Institutional Debt Holder Governance

Using data on the universe of US-based mutual funds, we find that two out of five fund families hold corporate bonds of firms in which they also own an equity stake. We show that the greater the fraction of debt a fund family holds in a given firm, the greater its propensity to vote in line with the interests of firm debt holders at shareholder meetings. Voting has direct policy consequences as firms that receive more votes in favor of creditors make corporate decisions more in line with the interests of debt holders

Constraints on scalar diffusion anomaly in three-dimensional flows having bounded velocity gradients

This study is concerned with the decay behaviour of a passive scalar $\theta$ in three-dimensional flows having bounded velocity gradients. Given an initially smooth scalar distribution, the decay rate $d/dt$ of the scalar variance $$ is found to be bounded in terms of controlled physical parameters. Furthermore, in the zero diffusivity limit, $\kappa\to0$, this rate vanishes as $\kappa^{\alpha_0}$ if there exists an $\alpha_0\in(0,1]$ independent of $\kappa$ such that $<\infty$ for $\alpha\le\alpha_0$. This condition is satisfied if in the limit $\kappa\to0$, the variance spectrum $\Theta(k)$ remains steeper than $k^{-1}$ for large wave numbers $k$. When no such positive $\alpha_0$ exists, the scalar field may be said to become virtually singular. A plausible scenario consistent with Batchelor's theory is that $\Theta(k)$ becomes increasingly shallower for smaller $\kappa$, approaching the Batchelor scaling $k^{-1}$ in the limit $\kappa\to0$. For this classical case, the decay rate also vanishes, albeit more slowly -- like $(\ln P_r)^{-1}$, where $P_r$ is the Prandtl or Schmidt number. Hence, diffusion anomaly is ruled out for a broad range of scalar distribution, including power-law spectra no shallower than $k^{-1}$. The implication is that in order to have a $\kappa$-independent and non-vanishing decay rate, the variance at small scales must necessarily be greater than that allowed by the Batchelor spectrum. These results are discussed in the light of existing literature on the asymptotic exponential decay $\sim e^{-\gamma t}$, where $\gamma>0$ is independent of $\kappa$.Comment: 6-7 journal pages, no figures. accepted for publication by Phys. Fluid

Robust transmission stabilization and dynamic switching in broadband hybrid waveguide systems with nonlinear gain and loss

We develop a method for transmission stabilization and robust dynamic switching for colliding optical soliton sequences in broadband waveguide systems with nonlinear gain and loss. The method is based on employing hybrid waveguides, consisting of spans with linear gain and cubic loss, and spans with linear loss, cubic gain, and quintic loss. We show that amplitude dynamics is described by a hybrid Lotka-Volterra (LV) model, and use the model to determine the physical parameter values required for enhanced transmission stabilization and switching. Numerical simulations with the coupled nonlinear Schr\"odinger equations confirm the predictions of the LV model, and show stable transmission over distances larger by an order of magnitude compared with uniform waveguides with linear gain and cubic loss. Moreover, multiple on-off and off-on dynamic switching events are demonstrated over a wide range of soliton amplitudes, showing the superiority of hybrid waveguides compared with static switching in uniform waveguides, considered in earlier studies.Comment: 19 pages, 3 figure

Fuzzy control system for a remote focusing microscope

Space Station Crew Health Care System procedures require the use of an on-board microscope whose slide images will be transmitted for analysis by ground-based microbiologists. Focusing of microscope slides is low on the list of crew priorities, so NASA is investigating the option of telerobotic focusing controlled by the microbiologist on the ground, using continuous video feedback. However, even at Space Station distances, the transmission time lag may disrupt the focusing process, severely limiting the number of slides that can be analyzed within a given bandwidth allocation. Substantial time could be saved if on-board automation could pre-focus each slide before transmission. The authors demonstrate the feasibility of on-board automatic focusing using a fuzzy logic ruled-based system to bring the slide image into focus. The original prototype system was produced in under two months and at low cost. Slide images are captured by a video camera, then digitized by gray-scale value. A software function calculates an index of 'sharpness' based on gray-scale contrasts. The fuzzy logic rule-based system uses feedback to set the microscope's focusing control in an attempt to maximize sharpness. The systems as currently implemented performs satisfactorily in focusing a variety of slide types at magnification levels ranging from 10 to 1000x. Although feasibility has been demonstrated, the system's performance and usability could be improved substantially in four ways: by upgrading the quality and resolution of the video imaging system (including the use of full color); by empirically defining and calibrating the index of image sharpness; by letting the overall focusing strategy vary depending on user-specified parameters; and by fine-tuning the fuzzy rules, set definitions, and procedures used

Strength and flexibility properties of advanced ceramic fabrics

The mechanical properties of four advanced ceramic fabrics are measured at a temperature range of 23 C to 1200 C. The fabrics evaluated are silica, high-and low-boria content aluminoborosilicate, and silicon carbide. Properties studied include fabric break strengths from room temperature to 1200 C, and bending durability after temperature conditioning at 1200 C and 1400 C. The interaction of the fabric and ceramic insulation is also studied for shrinkage, appearance, bend resistance, and fabric-to-insulation bonding. Based on these tests, the low-boria content aluminoborosilicate fabric retains more strength and fabric durability than the other fabrics studied at high temperature

Valence Bond Entanglement and Fluctuations in Random Singlet Phases

The ground state of the uniform antiferromagnetic spin-1/2 Heisenberg chain can be viewed as a strongly fluctuating liquid of valence bonds, while in disordered chains these bonds lock into random singlet states on long length scales. We show that this phenomenon can be studied numerically, even in the case of weak disorder, by calculating the mean value of the number of valence bonds leaving a block of $L$ contiguous spins (the valence-bond entanglement entropy) as well as the fluctuations in this number. These fluctuations show a clear crossover from a small $L$ regime, in which they behave similar to those of the uniform model, to a large $L$ regime in which they saturate in a way consistent with the formation of a random singlet state on long length scales. A scaling analysis of these fluctuations is used to study the dependence on disorder strength of the length scale characterizing the crossover between these two regimes. Results are obtained for a class of models which include, in addition to the spin-1/2 Heisenberg chain, the uniform and disordered critical 1D transverse-field Ising model and chains of interacting non-Abelian anyons.Comment: 8 pages, 6 figure