Growth patterns of medium-sized, fast-growing firms

This report examines rapidity of business expansion, by analysing potential organisational growth patterns, as well as potential theories explaining these patterns. Besides, the study examines sources of importance during the various growth phases. Finally, emphasis is put on the issue as to whether strategy and sources affect growth.

Glass foam granulate as growing medium for tomato and cucumber

Glass foam granulate was evaluated for use as a horticultural rooting medium with laboratory tests and cultivation experiments. The laboratory tests included moisture characteristics, rehydration rate and pH buffering analyses. Cucumbers and later on tomatoes were propagated in rockwool propagation cubes and planted on slabs of Growstones™ glass foam granulate. They were compared with cucumber respectively tomatoes grown on rockwool slabs. Lab results show that the coarse nature of the glass foam granulate (0.5-5 cm) limits the maximum moisture content to 50%. The rehydration rate is very high, reaching more than 80% of container capacity in 5 min. The tested material initially reacts with water, raising the pH to over 10 pH units. Based on lab results a recipe for rinsing the material prior to cultivation was calculated. Cucumber cultivation results show an equal production to plants grown on rockwool. The first yield on glass foam granulate is 1-2 days earlier. The susceptibility to Pythium is significantly lower than on rockwool. The wax layer on cucumbers grown on glass foam granulate is perceptibly thicker as consequence of an elevated silicon level of 0.25 to 1.6 mmol L-1 in the slab solution. Tomatoes on glass foam granulate show smaller stem diameters and recovered faster from blossom end rot. Yield levels on glass foam granulate and rockwool are equal. In conclusion growing on glass foam granulate is equally productive as rockwool growing. The material is drier and thus less susceptible to Pythium and more generative in nature. Glass foam granulate can be irrigated with small and frequent irrigation cycles and the material must be rinsed with an acid solution before planting. Small amounts of silicon are released into the nutrient solution

Growing media constituents determine the microbial nitrogen conversions in organic growing media for horticulture

Vegetables and fruits are an important part of a healthy food diet, however, the eco-sustainability of the production of these can still be significantly improved. European farmers and consumers spend an estimated Euro15.5 billion per year on inorganic fertilizers and the production of N-fertilizers results in a high carbon footprint. We investigated if fertilizer type and medium constituents determine microbial nitrogen conversions in organic growing media and can be used as a next step towards a more sustainable horticulture. We demonstrated that growing media constituents showed differences in urea hydrolysis, ammonia and nitrite oxidation and in carbon dioxide respiration rate. Interestingly, mixing of the growing media constituents resulted in a stimulation of the function of the microorganisms. The use of organic fertilizer resulted in an increase in amoA gene copy number by factor 100 compared to inorganic fertilizers. Our results support our hypothesis that the activity of the functional microbial community with respect to nitrogen turnover in an organic growing medium can be improved by selecting and mixing the appropriate growing media components with each other. These findings contribute to the understanding of the functional microbial community in growing media and its potential role towards a more responsible horticulture

On the mass function of stars growing in a flocculent medium

Stars form in regions of very inhomogeneous densities and may have chaotic orbital motions. This leads to a time variation of the accretion rate, which will spread the masses over some mass range. We investigate the mass distribution functions that arise from fluctuating accretion rates in non-linear accretion, $\dot{m} \propto m^{\alpha}$. The distribution functions evolve in time and develop a power law tail attached to a lognormal body, like in numerical simulations of star formation. Small fluctuations may be modelled by a Gaussian and develop a power-law tail $\propto m^{-\alpha}$ at the high-mass side for $\alpha > 1$ and at the low-mass side for $\alpha < 1$. Large fluctuations require that their distribution is strictly positive, for example, lognormal. For positive fluctuations the mass distribution function develops the power-law tail always at the high-mass hand side, independent of $\alpha$ larger or smaller than unity. Furthermore, we discuss Bondi-Hoyle accretion in a supersonically turbulent medium, the range of parameters for which non-linear stochastic growth could shape the stellar initial mass function, as well as the effects of a distribution of initial masses and growth times.Comment: 9 pages, 7 figures, MNRAS in pres

Seed germination and in vitro regeneration of the African medicinal and pesticidal plant, Bobgunnia madagascariensis

