317 research outputs found
Yield modeling of acoustic charge transport transversal filters
This paper presents a yield model for acoustic charge transport transversal filters. This model differs from previous IC yield models in that it does not assume that individual failures of the nondestructive sensing taps necessarily cause a device failure. A redundancy in the number of taps included in the design is explained. Poisson statistics are used to describe the tap failures, weighted over a uniform defect density distribution. A representative design example is presented. The minimum number of taps needed to realize the filter is calculated, and tap weights for various numbers of redundant taps are calculated. The critical area for device failure is calculated for each level of redundancy. Yield is predicted for a range of defect densities and redundancies. To verify the model, a Monte Carlo simulation is performed on an equivalent circuit model of the device. The results of the yield model are then compared to the Monte Carlo simulation. Better than 95% agreement was obtained for the Poisson model with redundant taps ranging from 30% to 150% over the minimum
Do nudges reduce borrowing and consumer confusion in the credit card market?
We study nudges that turn out to have precise null effects in reducing long-run credit card debt. We test nudges across two field experiments covering 183,441 UK cardholders. Our first experiment studies nudges added to monthly credit card statements. Our second experiment studies letters and email nudges (separate from monthly statements) sent to cardholders who signed up to automatically pay the minimum required payment.In a follow-up survey to our second experiment, we find that 96% of respondents underestimate the time it would take to fully repay a debt if the cardholder made only the minimum required payment. The nudges reduce this confusion, but underestimation remains overwhelmingly common
Quantitative trait loci affecting liver fat content in mice
Nonalcoholic fatty liver disease, a condition in which excess fat accumulates in the liver, is strongly associated with the metabolic syndrome, including obesity and other related conditions. This disease has the potential to progress from steatosis to steatohepatitis, fibrosis, and cirrhosis. The recent increase in the prevalence of the metabolic syndrome is largely driven by changes in diet and activity levels. Individual variation in the response to this obesogenic environment, however, is attributable in part to genetic variation between individuals, but very few mammalian genetic loci have been identified with effects on fat accumulation in the liver. To study the genetic basis for variation in liver fat content in response to dietary fat, liver fat proportion was determined using quantitative magnetic resonance imaging in 478 mice from 16 LG/J X SM/J recombinant inbred strains fed either a high-fat (42% kcal from fat) or low-fat (15% kcal from fat) diet. An analysis of variance confirmed that there is a genetic basis for variation in liver fat content within the population with significant effects of sex and diet. Three quantitative trail loci that contribute to liver fat content also were mapped
Macmillan, Verwoerd, and the 1960 `wind of change' speech
Just over fifty years ago, Prime Minister Macmillan made an extensive tour of Africa, culminating in his 'wind of change' speech in Cape Town. This article traces Macmillan's progress through Africa with particular emphasis on his intervention in South African politics. It offers a novel reading of the 1960 'wind of change' speech, arguing that the message was far more conciliatory with respect to white South African interests than is usually assumed. Pragmatism rather than principle was always the prime consideration. Far from being cowed by Macmillan's oratory or his message, Verwoerd stood up to Macmillan and, at least in the eyes of his supporters, gave as good as he got. The shock of the 'wind of change' speech was more evident in Britain and in British settler regions of Africa than in South Africa. Macmillan's advisers had an inflated view of the import of the speech and in many ways misread Verwoerd's brand of Afrikaner nationalism. One of the consequences of the speech was to embolden Verwoerd politically, and to prepare him for the declaration of republican status in 1961 and departure from the commonwealth
Nearest neighbours in least-squares data imputation algorithms with different missing patterns
