3,832 research outputs found
A CMOS Mixed Mode Non-Linear Processing Unit for Adaptive Sensor Conditioning in Portable Smart Systems
This paper presents the architecture of a novel non-linear digitally programmable analog unit for sensor output conditioning in battery-operated smart systems. Designed in an 180nm 1.8V standard CMOS technology, by properly setting the 6-bit registers in the arithmetic unit, the voltage inputs are weighted before being processed by a non-linear circuit. Thus, a processing system consisting of a set of these devices suitably tuned and interconnected can be applied to condition a non-linear sensor, improving its behavior both in linearity and operating range, while reducing the effects of cross sensitivity. The robustness of the digital weight tuning is tested simulating a chip-on-the-loop training using a Levenberg-Marquardt-based algorithm. Electric simulations of the proposed unit and the results of its application in a complete neural network-based processing system to improve the linear operating range of a thermistor are presented
A Fully-Integrated CMOS LDO Regulator for Battery-Operated On-Chip Measurement Systems
This paper presents a fully-integrated 0.18 mu m CMOS low drop-out (LDO) regulator designed to drive on-chip low power frontend sensor nodes. The proposed LDO is based on a simple telescopic amplifier stage with internal cascode compensation driving a PMOS pass-device, providing a high precision 1.8 V output voltage for input voltages from 3.6 V to 1.92 V up to a 50 mA load current with only 22 mu A quiescent current. Line and load regulation are respectively better than 0.017 mV/V and 0.003 mV/mA, while recovery times are below 4 mu s over a (-40 degrees C, 120 degrees C) temperature span
Local and Large scale Environment of Seyfert Galaxies
We present a three-dimensional study of the local (<100 h^-1} kpc) and the
large scale (<1 h^{-1} Mpc) environment of the two main types of Seyfert AGN
galaxies. For this purpose we use 48 Sy1 galaxies (with redshifts in the range
0.007<z<0.036) and 56 Sy2 galaxies (with 0.004<z<0.020), located at high
galactic latitudes, as well as two control samples of non-active galaxies
having the same morphological, redshift, and diameter size distributions as the
corresponding Seyfert samples. Using the Center for Astrophysics (CfA2) and
Southern Sky Redshift Survey (SSRS) galaxy catalogues (m_B~15.5) and our own
spectroscopic observations (m_B~18.5), we find that within a projected distance
of 100 h^-1 kpc and a radial velocity separation of dv<600 km/sec around each
of our AGNs, the fraction of Seyfert 2 galaxies with a close neighbor is
significantly higher than that of their control (especially within 75 h^{-1}
kpc) and Seyfert 1 galaxy samples, confirming a previous two-dimensional
analysis of Dultzin-Hacyan et al. We also find that the large-scale environment
around the two types of Seyfert galaxies does not vary with respect to their
control sample galaxies. However, in the Seyfert 2 and control galaxy samples
do differ significantly when compared to the corresponding Seyfert 1 samples.
