A comparison of methods for DPLL loop filter design

Four design methodologies for loop filters for a class of digital phase-locked loops (DPLLs) are presented. The first design maps an optimum analog filter into the digital domain; the second approach designs a filter that minimizes in discrete time weighted combination of the variance of the phase error due to noise and the sum square of the deterministic phase error component; the third method uses Kalman filter estimation theory to design a filter composed of a least squares fading memory estimator and a predictor. The last design relies on classical theory, including rules for the design of compensators. Linear analysis is used throughout the article to compare different designs, and includes stability, steady state performance and transient behavior of the loops. Design methodology is not critical when the loop update rate can be made high relative to loop bandwidth, as the performance approaches that of continuous time. For low update rates, however, the miminization method is significantly superior to the other methods

A rapid and easy method for the purification of the Neurospora crassa NADP-specific glutamate dehydrogenase

In order to study an oxidative modification of the Neurospora crassa NADP-specific glutamate dehydrogenase (GDH[NADP]) during aerial growth, we were compelled to purify this enzyme

Tests of the asymptotic large frequency separation of acoustic oscillations in solar-type and red giant stars

Asteroseismology, i.e. the study of the internal structures of stars via their global oscillations, is a valuable tool to obtain stellar parameters such as mass, radius, surface gravity and mean density. These parameters can be obtained using certain scaling relations which are based on an asymptotic approximation. Usually the observed oscillation parameters are assumed to follow these scaling relations. Recently, it has been questioned whether this is a valid approach, i.e., whether the order of the observed oscillation modes are high enough to be approximated with an asymptotic theory. In this work we use stellar models to investigate whether the differences between observable oscillation parameters and their asymptotic estimates are indeed significant. We compute the asymptotic values directly from the stellar models and derive the observable values from adiabatic pulsation calculations of the same models. We find that the extent to which the atmosphere is included in the models is a key parameter. Considering a larger extension of the atmosphere beyond the photosphere reduces the difference between the asymptotic and observable values of the large frequency separation. Therefore, we conclude that the currently suggested discrepancies in the scaling relations might have been overestimated. Hence, based on the results presented here we believe that the suggestions of Mosser et al. (2013) should not be followed without careful consideration.Comment: 6 pages, 4 figures, 1 table, accepted for publication by MNRAS as a Letter to the Edito

Copper Tolerance of \u3ci\u3eSaccharomyces cerevisiae\u3c/i\u3e Nonsense-Mediated mRNA Decay Mutants

The eukaryotic nonsense-mediated mRNA (NMD) is a specialized pathway that leads to the recognition and rapid degradation of mRNAs with premature termination codons, and importantly some natural mRNAs as well. Natural mRNAs with atypically long 3′-untranslated regions (UTRs) are degraded by NMD in Saccharomyces cerevisiae. A number of S. cerevisiae mRNAs undergo alternative 3′-end processing producing mRNA isoforms that differ in their 3′-UTR lengths. Some of these alternatively 3′-end processed mRNA isoforms have atypically long 3′-UTRs and would be likely targets for NMD-mediated degradation. Here, we investigated the role NMD plays in the regulation of expression of CTR2, which encodes a vacuolar membrane copper transporter. CTR2 pre-mRNA undergoes alternative 3′-end processing to produce two mRNA isoforms with 300-nt and 2-kb 3′-UTRs. We show that both CTR2 mRNA isoforms are differentially regulated by NMD. The regulation of CTR2 mRNA by NMD has physiological consequences, since nmd mutants are more tolerant to toxic levels of copper relative to wild-type yeast cells and the copper tolerance of nmd mutants is dependent on the presence of CTR2

Phenotypic variation and sexual dimorphism in anadromous threespine stickleback: Implications for postglacial adaptive radiation

Ancestral properties can influence patterns of evolutionary diversification, but ancestors can rarely be observed directly. We examined variation and sexual dimorphism of morphological traits in an anadromous threespine stickleback population representing the ancestral form for resident postglacial stickleback populations in the area. A combination of traditional and geometric morphometric methods were used to study variation over multiple years in an anadromous population that breeds in Rabbit Slough, Cook Inlet, Alaska. Major armor anomalies were extremely rare but their occurrence at measurable frequencies suggests that significant standing variation for armor phenotypes exists in anadromous populations. Sexual dimorphism was a major source of variation, and most traits differed significantly between sexes, particularly head length, length of the pelvic girdle, and body shape. Consequently, some degree of sexual dimorphism appears to be the ancestral condition for many traits in derived resident freshwater stickleback radiations. Morphological variation among years, especially in body shape, was significant in both sexes, but the magnitude of annual variation was always less than variation due to other factors. Phenotypic means were relatively stable over short time scales. Postglacial stickleback radiations are among the most enlightening cases of adaptive radiation, and our detailed study of variation in an anadromous stickleback population provides crucial insight into a key component of adaptive radiation, the variation on which directional selection acts at the onset of the radiation. © 2008 The Linnean Society of London

