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1

Dielectric and X-ray Studies of Eleventh and Twelfth Members of Two Isothiocyanato Mesogenic Compounds

100%

Jasiurkowska M., Budziak A., Czub J., Urban S.

Acta Physica Polonica A

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2006

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vol. 110

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issue 6

795-805

EN

Results of the dielectric and X-ray studies of the long-alkyl-chain members (n=11, 12) of two homologous series: nBT (4-n-alkyl-4'-isothiocyanato-biphenyl) and nCHBT (4-trans-4'-n-alkyl-cyclohexyl-isothiocyanato-benzene) in their liquid crystalline phases are presented. These compounds exhibit different polymorphisms: the nematic phase for $n$CHBTs and the smectic E and smectic A phases for nBTs. The dielectric measurements were performed in a wide frequency range of 1 kHz-3 GHz. The layer thickness in the smectic E and smectic A phases and the orthorhombic unit cell parameters of the smectic E phase were determined using the small angle X-ray diffraction method. In the smectic E phase the layer-thickness-to-molecular-length ratios are found to be close to 1. The corresponding ratios observed for the smectic A phase of $n$BTs are considerably higher (≈1.24), which indicates that an alternating head-to-tail arrangement of molecules in the layers is favored. The rotational dynamics of molecules in the smectic E phases is discussed in relation to their packing in a unit cell.

2

Dielectric Properties of Liquid Crystalline Isothiocyanato-tolane Derivatives with Fluorine Atom at Various Lateral Positions

100%

Czub J., Urban S., Dąbrowski R., Gestblom B.

Acta Physica Polonica A

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2005

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vol. 107

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issue 6

947-958

EN

Dielectric studies were performed for several isothiocyanato-tolane compounds having the F atom attached to the benzene rings at different lateral positions and the alkoxy or alkyl chain at the p-position. They form the nematic phase in broad temperature intervals. The static as well as dynamic properties of the compounds in the nematic and isotropic phases were studied. Tensor permittivity components: ε_ǁ, ε_⊥, Δε, as functions of temperature were measured. The complex dielectric permittivity, ε^*(f)=ε'(f)-iε''(f), was measured in the frequency range of 1 kHz - 3 GHz from which the relaxation times τ_ǁ and τ_⊥ were calculated. The order parameter S(T) was determined from the dielectric data. It was found that the close vicinity of the F atom and the alkoxy group results in blocking of the internal rotation of the wing around the O-phenyl bond.

3

Magnetic Properties of RSn_{2} (R = Tb, Dy) Compounds

88%

Szytuła A., Kaczorowski D., Gondek Ł., Czub J., Nenkov K.

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issue 4

586-589

EN

Polycrystalline samples of TbSn_{2} and DySn_{2} were studied by means of magnetic susceptibility, electrical resistivity and heat capacity measurements. Both compounds have been found to order antiferromagnetically at low temperatures with some extra features in the ordered state due to changes in their magnetic structures. The two stannides exhibit metallic conductivity. The estimated crystal field levels splitting of Tb^{3+} and Dy^{3+} ground multiplets do not exceed 75 K.

4

Heavy Ion Beams for Radiobiology: Dosimetry and Nanodosimetry at HIL

52%

Kaźmierczak U., Bantsar A., Banaś D., Braziewicz J., Czub J., Jaskóła M., Korman A., Kruszewski M., Lankoff A., Lisowska H., Pietrzak M., Pszona S., Stępkowski T., Szefliński Z., Wojewódzka M.

Acta Physica Polonica A

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2015

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vol. 127

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issue 5

1516-1519

EN

Ionizing radiation induces a variety of DNA lesions, including single and double strand breaks. Large energy deposition precisely localized along the ion track that occurs in the case of heavy ion irradiation can lead to complex types of DNA double strand breaks in exposed biological material. The formation of nuclear double strand breaks triggers phosphorylation of histone H2AX, which can be microscopically visualized as foci in the γ-H2AX assay. Studies with a carbon ion beam are being carried out at the Heavy Ion Laboratory of the University of Warsaw. The γ-H2AX assay as a method of measuring the biological response of cells irradiated with ^{12}C ions as well as the frequency cluster size distributions obtained in the nanodosimetry experiment at HIL will be presented.

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1 Szefliński Z.

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1 Wojewódzka M.

Dielectric and X-ray Studies of Eleventh and Twelfth Members of Two Isothiocyanato Mesogenic Compounds

Dielectric Properties of Liquid Crystalline Isothiocyanato-tolane Derivatives with Fluorine Atom at Various Lateral Positions

Magnetic Properties of RSn_{2} (R = Tb, Dy) Compounds

Heavy Ion Beams for Radiobiology: Dosimetry and Nanodosimetry at HIL