The Black Hole Mass Function Across Cosmic Times. I. Stellar Black Holes and Light Seed Distribution

This is the first paper in a series aimed at modeling the black hole (BH) mass function, from the stellar to the intermediate to the (super)massive regime. In the present work, we focus on stellar BHs and provide an ab initio computation of their mass function across cosmic times; we mainly consider the standard, and likely dominant, production channel of stellar-mass BHs constituted by isolated single/binary star evolution. Specifically, we exploit the state-of-the-art stellar and binary evolutionary code SEVN, and couple its outputs with redshift-dependent galaxy statistics and empirical scaling relations involving galaxy metallicity, star formation rate and stellar mass. The resulting relic mass function dN / dVd log m • as a function of the BH mass m • features a rather flat shape up to m • ≈ 50 M ⊙ and then a log-normal decline for larger masses, while its overall normalization at a given mass increases with decreasing redshift. We highlight the contribution to the local mass function from isolated stars evolving into BHs and from binary stellar systems ending up in single or binary BHs. We also include the distortion on the mass function induced by binary BH mergers, finding that it has a minor effect at the high-mass end. We estimate a local stellar BH relic mass density of ρ • ≈ 5 × 107 M ⊙ Mpc−3, which exceeds by more than two orders of magnitude that in supermassive BHs; this translates into an energy density parameter Ω• ≈ 4 × 10−4, implying that the total mass in stellar BHs amounts to ≲1% of the local baryonic matter. We show how our mass function for merging BH binaries compares with the recent estimates from gravitational wave observations by LIGO/Virgo, and discuss the possible implications for dynamical formation of BH binaries in dense environments like star clusters. We address the impact of adopting different binary stellar evolution codes (SEVN and COSMIC) on the mass function, and find the main differences to occur at the high-mass end, in connection with the numerical treatment of stellar binary evolution effects. We highlight that our results can provide a firm theoretical basis for a physically motivated light seed distribution at high redshift, to be implemented in semi-analytic and numerical models of BH formation and evolution. Finally, we stress that the present work can constitute a starting point to investigate the origin of heavy seeds and the growth of (super)massive BHs in high-redshift star-forming galaxies, that we will pursue in forthcoming papers.

Fruit and Vegetable Seed Production and Marketing: Existing Practice and Perception of Vegetbale Seed Farmers and Sellers in Bangladesh

Bangladesh has the largest river delta in the world and is known as the basin of South Asia. Accordingly, Bangladesh is naturally fertile, which is the main factor that provides the country with a huge opportunity to produce fruit and vegetable seeds. However, the lack of quality seed production, insufficient seed supply, and lack of seed preservation systems make the seed sector unstable. This research attempts to determine the cause of these problems and identify ways to mitigate them and make a sustainable marketing system. A descriptive research method was applied, based on a survey conducted in Bangladesh in three major seed producing divisions, namely: Dhaka, Chittagong, and Mymensingh. The data were gathered from 40 farmers and 40 retailers & wholesalers who were chosen at random, and the data was analysed in Microsoft Excel. The objective of the study is to analyze marketing practices of vegetable and fruit seeds, the problems of vegetable and fruit seed distribution, and to propose a method for the sustainable distribution of vegetable and fruit seeds. The results showed a lack of genuine and timely market information, poor institutions and arrangements, and poor marketing infrastructure. These findings are indicative of poor marketing efficiency and thereby suboptimal operation of the seed marketing system. Hence, the results found in this study should help to institute appropriate measures for production, market infrastructure, arrangements, and institutions to improve the inefficient functioning of the seed marketing system.

Community Seed Groups: Biological and Especially Social Investigations Can Support Crisis Response Capacity

The food system is comprised of biophysical and social processes affecting everyone, and food system citizen and community science offer opportunities for research, especially on unstudied aspects of that system, including responses to crises and disasters. We describe how community science work on food crop seeds responded to the crisis of the COVID-19 pandemic, and how this response built on the social investigations that are part of that ongoing work. To address a number of the crises of the Anthropocene, groups and individuals have been creating infrastructure supporting community-driven seed research and provision. Some organizations investigate community development of locally adapted crops, and introduction of novel materials for testing in new environments, as well as alternative social organization and processes supportive of this research and aligned with their values. Looking at examples of two active, United States–based, community seed organizations, represented by two of the co-authors, we outline the values and theoretical grounding of this work, and how responding to the acute crisis of the COVID-19 pandemic has challenged these organizations to rapidly develop seed distribution work in ways consistent with their values and missions. Meeting these immediate needs has meant temporarily pivoting from the longer-term evolutionary processes of their community science biological investigations; still, existing social investigations remained relevant and useful in their pandemic work. The effectiveness of this crisis response provides an example of explicitly values-driven research, and indicates the importance of recognizing the implicit social investigations of community science that sometimes experiment with alternative approaches to organizing society to achieve both immediate results, and longer term, prosocial change.

