A Note on Allowed and Realized Rates of Return in the Electric Utility Industry

Most empirical investigations of electric utility behavior use the realized rate of return as a proxy for the allowed rate of return, We examine the validity of this assumption and investigate the relationship of the allowed and realized rates to the cost of capital between 1973 and 1982, We use two measures of the cost of capital: one based on returns to book equity, the other derived from a market price of equity. While realized and allowed rates were generally higher than the book measure throughout the period, both of the rates of return were less than the market price of capital after 1979. We also find firms did not earn their allowed rate of return after 1974. Therefore, the use of the realized rate as a proxy for the allowed rate in empirical models will lead to biased parameter estimates. To help correct this bias, we give data for allowed rates

First Measurement of a Rapid Increase in the AGN Fraction in High-Redshift Clusters of Galaxies

We present the first measurement of the AGN fraction in high-redshift clusters of galaxies (z~0.6) with spectroscopy of one cluster and archival data for three additional clusters. We identify 8 AGN in all four of these clusters from the Chandra data, which are sensitive to AGN with hard X-ray (2-10keV) luminosity L_{X,H} > 10^43 erg/s in host galaxies more luminous than a rest frame M_R < -20 mag. This stands in sharp contrast to the one AGN with L_{X,H} > 10^43 erg/s we discovered in our earlier study of eight low-redshift clusters with z=0.06-0.31 (average z~0.2). Three of the four high-redshift cluster datasets are sensitive to nearly L_{X,H} > 10^42 erg/s and we identify seven AGN above this luminosity limit, compared to two in eight, low-redshift clusters. Based on membership estimates for each cluster, we determine that the AGN fraction at z~0.6 is f_A(L_X>10^42;M_R<-20) = 0.028 (+0.019/-0.012) and f_A(L_X>10^43;M_R<-20) = 0.020 (+0.012/-0.008). These values are approximately a factor of 20 greater than the AGN fractions in lower-redshift (average z~0.2) clusters of galaxies and represent a substantial increase over the factors of 1.5 and 3.3 increase, respectively, in the measured space density evolution of the hard X-ray luminosity function over this redshift range. Potential systematic errors would only increase the significance of our result. The cluster AGN fraction increases more rapidly with redshift than the field and the increase in cluster AGN indicates the presence of an AGN Butcher-Oemler Effect.Comment: ApJL Accepted, 5 pages, 2 figure

Multiwavelength transit observations of the candidate disintegrating planetesimals orbiting WD 1145+017

We present multiwavelength, ground-based follow-up photometry of the white dwarf WD 1145+017, which has recently been suggested to be orbited by up to six or more short-period, low-mass, disintegrating planetesimals. We detect nine significant dips in flux of between 10% and 30% of the stellar flux in our ~32 hr of photometry, suggesting that WD 1145+017 is indeed being orbited by multiple, short-period objects. Through fits to the asymmetric transits that we observe, we confirm that the transit egress is usually longer than the ingress, and that the transit duration is longer than expected for a solid body at these short periods, all suggesting that these objects have cometary tails streaming behind them. The precise orbital periods of the planetesimals are unclear, but at least one object, and likely more, have orbital periods of ~4.5 hr. We are otherwise unable to confirm the specific periods that have been reported, bringing into question the long-term stability of these periods. Our high-precision photometry also displays low-amplitude variations, suggesting that dusty material is consistently passing in front of the white dwarf, either from discarded material from these disintegrating planetesimals or from the detected dusty debris disk. We compare the transit depths in the V- and R-bands of our multiwavelength photometry, and find no significant difference; therefore, for likely compositions, the radius of single-size particles in the cometary tails streaming behind the planetesimals must be ~0.15 μm or larger, or ~0.06 μm or smaller, with 2σ confidence

Enhancing thermal conductivity of fluids with nanoparticles

Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in many industrial applications. In this paper we propose that an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat transfer fluids. The resulting {open_quotes}nanofluids{close_quotes} are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluids, and they represent the best hope for enhancement of heat transfer. The results of a theoretical study of the thermal conductivity of nanofluids with copper nanophase materials are presented, the potential benefits of the fluids are estimated, and it is shown that one of the benefits of nanofluids will be dramatic reductions in heat exchanger pumping power

