On the problem of spurious patterns in neural associative memory models

The problem of spurious patterns in neural associative memory models is discussed, Some suggestions to solve this problem from the literature are reviewed and their inadequacies are pointed out, A solution based on the notion of neural self-interaction with a suitably chosen magnitude is presented for the Hebb learning rule. For an optimal learning rule based on linear programming, asymmetric dilution of synaptic connections is presented as another solution to the problem of spurious patterns, With varying percentages of asymmetric dilution it is demonstrated numerically that this optimal learning rule leads to near total suppression of spurious patterns. For practical usage of neural associative memory networks a combination of the two solutions with the optimal learning rule is recommended to be the best proposition.

Microstructure dependent elastic modulus variation in NiTi shape memory alloy

Modulus variation of NiTi shape memory alloy has been investigated at microstructural level through nano dynamical mechanical analysis and compared with bulk experimental measurements. The differences between the modulus values at the macro and micro level as well as within the micro level are discussed and the corresponding variations have been explained based on the crystal structure, orientation and misorientation. The experimental results confirm a higher modulus value for the martensite phase that is in agreement with the theoretical predictions. (C) 2015 Elsevier B. V. All rights reserved.

Four decades of research in solid state chemistry

Solid state chemistry was in its infancy when the author got interested in the subject. In this article, the author outlines the manner in which the subject has grown over the last four decades, citing representative examples from his own contributions to the different facets of the subject. The various aspects covered include synthesis, structure, defects, phase transitions, transition metal oxides, catalysts, superconductors, metal clusters and fullerenes. In an effort to demonstrate the breadth and vitality of the subject, the author shares his own experiences and aspirations and gives expression to the agony and ecstacy in carrying out experimental research in such a frontier area in India.

Conserving Biodiversity as If People Matter: A Case Study from India

India has rich traditions of nature conservation as well as a vigorous official program of protection of nature reserves developed over the last 40 years. However, the officialp rograms uffers fromt otal relianceo n authoritarianm anagement arrangements in which decisions are made centrally and coercion is used to implement them. At the same time, the state apparatus organises subsidized resource flows to the urbanindustrial- intensivea griculturalc omplex which promote inefficient,n on-sustainable resource-use patterns that are inimical to conservation of biodiversity. These processes are illustrated within the concrete setting of the district of Uttara Kannada in southern India. It is suggested that the interests of conservation would be served far better by an approach that withdraws the subsidies to the elite so that a much more efficient, sustainable and equitable pattern of resource use, compatible with conservation of biodiversity, can be instituted. In conjunction with this, the larger society should involve local people in working out detailed plans for conservation of biodiversity and offer them adequate authority as well as appropriate financial incentives to implement these plans. The paper goes on to illustrate how such an approach may be implemented in the case of Uttara Kannada.

Memory effect in Dy0.5Sr0.5MnO3 single crystals

We have performed a series of magnetic aging experiments on single crystals of Dy0.5Sr0.5MnO3. The results demonstrate striking memory and chaos-like effects in this insulating half-doped perovskite manganite and suggest the existence of strong magnetic relaxation mechanisms of a clustered magnetic state. The spin-glass-like state established below a temperature T-sg approximate to 34 K originates from quenched disorder arising due to the ionic-radii mismatch at the rare earth site. However, deviations from the typical behavior seen in canonical spin glass materials are observed which indicate that the glassy magnetic properties are due to cooperative and frustrated dynamics in a heterogeneous or clustered magnetic state. In particular, the microscopic spin flip time obtained from dynamical scaling near the spin glass freezing temperature is four orders of magnitude larger than microscopic times found in atomic spin glasses. The magnetic viscosity deduced from the time dependence of the zero-field-cooled magnetization exhibits a peak at a temperature T < T-sg and displays a marked dependence on waiting time in zero field.

