Tully-Fisher relation

The observed radial velocity of a galaxy consists of two main components: the recession velocity caused by the smooth Hubble expansion and the peculiar velocity resulting from the gravitational attraction of growing structures due to matter density fluctuations. To isolate the recession velocity component and calculate the Hubble constant, accurate measurements of true distances are needed. The Tully-Fisher relation is an empirical correlation between the luminosity and rotational velocity of spiral galaxies that serves as a distance indicator to measure distances independent of redshift. The Tully-Fisher relation has played an important role in Hubble constant measurements since its inception. This chapter delves into the significance of the Tully-Fisher relation in such measurements and explores its implications. We begin by discussing the definition and historical background of the Tully-Fisher relation. We also explore the observational evidence supporting this relation and discuss its advantages and limitations. The chapter then focuses on the methodology of using the Tully-Fisher relation for Hubble constant measurements. This includes detailed explanations of calibration techniques and biases. We emphasize the advantages of utilizing the Tully-Fisher relation, such as its ability to provide accurate distance measurements even at significant redshift where other methods may encounter challenges.Comment: Invited chapter for the edited book Hubble Constant Tension (Eds. E. Di Valentino and D. Brout, Springer Singapore, expected in 2024

The HI mass function in the Parkes HI Zone of Avoidance survey

An HI mass function (HIMF) was derived for 751 galaxies selected from the deep Parkes HI survey across the Zone of Avoidance (HIZOA). HIZOA contains both the Great Attractor Wall and the Local Void, two of the most extreme environments in the local Universe, making the sample eminently suitable to explore the overall HIMF as well as its dependence on local environment. To avoid any selection bias because of the different distances of these large-scale structures, we first used the two-dimensional stepwise maximum-likelihood method for the definition of an average HIMF. The resulting parameters of a Schechter-type HIMF for the whole sample are $\alpha = -1.33\pm0.05$, $\log(M_{\rm HI}^*/M_{\odot})=9.93\pm0.04$, and $\phi^* = (3.9\pm0.6)\times 10^{-3}$ Mpc$^{-3}$. We then used the $k$-th nearest-neighbour method to subdivide the sample into four environments of decreasing local density and derived the Schechter parameters for each subsample. A strong trend is observed, for the slope $\alpha$ of the low-mass end of the HIMF. The slope changes from being nearly flat, i.e. $\alpha = -0.99\pm0.19$ for galaxies residing in the densest bin, to the steep value of $\alpha = -1.31\pm0.10$ in the lowest density bin. The characteristic mass, however, does not show a clear trend between the highest and lowest density bins. We find similar trends in the low-mass slope when we compare the results for a region dominated by the Great Attractor, and the Local Void, which are found to be over-, respectively underdense by 1.35 and 0.59 compared to the whole sample.Comment: 10 pages, 13 figures, 4 tables, accepted for publication in MNRA

A Formal Method for Selecting a Project Manager Based on Leadership Characteristics

Selecting the most suitable manager to lead a project is a non-trivial task especially if the need arises urgently. Our research presents a new method by which a new manager can be selected objectively by formally modeling the leadership characteristics, which are the core criteria of selection. The ideal characteristics sought by the company are modeled using a Configuration Profile, while the characteristics of each candidate manager are modeled using Candidate Profile. The value of each profile is computed and stored in a list. This list gets sorted and eventually the top candidate profile is selected. We show how to apply our methodology using the characteristics of leadership but any other arbitrary attributes, such as cultural or technical characteristics, can be used too

Nonlinear control of a grid connected hybrid energetic systems (HES) based on photovoltaic-fuel cells distributed power generation systems

This paper presents a discrete-time integral sliding mode control for a grid connected hybrid energetic systems (HES) based on photovoltaic-Solid oxide fuel cell (SOFC) for distributed power generation systems. The proposed HES systems employ solid oxide fuel cell (SOFC) and photovoltaic panels as main sources, supercapacitors as complementary sources, and controlled DC-DC boost converter and three levels NPC inverter. A maximum power point tracking (MPPT) control is used in order to maximize the power of the photovoltaic system. The proposed control consists of a power management grid interface inverter transferring the energy from the hybrid sources into the grid by controlling the main utility grid and the common DC voltage active and reactive power. The obtained simulation results show the effectiveness and robustness of the proposed control strategy. Keywords: Hybrid Energetic Systems (HES), Solid Oxide Fuel Cell (SOFC), Photovoltaic (PV), Sliding Mode Control, Maximum Power Point Tracking (MPPT), Grid power management

Las diferencias inter-poblacionales en la morfología del otolito de Aphanius fasciatus (Cyprinodontiformes) se codifican genéticamente

Inter-population differences in otolith shape, morphology and chemistry have been used effectively as indicators for stock assessment or for recognizing environmental adaptation in fishes. However, the precise parameters that affect otolith morphology remain incompletely understood. Here we provide the first direct support for the hypothesis that inter-population differences in otolith morphology are genetically encoded. The study is based on otolith morphology and two mitochondrial markers (D-loop, 16S rRNA) of three natural populations of Aphanius fasciatus (Teleostei: Cyprinodontidae) from Southeast Tunisia. Otolith and genetic data yielded congruent tree topologies. Divergence of populations likely results from isolation events in the course of the Pleistocene sea level drops. We propose that otolith morphology is a valuable tool for resolving genetic diversity also within other teleost species, which may be important for ecosystem management and conservation of genetic diversity. As reconstructions of ancient teleost fish faunas are often solely based on fossil otoliths, our discoveries may also lead to a new approach to research in palaeontology.Las diferencias en la forma del otolito entre poblaciones, la morfología o la química se han utilizado con efectividad como indicadores para la gestión de poblaciones o para el reconocimiento de adaptaciones ambientales en peces. Sin embargo, los parámetros precisos que afectan la morfología del otolito permanecen sin ser entendidos completamente. Aquí nosotros presentamos la primera evidencia directa para la hipótesis de que las diferencias inter-poblacionales en la morfología del otolito están codificadas genéticamente. El estudio se basa en la morfología del otolito y dos marcadores mitocondriales (D-loop, 16S rRNA) de tres poblaciones naturales de Aphanius fasciatus (Teleostei: Cyprinodontidae) del sudeste de Tunez. Los datos de otolitos y genéticos ofrecen tres topologías congruentes. Aparentemente la divergencia entre poblaciones resulta de los procesos de aislamiento durante los descensos del nivel del mar en el Pleistoceno. Proponemos que la morfología del otolito es una herramienta muy valiosa para entender la diversidad genética también con otras especies de peces, que puede ser importante para la gestión de los ecosistemas y la conservación de la diversidad genética. Ya que las reconstrucciones de la fauna antigua de peces teleósteos se basan a menudo en otolitos fósiles, nuestro hallazgo puede también ser importante como nueva aproximación en las investigaciones palentológicas

Remote Sensing And Geospatial Applications For Water Catchment Mapping And Assessment.

Identifying and mapping water catchment features that occur in mostly forest areas from aerial photography is a challenging task, but the use of remotely sensed data and data processing techniques can improve the process of providing preliminary data for modeling land use and land cover changes and assessment their impact on the catchemnt