Design study for LANDSAT-D attitude control system

The gimballed Ku-band antenna system for communication with TDRS was studied. By means of an error analysis it was demonstrated that the antenna cannot be open loop pointed to TDRS by an onboard programmer, but that an autotrack system was required. After some tradeoffs, a two-axis, azimuth-elevation type gimbal configuration was recommended for the antenna. It is shown that gimbal lock only occurs when LANDSAT-D is over water where a temporary loss of the communication link to TDRS is of no consequence. A preliminary gimbal control system design is also presented. A digital computer program was written that computes antenna gimbal angle profiles, assesses percent antenna beam interference with the solar array, and determines whether the spacecraft is over land or water, a lighted earth or a dark earth, and whether the spacecraft is in eclipse

The Role of Ligand Steric Bulk in New Monovalent Aluminum Compounds

The article of record as published may be located at https://doi.org/10.1021/acs.jpca.7b02075The tetrameric Al(I) cyclopentadienyl compound Al4Cp*4 (Cp* = C5Me5) is a prototypical low-valence Al compound, with delocalized bonding between four Al(I) atoms and η5 ligands bound to the cluster exterior. The synthesis of new [AlR]4 (R = C5Me4Pr, C5Me4iPr) tetramers is presented. Though these systems failed to crystallize, comparison of variable-temperature 27Al NMR data with density functional theory (DFT) calculations indicate that these are Al4R4 tetramers analogous to Al4Cp*4 but with increased ligand steric bulk. NMR, DFT, and Atoms in Molecules analyses show that these clusters are enthalpically more stable as tetramers than the Cp* variant, due in part to noncovalent interactions across the bulkier ligand groups. Thermochemistry calculations for the low-valence metal interactions were found to be extremely sensitive to the DFT methodology used; the M06-2X functional with a cc-pVTZ basis set is shown to provide very accurate values for the enthalpy of tetramerization and 27Al NMR shifts. This computational method is then used to predict geometrical structures, noncovalent ligand interactions, and monomer/tetramer equilibrium in solution for a series of Al(I) cyclopentadienyl compounds of varying steric bulk

Egg development and toxicity of insecticides to eggs, neonate larvae and adults of Xylotrechus arvicola, a pest in Iberian grapevines

Xylotrechus arvicola (Coleoptera: Cerambycidae) is a xylophagous species that is becoming an important pest in vineyards in the Iberian Peninsula. The most sensitive stages are adult and egg, but their neonate larvae can also be attacked during the first 24 h after hatching and before entering the wood. Adults were evaluated for seven days against the insecticides spinosad, Beauveria bassiana, imidacloprid and chlorpyrifos and neonate larvae (< 24 h) and eggs of different ages against the described insecticides, as well as flufenoxuron and pyriproxyfen. All insecticides were applied in a Potter tower at a maximum and minimum commercial dose, and showed significant differences both among insecticides as between the applied doses. Most of the hatching occurs eight days after oviposition by X. arvicola females. Chlorpyrifos had a quick and total control of eggs of different ages, neonate larvae and adults in both dosis applied, but its effectiveness could cause serious effects on other non-target species. Pyriproxifen and flufenoxuron had the best ovicidal control when the age of eggs increases and, B. bassiana also had a good ovicidal control, due its capacity to invade the eggs actively through their shell and proliferate inside them. Biological insecticides such as B. bassiana and spinosad, with a total control on adults and good rates of mortality of neonate larvae and eggs can be a great instrument to biological control of this pest

Biometric traits of Xylotrechus arvicola adults from laboratory and grape fields

Xylotrechus arvicola is a pest in vineyards on the Iberian Peninsula. The action of the larvae, associated to the spread of wood fungi, causes a direct and indirect damage in the crop. This article presents biometric traits of X. arvicola population adults captured in three grape fields with Protected Designation of Origin (PDO) from the Iberian Peninsula and one population of this beetle obtained in the laboratory. The aim of the study was to observe the influence of sex and environment on the size of adults. The adults showed intersexual differences for the length and width of the pronotum, the length and width of the elytra and total length. The wild females were larger than wild males and the males from grape fields were slender than wild females. The environment affected the size of the adults. The laboratory adults reached the greatest body size. The size of the adult reflects the volume of material that had been used as host where the insect had developed. The captured adults in PDO Toro, with Bush Vines Training System (BVTS) were larger than the other PDOs, leading to bigger galleries and exit holes, which could affect the structural resistance of the plant and increase pathogenic fungi infection. However, BVTS facilitates the renovation of attacked branches, which is more difficult and slower in the Bilateral Cordon Training System (BCTS)

