The evolving role of the Federal Home Loan Banks in mortgage markets

The Federal Home Loan Banks are part of a system created by the federal government to promote home ownership. This Commentary looks at new initiatives undertaken by these government-sponsored enterprises to expand their role in financial markets-and the attendant implications for their balance sheets.Federal home loan banks ; Mortgages ; Housing - Finance

The Effect of Risk on the Firm's Optimal Capital Stock: A Note

In this paper we extend the recent work on the choice of input mix under uncertainty. In particular, we demonstrate that the qualitative nature of the disturbance term, along with the decision sequence, is a crucial determinant of the overall effect of uncertainty on the optimal input mix of a firm. Using general demand and production functions in conjunction with a mean-variance framework for financial valuation, we demonstrate the differential effects of systematic and non-systematic risk on the firm's choice of an optimal input mix. Consistent with earlier work in economics, this analysis demonstrates that uncertainty, regardless of the source, has important implications for the firm's choice of technology.

Taxes, Default Risk, and Yield Spreads

This paper represents an extension and integration of recent empirical and theoretical research on default risk and taxability. The purpose of the paper is to develop and test a model of interest rate spreads which incorporates both the effect of taxes and differences in default probabilities in a theoretically correct manner. There is an important fundamental difference between our approach to explaining yield spreads and the approach most commonly taken in literature. Unlike nearly all of the previous work, we do not begin with a yield spread model, i.e.,one which begins by examining differences in yields, but rather begin with an expected return or pricing model, which can then be expressed in the yield spread format. This is a fundamental difference in approaches which we feel leads to a superior theoretical formulation which can then be tested empirically without many of the problems inherent in the alter-native approach. The theoretical model is a simple extension of earlierwork on default by Bierman and Hass (1975) and Yawitz (1977), altered appropriately to take explicit account of tax effects. While there is a considerable literature that analyzes the effect of taxability on rate spreads, we are unaware of any previous study that considers tax consequences in the event of default, a rather surprising omission.

“Small steps, or giant leaps?” Comparing game demands of U23, U18, and U16 English academy soccer and their associations with speed and endurance

The current study aimed to compare locomotive outputs across English U16, U18 and U23 academy soccer and investigate possible relationships with neuromuscular and aerobic capacities. Participants included 46 outfield players from an English Category Two soccer academy. Global positioning system (18Hz) data were utilised to analyse locomotive outputs across twenty eleven-a-side matches in each age group. Maximal sprinting speed (MSS) and aerobic speed (MAS) were assessed at the beginning of the season. Absolute total distance (TD), high-speed running (HSR), acceleration and deceleration workloads were higher in U18’s and U23’s vs. U16’s (g = 1.09-2.58; p < 0.05), and absolute sprinting distances were higher in U23’s vs. U16’s (g = 0.96; p < 0.05). In addition, relative HSR outputs were higher in U23’s vs. U18’s (g = 1.84-2.07; p < 0.05). Across the whole cohort, players’ MSS was positively associated with absolute HSR and sprinting distances (ρ = 0.53-0.79; p < 0.05) but not with relative parameters. MAS was positively associated with total distance, decelerations, and both absolute and relative HSR outputs (ρ = 0.33-0.56; p < 0.05). Overall, absolute locomotive outputs were significantly higher in U23’s and U18’s vs. U16’s. Locomotive outputs were also associated with maximal sprinting and aerobic speeds. Thus, training programmes should be tailored to competition demands to optimally prepare each age group for competition and reflect the increasing demands of each level of competition. Further, improving physical fitness (speed and endurance) is likely to drive greater outputs in competition

The Escape of Ionizing Photons from the Galaxy

The Magellanic Stream and several high velocity clouds have now been detected in optical line emission. The observed emission measures and kinematics are most plausibly explained by photoionization due to hot, young stars in the Galactic disk. The highly favorable orientation of the Stream allows an unambiguous determination of the fraction of ionizing photons, F_esc, which escape the disk. We have modelled the production and transport of ionizing photons through an opaque interstellar medium. Normalization to the Stream detections requires F_esc = 6%, in reasonable agreement with the flux required to ionize the Reynolds layer. Neither shock heating nor emission within a hot Galactic corona can be important in producing the observed H-alpha emission. If such a large escape fraction is typical of L_* galaxies, star-forming systems dominate the extragalactic ionizing background. Within the context of this model, both the three-dimensional orientation of the Stream and the distances to high-velocity clouds can be determined by sensitive H-alpha observations.Comment: 4 pages; LaTeX2e, emulateapj.sty, apjfonts.sty; 4 encapsulated PS figures. For correct labels, may need to print Fig. 3 separately due to psfig limitation. Astrophysical Journal (Letters), accepte

The Smith Cloud: HI associated with the Sgr dwarf?