Propagation of the medicinal and pesticidal tree, Bobgunnia madagascarensis is difficult due to poor and erratic germination of its seeds and slow growth of its seedlings. This study involved two separate experiments. The first evaluated the effect of pre-sowing treatments and growing medium on ex vitro seed germination and early seedling development. The second experiment involved in vitro germination, shoot initiation and rooting of shoots. Pre-sowing seed treatments involved soaking seeds in cold and hot water for 12 and 24 h and soaking in different concentrations (0, 100, 200, 400 and 800 mg/l) of gibberellic acid for 24 h. Soaking of seeds in cold or hot water for up to 24 h did not achieve more than 45% germination, while seeds treated with gibberellic acid achieved 76%) when seeds were sown in a growing medium without compost compared with a medium with compost (<43%). All shoot-tips isolated from the in vitro germinated seedlings on B5 media without plant growth regulators continued to grow as a single shoot, while shoot-tips cultured on B5 supplemented with 0.1 mg/l of naphthaleneacetic acid (NAA) and thidiazuron (TDZ) produced two shoots each after four weeks. It was concluded that B. madagascariensis seeds had very low ex vitro germination percentages. Although, in vitro cultures improved seed germination, axillary shoot multiplication and rooting were not satisfactory. Therefore, further studies are needed to develop an optimal in vitro multiplication protocol for B. madagascariensis

Universality in Bacterial Colonies

The emergent spatial patterns generated by growing bacterial colonies have been the focus of intense study in physics during the last twenty years. Both experimental and theoretical investigations have made possible a clear qualitative picture of the different structures that such colonies can exhibit, depending on the medium on which they are growing. However, there are relatively few quantitative descriptions of these patterns. In this paper, we use a mechanistically detailed simulation framework to measure the scaling exponents associated with the advancing fronts of bacterial colonies on hard agar substrata, aiming to discern the universality class to which the system belongs. We show that the universal behavior exhibited by the colonies can be much richer than previously reported, and we propose the possibility of up to four different sub-phases within the medium-to-high nutrient concentration regime. We hypothesize that the quenched disorder that characterizes one of these sub-phases is an emergent property of the growth and division of bacteria competing for limited space and nutrients.Comment: 12 pages, 5 figure

Sessile Legionella pneumophila is able to grow on surfaces and generate structured monospecies biofilms

Currently, models for studying Legionella pneumophila biofilm formation rely on multi-species biofilms with low reproducibility or on growth in rich medium, where planktonic growth is unavoidable. The present study describes a new medium adapted to the growth of L. pneumophila monospecies biofilms in vitro. A microplate model was used to test several media. After incubation for 6 days in a specific biofilm broth not supporting planktonic growth, biofilms consisted of 5.36 ± 0.40 log (cfu cm−2) or 5.34 ± 0.33 log (gu cm−2). The adhered population remained stable for up to 3 weeks after initial inoculation. In situ confocal microscope observations revealed a typical biofilm structure, comprising cell clusters ranging up to 300 μm in height. This model is adapted to growing monospecies L. pneumophila biofilms that are structurally different from biofilms formed in a rich medium. High reproducibility and the absence of other microbial species make this model useful for studying genes involved in biofilm formation

The home as a technological learning environment: children's early encounters with digital technologies

Today's children are growing up in homes with an ever-growing array of technologies supporting families as they work, play, communicate and learn. How have recent rapid changes to the home as a technological environment influenced what and how preschool children learn? This paper, based on a series of studies of young children's experiences with digital technology at home, identifies key factors - including the structure and layout of the home, family practices, family values and family interactions - which shape the ways in which children: a) learn to use technologies; b) learn about the world via the medium of technologies; c) develop learning dispositions; and d) learn about the role of different technologies in family and community contexts

Derivation of the physical parameters of the jet in S5 0836+710 from stability analysis

A number of extragalactic jets show periodic structures at different scales that can be associated with growing instabilities. The wavelengths of the developing instability modes and their ratios depend on the flow parameters, so the study of those structures can shed light on jet physics at the scales involved. In this work, we use the fits to the jet ridgeline obtained from different observations of S5 B0836$+$710 and apply stability analysis of relativistic, sheared flows to derive an estimate of the physical parameters of the jet. Based on the assumption that the observed structures are generated by growing Kelvin-Helmholtz (KH) instability modes, we have run numerical calculations of stability of a relativistic, sheared jet over a range of different jet parameters. We have spanned several orders of magnitude in jet-to-ambient medium density ratio, and jet internal energy, and checked different values of the Lorentz factor and shear layer width. This represents an independent method to obtain estimates of the physical parameters of a jet. By comparing the fastest growing wavelengths of each relevant mode given by the calculations with the observed wavelengths reported in the literature, we have derived independent estimates of the jet Lorentz factor, specific internal energy, jet-to-ambient medium density ratio and Mach number. We obtain a jet Lorentz factor $\gamma \simeq 12$, specific internal energy of $\varepsilon \simeq 10^{-2}\,c^2$, jet-to-ambient medium density ratio of $\eta\approx 10^{-3}$, and an internal (classical) jet Mach number of $M_\mathrm{j}\approx 12$. We also find that the wavelength ratios are better recovered by a transversal structure with a width of $\simeq 10\,\%$ of the jet radius. This method represents a powerful tool to derive the jet parameters in all jets showing helical patterns with different wavelengths.Comment: Accepted for publication in A&A, 15 pages, 12 figure