Social Security and the Retirement and Savings Behavior of Low Income Households

In this paper, we develop and estimate a model of retirement and savings incorporating limited borrowing, stochastic wage offers, health status and survival, social security benefits, Medicare and employer provided health insurance coverage, and intentional bequests. The model is estimated on sample of relatively poor households from the first three waves of the Health and Retirement Study (HRS), for whom we would expect social security income to be of particular importance. The estimated model is used to simulate the responses to several counterfactual experiments corresponding to changes in social security rules. These include changes in benefit levels, in the payroll tax, in the social security earnings tax and in early and normal retirement ages.Social Security, Retirement, Savings

Attacks Only Get Better:Password Recovery Attacks Against RC4 in TLS

Despite recent high-profile attacks on the RC4 algorithm in TLS, its usage is still running at about 30 % of all TLS traffic. This is attributable to the lack of practicality of the existing attacks, the desire to support legacy implementations, and resistance to change. We provide new attacks against RC4 in TLS that are focussed on recovering user passwords, still the pre-eminent means of user authentication on the Web today. Our attacks enhance the statistical techniques used in the existing attacks and exploit specific features of the password setting to produce attacks that are much closer to being practical. We report on extensive simulations that illustrate this. We also report on two “proof of concept ” implementations of the attacks for specific application layer protocols, namely BasicAuth and IMAP. Our work validates the truism that attacks only get better with time: we obtain good success rates in recovering user passwords with around 226 encryptions, whereas the previous generation of attacks required 234 encryptions to recover a

Macrostructural analysis : unravelling polyphase glacitectonic histories

Many Pleistocene glacial profiles look extremely simple, comprising till, or glacitectonite, overlying older sediments or bedrock (Figure 4.1). In more complex sequences the till may itself be overlain by younger sediments laid down as the ice retreated or during a completely separate, later phase of advance. Macroscopically, subglacial traction tills (Evans et al., 2007) are typically massive, unstructured deposits suggesting that it should be relatively straightforward to unravel the glacitectonic deformation history recorded by the sequence. Many reconstructions do indeed look very simple, slabs of sediment have been tilted and stacked and then overridden by the glacier to cap the structure with till. Added to this is the use of vertical exaggeration which makes the whole structure look like alpine tectonics (for an example see fig. 5 in van Gijssel, 1987). Dropping the exaggeration led to the recognition that actually we were looking at much more horizontal structures, i.e. overriding nappes and not imbricated slabs (van der Wateren, 1987). Traditionally (van der Meer, 1987) glaciotectonics was thought to relate to large structures like big push moraines and not to smaller structures like drag structures underneath tills (Figure 4.2), let alone to the tills themselves. With the notion that deforming bed tills are tectonically and not sedimentologically structured and could be regarded as tectomicts (Menzies et al., 2006), comes the realisation that glacitectonics happens across a wide range of scales, from the microscopic to tens of kilometres. Only by realising the full range of glaciotectonic scales can we hope to understand the processes

The dark matter halo shape of edge-on disk galaxies: IV. UGC 7321

This is the fourth paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. We observed for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flaring and rotation curve decomposition respectively. As reported in earlier papers in this series we have for this purpose analysed the HI channel maps to accurately measure all four functions that describe as a function of galactocentric radius the planar HI kinematics and 3D HI distribution of a galaxy: the radial HI surface density, the HI vertical thickness, the rotation curve and the HI velocity dispersion. In this paper we analyse these data for the edge-on galaxy UGC 7321. We measured the stellar mass distribution (M=3 × 108 M⊙ with M/LR\la≈ 0.2), finding that the vertical force of the gas disk dominates the stellar disk at all radii. Measurements of both the rotation curve and the vertical force field showed that the vertical force puts a much stronger constraint on the stellar mass-to-light ratio than rotation curve decomposition. Fitting of the vertical force field derived from the flaring of the HI layer and HI velocity dispersion revealed that UGC 7321 has a spherical halo density distribution with a flattening of q = c/a = 1.0 ± 0.1. However, the shape of the vertical force field showed that a non-singular isothermal halo was required, assuming a vertically isothermal HI velocity dispersion. A pseudo-isothermal halo and a gaseous disk with a declining HI velocity dispersion at high latitudes may also fit the vertical force field of UGC 7321, but to date there is no observational evidence that the HI velocity dispersion declines away from the galactic plane. We compare the halo flattening of UGC 7321 with other studies in the literature and discuss its implications. Our result is consistent with new n-body simulations which show that inclusion of hydrodynamical modelling produces more spherical halos