The Smith high velocity cloud (V(LSR) = 98 kms) has been observed at two locations in the emission lines [OIII]5007, [NII]6548 and H-alpha. Both the [NII] and H-alpha profiles show bright cores due to the Reynolds layer, and red wings with emission extending to V(LSR) = 130 kms. This is the first simultaneous detection of two emission lines towards a high velocity cloud, allowing us to form the ratio of these line profiles as a function of LSR velocity. At both cloud positions, we see a clear distinction between emission at the cloud velocity, and the Reynolds layer emission (V(LSR) = 0). The [NII]/H-alpha ratio (=0.25) for the Reynolds layer is typical of the warm ionised medium. At the cloud velocity, this ratio is enhanced by a factor of 3-4 compared to emission at rest with respect to the LSR. A moderately deep upper limit at [OIII] (0.12R at 3-sigma) was derived from our data. If the emission arises from dilute photoionisation from hot young stars, the highly enhanced [NII]/H-alpha ratio, the [OIII] non-detection and weak H-alpha emission (0.24-0.30R) suggest that the Smith Cloud is 26+/-4 kpc from the Sun, at a Galactocentric radius of 20+/-4 kpc. This value assumes that the emission arises from an optically thick slab, with a covering fraction of unity as seen by the ionizing photons, whose orientation is either (a) parallel to the Galactic disk, or (b) such as to maximize the received flux from the disk. The estimated mass and size of the cloud are 4x10^6 Msun and 6 kpc. We discuss a possible association with the much larger Sgr dwarf, at a galactocentric radius of 16+/-2 kpc, which lies within 35 degrees (~12 kpc) of the Smith Cloud.Comment: 18 pages, 14 figures, mn.sty. Our first application of a new method for establishing distances to high velocity clouds. This version matches paper to appear in MNRAS, 299, 611-624 (Sept. 11 issue

Evolution of displacements and strains in sheared amorphous solids

The local deformation of two-dimensional Lennard-Jones glasses under imposed shear strain is studied via computer simulations. Both the mean squared displacement and mean squared strain rise linearly with the length of the strain interval $\Delta \gamma$ over which they are measured. However, the increase in displacement does not represent single-particle diffusion. There are long-range spatial correlations in displacement associated with slip lines with an amplitude of order the particle size. Strong dependence on system size is also observed. The probability distributions of displacement and strain are very different. For small $\Delta \gamma$ the distribution of displacement has a plateau followed by an exponential tail. The distribution becomes Gaussian as $\Delta \gamma$ increases to about .03. The strain distributions consist of sharp central peaks associated with elastic regions, and long exponential tails associated with plastic regions. The latter persist to the largest $\Delta \gamma$ studied.Comment: Submitted to J. Phys. Cond. Mat. special volume for PITP Conference on Mechanical Behavior of Glassy Materials. 16 Pages, 8 figure

Remodelling of the natural product fumagillol employing a reaction discovery approach

In the search for new biologically active molecules, diversity-oriented synthetic strategies break through the limitation of traditional library synthesis by sampling new chemical space. Many natural products can be regarded as intriguing starting points for diversity-oriented synthesis, wherein stereochemically rich core structures may be reorganized into chemotypes that are distinctly different from the parent structure. Ideally, to be suited to library applications, such transformations should be general and involve few steps. With this objective in mind, the highly oxygenated natural product fumagillol has been successfully remodelled in several ways using a reaction-discovery-based approach. In reactions with amines, excellent regiocontrol in a bis-epoxide opening/cyclization sequence can be obtained by size-dependent interaction of an appropriate catalyst with the parent molecule, forming either perhydroisoindole or perhydroisoquinoline products. Perhydroisoindoles can be further remodelled by cascade processes to afford either morpholinone or bridged 4,1-benzoxazepine-containing structures.P50 GM067041 - NIGMS NIH HHS; P50 GM067041-07 - NIGMS NIH HHS; P50 GM067041-08 - NIGMS NIH HHS; P50 GM067041-09 - NIGMS NIH HH

Simple de Sitter Solutions

We present a framework for de Sitter model building in type IIA string theory, illustrated with specific examples. We find metastable dS minima of the potential for moduli obtained from a compactification on a product of two Nil three-manifolds (which have negative scalar curvature) combined with orientifolds, branes, fractional Chern-Simons forms, and fluxes. As a discrete quantum number is taken large, the curvature, field strengths, inverse volume, and four dimensional string coupling become parametrically small, and the de Sitter Hubble scale can be tuned parametrically smaller than the scales of the moduli, KK, and winding mode masses. A subtle point in the construction is that although the curvature remains consistently weak, the circle fibers of the nilmanifolds become very small in this limit (though this is avoided in illustrative solutions at modest values of the parameters). In the simplest version of the construction, the heaviest moduli masses are parametrically of the same order as the lightest KK and winding masses. However, we provide a method for separating these marginally overlapping scales, and more generally the underlying supersymmetry of the model protects against large corrections to the low-energy moduli potential.Comment: 37 pages, harvmac big, 4 figures. v3: small correction