Memory Bandwidth and Power Reduction Using Lossy Reference Frame Compression in Video Encoding

Large external memory bandwidth requirement leads to increased system power dissipation and cost in video coding application. Majority of the external memory traffic in video encoder is due to reference data accesses. We describe a lossy reference frame compression technique that can be used in video coding with minimal impact on quality while significantly reducing power and bandwidth requirement. The low cost transformless compression technique uses lossy reference for motion estimation to reduce memory traffic, and lossless reference for motion compensation (MC) to avoid drift. Thus, it is compatible with all existing video standards. We calculate the quantization error bound and show that by storing quantization error separately, bandwidth overhead due to MC can be reduced significantly. The technique meets key requirements specific to the video encode application. 24-39% reduction in peak bandwidth and 23-31% reduction in total average power consumption are observed for IBBP sequences.

Evidence for low temperature glassy behavior in La0.5Sr0.5CoO3

We report the observed low temperature spin glass like feature in the optimally doped La0.5Sr0.5CoO3 ferromagnetic system. The characteristic of glassy behavior has been identified by noting (i) the frequency-dependent shift of the low temperature hump position in the out of phase ac susceptibility component; (ii) evolution of freezing temperature with dc biasing field that adheres to de Almeida-Thouless relation; (iii) memory effect; and (iv) sluggish magnetic relaxation. The results of magnetic measurements demonstrate that neither the inter-cluster interaction nor the spin disorder at the interface between ferromagnetic clusters is responsible for the manifestation of such collective glassy behavior. Rather, it is believed to arise from a distinct cluster glass like phase that possibly coexists with the dominant ferromagnetic phase. (C) 2012 American Institute of Physics. [doi:10.1063/1.3684610]

Memory effect in SrRu(1-x)O3 (0.01 < x < 0.07)

SrRuO3 is widely known to be an itinerant ferromagnet with a T-C similar to 160 K. It is well known that glassy materials exhibit time dependent phenomena such as memory effect due to their generic slow dynamics. However, for the first time, we have observed memory effect in SrRu(1-x)O3 (0.01ing temperature. Generally, time dependent phenomena such as aging, memory etc. arise in disordered glassy systems. Thus the observation of memory effect in case of an itinerant ferromagnetic system like SrRuO3 is quite strange. The emergence of such unusual magnetic response is strongly believed to be connected with a cryptic interactions arises in the low temperature. Our effort on neutron diffraction study has been able to trace the cause of such hidden magnetic interaction responsible for bringing glassiness in a ferromagnet.

Some Methods for Summarizing Survivorship Data in Nonstandard Situations

One difficulty in summarising biological survivorship data is that the hazard rates are often neither constant nor increasing with time or decreasing with time in the entire life span. The promising Weibull model does not work here. The paper demonstrates how bath tub shaped quadratic models may be used in such a case. Further, sometimes due to a paucity of data actual lifetimes are not as certainable. It is shown how a concept from queuing theory namely first in first out (FIFO) can be profitably used here. Another nonstandard situation considered is one in which lifespan of the individual entity is too long compared to duration of the experiment. This situation is dealt with, by using ancilliary information. In each case the methodology is illustrated with numerical examples.

Antifertility effect of tamoxifen as tested in the female bonnet monkey (Macaca radiata)

The administration of a potent antiestrogen, tamoxifen at a dose of 3 mg/kg body weight/day orally post-coitally to cycling mated bonnet monkeys(Macaca radiata) from days 18–30 of cycle resulted in inhibition of establishment of pregnancy in 9 out of 10 monkeys. Tamoxifen effect was not due to interference with luteal function. The effect was specific to tamoxifen as exogenously administered progesterone could not reverse it. In addition to suggesting a role for estrogen in maintenance of early pregnancy in the primate the present study could be a prelude to the development of an effective post-ovulatory approach for regulation of fertility in the human female

Ordered spin-ice state in the geometrically frustrated metallic ferromagnet Sm2Mo2O7

The recent discovery of spin ice is a spectacular example of the noncoplanar spin arrangements that can arise in the pyrochlore A2B2O7 structure. We present magnetic and thermodynamic studies on the metallic ferromagnet pyrochlore Sm2Mo2O7. Our studies, carried out on oriented crystals, suggest that the Sm spins have an ordered spin-ice ground state below about T*=15 K. The temperature and field evolution of the ordered spin-ice state are governed by an antiferromagnetic coupling between the Sm and Mo spins. We propose that as a consequence of a robust feature of this coupling, the tetrahedra aligned with the external field adopt a one-in, three-out spin structure as opposed to the three-in, one-out structure in dipolar spin ices, as the field exceeds a critical value.

