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OALib Journal期刊

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Biology of flowering and nectar production in the flowers of the beauty bush (Kolkwitzia amabilis Graebn.)
Marta Dmitruk
Acta Agrobotanica , 2012, DOI: 10.5586/aa.2012.017
Abstract: Nectar production and the morphology of the nectary and pollen grains of Kolwitzia amabilis Graebn. were studied during the period 2008–2009 and in 2011. The blooming of beauty bush flowers started in the third decade of May and ended in the middle of June; flowering lasted 22–23 days. The flower life span was 4–5 days. Nectar production began at the bud break stage. The tube of the corolla in beauty bush flowers forms a spur inside which the nectary is located. The secretory surface of the nectary consists of two layers of glandular epidermal outgrowths: unicellular trichomes, with their length ranging 54.6 μm – 70.2 μm, and papillae with a length of 13.0 μm – 20.6 μm. The mean weight of nectar per 10 flowers, determined for the three years of the study, was 8.6 mg, with a sugar concentration of 50.8%. The weight of nectar sugar was on average 4.4 mg. In terms of the size, beauty bush pollen grains are classified as medium-sized. These are tricolporate grains.
Morphological differentiation and distribution of non-glandular and glandular trichomes on Dracocephalum moldavicum L. shoots
El？bieta Weryszko-Chmielewska,Marta Dmitruk
Acta Agrobotanica , 2010, DOI: 10.5586/aa.2010.002
Abstract: The structure, micromorphology and distribution of trichomes on Dracocephalum moldavicum L. shots were investigated using light and scanning electron microscopy (SEM). There were distinguished 3 types of non-glandular trichomes, 3 types of glandular trichomes and papillae of the osmophore in the epidermis of the corolla. The highest density of non-glandular and glandular trichomes was found on the abaxial surface of the calyx, on bracts and in the upper part of the stem. Structural variations in the head and stalk of long glandular trichomes were demonstrated. The dimensions of particular types of trichomes are given in the present paper. Differences in the structure of the trichomes of this species are presented, compared to literature data. The micromorphology of particular trichome types is documented in numerous photographs showing the rich ornamentation of the cuticle of non-glandular trichomes.
Nectar and pollen production of Helianthus tuberosus L. – an exotic plant with invasiveness potential
Denisow, Bo？ena,Dmitruk, Marta,Tymoszuk, Karolina
- , 2019, DOI: 10.2478/botcro-2019-0019
Abstract: Sa？etak In Central Europe, Helianthus tuberosus L. is a late summer/autumn bloomer (August/November). The disc florets produce both nectar and pollen. Floral reward is available in male-phase flowers (pollen and nectar) and in female-phase flowers (nectar). The floral reward is attractive to a variety of insect visitors (honey bees, wasps, flies and butterflies). The season of blooming as well as the total sugar yield (25.4 – 47.4 kg ha–1) and pollen yield (57.8 – 212.7 kg ha–1) indicate that H. tuberosus is important in the enhancement of food resources for pollinators. The generative reproduction in H. tuberosus is impaired (the species does not set seeds/fruits). However, due to its attractiveness for a variety of pollinators in both rural and urban areas, the spread of H. tuberosus should be monitored. Moreover, its propagation needs to be attended with restrictions
Scaling law for the heating of solar coronal loops
Pablo Dmitruk,Daniel Gomez
Physics , 1999, DOI: 10.1086/312390
Abstract: We report preliminary results from a series of numerical simulations of the reduced magnetohydrodynamic equations, used to describe the dynamics of magnetic loops in active regions of the solar corona. A stationary velocity field is applied at the photospheric boundaries to imitate the driving action of granule motions. A turbulent stationary regime is reached, characterized by a broadband power spectrum $E_k\simeq k^{-3/2}$ and heating rate levels compatible with the heating requirements of active region loops. A dimensional analysis of the equations indicates that their solutions are determined by two dimensionless parameters: the Reynolds number and the ratio between the Alfven time and the photospheric turnover time. From a series of simulations for different values of this ratio, we determine how the heating rate scales with the physical parameters of the problem, which might be useful for an observational test of this model.