Since the main difference between these samples is their morphological type
distribution, we argue that the large-scale environmental difference cannot be
attributed to differences in nuclear activity but rather to their different
type of host galaxies.Comment: accepted for publication in ApJ, Abstract size reduced (according to
new rules) and corrected reference
A New Empirical Model for the Structural Analysis of Early-type Galaxies and a Critical Review of the Nuker Model
The Nuker law was designed to match the inner few (~3-10) arcseconds of
predominantly nearby (< 30 Mpc) early-type galaxy light-profiles; it was never
intended to describe an entire profile. The Sersic model, on the other hand,
was developed to fit the entire profile; however, due to the presence of
partially depleted galaxy cores, the Sersic model cannot always describe the
very inner region. We have therefore developed a new empirical model consisting
of an inner power-law, a transition region, and an outer Sersic model to
connect the inner and outer structure of elliptical galaxies. Moreover, the
stability of the Nuker model parameters are investigated. Surprisingly, none
are found to be stable quantities; all are shown to vary systematically with a
profile's fitted radial extent, and often by more than 100%. Considering
elliptical galaxies spanning a range of 7.5 magnitudes, the central stellar
density of the underlying host galaxy is observed to increase with galaxy
luminosity until the onset of core formation, detected only in the brightest
elliptical galaxies. We suggest that the so-called ``power-law'' galaxies may
actually be described by the Sersic model over their entire radial range
HST FOC spectroscopy of the NLR of NGC 4151. I. Gas kinematics
We present the results from a detailed kinematic analysis of both
ground-based, and Hubble Space Telescope/Faint Object Camera long-slit
spectroscopy at sub-arcsec spatial resolution, of the narrow-line region of NGC
4151. In agreement with previous work, the extended emission gas (R > 4") is
found to be in normal rotation in the galactic plane, a behaviour that we were
able to trace even across the nuclear region, where the gas is strongly
disturbed by the interaction with the radio jet, and connects smoothly with the
large scale rotation defined by the neutral gas emission. The HST data, at
0.029" spatial resolution, allow us for the first time to truly isolate the
kinematic behaviour of the individual clouds in the inner narrow-line region.
We find that, underlying the perturbations introduced by the radio ejecta, the
general velocity field can still be well represented by planar rotation down to
a radius of ~ 0.5" (30 pc), distance at which the rotation curve has its
turnover.
The most striking result that emerges from our analysis is that the galaxy
potential derived fitting the rotation curve changes from a "dark halo" at the
ENLR distances to dominated by the central mass concentration in the NLR, with
an almost Keplerian fall-off in the 1"< R < 4" interval. The observed velocity
of the gas at 0.5" implies a mass of M ~ 10E9 M(sol) within the inner 60 pc.
The presence of a turnover in the rotation curve indicates that this central
mass concentration is extended. The first measured velocity point (outside the
region saturated by the nucleus) would imply an enclosed mass of ~ 5E7 M(sol)
within R ~ 0.15" (10 pc) which represents an upper limit to any nuclear point
mass.Comment: 30 pages (aaspp4.sty), 14 figures. Fig. 1, 2 and 4 available by
anonymous FTP at 143.54.2.51 (cd /pub/winge) as GIF files; or upon request to
[email protected]. Accepted for publication in the Astrophysical Journal
(part 1
In situ measurements of speciated atmospheric mercury and the identification of source regions in the Mexico City Metropolitan Area
In order to expand the currently limited understanding of atmospheric mercury source-receptor relationships in the Mexico City Metropolitan Area, real time measurements of atmospheric mercury were made at a downtown urban site, and a rural site on the outskirts of Mexico City, during March 2006.
Numerous short-lived increases in particulate mercury (PHg) and reactive gaseous mercury (RGM) concentrations were observed at the urban site during the 17 day study, and less frequent increases in gaseous elemental mercury (GEM) concentrations were measured at both the urban and rural sites. The episodic increases observed were attributed to plume impacts from industrial point source emissions in and around Mexico City. Average concentrations and standard deviations measured during the study were as follows: i) urban site; PHg=187±300 pg mâ3 [m superscript -3], RGM=62±64 pg mâ3 [m superscript -3], GEM=7.2±4.8 ng mâ3 [m superscript -3], and; ii) rural site; GEM=5.0±2.8 ng mâ3 [m superscript -3].
Several source regions of atmospheric mercury to the urban and rural sites were determined using Concentration Field Analysis, in which atmospheric mercury measurements were combined with back trajectory data to determine source regions. Only some source regions correlated to mercury emission sources listed in the Federal Pollutant Release and Transfer Register, leaving the rest unaccounted for. Contributions of anthropogenic mercury point sources in and around Mexico City to concentration averages measured at the urban site during the study were estimated to be: 93±3% of reactive mercury (PHg and RGM), and; 81±0.4% of GEM. Point source contributions to GEM measured at the rural site were 72±1%. GEM and reactive mercury (PHg+RGM) were not found to correlate with biomass burning at either of the measurement sites.National Science Foundation (U.S.) (Grant 0514280)National Science Foundation (U.S.) (Grant 0511803)Science to Achieve Results Program (U.S.) (Grant R829798)United States. Environmental Protection Agenc
Consumer credit information systems: A critical review of the literature. Too little attention paid by lawyers?
