Spin-Transfer-Torque Driven Magneto-Logic OR, AND and NOT Gates

We show that current induced magneto-logic gates like AND, OR and NOT can be designed with the simple architecture involving a single nano spin-valve pillar, as an extension of our recent work on spin-torque-driven magneto-logic universal gates, NAND and NOR. Here the logical operation is induced by spin-polarized currents which also form the logical inputs. The operation is facilitated by the simultaneous presence of a constant controlling magnetic field, in the absence of which the same element operates as a magnetoresistive memory element. We construct the relevant phase space diagrams for the free layer magnetization dynamics in the monodomain approximation and show the rationale and functioning of the proposed gates. The flipping time for the logical states of these non-universal gates is estimated to be within nano seconds, just like their universal counter parts.Comment: 9 pages,7 figure

Synchronization and chaos in spin-transfer-torque nano-oscillators coupled via a high speed Op Amp

We propose a system of two coupled spin-torque nano-oscillators (STNOs), one driver and another response, and demonstrate {using numerical studies} the synchronization of the response system to the frequency of the driver system. To this end we use a high speed operational amplifier in the form of a voltage follower which essentially isolates the drive system from the response system. We find the occurrence of 1:1 as w ell as 2:1 synchronization in the system, wherein the oscillators show limit cycle dynamics. An increase in power output is noticed when the two oscillators are locked in 1:1 synchronization. Moreover in the cro ssover region between these two synchronization dynamics we show the existence of chaotic dynamics in the slave system. The coupled dynamics under periodic forcing, using a small ac input current in addition to that of the dc part, is also studied. The slave oscillator is seen to retain its qualitative identity in the parameter space in spite of being fed in, at times, a chaotic signal. Such electrically coupled STNOs will be highly useful in fabricating commercial spin-valve oscillators with high power output, when integrated with other spintronic devices.Comment: 17 pages, 11 figures. To appear in J. Phys. D: Applied Physic

Bifurcation and chaos in spin-valve pillars in a periodic applied magnetic field

We study the bifurcation and chaos scenario of the macro-magnetization vector in a homogeneous nanoscale-ferromagnetic thin film of the type used in spin-valve pillars. The underlying dynamics is described by a generalized Landau-Lifshitz-Gilbert (LLG) equation. The LLG equation has an especially appealing form under a complex stereographic projection, wherein the qualitative equivalence of an applied field and a spin-current induced torque is transparent. Recently chaotic behavior of such a spin vector has been identified by Zhang and Li using a spin polarized current passing through the pillar of constant polarization direction and periodically varying magnitude, owing to the spin-transfer torque effect. In this paper we show that the same dynamical behavior can be achieved using a periodically varying applied magnetic field, in the presence of a constant DC magnetic field and constant spin current, which is technically much more feasible, and demonstrate numerically the chaotic dynamics in the system for an infinitely thin film. Further, it is noted that in the presence of a nonzero crystal anisotropy field chaotic dynamics occurs at much lower magnitudes of the spin-current and DC applied field.Comment: 8 pages, 7 figures. To appear in Chao

New geometries associated with the nonlinear Schr\"{o}dinger equation

We apply our recent formalism establishing new connections between the geometry of moving space curves and soliton equations, to the nonlinear Schr\"{o}dinger equation (NLS). We show that any given solution of the NLS gets associated with three distinct space curve evolutions. The tangent vector of the first of these curves, the binormal vector of the second and the normal vector of the third, are shown to satisfy the integrable Landau-Lifshitz (LL) equation ${\bf S}_u = {\bf S} \times {\bf S}_{ss}$, (${\bf S}^2=1$). These connections enable us to find the three surfaces swept out by the moving curves associated with the NLS. As an example, surfaces corresponding to a stationary envelope soliton solution of the NLS are obtained.Comment: 13 pages, 3 figure

Information Disclosure Strategies for Green Industries

Environmental information disclosure strategies, which involve corporate attempts to increase the availability of information on pollution and emissions, can become a basis for a new wave of environmental protection policy that follows and has the potential to complement traditional command and control and market-based approaches. Although a growing body of literature and operational programs suggest that publicly disclosing the information can motivate improved corporate environmental performance, this phenomenon remains poorly understood. This paper reviews the economic and legitimacy theory behind information disclosure and analyses the current practice and programs adopted in industrialized and industrializing countries.environmental information disclosure; toxic release inventory; government disclosure programs; materials accounting; sector facility indexing; pollution and emissions; environmental performance

Evaluation of antipyretic activity of ethyl acetate extract of Adenema hyssopifolium G. Don in a rat model

AbstractObjectiveTo evaluate the effect of ethyl acetate extract of Adenema hyssopifolium (AHEAE) on normal body temperature and brewer's yeast-induced pyrexia rats.MethodsPreliminary phytochemical tests, acute toxicity tests and antipyretic evaluation were carried out in ethyl acetate extract of Adenema hyssopifolium. Two doses of the extract (300 or 600 mg/kg orally) and standard antipyretic agent, paracetamol at a dose of 150 mg/kg were administered to various group of the rats. Mean rectal temperature before and after treatment was noted.ResultsThe phytochemical analysis of AHEAE revealed the presence of flavonoid and iridoid glycosides as major phytoconstituents. The administration of AHEAE at a dose of 300 or 600 mg/kg produced significant reduction (P<0.001 and P<0.01) of the body temperature in normal and pyrexia rats on a dose dependent manner. The antipyretic influence of AHEAE was comparable to that of standard antipyretic agent, paracetamol (150 mg/kg), and onset of action and reduction in pyrexia towards normal body temperature was delayed when compared to paracetamol treatment. At dose of 600 mg/kg, AHEAE reduced pyrexia to normal body temperature at 4 h after its administration compared to reduction of pyrexia to normal body temperature at 2 h by standard drug. The reduction of fever was consistent in paracetamol group from 2 to 4 h after its administration to normal body temperature compared to AHEAE treatments.ConclusionsOur present results corroborate with the traditional notion of Adenema hyssopifolium G. DON that is being used as an effective cure of fever and add authenticity to claim of indigenous healers that the taxon is a potential antipyretic agent