Evolution Equation of Phenotype Distribution: General Formulation and Application to Error Catastrophe

An equation describing the evolution of phenotypic distribution is derived using methods developed in statistical physics. The equation is solved by using the singular perturbation method, and assuming that the number of bases in the genetic sequence is large. Applying the equation to the mutation-selection model by Eigen provides the critical mutation rate for the error catastrophe. Phenotypic fluctuation of clones (individuals sharing the same gene) is introduced into this evolution equation. With this formalism, it is found that the critical mutation rate is sometimes increased by the phenotypic fluctuations, i.e., noise can enhance robustness of a fitted state to mutation. Our formalism is systematic and general, while approximations to derive more tractable evolution equations are also discussed.Comment: 22 pages, 2 figure

VerdictDB: Universalizing Approximate Query Processing

Despite 25 years of research in academia, approximate query processing (AQP) has had little industrial adoption. One of the major causes of this slow adoption is the reluctance of traditional vendors to make radical changes to their legacy codebases, and the preoccupation of newer vendors (e.g., SQL-on-Hadoop products) with implementing standard features. Additionally, the few AQP engines that are available are each tied to a specific platform and require users to completely abandon their existing databases---an unrealistic expectation given the infancy of the AQP technology. Therefore, we argue that a universal solution is needed: a database-agnostic approximation engine that will widen the reach of this emerging technology across various platforms. Our proposal, called VerdictDB, uses a middleware architecture that requires no changes to the backend database, and thus, can work with all off-the-shelf engines. Operating at the driver-level, VerdictDB intercepts analytical queries issued to the database and rewrites them into another query that, if executed by any standard relational engine, will yield sufficient information for computing an approximate answer. VerdictDB uses the returned result set to compute an approximate answer and error estimates, which are then passed on to the user or application. However, lack of access to the query execution layer introduces significant challenges in terms of generality, correctness, and efficiency. This paper shows how VerdictDB overcomes these challenges and delivers up to 171$\times$ speedup (18.45$\times$ on average) for a variety of existing engines, such as Impala, Spark SQL, and Amazon Redshift, while incurring less than 2.6% relative error. VerdictDB is open-sourced under Apache License.Comment: Extended technical report of the paper that appeared in Proceedings of the 2018 International Conference on Management of Data, pp. 1461-1476. ACM, 201

Building blocks of a black hole

What is the nature of the energy spectrum of a black hole ? The algebraic approach to black hole quantization requires the horizon area eigenvalues to be equally spaced. As stressed long ago by by Mukhanov, such eigenvalues must be exponentially degenerate with respect to the area quantum number if one is to understand black hole entropy as reflecting degeneracy of the observable states. Here we construct the black hole states by means of a pair of "creation operators" subject to a particular simple algebra, a slight generalization of that for the harmonic oscillator. We then prove rigorously that the n-th area eigenvalue is exactly 2 raised to the n-fold degenerate. Thus black hole entropy qua logarithm of the number of states for fixed horizon area comes out proportional to that area.Comment: PhysRevTeX, 14 page

Late-time evolution of the Yang-Mills field in the spherically symmetric gravitational collapse

We investigate the late-time evolution of the Yang-Mills field in the self-gravitating backgrounds: Schwarzschild and Reissner-Nordstr\"om spacetimes. The late-time power-law tails develop in the three asymptotic regions: the future timelike infinity, the future null infinity and the black hole horizon. In these two backgrounds, however, the late-time evolution has quantitative and qualitative differences. In the Schwarzschild black hole background, the late-time tails of the Yang-Mills field are the same as those of the neutral massless scalar field with multipole moment l=1. The late-time evolution is dominated by the spacetime curvature. When the background is the Reissner-Nordstr\"om black hole, the late-time tails have not only a smaller power-law exponent, but also an oscillatory factor. The late-time evolution is dominated by the self-interacting term of the Yang-Mills field. The cause responsible for the differences is revealed.Comment: Revtex, 14 pages, no figure