265,978 research outputs found
HSPICE implementation of a numerically efficient model of CNT transistor
No full textThis paper presents the algorithms of an implementation of a numerically efficient carbon nanotube transistor (CNT) model in HSPICE. The model is derived from cubic spline non-linear approximation of the non-equilibrium mobile charge density. The spline algorithm exploits a rapid and accurate solution of the numerical relationship between the charge density and the self-consistent voltage, which results in the acceleration of deriving the current through the channel without losing much accuracy. The output I-V characteristics of the proposed model have been compared with those of a recent HSPICE implementation of the Stanford CNT model and published experimental I-V curves. The results show superior accuracy of the proposed model while maintaining similar CPU time performance. Two versions of the HSPICE macromodel implementation have been developed and validated, one to reflect ballistic transport only and another with non-ballistic effects. To further validate the model a complementary logic inverter has also been implemented using the proposed technique and simulated in HSPICE
Quasi-Static Voltage Scaling for Energy Minimization with Time Constraints
No full textSupply voltage scaling and adaptive body-biasing are important tech-niques that help to reduce the energy dissipation of embedded systems. This is achieved by dynamically adjusting the voltage and performance settings according to the application needs. In order to take full ad-vantage of slack that arises from variations in the execution time, it is important to recalculate the voltage (performance) settings during run-time, i.e., online. However, voltage scaling (VS) is computationally ex-pensive, and thus significantly hampers the possible energy savings. To overcome the online complexity, we propose a quasi-static voltage scal-ing scheme, with a constant online time complexity O(1). This allows to increase the exploitable slack as well as to avoid the energy dissipated due to online recalculation of the voltage settings. We conduct several experiments that demonstrate the advantages of the proposed technique over the previously published voltage scaling approaches
Constitutively active group I mGlu receptors and PKMzeta regulate synaptic transmission in developing perirhinal cortex
No full textSynaptic transmission is essential for early development of the central nervous system. However, the mechanisms that regulate early synaptic transmission in the cerebral cortex are unclear. PKM zeta is a kinase essential for the maintenance of LTP. We show for the first time that inhibition of PKM zeta produces a profound depression of basal synaptic transmission in neonatal, but not adult, rat perirhinal cortex. This suggests that synapses in early development are in a constitutive LTP-like state. Furthermore, basal synaptic transmission in immature, but not mature, perirhinal cortex relies on persistent activity of metabotropic glutamate (mGlu) receptor, PI3Kinase and mammalian target of rapamycin (mTOR). Thus early in development, cortical synapses exist in an LTP-like state maintained by tonically active mGlu receptor-, mTOR- and PKM zeta- dependent cascades. These results provide new understanding of the molecular mechanisms that control synapses during development and may aid our understanding of developmental disorders such as autism and schizophrenia. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'. (c) 2012 Elsevier Ltd. All rights reserved
LTP and PKM zeta in perirhinal cortex
No full textLong-term potentiation (LTP) is thought to underlie learning and memory processes. Protein Kinase M Zeta, the independently active PKC Zeta isoform, is both necessary and sufficient for the maintenance of the late-phase of LTP in the hippocampus and for the long-term storage of spatial information in behavioural tests (Pastalkova et al., 2006). However, little is known about the mechanisms underlying the maintenance of LTP in perirhinal cortex, a cortical region critical for recognition memory. We demonstrate that a ÒspacedÓ tetra-burst stimulation (four 100-Hz bursts at 5-min interburst interval) in perirhinal cortex is able to induce an LTP lasting longer than 5 hours, which is sensitive to protein synthesis inhibitors. The crucial role of PKM Zeta is confirmed by the reversal of LTP maintenance following the application of the peptide inhibitor ZIP. We are currently studying the role of PKM Zeta in depotentiation and investigating mechanisms involved in modifying the synthesis and/or the activation of this Kinase. Pastalkova E et al. (2006) Storage of spatial information by the maintenance mechanism of LTP. Science 313:1141-4
Reconstructing female emotionality
No full textI examine the use of emotion discourse in the management of blame and accountability, using as an empirical case, the Panorama interview between Princess Diana and Martin Bashir. Diana’s talk is examined to determine how she uses notions of emotionality attributed to her in her discourse for accounting purposes. I argue that Diana provides the background for her ‘emotional’ label and through doing so,
allocates blame by accusing the media and royal family of fabricating that label for her. She further constructs their motive as being due to their being threatened by her strength of character, rather than her perceived instability. Finally Diana reconstructs
her emotional nature into a positive attribute whilst marking the royal family as ‘unemotional’ and uncaring. This study is linked to a broader discursive psychology of emotion concepts and their use
A Fast and Accurate Process Variation-aware Modeling Technique for Resistive Bridge Defects
No full textRecent research has shown that tests generated without taking process variation into account may lead to loss of test quality. At present there is no efficient device-level modeling technique that models the effect of process variation on resistive bridge defects. This paper presents a fast and accurate technique to achieve this, including modeling the effect of voltage and temperature variation using BSIM4 transistor model. To speedup the computation time and without compromising simulation accuracy (achieved through BSIM4) two efficient voltage approximation algorithms are proposed for calculating logic threshold of driven gates and voltages on bridged lines of a fault-site to calculate bridge critical resistance. Experiments are conducted on a 65-nm gate library (for illustration purposes), and results show that on average the proposed modeling technique is more than 53 times faster and in the worst case, error in bridge critical resistance is 2.64% when compared with HSPICE
Evaluation of desirable characteristics of wild potatoes for the improvement of cultivated potato.
