The need to find low power alternatives to digital electronic circuits has led to increasing interest in alternative switching schemes like the magnetic quantum cellular automata(MQCA) that store information in nanomagnets which communicate through their magnetic fields. A recent proposal called all spin logic (ASL) proposes to communicate between nanomagnets using spin currents which are spatially localized and can be conveniently routed. The objective of this paper is to present a model for ASL devices that is based on established physics and is benchmarked against available experimental data and to use it to investigate switching energy-delay of ASL devices.Digital electronic circuits store information in the form of capacitor charges that are manipulated using transistor-based switches. Switches of this type currently operate with a supply voltage of one volt involving ≈ 10 4 − 10 5 electrons, requiring 1 − 10 femto-Joules (fJs), dissipating 1-10 µW per switch if operating at 1 GHz. This dissipation per switch is believed to be the single most important impediment to continued miniaturization and there is a serious attempt to "reinvent the transistor" 1 so as to operate at lower voltages.A more radical approach is to replace the entire chargebased architecture with an architecture based on some other state variable such as spin 2 . For example, MQCA 3 uses nanomagnets to represent digital information (0 and 1). Recently an all spin logic (ASL) device 4 has been proposed whereby information is similarly stored in nanomagnets but is communicated via spin currents that are spatially localized and can be conveniently routed within a spin-coherence length which can be 100's of nanometers 5 to microns 6 .It has been argued that ASL devices could potentially lead to ultralow power switches since a stable nanomagnet with an activation barrier of 40 kT could be switched with less than an attoJoule (aJ) 4 . Experimentally, however, nanomagnet memory devices typically require tens of fJs to switch at speeds that are a factor of 100 to 1000 lower, raising questions about the potential of ASL devices to provide a low-power alternative to today's transistors. This is because most of the dissipation in switching magnets is associated not with the dynamics of magnets but with the spin transport process and we need a suitable model that incorporates both to make reliable predictions. This paper presents such a model that is based on established physics and is benchmarked against the recent experimental result of Yang et al. 7 .In general, the switching energy and energy-delay can be written as:V and I are the charge voltage and current respectively and t sw is the switching delay. Q tot = It sw is the total charge involved in a switching event. Equation 1 permits a simple comparison with charge-based devices likeFIG. 1: (a) An ASL device consisted of input and output magnets. (b) Illustrates the self-consistent model. (c) Shows the conductance matrices describing the spin-transport.today's transistors where Q tot is the amou...
The high level of functional diversity and plasticity in monocytes/macrophages has been defined within in vitro systems as M1 (classically activated), M2 (alternatively activated) and deactivated macrophages, of which the latter two subtypes are associated with suppression of cell mediated immunity, that confers susceptibility to intracellular infection. Although the Leishmania parasite modulates macrophage functions to ensure its survival, what remains an unanswered yet pertinent question is whether these macrophages are deactivated or alternatively activated. This study aimed to characterize the functional plasticity and polarization of monocytes/macrophages and delineate their importance in the immunopathogenesis of Post kala-azar dermal leishmaniasis (PKDL), a chronic dermatosis of human leishmaniasis. Monocytes from PKDL patients showed a decreased expression of TLR-2/4, along with an attenuated generation of reactive oxidative/nitrosative species. At disease presentation, an increased mRNA expression of classical M2 markers CD206, ARG1 and PPARG in monocytes and lesional macrophages indicated M2 polarization of macrophages which was corroborated by increased expression of CD206 and arginase-1. Furthermore, altered vitamin D signaling was a key feature in PKDL, as disease presentation was associated with raised plasma levels of monohydroxylated vitamin D3 and vitamin D3- associated genes, features of M2 polarization. Taken together, in PKDL, monocyte/macrophage subsets appear to be alternatively activated, a phenotype that might sustain disease chronicity. Importantly, repolarization of these monocytes to M1 by antileishmanial drugs suggests that switching from M2 to M1 phenotype might represent a therapeutic opportunity, worthy of future pharmacological consideration.
Leishmania donovani is considered the causative organism of visceral leishmaniasis (VL) and post-kala-azar dermal leishmaniasis (PKDL). Testing of 4/29 DNA samples from VL and PKDL patients as well as 2/7 field isolates showed an aberrant internal transcribed spacer 1 (ITS1) restriction fragment length polymorphism (RFLP) pattern, which upon sequencing strongly matched Leptomonas seymouri, thus confirming its presence in Indian leishmaniasis.
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