Performance and Reliability Analysis of Cross-Layer Optimizations of NAND Flash Controllers

NAND flash memories are becoming the predominant technology in the implementation of mass storage systems for both embedded and high-performance applications. However, when considering data and code storage in non-volatile memories (NVMs), such as NAND flash memories, reliability and performance be- come a serious concern for systems' designer. Designing NAND flash based systems based on worst-case scenarios leads to waste of resources in terms of performance, power consumption, and storage capacity. This is clearly in contrast with the request for run-time reconfigurability, adaptivity, and resource optimiza- tion in nowadays computing systems. There is a clear trend toward supporting differentiated access modes in flash memory controllers, each one setting a differentiated trade-off point in the performance-reliability optimization space. This is supported by the possibility of tuning the NAND flash memory performance, reli- ability and power consumption acting on several tuning knobs such as the flash programming algorithm and the flash error correcting code. However, to successfully exploit these degrees of freedom, it is mandatory to clearly understand the effect the combined tuning of these parameters have on the full NVM sub-system. This paper performs a comprehensive quantitative analysis of the benefits provided by the run-time reconfigurability of an MLC NAND flash controller through the combined effect of an adaptable memory programming circuitry coupled with run-time adaptation of the ECC correction capability. The full non- volatile memory (NVM) sub-system is taken into account, starting from the characterization of the low level circuitry to the effect of the adaptation on a wide set of realistic benchmarks in order to provide the readers a clear figure of the benefit this combined adaptation would provide at the system leve

Lateral frontal cortex volume reduction in Tourette syndrome revealed by VBM

<p>Abstract</p> <p>Background</p> <p>Structural changes have been found predominantly in the frontal cortex and in the striatum in children and adolescents with Gilles de la Tourette syndrome (GTS). The influence of comorbid symptomatology is unclear. Here we sought to address the question of gray matter abnormalities in GTS patients <it>with </it>co-morbid obsessive-compulsive disorder (OCD) and/or attention deficit hyperactivity disorder (ADHD) using voxel-based morphometry (VBM) in twenty-nine adult actually unmedicated GTS patients and twenty-five healthy control subjects.</p> <p>Results</p> <p>In GTS we detected a cluster of decreased gray matter volume in the left inferior frontal gyrus (IFG), but no regions demonstrating volume increases. By comparing subgroups of GTS with comorbid ADHD to the subgroup with comorbid OCD, we found a left-sided amygdalar volume increase.</p> <p>Conclusions</p> <p>From our results it is suggested that the left IFG may constitute a common underlying structural correlate of GTS with co-morbid OCD/ADHD. A volume reduction in this brain region that has been previously identified as a key region in OCD and was associated with the active inhibition of attentional processes may reflect the failure to control behavior. Amygdala volume increase is discussed on the background of a linkage of this structure with ADHD symptomatology. Correlations with clinical data revealed gray matter volume changes in specific brain areas that have been described in these conditions each.</p

Reactive hyperemia during short-term blood flow and pressure changes in the hypertensive forearm.

The aim of the present study was to further validate our method for the determination of minimal forearm vascular resistance after ischemia (13 min arterial occlusion and 1 min hand exercise) in patients with hypertension. This parameter, calculated as the ratio of mean blood pressure (intra-arterial recordings on the experimental side) to forearm blood flow (strain-gauge venous plethysmography), was measured basally and after either increasing (through unrelated vasodilators such as sodium nitroprusside or the calcium antagonist nicardipine in six mild-to-moderate uncomplicated hypertensives) or decreasing (norepinephrine, n = 4) flow without changes in systemic pressure. In spite of the divergent starting flow values, minimal postischemic forearm vascular resistance was unchanged, indicating a lack of relationship with functional arteriolar tone and the achievement of maximal dilatation. In two additional groups of patients, systemic arterial pressure was decreased by approximately equipotent oral doses of either nifedipine, a calcium antagonist (n = 6), or captopril, an angiotension converting enzyme inhibitor (n = 5). Under these conditions, minimal forearm vascular resistance was unchanged from pretreatment values, suggesting that local autoregulatory mechanisms were overridden during the reactive hyperemia, and that the vessel lumen was dependent on the distending pressure. Overall, the data show that our experimental conditions are suitable for measuring minimal forearm vascular resistance as a functional correlate of the morphological status of systemic arterioles in arterial hypertension

Method for determination of the displacement field in patterned nanostructures by TEM/CBED analysis of split high-order Laue zone line profiles

