Tc = 150 K and the ferromagnetic
insulating state is realized for temperatures, T <~ 130 K. The colossal
electroresistance, arising from a strongly nonlinear dependence of resistivity
() on current density (j), attains a large value () in the
ferromagnetic insulating state. The severity of this nonlinear behavior of
resistivity at high current densities is progressively enhanced with decreasing
temperature, resulting ultimately, in a regime of negative differential
resistivity (NDR, d/dj < 0) for temperatures <~ 25 K. Concomitant with
the build-up of the ER however, is a collapse of the MR to a small value (<
20%) even in magnetic field, H = 7 T. This demonstrates that the mechanisms
that give rise to ER and MR are effectively decoupled in the ferromagnetic
insulating phase of manganites. We establish that, the behavior of
ferromagnetic insulating phase is distinct from the ferromagnetic metallic
(FMM) phase as well as the charge ordered insulating (COI) phase, which are the
two commonly realized ground state phases of manganites.Comment: 24 pages (RevTeX4 preprint), 8 figures, submitted to PR
Critical properties of the double exchange ferromagnet Nd0.4Pb0.4MnO3
Results of a study of dc-magnetization M(T, H), performed on a Nd0.6Pb0.4MnO3
single crystal in the temperature range around T_C (Curie temperature) which
embraces the critical region | epsilon | = |T -T_C |/T_C <= 0.05 are reported.
The magnetic data analyzed in the critical region using the Kouvel-Fisher
method give the values for the T_C =156.47 +/- 0.06 K and the critical
exponents, beta = 0.374 +/- 0.006 (from the temperature dependence of
magnetization), and gamma = 1.329 +/- 0.003 (from the temperature dependence of
initial susceptibility). The critical isotherm M(T_C, H) gives delta = 4.547
+/- 0.1. Thus the scaling law gamma+beta=delta beta is fulfilled. The critical
exponents obey the single scaling-equation of state M(H, epsilon) = epsilon^b
f_+/- (H/epsilon^(beta + gamma)) where, f_+ for T > T_C and f_- for T< T_C. The
exponent values are very close to those expected for the universality class of
3D Heisenberg ferromagnets with short-range interactions.Comment: 19 pages, including 6 figure
Electron paramagnetic resonance studies of the insulating ferromagnetic manganite Nd_0.8Pb_0.2MnO_3 above the transition temperature
Single crystals of Nd_{1-x}Pb_{x}MnO_{3} with x=0.2 are grown by high
temperature solution growth technique using PbO-PbF_{2} flux. Magnetization
studies on the samples show a transition to a ferromagnetic state below T_c ~
125 K and the resistivity measurements show it to be an insulator throughout
the temperature range 50 - 300 K. Electron Paramagnetic Resonance studies have
been performed for T > T_{C} with a view to comparing the results with those on
metallic ferromagnetic manganites. The temperature dependence of various
parameters like g-value, linewidth and intensity has been studied in the
temperature range 150 - 300 K. It is found that they behave in a manner similar
to that exhibited by metallic ferromagnetic manganites.Comment: 8 pages, 4 figure
Chondrocyte Hypertrophy in Osteoarthritis: Mechanistic Studies and Models for the Identification of New Therapeutic Strategies
Articular cartilage shows limited self-healing ability owing to its low cellularity and
avascularity. Untreated cartilage defects display an increased propensity to degenerate, leading
to osteoarthritis (OA). During OA progression, articular chondrocytes are subjected to significant
alterations in gene expression and phenotype, including a shift towards a hypertrophic-like state
(with the expression of collagen type X, matrix metalloproteinases-13, and alkaline phosphatase)
analogous to what eventuates during endochondral ossification. Present OA management strategies
focus, however, exclusively on cartilage inflammation and degradation. A better understanding
of the hypertrophic chondrocyte phenotype in OA might give new insights into its pathogenesis,
suggesting potential disease-modifying therapeutic approaches. Recent developments in the field
of cellular/molecular biology and tissue engineering proceeded in the direction of contrasting the
onset of this hypertrophic phenotype, but knowledge gaps in the cause–effect of these processes are
still present. In this review we will highlight the possible advantages and drawbacks of using this
approach as a therapeutic strategy while focusing on the experimental models necessary for a better
understanding of the phenomenon. Specifically, we will discuss in brief the cellular signaling pathways associated with the onset of a hypertrophic phenotype in chondrocytes during the progression
of OA and will analyze in depth the advantages and disadvantages of various models that have
