178,993 research outputs found
Comparison of two sealing coupling geometries for a direct fuel injector
No full textThe present paper describes some Finite Elements simulations carried out in order to investigate the contact problem in the sealing region of a direct fuel injector. In particular two different design solutions have been analyzed, both patent pending, one characterized by a conformal contact of two conic surfaces and the other one by a non-conformal contact between a cone and a sphere. Pressure distribution, contact width and von Mises equivalent stress have been calculated and employed as comparison parameters. Two different loading conditions have been considered: nominal loads and nominal loads plus undesired effects. Also deviations from the nominal geometry, obtained from profile detection of 40 samples, have been introduced for considering a real-like case. Numerical results stress the robustness of the non-conformal solution with respect to geometrical tolerances and real loading conditions
Soil biological activities during the bioremediation of diesel contaminated soils
No full textThe responses of six agricultural soils, different in chemical, physical and biological characteristics, to diesel contamination were monitored during a 90-d incubation period. An evaluation of some enzyme activities and soil basal respiration as biological soil parameters to monitor soil status and quality during the decontamination process from total petroleum hydrocarbons (TPH) was carried out. Three samples were used: S (control, uncontaminated soil), CS (contaminated soil), SCS (sterilized contaminated soil). The relationships between soil parameters and the levels of TPH residues were investigated.
Results showed large loss of TPH, ranging between 28% and 40%, due to volatilization in all treatments during the first 10-d incubation period. The most effective biodegradation ability was in organic and coarse-textured soils. TPH strongly inhibited enzyme activities, mainly lipase and dehydrogenase. The soil respiration dynamics was reproduced satisfactorily by a kinetic model able to fit a flush of C mineralization followed by a stabilization phase. β-glucosidase activity and basal respiration were the best biochemical parameters for monitoring soil status and quality during the bioremediation process
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Impact of salinity on soil biological activities: a laboratory experiment
No full textIn a laboratory study, the impact of sodium chloride (NaCl) on soil quality was examined through the monitoring of soil biological activity. Artificially salinized samples were prepared from the nonsaline soil by adding NaCl at electrical conductivities (EC) 2, 4, and 8 dS · m -1 in saturated extracts. The samples were kept at 25 °C and at 50% field capacity during an incubation period of 40 days. The ATP, soil basal respiration, protease, amylase, alkaline phosphatase, dehydrogenase, and catalase activities were monitored. The biological index of fertility (BIF), the enzyme activity number (EAN), and the metabolic potential (MP) were calculated. A regression analysis was used to calculate parameters from cumulative data of carbon dioxide (CO 2) evolution. The size of microbial biomass, measured throughout the determination of ATP, was decreased by increasing salinity. Increasing concentrations of salt up to an EC of 4 dS · m -1 led to an increase of soil respiration. During incubation, protease and dehydrogenase were inhibited by NaCl; however, amylase, alkaline phosphatase, and catalase were not affected by the salt addition. Between indices, EAN confirmed the general depressive effect of NaCl on the biological properties of soil, while MP showed a pattern similar to that of soil respiration. Results of this study chiefly indicate that ATP, soil respiration, protease, dehydrogenase, EAN, and MP were able to put in evidence the effects of NaCl on soil biological activity and may be regarded as suitable tools to show the physiological reaction of soil microbial biomass under saline stress
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Delayed neonatal visual evoked potentials are associated to asymmetric growth pattern in twins
No full textObjectives: To study the association between intrauterine growth and visual pathways maturation by neonatal visual evoked potentials (VEPs) in twins, in view of a possible prognostic role. Methods: Seventy-four twin neonates from 37 pregnancies were selected based on gestational age of more than 30 weeks and uneventful perinatal clinical course. Flash VEPs were recorded at the same postmenstrual age in each twin pair. The association between P2 latency and anthropometric variables at birth was analyzed by comparison within each twin pair and regarding each variable as ordered difference between the two twins. Results: Analysis of differences within each twin pair highlighted that inter-twin difference in P2 latency was significantly related to difference in ponderal index (PI) (p = 0.048). Expressing the difference in latency as a categorical binary variable, the correlation was significant for both difference in PI, (median difference = −0.36, 95% CI −0.54 to −0.14, p = 0.001) and difference in body mass index (BMI), (median difference = −1.06, 95% CI −1.74 to −0.29, p = 0.006). Conclusions: Lower values of PI and BMI differences are associated to delayed VEP latency in twin pairs. Significance: VEP latency suggests reduced myelination of visual pathways when difference in growth pattern occurs in twins
Teselaciones simultáneas por traslación y dilatación
No full textDadas A una matriz inversible de n × n y Γ una lattice de rango completo en R n, una (A, Γ )-wavelet es una función de L 2 (R n) que genera una base ortonormal de L 2 (R n) vía sucesivas traslaciones de Γ y dilataciones de A. Una Wavelet Mnimamente Soportada en Frecuencia (MSF wavelet) es un tipo particular de wavelet cuya transformada de Fourier es la función característica de un conjunto medible de R n. En 2021 M. Bownik y D. Speegle resolvieron una pregunta geométrica planteada 25 años atrás en el contexto de la teoría de wavelets: determinar para que pares (A, Γ ) existe un conjunto medible W que tesela el espacio vía traslaciones de Γ y dilataciones de A. Tal conjunto es llamado un (A, Γ )-wavelet set. La motivación original de esta pregunta reside en el hecho de que W es un (A, Γ )-wavelet set si y solo si la antitransformada de Fourier de la función característica de W es una (A⊤, Γ ∗ )-wavelet. En esta tesis se expone la historia de este problema, su relación con la teoría de wavelets y los distintos resultados parciales que fueron esenciales para su investigación. Finalmente se da la demostración del teorema de Bownik y Speegle con el que esta pregunta abierta fue resuelta.Fil: López Puccio, Teo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
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