Methods for imputation of missing data in the so-called least-squares approximation approach, a non-parametric computationally efficient multidimensional technique, are experimentally compared. Contributions are made to each of the three components of the experiment setting: (a) algorithms to be compared, (b) data generation, and (c) patterns of missing data. Specifically, "global" methods for least-squares data imputation are reviewed and extensions to them are proposed based on the nearest neighbours (NN) approach. A conventional generator of mixtures of Gaussian distributions is theoretically analysed and, then, modified to scale clusters differently. Patterns of missing data are defined in terms of rows and columns according to three different mechanisms that are referred to as Random missings, Restricted random missings, and Merged database. It appears that NN-based versions almost always outperform their global counterparts. With the Random missings pattern, the winner is always the authors' two-stage method M, which combines global and local imputation algorithms
Molecular gas in NUclei of GAlaxies (NUGA). XI. A complete gravity torque map of NGC4579: new clues on bar evolution
We create a complete gravity torque map of the disk of the LINER/Seyfert 1.9
galaxy NGC4579. We quantify the efficiency of angular momentum transport and
search for signatures of secular evolution in the fueling process from r~15kpc
down to the inner r~50pc around the Active Galactic Nucleus (AGN). We use both
the 1-0 and 2-1 line maps of CO obtained with the Plateau de Bure
Interferometer (PdBI) as part of the NUclei of Galaxies-(NUGA)-project. We
derive the stellar potential from a NIR (K band) wide field image of the
galaxy. The K-band image, which reveals a stellar bar, together with a high
resolution HI map of NGC4579 obtained with the Very Large Array (VLA), allow us
to extend the gravity torque analysis to the outer disk. The bulk of the gas
response traced by the CO PdBI maps follows the expected gas flow pattern
induced by the bar potential in the presence of two Inner Lindblad Resonances
(ILR). We also detect an oval distortion in the inner r~200pc of the K-band
image. The oval is not aligned with the large-scale bar, a signature of
dynamical decoupling. The morphology of the outer disk suggests that the
neutral gas is currently piling up in a pseudo-ring formed by two winding
spiral arms that are morphologically decoupled from the bar structure. In the
outer disk, the decoupling of the spiral allows the gas to efficiently produce
net gas inflow on intermediate scales. The corotation barrier seems to be
overcome due to secular evolution processes. The gas in the inner disk is
efficiently funneled by gravity torques down to r~300pc. Closer to the AGN, the
two m=2 modes (bar and oval) act in concert to produce net gas inflow down to
r~50pc, providing a clear smoking gun evidence of fueling with associated short
dynamical time-scales.Comment: Submitted for publication in A&A. 21 pages, 21 figure
Default Effects of Credit Card Minimum Payments
Credit card minimum payments are designed to ensure that individuals pay down their debt over time, and scheduling minimum automatic repayments helps to avoid forgetting to repay. Yet minimum payments have additional, unintended psychological default effects by drawing attention away from the card balance due. First, once individuals set the minimum automatic repayment as the default, they then neglect to make the occasional larger repayments they made previously. As a result, individuals incur considerably more credit card interest than late payment fees avoided. Using detailed transaction data, the authors show that approximately 8% of all of the interest ever paid is due to this effect. Second, manual credit card payments are lower when individuals are prompted with minimum payment information. Two new interventions to mitigate this effect are tested in an experiment, prompting full repayment and prompting those repaying little to pay more, with large counter effects. Hence, shrouding the minimum payment option for automatic and manual payments and directing attention to the full balance may remedy these unintended effects
Molecular Gas in NUclei of GAlaxies (NUGA) I.The counter-rotating LINER NGC4826
We present new high-resolution observations of the nucleus of the
counter-rotating LINER NGC4826, made in the J=1-0 and J=2-1 lines of 12CO with
the IRAM Plateau de Bure mm-interferometer(PdBI).The CO maps, which achieve
0.8''(16pc) resolution in the 2-1 line, fully resolve an inner molecular gas
disk which is truncated at an outer radius of 700pc. The total molecular gas
mass is distributed in a lopsided nuclear disk of 40pc radius and two one-arm
spirals, which develop at different radii in the disk. The distribution and
kinematics of molecular gas in the inner 1kpc of NGC4826 show the prevalence of
different types of m=1 perturbations in the gas. Although dominated by
rotation, the gas kinematics are perturbed by streaming motions related to the
m=1 instabilities. The non-circular motions associated with the inner m=1
perturbations agree qualitatively with the pattern expected for a trailing wave
developed outside corotation ('fast' wave). In contrast, the streaming motions
in the outer m=1 spiral are better explained by a 'slow' wave. A paradoxical
consequence is that the inner m=1 perturbations would not favour AGN feeding.