On the proof of Pontryagin's maximum principle by means of needle variations
Andrei Dmitruk,Nikolai Osmolovskii
Mathematics , 2014,
Abstract: We propose a proof of the maximum principle for the general Pontryagin type optimal control problem, based on packages of needle variations. The optimal control problem is first reduced to a family of smooth finite-dimensional problems, the arguments of which are the widths of the needles in each packet, then, for each of these problems, the standard Lagrange multipliers rule is applied, and finally, the obtained family of necessary conditions is "compressed" in one universal optimality condition by using the concept of centered family of compacta.
Classification of extremals in a simplified Goddard model on the maximal height of rocket flight
Andrei Dmitruk,Ivan Samylovskiy
Mathematics , 2014,
Abstract: We consider a problem on maximizing the height of vertical flight of a material point ("meteorological rocket") in the presence of a nonlinear friction and a constant flat gravity field under a bounded thrust and fuel expenditure. The original Goddard problem is simplified by removing the dependence on the rocket mass from the equations of motion. Using the maximum principle we find all possible types of Pontryagin extremals and classify them w.r.t. problem parameters. Since the velocity of the point can be negative, we obtain some new types of extremals with two or three switching points, which optimality should be further investigated.
Turbulent coronal heating and the distribution of nanoflares
Pablo Dmitruk,Daniel O. Gomez
Physics , 1997, DOI: 10.1086/310760
Abstract: We perform direct numerical simulations of an externally driven two-dimensional magnetohydrodynamic system over extended periods of time to simulate the dynamics of a transverse section of a solar coronal loop. A stationary and large-scale magnetic forcing was imposed, to model the photospheric motions at the magnetic loop footpoints. A turbulent stationary regime is reached, which corresponds to energy dissipation rates consistent with the heating requirements of coronal loops. The temporal behavior of quantities such as the energy dissipation rate show clear indications of intermittency, which are exclusively due to the strong nonlinearity of the system. We tentatively associate these impulsive events of magnetic energy dissipation to the so-called nanoflares. A statistical analysis of these events yields a power law distribution as a function of their energies with a negative slope of 1.5, which is consistent with those obtained for flare energy distributions reported from X-ray observations.
Modelling 3D scene based on rapid face tracking and objects recognition
Krzysztof Dmitruk, Grzegorz M. Wójcik
Annales UMCS, Informatica , 2010, DOI: 10.2478/v10065-010-0053-5
Abstract: Mixed reality techniques are presented. Implementation and application of CAMSHIFT algorithm is discussed to some extent. In the initial stage of the research the technology of real object's edge detection and geometrical figures' representation in the virtual scene has been worked out.
Slow and fast magneto-optical response of magnetite nanoparticles suspension
N. Dmitruk,I. Moroz,S. Malynych
Atti della Accademia Peloritana dei Pericolanti : Classe di Scienze Fisiche, Matematiche e Naturali , 2011, DOI: 10.1478/c1v89s1p029
Abstract: DC magnetic field applied to Fe O ; nanoparticle suspension affects its light scattering. Time dependent variations in the light intensity transmitted through a suspension are observed after the magnetic field is switched-on. Two types of variations can be distinguished. Fast response takes less than millisecond while slow variations occur at the time interval from seconds to hundreds of minutes. Possible mechanisms of these variations are discussed.
Investigation of the Role of Electrogenerated N-Heterocyclic Carbene in the Staudinger Synthesis in Ionic Liquid  [PDF]
Marta Feroci
International Journal of Organic Chemistry (IJOC) , 2011, DOI: 10.4236/ijoc.2011.14028
Abstract: Electrogenerated N-heterocyclic carbene (NHC), obtained by cathodic reduction of Bmim-BF4, behaves as organocatalyst and base in the Staudinger synthesis from an acyl chloride and a deactivated imine in ionic liquid to yield ?-lactams. The effect of many parameters (temperature, amount of electricity, substituents, presence of an external base) has been evaluated and a tentative mechanism for the Staudinger synthesis in a very polar medium like the ionic liquid reported. The yields of isolated ?-lactams are good, starting from non-electrophilic imines, and predominantly trans lactams are obtained with a good diastereomeric ratio.
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