A Note on Allowed and Realized Rates of Return in the Electric Utility Industry

Most empirical investigations of electric utility behavior use the realized rate of return as a proxy for the allowed rate of return, We examine the validity of this assumption and investigate the relationship of the allowed and realized rates to the cost of capital between 1973 and 1982, We use two measures of the cost of capital: one based on returns to book equity, the other derived from a market price of equity. While realized and allowed rates were generally higher than the book measure throughout the period, both of the rates of return were less than the market price of capital after 1979. We also find firms did not earn their allowed rate of return after 1974. Therefore, the use of the realized rate as a proxy for the allowed rate in empirical models will lead to biased parameter estimates. To help correct this bias, we give data for allowed rates

Analytical modeling for the heat transfer in sheared flows of nanofluids

We developed a model for the enhancement of the heat flux by spherical and elongated nano- particles in sheared laminar flows of nano-fluids. Besides the heat flux carried by the nanoparticles the model accounts for the contribution of their rotation to the heat flux inside and outside the particles. The rotation of the nanoparticles has a twofold effect, it induces a fluid advection around the particle and it strongly influences the statistical distribution of particle orientations. These dynamical effects, which were not included in existing thermal models, are responsible for changing the thermal properties of flowing fluids as compared to quiescent fluids. The proposed model is strongly supported by extensive numerical simulations, demonstrating a potential increase of the heat flux far beyond the Maxwell-Garnet limit for the spherical nanoparticles. The road ahead which should lead towards robust predictive models of heat flux enhancement is discussed.Comment: 14 pages, 10 figures, submitted to PR

Tempo and mode of performance evolution across multiple independent origins of adhesive toe pads in lizards

Understanding macroevolutionary dynamics of trait evolution is an important endeavor in evolutionary biology. Ecological opportunity can liberate a trait as it diversifies through trait space, while genetic and selective constraints can limit diversification. While many studies have examined the dynamics of morphological traits, diverse morphological traits may yield the same or similar performance and as performance is often more proximately the target of selection, examining only morphology may give an incomplete understanding of evolutionary dynamics. Here, we ask whether convergent evolution of pad‐bearing lizards has followed similar evolutionary dynamics, or whether independent origins are accompanied by unique constraints and selective pressures over macroevolutionary time. We hypothesized that geckos and anoles each have unique evolutionary tempos and modes. Using performance data from 59 species, we modified Brownian motion (BM) and Ornstein–Uhlenbeck (OU) models to account for repeated origins estimated using Bayesian ancestral state reconstructions. We discovered that adhesive performance in geckos evolved in a fashion consistent with Brownian motion with a trend, whereas anoles evolved in bounded performance space consistent with more constrained evolution (an Ornstein–Uhlenbeck model). Our results suggest that convergent phenotypes can have quite distinctive evolutionary patterns, likely as a result of idiosyncratic constraints or ecological opportunities

Secondhand Smoke Exposure and Preclinical Markers of Cardiovascular Risk in Toddlers

Objective: Links between secondhand smoke (SHS) exposure and cardiovascular disease in adults are well established but seldom reported during childhood. Although rates of smoking have decreased, young children from low-income backgrounds remain likely to be exposed to SHS. The purpose of this study was to investigate relationships between SHS exposure in young children and several preclinical markers of cardiovascular risk that have been established as relevant to adult populations. Methods: 139 children, 2–5 years of age, were enrolled in a cross-sectional study. SHS exposure was objectively determined by hair nicotine level; a comprehensive panel of clinical markers (AM blood pressure, fasting glucose & insulin, lipid profiles, inflammation) and research markers (markers of oxidation, endothelial stress, and endothelial repair) of cardiovascular risk status were assessed. Univariate and multivariate linear regression were used to evaluate relationships between SHS exposure and cardiovascular risk markers. Results: Hair nicotine levels were directly correlated with blood pressure and serum CRP, and inversely correlated with serum HDL and endothelial cell progenitor cell prevalence. In multivariate analyses, these relationships remained when controlled for age, sex, BMI z-score, maternal education, and method of payment. Additionally, in multivariate analyses, hair nicotine level was significantly negatively correlated with total anti-oxidant capacity. Conclusions: These results support the view that SHS exposure in the very young has a detectable relationship with several markers of cardiovascular risk, long before the emergence of clinical disease. Further studies to define mechanisms and strategies to prevent and mitigate these risks early in life are warranted