Tracking Random Walk of Individual Domain Walls in Cylindrical Nanomagnets with Resistance Noise

The stochasticity of domain-wall (DW) motion in magnetic nanowires has been probed by measuring slow fluctuations, or noise, in electrical resistance at small magnetic fields. By controlled injection of DWs into isolated cylindrical nanowires of nickel, we have been able to track the motion of the DWs between the electrical leads by discrete steps in the resistance. Closer inspection of the time dependence of noise reveals a diffusive random walk of the DWs with a universal kinetic exponent. Our experiments outline a method with which electrical resistance is able to detect the kinetic state of the DWs inside the nanowires, which can be useful in DW-based memory designs.

A methodology for supporting ``transfer'' in biomimetic design

Biomimetics involves transfer from one or more biological examples to a technical system. This study addresses four questions. What are the essential steps in a biomimetic process? What is transferred? How can the transferred knowledge be structured in a way useful for biologists and engineers? Which guidelines can be given to support transfer in biomimetic design processes? In order to identify the essential steps involved in carrying out biomimetics, several procedures found in the literature were summarized, and four essential steps that are common across these procedures were identified. For identification of mechanisms for transfer, 20 biomimetic examples were collected and modeled according to a model. of causality called the SAPPhIRE model. These examples were then analyzed for identifying the underlying similarity between each biological and corresponding analogue technical system. Based on the SAPPhIRE model, four levels of abstraction at which transfer takes place were identified. Taking into account similarity, the biomimetic examples were assigned to the appropriate levels of abstraction of transfer. Based on the essential steps and the levels of transfer, guidelines for supporting transfer in biomimetic design were proposed and evaluated using design experiments. The 20 biological and analogue technical systems that were analyzed were similar in the physical effects used and at the most abstract levels of description of their functionality, but they were the least similar at the lowest levels of abstraction: the parts involved. Transfer most often was carried out at the physical effect level of abstraction. Compared to a generic set of guidelines based on the literature, the proposed guidelines improved design performance by about 60%. Further, the SAPPhIRE model turned out to be a useful representation for modeling complex biological systems and their functionality. Databases of biological systems, which are structured using the SAPPhIRE model, have the potential to aid biomimetic concept generation.

Structural Transitions of Nitrogen Confined in Slit Graphite Pores

The structure of ordered phases that are formed when nitrogen is confined in slit graphite pores of height h is investigated using Monte Carlo simulations. The pore wall consists of a single-structured graphite sheet. Canonical ensemble simulations are carried out for temperatures ranging from 15 to 70Kwith layer density distributions, in-plane, out-of-plane angular distributions and snapshots evaluated at different temperatures. At each pore height the pore densities are obtained from independent grand ensemble simulations. At the smallest pore height studied (h)7 Å), where a single layer of molecules is accommodated at the center of the pore, the orientations are predominantly wall parallel, forming a biaxially incommensurate herringbone structure.Whentwo or more fluid layers are formed in the slit pore, the orientation of molecules adsorbed next to the wall can exist in either the herringbone or hexagonal phases. In all the multilayered cases studied, with the exception of the h ) 10 Å pore, where both wall layers form a commensurate herringbone structure, the low-temperature wall structures are incommensurate, possessing 6-fold hexagonal symmetry. The presence of the pinwheel structures, which were observed at low temperatures in the h ) 12 Å and h ) 14 Å pores, is determined by the pore height or the proximity and/or density of the adjacent fluid layers when inner layers are present.