Design and Research Sowing Devices for Aerial Sowing of Forest Seeds with UAVs

Modern unmanned aerial vehicles (UAV) can be effectively used for aerial sowing of forests. A feature of aerial sowing is the possibility of rapid reforestation at low costs, which is extremely important in the current environmental situation. The purpose of this study is to develop a set of sowing devices intended for use with UAVs. For this, the metering devices and seed distribution devices were analyzed, used on the UAV or having prospects for such use. The existing studies of metering devices, implemented by numerical methods, are analyzed. Further, the synthesis of eight different designs of sowing devices in the 3D CAD was carried out and their comparative assessment was completed in terms of mass and a set of technological parameters. Based on its results, a sowing device was selected that is most suitable for a specific given technology. Discrete Element Method (DEM) was used to simulate the workflow: imitation of loading of the sowing device, study of work in various modes, study of the process of impact interaction of seeds with the soil environment. The complex of developed sowing devices can provide sowing of almost any type of forest seeds within the framework of various technologies and soil climatic conditions.

Scheme to support coconut replanting program on smallholder plantation

Coconut plantations are dominated by smallholders characterized by limited land area, low productivity, and low added value. The low productivity is partly due to the old age of the plants. The performance of coconut plantations can be improved, among others, through replanting smallholder plantations, but the implementation is still low, mainly due to financing constraints. This study aims to develop a financing scheme to support coconut replanting programs in smallholder plantations. The analysis used is Interpretative Structural Modelling for strategy mapping. The strategy for accelerating the smallholder coconut replanting program is related to developing the seed system, capacity building of farmers and farmer organizations, and technology support. The implementation of coconut replanting consists of nursery establishment, seed distribution, and planting and cultivation management. The financing scheme is a replanting financing method that includes the provision of funds, the scope of the use of funds, and the mechanism for using funds. Various financing models were built, consisting of the Self-Financing Scheme, the Companion Fund Financing Scheme, and the Program-Based Financing Scheme. These various schemes accommodate variations in conditions in coconut development centers in Indonesia. Through the financing scheme, it is also possible to map the roles of each stakeholder involved.

Invasive alien species in protected areas: the dynamics of Pinus taeda at Rio Canoas State Park – Brazil

Biological invasion is a growing problem, and species of the genus <i>Pinus</i> are known to be a problem in the forests southern Brazil, including Conservation Units (CUs). Here, we studied the ecology of <i>Pinus taeda</i> invasion at Rio Canoas State Park (PAERC) based on forest inventory, soil seed bank analysis and seed rain assessment in three distinct successional stages inside the park denoted as “Pinus invasion”, “Old Growth Vegetation” and “Initial Vegetation”. Forest inventory of 33 (20x20m) plots, found <i>Pinus</i> in 2 of the 3 evaluated environments. Seed rain was collected bimonthly using 33 (1x1m) seed traps for a period of one year. The major seed distribution periods were in April and June, confirming data found in the literature. The seed bank was analyzed in February (summer) and June (winter) of 2018. Samples were kept in a greenhouse for a period of 120 days each. Summer evaluation showed no emergence of <i>Pinus taeda</i> seedlings, but the winter evaluation (June) did show the emergence of seedlings. Results showed that the soil seed bank is not persistent. Accordingly, the <i>Pinus</i> invasion reported at PAERC requires a restoration program, as well as one that controls reinfestation.