A 1.2 V, 38 micro\u3ci\u3eW \u3c/i\u3eSecond-Order DeltaSigma Modulator with Signal Adaptive Control Architecture

A 1.2 V, 38 μW second-order ΔΣ modulator (ΔΣM) with a Signal Adaptive Control (SAC) architecture is fabricated in a 0.35 μm standard CMOS technology (Vt,n = 0.6V, Vt,p = -0.8V). This modulator achieves 75 dB dynamic range and 63 dB of peak SNDR at 6.8kHz Nyquist rate and an oversample ratio of 64. The proposed architecture effectively reduces the power dissipation while keeping the modulator performance almost unchanged

EEG Biometrics: On the Use of Occipital Cortex Based Features from Visual Evoked Potentials

The potential of using Electro-Encephalo-Gram (EEG) data as a biometric identifier is studied. This is the first study that assesses looming stimuli for the creation of biometrically useful Visual Evoked Potentials (VEP), i.e. EEG responses due to visual stimuli. A novel method for the detection of VEP responses with minimal expert interaction is introduced. The EEG data, segmented based on the VEP, are used to create a reliable feature vector. In contrast to previous studies, we provide a publicly available evaluation dataset based on infants which is therefore not biased due to unhealthy individuals. Only data from the occipital cortex are used (i.e. about 3 of the many possible electrode positions in the scalp), making the potential EEG biometric capture devices relatively simpler

Tunable Conductivity and Conduction Mechanism in a UV light activated electronic conductor

A tunable conductivity has been achieved by controllable substitution of a novel UV light activated electronic conductor. The transparent conducting oxide system H-doped Ca12-xMgxAl14O33 (x = 0; 0.1; 0.3; 0.5; 0.8; 1.0) presents a conductivity that is strongly dependent on the substitution level and temperature. Four-point dc-conductivity decreases with x from 0.26 S/cm (x = 0) to 0.106 S/cm (x = 1) at room temperature. At each composition the conductivity increases (reversibly with temperature) until a decomposition temperature is reached; above this value, the conductivity drops dramatically due to hydrogen recombination and loss. The observed conductivity behavior is consistent with the predictions of our first principles density functional calculations for the Mg-substituted system with x=0, 1 and 2. The Seebeck coefficient is essentially composition- and temperature-independent, the later suggesting the existence of an activated mobility associated with small polaron conduction. The optical gap measured remains constant near 2.6 eV while transparency increases with the substitution level, concomitant with a decrease in carrier content.Comment: Submitted for publicatio

Fully Integrated CMOS Phase-Locked Loop With 30MHz to 2GHz Locking Range and +-35ps Jitter

A fully integrated phase-locked loop (PLL) fabricated in a 0.24 micrometer, 2.5v digital CMOS technology is described. The PLL is intended for use in multi-gigabit-per-second clock recovery circuits in fiber-optic communication chip. This PLL first time achieved a very large locking range measured to be from 30MHz up to 2GHz in 0.24 micrometer CMOS technology. Also it has very low peak-to-peak jitter less than +-35ps at 1.25GHz output frequency

Jakobshavn Glacier, west Greenland: 30 years of spaceborne observations

This is the published version, also available here: http://dx.doi.org/10.1029/98GL01973.Early 1960's reconnaissance satellite images are compared to more recent image and map data in an interannual and seasonal study of West Central Greenland margin fluctuations. From 1962 to 1992, ice sheet margins to the north and south of Jakobshavn Glacier retreated despite a decline in average summer temperatures. The retreat may be reversing along the southern flank of the ice stream where regional mass balance estimates are positive. From 1950 to 1996, the terminus of Jakobshavn Glacier seasonally fluctuated ∼2.5 km around its annual mean position. The total calving flux during the summer is more than six times that during winter. We identified that summer melting and the break-up of sea ice and icebergs in the fjord are important in controlling the rate of iceberg production. If correct, calving rates may be expected to increase should climate become warmer in the near future