No full textEstresses abióticos, especialmente calor e seca, são os principais fatores que reduzem a produtividade da batata (Solanum tuberosum, Solanaceae) limitando a atividade fotossintética, diminuindo a produção e o particionamento de assimilados para os tubérculos. As batatassilvestres são uma fonte natural de características valiosas para o melhoramento genético da batata, como a tolerância a estresses abióticos. Entretanto, é necessário identificar os fenótipos com base em caracteres morfoagronômicos e fisiológicos, para permitir incrementar a resiliência desse cultivo, pois as trocas gasosas, índice de clorofila, e fluorescência de clorofila são os principais fatores que influenciam a produção e atividade fotossintética. De modo a avançar na avaliação de características desejáveis das batatas-silvestres em prol do melhoramento genético da batata, está tese está organizada em quatro capítulos. O Capítulo 1 apresenta uma revisão de literatura sobre o papel promissor dos parentes silvestres da batata como um reservatório de novas características genéticas desejáveis para o melhoramento da batata. O Capítulo 2 apresenta um estudo da resposta genotípica e seleção de parentes silvestres da batata quanto características dos tubérculos em condições de estresse por calor. Duas condições de temperatura foram aplicadas: controle (14-27°C) e estresse de calor (24-34°C). Ao final do ciclo de vida das plantas, os caracteres morfoagronômicos foram analisados por meio de modelos estatísticos mistos para ranquear os genótipos de acordo com os valores genotípicos reais. O Capítulo 3 trata da avaliação sob as mesmas condições de temperatura do capítulo anterior e avalia a resposta fisiológica (taxa fotossintética - Pn), taxa de transpiração (Tr), condutância dos estômatos (Gs), concentração de CO2 intra e extracelular (Ci/Ca), e a fluorescência de clorofila. Estas características fisiológicas foram submetidas a análises de componentes principais que permitiram agrupar os acessos expostos ao estresse de calor, permitindo reconhecer um conjunto de genótipos tolerante às temperaturas elevadas. No Capítulo 4, acessos adicionais de S. commersonii e S. chacoense e características adicionais de trocas gasosas (Pn, Tr, Gs), fluorescência de clorofila (YII, NPQ, Fv/Fm), conteúdo de clorofila a e b e de carotenóides, também foram medidos 1 dia após o estresse (DAS), 15 DAS e 35 DAS. Ao final do ciclo de vida, as amostras tiveram o conteúdo total de água e os conteúdos de matéria fresca e seca observados. Os resultados demonstram que os genótipos de S. chacoense foram mais tolerantes e tiveram melhor desempenho sob condições de estresse de calor. Portanto, a introdução e caracterização de genótipos com características fisiológicas de batatas-silvestres é necessária para atender os esforços de ganho requeridos em programas de melhoramento genético da batata visando enfrentar cenários previstos de incremento de calor e seca globais.Tese (Doutorado em Ciências) - Pós Graduação em Agronomia, Faculdade de Agronomia Eliseu Maciel, Universidade Federal de Pelotas. Orientador: Gustavo Heiden (CPACT); Co-orientadora: Caroline M. Castro (CPACT)
VHDL-AMS implementation of a numerical ballistic CNT model for logic circuit simulation
No full textThis paper introduces a novel numerical carbon nanotube transistor (CNT) modelling approach which brings in a flexible and efficient cubic spline non-linear approximation of the non-equilibrium mobile charge density. The spline algorithm creates a rapid and accurate solution of the numerical relationship between the charge density and the self-consistent voltage, which leads to the speed-up of deriving the current through the channel without losing much accuracy. This modelling method also allows the flexibility of choosing different cubic spline intervals which may affect the performance of the model, but it is still capable of obtaining an acceleration of more than a 100 times while maintaining the accuracy within less than 1.5% normalised RMS error compared with previous reported theoretical modelling approach. The model has been proved working as transistors in a logic inverter implemented using VHDL-AMS and simulated in SystemVision, which shows the availability of implementing a circuit-level simulators with our proposed model. Additionally, although this model is originally based on the ideal ballistic transport characteristics, it shows good flexibility that the extension with numbers of non-ballistic features are certainly acceptable
Numerically efficient modeling of CNT transistors with ballistic and non-ballistic effects for circuit simulation
No full textThis paper presents an efficient carbon nanotube (CNT) transistor modeling technique which is based on cubic spline approximation of the non-equilibrium mobile charge density. The approximation facilitates the solution of the selfconsistent voltage equation in a carbon nanotube so that calculation of the CNT drain-source current is accelerated by at least two orders of magnitude. A salient feature of the proposed technique is its ability to incorporate both ballistic and nonballistic transport effects without a significant computational cost. The proposed models have been extensively validated against reported CNT ballistic and non-ballistic transport theories and experimental results
Efficient circuit-level modelling of ballistic CNT using piecewise non-linear approximation of mobile charge density
No full textThis paper presents a new carbon nanotube transistor (CNT) modelling technique which is based on an efficient numerical piece-wise non-linear approximation of the non-equilibrium mobile charge density. The technique facilitates the solution of the self-consistent voltage equation in a carbon nanotube such that the CNT drain-source current evaluation is accelerated by more than three orders of magnitude while maintaining high modelling accuracy. The model is currently limited to ballistic transport but can be extended to non-ballistic modes of transport when a suitable theory is developed while researchers study phenomena that sometimes prevent electrons in a carbon nanotube from going ballistic. Our results show that while the accuracy and speed of the proposed model vary with the number of piece-wise segments in the mobile charge approximation, it is possible to obtain a speed-up of more than 1000 times while maintaining the accuracy within less than 2% in terms of average RMS error compared with the state of the art theoretical reference CNT model implemented in FETToy. This numerical efficiency makes our model particularly suitable for implementation in circuit-level, eg. SPICE-like, simulators where large numbers of such devices may be used to build complex circuits
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