Determination of the design parameters of the beet planter for uniform seed distribution

In the Tambov region, due to the widespread introduction of promising technologies for growing sugar beets, its yield has significantly increased, at the same time, the used seeding machines are not always able to provide the required depth of planting seeds, which leads to loss of yield and difficulty in applying fertilizers. In the course of previous studies, it was determined that with an increase in the angle of the scraper over 60 degrees, an increase in the percentage of filling the cells of the disc with seeds in various hybrids occurs, so research has established that in the hybrid PMC-120 at an angle of installation of the scraper of 70 degrees, 100 percent of the cells are filled with seeds, while in hybrids XM-1820 and Troika, the cells were filled only by 93.3%. It should also be noted that the PMC-120 hybrid with a scraper angle of 70 degrees had the lowest damage to the pellets - 0.67%, while the XM-1820 and Troika hybrids had 0.83 and 0.73%, respectively. With an increase in the angle of installation of the scraper over 80 degrees, the percentage of damaged seeds increased from 0.4 to 0.66%, on the basis of this, the design of the seeding device was proposed and theoretically substantiated, a feature of which is the reverse rotation of the seeding disc, while the rear wall of the opener is made in the form of a parabola appropriate trajectory of movement of seeds, which ensures their distribution in the immediate vicinity of its rear wall, thereby reducing the risk of falling asleep to the bed of the furrow before the granules get there. It has been determined that the trajectory of the granule movement directly depends on the angular speed of the seeding disc, which in turn depends on the geometric characteristics of the cells of the seeding disc. It is theoretically substantiated that the speed of the seed in the disc cell is determined by the sum of the projections, which makes it possible to calculate the curved surface of the opener.

Substantiation of the presence and parameters of seed guides in the openers, which increase the quality of sowing and yield

One of the promising methods for improving the uniformity of seed distribution in the soil is the control of the grain flow by guiding elements in the openers. This creates favorable conditions for the flight of seeds in the openers and when leaving them backwards, which equalizes the speed, in modulus, of seeds and the unit, improves the uniformity of their distribution in the soil. The presence and parameters of the guiding elements of the openers was theoretically substantiated, which gave the development of the process of controlling the grain flow in the openers and at the exit from them by using the guiding elements. Analytical expressions have been obtained to determine the characteristics of the movement of particles on various surfaces, which are recommended to be used for guides in the openers. Experimental studies have shown that openers with guides reduce the coefficient of variation along the row by 20 ... 45% and have it 88 ... 98%, and in depth - 24 ... 27%. On the basis of experiments, it is recommended that 3 ... 4 guides are recommended for front openers (arithmetic mean interval along the row 18.5 ... 23.5 mm, coefficient of variation 88 ... 98%). The advantage of the experimental opener in the distribution of seeds by depth is due to the use of guide elements in combination with an improved soil shedding process. This eliminated the technological drawback - the formation of a sub-opener inclined surface (arithmetic mean interval 42 ... 37 mm, coefficient of variation 24 ... 27%). For a double disc opener, an improved guide is recommended, the bottom edge of which protrudes 2 cm in front of the vertical diameter of the discs and is located at a distance of 9 cm from the reference plane. The arithmetic mean spacing along the row of this opener is 15 mm, the coefficient of variation is 106%.

Determinants of Seed Distribution System: The Case of Womberma District, North West Ethiopia

Bread wheat also known as common wheat is one of the most important crops for food security and job opportunities for many smallholders as well as the urban population in Ethiopia. Farmers obtain seed from both formal and informal seed distribution systems. The informal seed sector in the study area is the major supplier of seed for many crops grown in the Womberma district. However, access to the formal seed sector was limited for the farmers. Hence, this study initiated to analyze seed distribution system and determinants of smallholder farmers in selecting seed of bread wheat distribution system in the study areas. The primary data was collected through distributing research questionnaires for the seed distribution systems of bread wheat. The study was based on the data collected from 150 households by using the multistage probability sampling method. The survey result shows that the contribution of public companies for supplying improved bread wheat seed was only 33% whereas 100% of producers confirmed that sources of bread wheat seed were from farm saved and local market which were uncertified leading to production deterioration. In line with these, conducted focus group and key informants confirmed that the major problems of formal seed distribution system were lack of timely supply, price fluctuation, limited quantity, and lack of certified seed suppliers while those of the informal seed distribution system were adulteration, high price, low quality, unable to get the right amount, and lack of timely supply, which concluded that the distribution system was inefficient. The econometrics model was used to analyze determinants of selection in seed distribution system of bread wheat in the study areas. Hence, the result of logit model shows that the level of education, access to credit, household income, extension services, and seed quality significantly and positively influenced farmers’ selection of formal seed distribution system while distance to the nearest seed distribution area influenced negatively the selection of formal seed distribution system in the study areas. Therefore, any concerned bodies should give more attention to establish for farmers formal seed distribution systems of bread wheat seed so as to increase production and productivity of bread wheat in the study areas.