A. Twardowski - Academia.edu (original) (raw)

Papers by A. Twardowski

Acta Physica Polonica A, 1997

Semiconductor Science and Technology, 1989

ABSTRACT

Electroluminescence (EL) from a forward-biased Schottky diode on modulation Si δ-doped pseudomorp... more Electroluminescence (EL) from a forward-biased Schottky diode on modulation Si δ-doped pseudomorphic GaAs/InGaAs/AlGaAs heterostructure grown by metalorganic vapor phase epitaxy is investigated in this work. Comparative study of the EL and the photoluminescence (PL) at low temperature is presented. Linear current dependence and a nonmonotonic temperature dependence of the EL intensity with a maximum around T=60 K were observed. We propose that hole injection from the Schottky gate is responsible for the optical recombination within the InGaAs channel of our structure

Acta Physica Polonica A, 1990

The magnetic specific heat of ZnCoSe data are reported in the temperature range 1.5 <T <50 ... more The magnetic specific heat of ZnCoSe data are reported in the temperature range 1.5 <T <50 K and magnetic field B <3 T. The experimental data are interpreted in the Extended Nearest Neighbour Pair Approximation taking into account short and long ranged d-d exchange interaction.

Biomacromolecules, 2013

Many phosphorylated nucleoside derivatives have therapeutic potential, but their application is l... more Many phosphorylated nucleoside derivatives have therapeutic potential, but their application is limited by problems with membrane permeability and with intracellular delivery. Here, we prepared polypyrrole microvessel structures modified with superparamagnetic nanoparticles for use as potential carriers of nucleotides. The microvessels were prepared via the photochemical polymerization of the monomer onto the surface of aqueous ferrofluidic droplets. A complementary physicochemical analysis revealed that a fraction of the nanoparticles was embedded in the microvessel walls, while the other nanoparticles were in the core of the vessel. SQUID (superconducting quantum interference device) measurements indicated that the incorporated nanoparticles retained their superparamagnetic properties; thus, the resulting nanoparticle-modified microvessels can be directed by an external magnetic field. As a result of these features, these microvessels may be useful as drug carriers in biomedical applications. To demonstrate the encapsulation of drug molecules, two labeled mRNA cap analogues, nucleotide-derived potential anticancer agents, were used. It was shown that the cap analogues are located in the aqueous core of the microvessels and can be released to the external solution by spontaneous permeation through the polymer walls. Mass spectrometry analysis confirmed that the cap analogues were preserved during encapsulation, storage, and release. This finding provides a foundation for the future development of anticancer therapies and for the delivery of nucleotide-based therapeutics.

Physical Review B, 1996

The exciton splitting induced by the s-d and p-d exchange interaction in Zn1-xFexTe (x<0.005) ... more The exciton splitting induced by the s-d and p-d exchange interaction in Zn1-xFexTe (x<0.005) was studied by polarized magnetoreflectance. Data were taken at 2 K in magnetic fields up to 5 T. Combining these results with magnetization data, a value (N0alpha-N0beta) = 2.1+/-0.4 eV was obtained for the difference between the s-d and p-d exchange constants. Assuming that N0alpha=+0.2 eV, the p-d exchange is antiferromagnetic, with a magnitude N0beta=-1.9 eV.

Solid State Communications, 1987

Journal of Alloys and Compounds, 2008

... Recent optical and magnetic studies indicate that tuning of the Fermi level in GaMnN indeed r... more ... Recent optical and magnetic studies indicate that tuning of the Fermi level in GaMnN indeed results in switching ... Structural, optical and magnetic properties of obtained crystals will be presented ... it is mentioned in Section 4 this etching plays a crucial role in magnetic properties of ...

Acta Physica Polonica A, 1993

physica status solidi (b), 1983

The fundamental absorption edge in Cd1−xMnxTe for x = 0.01, 0.05, 0.10, 0.20 in the Faraday confi... more The fundamental absorption edge in Cd1−xMnxTe for x = 0.01, 0.05, 0.10, 0.20 in the Faraday configuration, at magnetic fields up to 5 T and in the temperature range 1.8 to 293 K is studied. Moreover the exciton spectrum of extremely thin samples (of less than 1μm) is measured. An additional structure on the σ-edge is found. The appearance of that structure is supposed to be the effect of the mixing of exciton states in the zincblende structure. Die Grundgitterabsorptionskante in Cd1−xMnxTe fur x = 0,01; 0,05; 0,10; 0,20 wird in Faraday-Konfiguration in Magnetfeldern bis zu 5 T und im Temperaturbereich 1,8 bis 293 K untersucht. Daruberhinaus wird das Exzitonenspektrum von extrem dunnen Proben (dunner als 1 μm) gemessen. Eine zusatzliche Struktur an der σ-Kante wird gefunden. Es wird angenommen, das das Auftreten dieser Struktur die Folge von Mischung von Exzitonenzustanden in der Zinkblende-struktur ist.

Journal of the Magnetics Society of Japan, 2014

Physical Review B, 2004

... Rev. 160, 627 (1967). 44 B. Clerjaud, AM Hennel, and G. Martinez, Solid State Commun. 33, 983... more ... Rev. 160, 627 (1967). 44 B. Clerjaud, AM Hennel, and G. Martinez, Solid State Commun. 33, 983 (1980). 45 PJ Williams, L. Eaves, PE Simmonds, MO Henry, EC Lightowlers, and Ch. Uihlein, J. Phys. C 15, 1337 (1982). Y. Korotkov, JM Gregie, and BW Wessels, Appl. Phys. Lett. ...

$Research paper thumbnail of Ferromagnetic resonance in epitaxial (In_ {0.53} Ga_ {0.47}) _ {1− x} Mn_ {x} As: Angle-and temperature-dependent studies$

Physical Review B, 2004

... K. Dziatkowski,1,* M. Palczewska,2 T. Słupiński,1 and A. Twardowski1 1Institute of Experiment... more ... K. Dziatkowski,1,* M. Palczewska,2 T. Słupiński,1 and A. Twardowski1 1Institute of Experimental Physics, Warsaw University, Hoża 69, 00-681 Warsaw, Poland ... nance with the effective g-factor equal 3.3428 was relevant in a precise determination of the microwave frequency. ...

Journal of Applied Physics, 2005

Superconductor Science and Technology, 2008

... Recently, we observed similar phenomena in polycrystalline GaN:Mn [7]. We propose that the ap... more ... Recently, we observed similar phenomena in polycrystalline GaN:Mn [7]. We propose that the appearance of Ga ... 12] Ponce FA, Wang FC and Hiskes R 1984 Semi-insulating IIIV Materials,KahNeeTa ed ... Nantwich: Shiva) p 68 [13] He H, Fei GT, Cui P, Zheng K, Liang LM, Li ...