been used to mimic it. Afterwards, we will present the strategies developed and proposed to impede
chondrocyte hypertrophy and cartilage matrix mineralization/calcification. Finally, we will examine the future perspectives of OA therapeutic strategies
Hard Knapsack Problems That Are Easy for Local Search
Chv'atal (1980) describes a class of zero-one knapsack problems provably difficult for branch and bound and dynamic programming algorithms. Chung et al. (1988) identifies a class of integer knapsack problems hard for branch and bound algorithms. We show that for both classes of problems local search provides optimal solutions quickly. Keywords : knapsack problem * local search * computational complexity Correspondence should be directed to the second author 1 Introduction Chv'atal (1980) describes a class of instances of zero-one knapsack problems due to Todd. ( We shall henceforth refer to these problems as the TODD class of problems. ) He shows that a wide class of algorithms --- including all based on branch and bound or dynamic programming --- find it difficult to solve problems in the TODD class. More precisely, the time required by these algorithms to solve instances of problems belonging to the TODD class grows as an exponential function of the problem parameters. Chung et a..
Impact of Climate Change on Livestock Production: A Review
ABSTRACT Climate change is seen as a major threat to the survival of many species, ecosystems and the sustainability of livestock production systems in many parts of the world. Green house gases (GHG) are released in the atmosphere both by natural sources and anthropogenic (human related) activities. An attempt has been made in this article to understand the contribution of ruminant livestock to climate change and to identify the mitigation strategies to reduce enteric methane emission in livestock. In Indian subcontinent, heat stress is the most important climatic stress. Heat stress adversely affecting productive and reproductive performance of livestock, and hence reducing the total area where high yielding dairy cattle may be economically reared. The livestock sector which will be a sufferer of climate change is itself a large source of methane emissions contributing about 18% of total enteric methane budget. Ruminant livestock such as cattle, buffalo, sheep and goats contributes the major proportion of total agricultural emission of methane .In India, although the emission rate per animal is much lower than the developed countries, due to vast livestock population the total annual methane emissions from Indian livestock ranged from 7.26 to 10.4 MT/year. In India more than 90% of the total methane emission from enteric fermentation is being contributed by the large ruminants (cattle and buffalo) and rest from small ruminants and others. Generally CH 4 reduction strategies can be grouped under two broad categories such as management and nutritional strategies. Although the reduction in GHG emissions from livestock industries are seen as high priorities, strategies for reducing emissions should not reduce the economic viability of enterprises if they are to find industry acceptability. Keywords: Climate change, methane, mitigation, ruminants, livestock production The crop livestock system is one of the most important characteristics of Indian agrarian economy and livestock sector is the integral part of India's agriculture sector. Indian livestock sector provides sustainability and stability to the national economy by contributing to farm energy and food security. Livestock sector no
Growth and characteristics of lead-substituted rare earth manganites
The growth of (R=La, Nd, [La,Nd]) single crystals by flux is described with optimized growth conditions. The structure of changes from orthorhombic (x=0, Pnma) to tetragonal (x=0.25, P4/mmm) to cubic (x=0.38, Pm3¯m) as x increases. These changes are attributed to the progressive removal of inter-octahedral tilting and minimization of octahedral distortion leading to a higher symmetry as doping concentration increases. The of this system increases from 110 to 192 K for Pb concentration varying from x=0.15 to 0.42. The also follows a similar trend. It is observed that and are the controlling parameters which influence the transport and magnetic properties of . The presence of spin wave excitations are observed prominently in at low-temperature which is not so in case of Nd-based compounds. The total magnetic moments of all the Nd-based systems at low-temperature are influenced by Nd. The low-temperature specific heat data of is analyzed and contributions of different mechanisms are discussed. It is noticed that the Schottky anomaly is present in specific heat at low-temperature only in Nd-based compounds