Exploiting the high-frequency performance of low-voltage low-power SC filters

This paper investigates the design of low-voltage low-power switched-capacitor (SC) filters for high-frequency applications by using the clock-booster approach. In particular, our proposed SC filter architecture uses single-ended double-sampling integrator cells based on low-voltage operational transconductance amplifiers which take advantage of dynamic biasing and the clock-booster technique to drive the switch transistors. To validate its high-frequency capability, two low-pass elliptic SC filters respectively with a corner frequency of 6 and 8-MHz, were designed in a 0.35-/spl mu/m CMOS process. Both are suitable for telecom applications and can operate with a power supply as low as 1.5 V, while dissipating 11 mW. Measurements showed that for an output amplitude of 1 V/sub pp/, their total harmonic distortions were maintained well below -40 dB in their bandwidths. Comparisons with other SC filter implementations in the literature, which highlight the quality of our implementation are also provided.     

Microglia are more efficient than astrocytes in antigen processing and in Th1 but not Th2 cell activation

Microglia and astrocytes, two glial cell populations of the central nervous system, present Ag and stimulate T cell proliferation, but it is unclear whether they preferentially activate Th1 or Th2 responses. We have investigated the efficiency of microglia and astrocytes in the presentation of OVA peptide 323-339 or native OVA to Th1 and Th2 cell lines from DO11.10 TCR transgenic mice. Upon stimulation with IFN-gamma, microglia express MHC class II molecules, CD40, and ICAM-1 and efficiently present OVA 323-339, leading to T cell proliferation and production of IL-2 and IFN-gamma by Th1 and of IL-4 by Th2 cells. IFN-gamma-treated astrocytes, which express MHC class II and ICAM-1, present OVA 323-339 less efficiently to Th1 cells but are as efficient as microglia in inducing IL-4 secretion by Th2 cells. However, astrocytes are much less potent than microglia in presenting naturally processed OVA peptide to either T cell subset, indicating inefficient Ag processing. The capacity of astrocytes and microglia to stimulate Th1 and Th2 cells depends on their MHC class II expression and does not involve ICAM-1, B7-1, or B7-2 molecules. However, CD40-CD40L interactions contribute to Th1 activation by microglia. These data suggest that microglia may play a role in the activation of Th1 and Th2 cells, whereas astrocytes would restimulate mainly Th2 responses in the presence of appropriate peptides. This differential capacity of brain APC to restimulate Th1 and Th2 responses may contribute to the reactivation and regulation of local inflammatory processes during infectious and autoimmune diseases.     

Use of scanning probe microscopy to study the evolution of nanometer sized liquid structures

The evolution of the profile of nanometer sized water drops on a mica surface has been studied through hydration scanning probe microscopy. A time range from a few seconds down to a fraction of millisecond after the formation of the drop has been explored. This high time resolution has been obtained by sampling a series of statistically equivalent drops. This approach also avoids any probe interference during the drop evolution process.     

Effects of novelty and pain on behavior and hippocampal extracellular ACh levels in male and female rats

In vivo microdialysis was used to assess the effects of novelty and pain on hippocampal ACh release in male and female rats. Experiments were carried out during the dark phase and consisted of 2 days of tests: on Day 1, after Baseline 1, animals were exposed to a new cage (Novelty) to which, 30 min later, a plastic cylinder (Object) was introduced. On Day 2, after Baseline 2, the Formalin test (50 microl of formalin 10%, s.c. injected in the dorsal hindpaw) was carried out in the animal's home cage. All behaviors were recorded. The extracellular levels of ACh in the dorsal hippocampus were estimated, in 10-min samples, by assay of ACh in the dialysates by HPLC. On Day 1 the raw values of ACh were higher in females than in males, but no sex difference was present when the percentage of change was considered. In both sexes the Novelty and Object tests induced an increase in ACh levels with respect to Baseline. Higher levels of exploration were present in females than males during the first 10 min of Novelty. On Day 2, ACh release increased in both sexes during the Formalin test. No sex difference in either ACh raw values or the percentages of change were found. Females showed higher levels of licking and lower levels of activity than males. The present study shows that novelty and pain induce similar hippocampal cholinergic activation in male and female rats but different behaviors. The results are discussed in light of the several anatomical and functional sex differences present in the hippocampus.     

