The Contribution of EUV from Clusters of Galaxies to the Cosmic Ionizing Background

Recent observations with the Extreme Ultraviolet Explorer (EUVE) suggest that at least some clusters of galaxies are luminous sources of extreme ultraviolet (EUV) radiation. It is not clear yet whether EUV emission is a general feature of clusters; for the purposes of limiting the contribution to the background radiation, we assume that it is true of most clusters. Assuming that the source of the EUV emission is inverse Compton (IC) scattering of the Cosmic Microwave Background photons by relativistic electrons, we construct a simple model for the expected average emission from clusters as a function of their mass and the redshift of interest. Press-Schechter theory is used to determine the abundance of clusters of various masses as a function of redshift. We determine the amount of background radiation produced by clusters. The total mean intensity, spectrum, and the ionization rates for HI and HeII are determined at present and at a variety of redshifts. Because clusters form by the merger of smaller subclusters, the amount of EUV background radiation should be larger at present than in the past. We compare our results to the ionizing background expected from quasars. We find that while clusters do contribute a significant EUV background, it is less than a percent of that expected from quasars.Comment: 13 pages in emulateapj5 style with 7 figures, accepted for publication in Astrophysical Journa

"It's Time to Rein In the Fed"

Scott Fullwiler and Senior Scholar L. Randall Wray review the roles of the Federal Reserve and the Treasury in the context of quantitative easing, and find that the financial crisis has highlighted the limited oversight of Congress and the limited transparency of the Fed. And since a Fed promise is ultimately a Treasury promise that carries the full faith and credit of the US government, the question is whether the Fed should be able to commit the public purse in times of national crisis.

"Quantitative Easing and Proposals for Reform of Monetary Policy Operations"

Beyond its original mission to "furnish an elastic currency" as lender of last resort and manager of the payments system, the Federal Reserve has always been responsible (along with the Treasury) for regulating and supervising member banks. After World War II, Congress directed the Fed to pursue a dual mandate, long interpreted to mean full employment with reasonable price stability. The Fed has been left to decide how to achieve these objectives, and it has over time come to view price stability as the more important of the two. In our view, the Fed's focus on inflation fighting diverted its attention from its responsibility to regulate and supervise the financial sector, and its mandate to keep unemployment low. Its shift of priorities contributed to creation of the conditions that led to this crisis. Now in its third phase of responding to the crisis and the accompanying deep recession-so-called "quantitative easing 2," or "QE2'-the Fed is currently in the process of purchasing $600 billion in Treasuries. Like its predecessor, QE1, QE2 is unlikely to seriously impact either of the Fed's dual objectives, however, for the following reasons: (1) additional bank reserves do not enable greater bank lending; (2) the interest rate effects are likely to be small at best given the Fed's tactical approach to QE2, while the private sector is attempting to deleverage at any rate, not borrow more; (3) purchases of Treasuries are simply an asset swap that reduce the maturity and liquidity of private sector assets but do not raise incomes of the private sector; and (4) given the reduced maturity of private sector Treasury portfolios, reduced net interest income could actually be mildly deflationary. The most fundamental shortcoming of QE—or, in fact, of using monetary policy in general to combat the recession-is that it only "works" if it somehow induces the private sector to spend more out of current income. A much more direct approach, particularly given much-needed deleveraging by the private sector, is to target growth in after tax incomes and job creation through appropriate and sufficiently large fiscal actions. Unfortunately, stimulus efforts to date have not met these criteria, and so have mostly kept the recession from being far worse rather than enabling a significant economic recovery. Finally, while there is identical risk to the federal government whether a bailout, a loan, or an asset purchase is undertaken by the Fed or the Treasury, there have been enormous, fundamental differences in democratic accountability for the two institutions when such actions have been taken since the crisis began. Public debates surrounding the wisdom of bailouts for the auto industry, or even continuing to provide benefits to the unemployed, never took place when it came to the Fed committing trillions of dollars to the financial system—even though, again, the federal government is "on the hook" in every instance.Quantitative Easing; Monetary Policy; Fiscal Policy; Macroeconomic Stabilization; Interest Rates; Central Bank Operations

The development of rapid online control in children with and without Developmental Coordination Disorder

The online control of manual actions is critical for the development of functional skills in children, not the least because demands on behaviour and complexity of the environment increase with age. When unexpected changes occur during the course of action, rapid online corrections are necessary to ensure that movement parameters (like force and timing) can be quickly updated. Developmentally, the motor network supporting online control is thought to mature rapidly over childhood; however, cross-sectional research suggests that the trajectory of change is not linear because the mode of control undergoes reorganisation during middle childhood. At the same time, development of frontal executive systems (particularly inhibition) may influence the way children enlist motor functions like online (predictive) control. Maturational theories that once considered these systems to be unitary in their development are now being challenged by a more parsimonious neuro-behavioural hypothesis—interactive specialization; this suggests behaviour can be strengthened and supported by the interaction of separate but overlapping neural networks. growing body of research indicates that online control processes may be disrupted for children with motor coordination problems (aka Developmental Coordination Disorder; DCD). As well, it has been widely reported that these children show problems related to executive function including tasks that involve response inhibition. It is argued here that deficits in predictive online control may be exacerbated under task conditions that require concurrent inhibitory control as when one is required to withhold a response to a compelling cue and move to an alternate location. However, there is not a clear picture of developmental change in the ability to couple motor and executive systems, nor of differences in growth patterns between typically developing children (TDC) and children with DCD. The purpose of my research was to address this knowledge gap by conducting cross-sectional and longitudinal studies of development to examine the unfolding interaction between online and executive systems in healthy and atypically developing children. Specifically, I examined how TDC and DCD groups corrected their arm movement mid-flight during a step-perturbation paradigm, and how a concurrent inhibitory load constrained their responses to a target shift

Application of Reynolds Stress Model Using Direct Modeling and Actuator Disk Approaches for a Small-Scale Wind Turbine

The Reynolds Stress Model (RSM) has been avoided for turbulence closure in CFD simulations of wind turbines, largely due to the computational expense and the high potential for numerical instability. The advantage of using RSM is having access to shear stresses that are not available from two-equation RANS-based closure models like k-e and k-w. Access to the shear stresses will aide in the understanding of how the blade design will affect the wake, particularly in the near-wake region. In this research, the RSM turbulence model has been successfully applied in simulating a three-bladed small-scale wind turbine through a direct-model approach and an actuator disk approach. In the direct-model method, the turbine blades were discretized within a rotating subdomain and in the actuator disk method, the turbine blades were modeled as a rotating disk using the Virtual Disk model available in Star CCM+. The transient Rigid Body Motion (RBM) simulation was able to accurately predict velocity deficit and tip vortices that compared well with hot-wire measurements and high speed images. The actuator disk method is more practical in simulating wind farms due to the simplified mesh and requires accurate information for lift and drag coefficients. Experimental results showed interaction between the tower and rotating blades can create significant turbulence in the wake. Experiments with multiple turbines showed how each turbine contributed to the velocity deficit and total turbulence intensity. For the experimental blade design, the velocity deficit recovered and turbulence intensity had dissipated within three rotor diameters