This paper reviews the existing literature on consumer credit reporting, the most extensively used instrument to overcome information asymmetry and adverse selection problems in credit markets. Despite the copious literature in economics and some research in regulatory policy, the legal community has paid almost no attention to the legal framework of consumer credit information systems, especially within the context of the European Union. Studies on the topic, however, seem particularly relevant in view of the establishment of a single market for consumer credit. This article ultimately calls for further legal research to address consumer protection concerns and inform future legislation
Self-Assembly of Amphiphilic Dendrimers: The Role of Generation and Alkyl Chain Length in siRNA Interaction
Citation: Marquez-Miranda, V., Araya-Duran, I., Camarada, M. B., Comer, J., Valencia-Gallegos, J. A., & Gonzalez-Nilo, F. D. (2016). Self-Assembly of Amphiphilic Dendrimers: The Role of Generation and Alkyl Chain Length in siRNA Interaction. Scientific Reports, 6, 15. https://doi.org/10.1038/srep29436An ideal nucleic-acid transfection system should combine the physical and chemical characteristics of cationic lipids and linear polymers to decrease cytotoxicity and uptake limitations. Previous research described new types of carriers termed amphiphilic dendrimers (ADs), which are based on polyamidoamine dendrimers (PAMAM). These ADs display the cell membrane affinity advantage of lipids and preserve the high affinity for DNA possessed by cationic dendrimers. These lipid/dendrimer hybrids consist of a low-generation, hydrophilic dendron (G2, G1, or G0) bonded to a hydrophobic tail. The G2-18C AD was reported to be an efficient siRNA vector with significant gene silencing. However, shorter tail ADs (G2-15C and G2-13C) and lower generation (G0 and G1) dendrimers failed as transfection carriers. To date, the self-assembly phenomenon of this class of amphiphilic dendrimers has not been molecularly explored using molecular simulation methods. To gain insight into these systems, the present study used coarse-grained molecular dynamics simulations to describe how ADs are able to self-assemble into an aggregate, and, specifically, how tail length and generation play a key role in this event. Finally, explanations are given for the better efficiency of G2/18-C as gene carrier in terms of binding of siRNA. This knowledge could be relevant for the design of novel, safer ADs with well-optimized affinity for siRNA
The effects of spatial resolution on Integral Field Spectrograph surveys at different redshifts. The CALIFA perspective
Over the past decade, 3D optical spectroscopy has become the preferred tool
for understanding the properties of galaxies and is now increasingly used to
carry out galaxy surveys. Low redshift surveys include SAURON, DiskMass,
ATLAS3D, PINGS and VENGA. At redshifts above 0.7, surveys such as MASSIV, SINS,
GLACE, and IMAGES have targeted the most luminous galaxies to study mainly
their kinematic properties. The on-going CALIFA survey () is the
first of a series of upcoming Integral Field Spectroscopy (IFS) surveys with
large samples representative of the entire population of galaxies. Others
include SAMI and MaNGA at lower redshift and the upcoming KMOS surveys at
higher redshift. Given the importance of spatial scales in IFS surveys, the
study of the effects of spatial resolution on the recovered parameters becomes
important. We explore the capability of the CALIFA survey and a hypothetical
higher redshift survey to reproduce the properties of a sample of objects
observed with better spatial resolution at lower redshift. Using a sample of
PINGS galaxies, we simulate observations at different redshifts. We then study
the behaviour of different parameters as the spatial resolution degrades with
increasing redshift.Comment: 20 pages, 16 figures. Accepted for publication in A&
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