1 V CMOS output stage with excellent linearity

A CMOS low-voltage output stage based on a push-pull topology is proposed. It is driven by a differential signal and its symmetric topology provides excellent intrinsic linearity. It can work with a power supply as low as 1 V and when loaded with a 500 /spl Omega/ resistor it exhibits negligible even harmonic components whilst odd components are maintained well below -20 dB up to 900 mV/sub pp/ of the output signal. Moreover, the output stage includes a simple current control which accurately sets the bias condition.     

Response of cat cortical neurons to position and movement of the femur

The contribution of joint afferents to the response of cortical neurons in area 3a to mechanical stimulation of the contralateral hindlimb was evaluated in cats anesthetized with sodium pentobarbital and paralyzed with pancuronium bromide. The hindlimb projection to the pericruciate cortex was established by recording the evoked potentials to electrical stimulation of the sciatic nerve and some of its branches, the bicepssemitendinosus and the quadratus femoris. Out of 169 neurons, 63 responded exclusively to cutaneous stimuli (superficial), whereas the others could be activated by local pressure of hindlimb muscles and/or by joint rotation (deep). Deep neurons were classified as slowly adapting (SA) or rapidly adapting (RA) units. In the neurons responding exclusively to joint rotation, the site of the receptive field could not be identified with certainty. In 13 deep neurons, their firing was affected by rotation of multiple joints of the contralateral hindlimb. In an attempt to identify the source of activation of cortical neurons, partial denervations and muscle disconnections were performed in five animals to isolate and stimulate the hip capsule. In these preparations, in 14 of 15 cortical neurons the source of activation was localized in the periarticular muscles, with no response to mechanical stimulation of the joint capsule. Only one neuron (SA) could be selectively excited by punctate pressure on the hip capsule. Our results suggest that in neurons of area 3a of the cat, the information about the position of the femur relies mainly on muscle afferents.     

Design guidelines of CMOS class-AB output stages: a tutorial

This article presents useful guidelines for designing CMOS class-AB output stages. Three Quality Factors, which allow analysis and comparison of different output stages, are used to design two CMOS class-AB stages. We show that using the proposed Quality Factors and the related strategy leads to an efficient design in terms trade-off among area, current consumption, bandwidth and distortion. Indeed, for one of the two stages adopted as example, the design through the Quality Factors results in superior distortion performance with respect to the design suggested in the original article. Design examples and simulations are provided to validate the design strategy.     

Using iterated rational filter banks within the ARSIS concept for producing 10m Landsat multispectral images

The ARSIS concept is designed to increase the spatial resolution of an image without modification of its spectral contents, by merging structures extracted from a higher resolution image of the same scene, but in a different spectral band. It makes use of wavelet transforms and multiresolution analysis. It is currently applied in an operational way with dyadic wavelet transforms that limit the merging of images whose ratio of their resolution is a power of 2. Nevertheless, provided some conditions rational discrete wavelet transforms can be approximated numerically by rational filter banks which would enable a more general merging. Indeed, in theory, the ratio of the resolution of the images to merge is a power of a certain family of rational numbers. The aim of this paper is to examine whether the use of those approximations of rational wavelet transforms are efficient within the ARSIS concept. This work relies on a particular case: the merging of a 10 m SPOT Panchromatic image and a 30 m Landsat Thematic Mapper multispectral image to synthesize 10 m multispectral image TM-HR.     

Gated-Clock Design of Linear-Feedback Shift Registers

In this paper, we will present a method to reduce the power consumption of the popular linear feedback shift register. The proposed scheme is based on the gated clock design approach and it can offer a significant power reduction, depending on technological characteristics of the employed gates. Moreover, the analytical condition that must be satisfied to achieve a power reduction of the gated-clock circuit has been found. Theoretical analysis was validated through many transistor-level SPECTRE simulations in CADENCE environment by using the 0.35- mum digital standard cells technology supplied by AMS. Simulation results have shown a power reduction of about 10% with a mean error of about 3% with respect to theoretical derivations.