Who responds to whom and for what? A grounded theory analysis of social responsibility in the 1857 Frankfurt Bienfaisance Congress

The purpose of this study is to examine and interpret the characteristics of social responsibility in general, and business responsibility in particular, that were evident during a period in European history that was plagued by widespread social problems and change. Based on that interpretation we explore the lessons those characteristics may have for social responsibility in a contemporary world that is facing similar conditions. The paper presents a qualitative analysis of the proceedings of the Bienfaisance Congress held in Frankfurt in 1857, where societal leaders from different nations met to answer the question, who has responsibility for whom, and for what? We use grounded theory, as it is operationalized in what is known as the “Gioia template,” to conduct a structured analysis of this particular text, and to in turn produce a theoretical interpretation of how that question was answered. Our interpretation is that congress participants articulated certain established dimensions of responsibility (individual, organizational, national), as well as one new dimension (international), and did so by differentiating boundaries of responsibility; in turn, we suggest that these dimensions and boundaries work together to form a nested system of responsibilities. There is limited empirical evidence available that documents the variety of responsibility-based initiatives that were being conducted during the 19th-century. An analysis of the congress proceedings allows us to gain a better understanding of how the 19th-century world, particularly the upper echelons of European society, approached the question of under what conditions actors in different domains have responsibility for another. While our implications are limited by our analysis of the proceedings of one congress that was attended by elites, they do provide a snapshot of how Europe sought to articulate a system of bounded responsibilities during a time of widespread social problems and change. Although the nested system of responsibilities framework that emerged from our grounded-theory analysis is not applicable to all situations, it should sensitize policy makers and business leaders to the need to address social problems in a systemic way. The authors both present a systems-based framework for understanding how responsibility is differentiated among actors (individual, organizational, state, and international) and demonstrate how a theoretical interpretation of historical documents can be accomplished through the use of grounded theory, as operationalized through the Gioia template.ITESO, A.C

General Relativistic Radiant Shock Waves in the Post-Quasistatic Approximation

An evolution of radiant shock wave front is considered in the framework of a recently presented method to study self-gravitating relativistic spheres, whose rationale becomes intelligible and finds full justification within the context of a suitable definition of the post-quasistatic approximation. The spherical matter configuration is divided into two regions by the shock and each side of the interface having a different equation of state and anisotropic phase. In order to simulate dissipation effects due to the transfer of photons and/or neutrinos within the matter configuration, we introduce the flux factor, the variable Eddington factor and a closure relation between them. As we expected the strength of the shock increases the speed of the fluid to relativistic values and for some critical ones is larger than light speed. In addition, we find that energy conditions are very sensible to the anisotropy, specially the strong one. As a special feature of the model, we find that the contribution of the matter and radiation to the radial pressure are the same order of magnitude as in the mant as in the core, moreover, in the core radiation pressure is larger than matter pressure.Comment: To appear in Journal of Physics:Conference Series:"XXIX Spanish Relativity Meeting (ERE 2006): Einstein's Legacy: From the Theoretical Paradise to Astrophysical Observations

Animal modelling for inherited central vision loss.

Disease-causing variants of a large number of genes trigger inherited retinal degeneration leading to photoreceptor loss. Because cones are essential for daylight and central vision such as reading, mobility, and face recognition, this review focuses on a variety of animal models for cone diseases. The pertinence of using these models to reveal genotype/phenotype correlations and to evaluate new therapeutic strategies is discussed. Interestingly, several large animal models recapitulate human diseases and can serve as a strong base from which to study the biology of disease and to assess the scale-up of new therapies. Examples of innovative approaches will be presented such as lentiviral-based transgenesis in pigs and adeno-associated virus (AAV)-gene transfer into the monkey eye to investigate the neural circuitry plasticity of the visual system. The models reported herein permit the exploration of common mechanisms that exist between different species and the identification and highlighting of pathways that may be specific to primates, including humans