An independent confirmation that the AGN is not being generously fueled at
present is found in the low values of the gravitational torques exerted by the
stellar potential for R<530pc. The distribution of star formation in the disk
of NGC4826 is also strongly asymmetrical. Massive star formation is still
vigorous, fed by the significant molecular gas reservoir at R<700pc. There is
supporting evidence for a recent large mass inflow episode in NGC4826.
These observations have been made in the context of the NUclei of GAlaxies
(NUGA) project, aimed at the study of the different mechanisms for gas fueling
of AGN.Comment: A&A, 2003, Paper accepted (04/06/03). For a full-resolution version
of this paper see http://www.oan.es/preprint
Evolution along the sequence of S0 Hubble types induced by dry minor mergers. I - Global bulge-to-disk structural relations
Recent studies have argued that galaxy mergers are not important drivers for
the evolution of S0's, on the basis that mergers cannot preserve the coupling
between the bulge and disk scale-lengths observed in these galaxies and the
lack of correlation of their ratio with the S0 Hubble type. We investigate
whether the remnants resulting from collision-less N-body simulations of
intermediate and minor mergers onto S0 galaxies evolve fulfilling global
structural relations observed between the bulges and disks of these galaxies.
Different initial bulge-to-disk ratios of the primary S0 have been considered,
as well as different satellite densities, mass ratios, and orbits of the
encounter. We have analysed the final morphology of the remnants in images
simulating the typical observing conditions of S0 surveys. We derive bulge+disk
decompositions of the final remnants to compare their global bulge-to-disk
structure with observations. We show that all remnants present undisturbed S0
morphologies according to the prescriptions of specialized surveys. The dry
intermediate and minor mergers induce noticeable bulge growth (S0c --> S0b and
S0b --> S0a), but affect negligibly to the bulge and disk scale-lengths.
Therefore, if a coupling between these two components exists prior to the
merger, the encounter does not break this coupling. This fact provides a simple
explanation for the lack of correlation between the ratio of bulge and disk
scale-lengths and the S0 Hubble type reported by observations. These models
prove that dry intermediate and minor mergers can induce global structural
evolution within the sequence of S0 Hubble types compatible with observations,
meaning that these processes should not be discarded from the evolutionary
scenarios of S0's just on the basis of the strong coupling observed between the
bulge and disk scale-lengths in these galaxies (abridged).Comment: Accepted for publication in Astronomy & Astrophysics, 12 pages, 11
figures. Definitive version after proofs. Corrected typo in the legend of
Fig. 2. Definitive version of Fig. 7 (pending copyright implications in the
previous version). Added references and corrected typo
The Herschel Virgo Cluster Survey. IX. Dust-to-gas mass ratio and metallicity gradients in four Virgo spiral galaxies
Using Herschel data from the Open Time Key Project the Herschel Virgo Cluster
Survey (HeViCS), we investigated the relationship between the metallicity
gradients expressed by metal abundances in the gas phase as traced by the
chemical composition of HII regions, and in the solid phase, as traced by the
dust-to-gas mass ratio. We derived the radial gradient of the dust-to-gas mass
ratio for all galaxies observed by HeViCS whose metallicity gradients are
available in the literature. They are all late type Sbc galaxies, namely
NGC4254, NGC4303, NGC4321, and NGC4501. We examined different dependencies on
metallicity of the CO-to-H conversion factor (\xco), used to transform the
CO observations into the amount of molecular hydrogen. We found that in
these galaxies the dust-to-gas mass ratio radial profile is extremely sensitive
to choice of the \xco\ value, since the molecular gas is the dominant component
in the inner parts. We found that for three galaxies of our sample, namely
NGC4254, NGC4321, and NGC4501, the slopes of the oxygen and of the dust-to-gas
radial gradients agree up to 0.6-0.7R using \xco\ values in the
range 1/3-1/2 Galactic \xco. For NGC4303 a lower value of \xco
10 is necessary. We suggest that such low \xco\ values might be due to a
metallicity dependence of \xco (from close to linear for NGC4254, NGC4321, and
NGC4501 to superlinear for NGC4303), especially in the radial regions
R0.6-0.7R where the molecular gas dominates. On the other hand, the
outer regions, where the atomic gas component is dominant, are less affected by
the choice of \xco, and thus we cannot put constraints on its value.Comment: 13 pages, 8 figures, A&A accepte
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