A method to extract accurate information on the displacement field distribution from split high-order Laue zones lines in a convergent-beam electron diffraction pattern of nanostructures has been developed. Starting from two-dimensional many beam dynamical simulation of HOLZ patterns, we assembled a recursive procedure to reconstruct the displacement field in the investigated regions of the sample, based on the best fit of a parametrized model. This recursive procedure minimizes the differences between simulated and experimental patterns, taken in strained regions, by comparing the corresponding rocking curves of a number of high-order Laue zone reflections. Due to its sensitivity to small displacement variations along the electron beam direction, this method is able to discriminate between different models, and can be also used to map a strain field component in the specimen. We tested this method in a series of experimental convergent-beam electron diffrac tion patterns, taken in a shallow trench isolation structure. The method presented here is of general validity and, in principle, it can be applied to any sample where not negligible strain gradients along the beam direction are present

Quantitative strain mapping in nano electronic silicon dvices by convergent beam electron diffraction

Lattice deformations which are generated in thedifferent process steps of the current technology fornanoelectronic devices can affect either positively ornegatively their electrical performances. In both casesquantitative information on strains at the nanometerscale are necessary, and presently this can only beachieved by convergent beam electron diffraction(CBED), a technique available in any moderntransmission electron microscope (TEM). In this paper the basic principles of CBED, the method to extract the local strain tensorfrom an experimental diffraction pattern and its application to twodimensional strain mapping in the active silicon region of ultra-scaled isolation structures are reported. The limitations of this method, particularly in the case of high strain gradients along a direction perpendicular to the plane of the device TEM cross section, are discussed. Possible solutions to obtain the displacement field distribution, with reference to a practical case, are described

Strain field reconstruction in shallow trench isolation structures by CBED and LACBED

Using a combination of the CBED and the LACBED techniques in the transmission electron microscopy (TEM), we have investigated the strain field in the silicon active region of a shallow trench isolation structure, underlying a TiSi2 layer. Starting from the analysis of the deformation in a sample, thinned for TEM analysis, we have reconstructed the displacement field, simulating the split HOLZ lines visible in the experimental CBED patterns. From the comparison between the experimental LACBED patterns, taken in a suitable sample orientation to evidence the stressors distribution in the polycrystalline silicide layer, and the corresponding dynamically simulated ones, we have reproduced the strain field in the unthinned, bulk sample. (c) 2006 Elsevier B.V. All rights reserved

Method for determination of the displacement field in patterned nanostructures by TEM/CBED analysis of split high-order Laue zone line profiles

A method to extract accurate information on the displacement field distribution from split high-order Laue zones lines in a convergent-beam electron diffraction pattern of nanostructures has been developed. Starting from two-dimensional many beam dynamical simulation of HOLZ patterns, we assembled a recursive procedure to reconstruct the displacement field in the investigated regions of the sample, based on the best fit of a parametrized model. This recursive procedure minimizes the differences between simulated and experimental patterns, taken in strained regions, by comparing the corresponding rocking curves of a number of high-order Laue zone reflections. Due to its sensitivity to small displacement variations along the electron beam direction, this method is able to discriminate between different models, and can be also used to map a strain field component in the specimen. We tested this method in a series of experimental convergent-beam electron diffraction patterns, taken in a shallow trench isolation structure. The method presented here is of general validity and, in principle, it can be applied to any sample where not negligible strain gradients along the beam direction are present

Transmission Electron Microscopy characterization and sculpting of sub-1 nm Si-O-C freestanding nanowires grown by electron beam induced deposition

The authors present a transmission electron microscopy characterization and sculpting of freestanding Si-O-C nanowires, fabricated by electron beam induced deposition from a tetraethylorthosilicate precursor, in a dual beam system. Electron energy loss spectroscopy and near edge structure analyses performed on as deposited wires show the formation of amorphous silicon dioxide with extra oxygen and carbon content. Subsequent electron beam sculpting by 200 keV transmission electron microscope irradiation decreases carbon and oxygen contents leaving the silicon oxidation state unchanged and narrows Si-O-C wire width to less than 1 nm. (c) 2006 American Institute of Physics

TEM study of annealed Pt nanostructures grown by electron beam induced deposition

In this paper we report on the microstructural characterization of Pt nanostructures fabricated by electron beam-induced deposition in a dual beam system and subsequently annealed in furnace. The as-deposited natiostructures are made of a mixture of nanocrystalline Pt and amorphous carbon. We show by transmission electron microscopy and electron energy loss spectroscopy that the annealing in presence of oxygen at 550 degrees C for 30 min is able to remove the amorphous carbon from the nanostructure, leaving polycrystalline Pt grains. (c) 2006 Elsevier B.V. All rights reserved