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Wyświetlanie 1-2 z 2
Tytuł:
Fossilized pollination droplet in a new seed genus from the Middle Triassic of Nidpur, India
Autorzy:
Bhowmik, N.
Parveen, S.
Powiązania:
https://bibliotekanauki.pl/articles/946032.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
plantae
ginkgoopsida
rugaspermum
pollen
seed
pollination
micropyle
compression
triassic
india
Opis:
The present article reports a fossilized pollination droplet at the micropylar orifice in a compressed seed Gopadispermum papillatus gen. et sp. nov. from the Middle Triassic beds of Nidpur, Madhya Pradesh, India. The shapeless droplet forming a convexity above the micropylar orifice is comprised of a resinous crystalline substance. Entrapped within the droplet are a few saccate pollen grains. The seeds are small, oblong to widely elliptical in shape, about 3 mm long and generally 2 mm broad. The micropylar end shows a short straight beak-like micropyle often extended beyond a persistently adhering wrinkled tissue lying outside the seed coat. The seed is composed of four membranes excluding the adherent tissue. They are the outer and inner cuticles of integument, the nucellar cuticle distally modified to form a dark collar-like pollen chamber and the innermost megaspore membrane. Cuticles of the tissue adhering to seed coat are different from seed coat cuticles. The pollen grains inside the pollen chamber are frequently clumped together forming a pollen mass. Individual pollen grains appear spheroidal to ellipsoidal in shape and are saccate. This is the first report of the preservation of a pollination droplet in a compressed seed specimen from the Nidpur Triassic beds. Preservation of the droplet can be attributed to its supposed resinous constitution and the entrapped organic contents (pollen grains). Occurrence of clumped pollen grains inside the pollen chamber also indicated possibility of fluid feeding, pollinivory, and insect pollination in the seeds.
Źródło:
Acta Palaeontologica Polonica; 2014, 59, 2; 491-503
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies on the Effect of Nitrate Esters on the Properties of Advanced Energetic Propellants
Autorzy:
Kumar, Amit
Chavan, Prakash V
Sadavarte, Vaibhav S
Bhowmik, Debdas
Mada, S.S.N.M. Santosh
Pande, Shrikant M.
Powiązania:
https://bibliotekanauki.pl/articles/1062883.pdf
Data publikacji:
2020
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
nitroglycerine
NG
butanetriol trinitrate
BTTN
strain capability
thermal decomposition
Opis:
Propulsion designers all over the world are exploring the possibility of achieving higher performance by enhancing the energy of solid propellants. This can be achieved by replacing non-energetic ingredients with energetic ones or by replacing low density ingredients, particularly binders, with higher density ones, without affecting the processibility and ageing characteristics. The same has been attempted by using nitroglycerine (NG) and butanetriol trinitrate (BTTN) as plasticizers in propellant compositions. In the present study, NG and BTTN have been used in different plasticizer to polymer ratios (Pl/Po) and various parameters of each composition have been theoretically predicted. Three propellant compositions plasticized with NG, BTTN and a 1:1 combination of NG and BTTN, have been processed and analyzed for targeted properties. From the theoretical data, it was observed that there is a negligible increase in density impulse beyond a Pl/Po ratio of 2, apart from the higher density and calorimetric values of the NG-plasticized propellant; these plasticizers have a significant effect on the ballistic and mechanical properties. Another observation was that the elongation of BTTN and NG/BTTN (1:1) plasticized propellants is significantly higher at a low crosshead rate than NG-plasticized propellant, implying that the two former propellants have higher strain capabilities at low temperatures and can be used for missiles having long term low temperature storage requirements. Thermal decomposition studies have been carried out by DSC, and for each composition 5 distinct peaks were observed.
Źródło:
Central European Journal of Energetic Materials; 2020, 17, 3; 384-407
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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