Papers by Łukasz Michalak
Neopterin as a marker of cellular immunological response
Postȩpy higieny i medycyny doświadczalnej, Aug 24, 2017
Neopterin is a pyrazino-pyrimidine compound that belongs to the pteridine group. It is known to b... more Neopterin is a pyrazino-pyrimidine compound that belongs to the pteridine group. It is known to be a biochemical marker associated with cell-mediated immunity. It is produced by human monocytes/macrophages and dendritic cells from guanosine triphosphate (GTP) upon stimulation with interferon gamma (IFNγ), which is released by activated limphocytes Th. Neopterin is a very important clinic parameter, though the physiological role has not been exactly definited thus far. The level of neopterin reflects the stage of activation of the cellular immune system, which is important in the pathogenesis and progression of various diseases. Measuring its concentration in body fluids is used in many different areas of modern medicine, such as infectious disease, gastroenterology, transplantology and transfusiology, rheumatology or oncology. In neurological, cardio-vascular and autoimmune diseases, cell-mediated immunity is also activated, which is proved by the elevated level of this marker. Measurements of neopterin concentrations are also helpful in monitoring the therapy of patients infected with the HIV virus or treated by using immunomudulating therapy. As a result of measuring levels of neopterin in patients with neoplasms of digestive tract, increased concentration was proved, but it is not routinely used in everyday clinic practice.
Postȩpy higieny i medycyny doświadczalnej, Jan 4, 2016
Discrete & Computational Geometry, 2021
We prove that, up to homeomorphism, any graph subject to natural necessary conditions on orientat... more We prove that, up to homeomorphism, any graph subject to natural necessary conditions on orientation and the cycle rank can be realized as the Reeb graph of a Morse function on a given closed manifold M. Along the way, we show that the Reeb number R(M), i.e., the maximum cycle rank among all Reeb graphs of functions on M, is equal to the corank of fundamental group π 1 (M), thus extending a previous result of Gelbukh to the non-orientable case.
We report on the fabrication and magneto-transport measurements of Ni/Au/Ni ferromagnetic single-... more We report on the fabrication and magneto-transport measurements of Ni/Au/Ni ferromagnetic single-electron transistors (F-SETs), fabricated by atomic force microscopy. By positioning a single Au disc (30 nm in diameter) into the gap between the Ni drain and source electrodes (of width 220 nm and 80 nm, respectively) step-by-step with Angstrom precision, and using plasma-processed NiOx as tunneling barriers, we can
Giant-spin Hamiltonians versus first-principles approaches in the tunneling transport in single-molecule magnets
Giant-spin Hamiltonians versus first-principles approaches in the tunneling transport in single-m... more Giant-spin Hamiltonians versus first-principles approaches in the tunneling transport in single-molecule magnets
Nanoscaled ferromagnetic single-electron transistors
2007 7th IEEE Conference on Nanotechnology (IEEE NANO), 2007
We report on a summary of fabricating and characterizing nanoscaled ferromagnetic single-electron... more We report on a summary of fabricating and characterizing nanoscaled ferromagnetic single-electron transistors (F-SETs). One type of device is assembled with an atomic force microscope. A single 30 nm Au disc, forming the central island of the transistor, is manipulated with Angstrom precision into the gap between plasma oxidized Ni source and drain electrodes which are designed with different geometries
Physical Review Letters, 2010
We consider tunneling transport through a Mn12 molecular magnet using spin density functional the... more We consider tunneling transport through a Mn12 molecular magnet using spin density functional theory. A tractable methodology for constructing many-body wavefunctions from Kohn-Sham orbitals allows for the determination of spin-dependent matrix elements for use in transport calculations. The tunneling conductance at finite bias is characterized by peaks representing transitions between spin multiplets, separated by an energy on the order of the magnetic anisotropy. The energy splitting of the spin multiplets and the spatial part of their many-body wave functions, describing the orbital degrees of freedom of the excess charge, strongly affect the electronic transport, and can lead to negative differential conductance.
Physical Review Letters, 2006
We present a theory of single-electron tunneling transport through a ferromagnetic nanoparticle i... more We present a theory of single-electron tunneling transport through a ferromagnetic nanoparticle in which particle-hole excitations are coupled to spin collective modes. The model employed to describe the interaction between quasiparticles and collective excitations captures the salient features of a recent microscopic study. Our analysis of nonlinear quantum transport in the regime of weak coupling to the external electrodes is based on a rate-equation formalism for the nonequilibrium occupation probability of the nanoparticle many-body states. For strong electron-boson coupling, we find that the tunneling conductance as a function of bias voltage is characterized by a large and dense set of resonances. Their magnetic field dependence in the large-field regime is linear, with slopes of the same sign. Both features are in agreement with recent tunneling experiments.
Nano letters, 2007
We have investigated spin accumulation in Ni/Au/Ni single-electron transistors assembled by atomi... more We have investigated spin accumulation in Ni/Au/Ni single-electron transistors assembled by atomic force microscopy. The fabrication technique is unique in that unconventional hybrid devices can be realized with unprecedented control, including real-time tunable tunnel resistances. A grid of Au disks, 30 nm in diameter and 30 nm thick, is prepared on a SiO2 surface by conventional e-beam writing. Subsequently, 30 nm thick ferromagnetic Ni source, drain, and side-gate electrodes are formed in similar process steps. The width and length of the source and drain electrodes were different to exhibit different coercive switching fields. Tunnel barriers of NiO are realized by sequential Ar and O2 plasma treatment. By use of an atomic force microscope with specially designed software, a single nonmagnetic Au nanodisk is positioned into the 25 nm gap between the source and drain electrodes. The resistance of the device is monitored in real time while the Au disk is manipulated step-by-step w...
Applied Physics Letters, 2007
The authors report on magnetotransport investigations of nanoscaled ferromagnetic Co∕Ni∕Co single... more The authors report on magnetotransport investigations of nanoscaled ferromagnetic Co∕Ni∕Co single electron transistors. As a result of reduced size, the devices exhibit single electron transistor characteristics at 4.2K. Magnetotransport measurements carried out at 1.8K reveal tunneling magnetoresistance (TMR) traces with negative coercive fields, which the authors interpret in terms of a switching mechanism driven by the shape anisotropy of the central wirelike Ni island. A large TMR of about 18% is observed within a finite source-drain bias regime. The TMR decreases rapidly with increasing bias, which the authors tentatively attribute to excitation of magnons in the central island.
Postępy Higieny i Medycyny Doświadczalnej, 2016
Uploads
Papers by Łukasz Michalak