Anisotropic intrinsic anomalous Hall effect in ordered 3dPt alloys

By performing first principles calculations we investigate the intrinsic anomalous Hall conductivity (AHC) and its anisotropy in ordered L1o FePt, CoPt and NiPt ferromagnets, and their intermediate alloys. We demonstrate that the AHC in this family of compounds depends strongly on the direction of the magnetization in the crystal. We predict that such pronounced orientational dependence in combination with the general decreasing trend of the AHC when going from FePt to NiPt leads to a sign change of the AHC upon rotating the magnetization direction in the crystal of CoPt alloy. We also suggest that for a range of concentration x in Co(x)Ni(1-x)Pt alloy it is possible to achieve a complete quenching of the anomalous Hall current for a certain direction of the magnetization in the crystal. By analyzing the spin-resolved AHC in 3dPt alloys we endeavor to relate the overall trend of the AHC in these compounds to the changes in their densities of d-states around the Fermi energy upon varying the atomic number. Moreover, we show the generality of the phenomenon of anisotropic anomalous Hall effect by demonstrating its occurrence within the three-band tight-binding model.Comment: 10 page

Stretching Semiflexible Polymer Chains: Evidence for the Importance of Excluded Volume Effects from Monte Carlo Simulation

Semiflexible macromolecules in dilute solution under very good solvent conditions are modeled by self-avoiding walks on the simple cubic lattice ($d=3$ dimensions) and square lattice ($d=2$ dimensions), varying chain stiffness by an energy penalty $\epsilon_b$ for chain bending. In the absence of excluded volume interactions, the persistence length $\ell_p$ of the polymers would then simply be $\ell_p=\ell_b(2d-2)^{-1}q_b^{-1}$ with $q_b= \exp(-\epsilon_b/k_BT)$, the bond length $\ell_b$ being the lattice spacing, and $k_BT$ is the thermal energy. Using Monte Carlo simulations applying the pruned-enriched Rosenbluth method (PERM), both $q_b$ and the chain length $N$ are varied over a wide range $(0.005 \leq q_b \leq 1, \; N \leq 50000$), and also a stretching force $f$ is applied to one chain end (fixing the other end at the origin). In the absence of this force, in $d=2$ a single crossover from rod-like behavior (for contour lengths less than $\ell_p$) to swollen coils occurs, invalidating the Kratky-Porod model, while in $d=3$ a double crossover occurs, from rods to Gaussian coils (as implied by the Kratky-Porod model) and then to coils that are swollen due to the excluded volume interaction. If the stretching force is applied, excluded volume interactions matter for the force versus extension relation irrespective of chain stiffness in $d=2$, while theories based on the Kratky-Porod model are found to work in $d=3$ for stiff chains in an intermediate regime of chain extensions. While for $q_b \ll 1$ in this model a persistence length can be estimated from the initial decay of bond-orientational correlations, it is argued that this is not possible for more complex wormlike chains (e.g. bottle-brush polymers). Consequences for the proper interpretation of experiments are briefly discussed.Comment: 23 pages, 17 figures, 2 tables, to be published in J. Chem. Phys. (2011

Magnetic, magnetocaloric and magnetotransport properties of RSn_{1+x}Ge_{1-x} compounds (R=Gd, Tb, Er; x=0.1)

We have studied the magnetic, magnetocaloric and magnetotransport properties of RSn1+xGe1-x(R=Gd, Tb, Er; x=0.1) series by means of magnetization, heat capacity and resistivity measurements. It has been found that all the compounds crystallize in the orthorhombic crystal structure described by the centrosymmetric space group Cmcm (No. 63). The magnetic susceptibility and heat capacity data suggest that all the compounds are antiferromagnetic. Large negative values of {\theta}p in case of GdSn1.1Ge0.9 and TbSn1.1Ge0.9 indicate that strong antiferromagnetic interactions are involved, which is also reflected in the magnetization isotherms. On the other hand ErSn1.1Ge0.9 shows weak antiferromagnetic interaction. The heat capacity data have been analyzed by fitting the temperature dependence and the values of {\theta}D and {\gamma} have been estimated. Among these three compounds, ErSn1.1Ge0.9 shows considerable magnetic entropy change of 9.5 J/kg K and an adiabatic temperature change of 3.2 K for a field of 50 kOe. The resistivity data in different temperature regimes have been analyzed and the dominant contributions have been identified. All the compounds show small but positive magnetoresistance.Comment: 23 pages,11 figure

Measurement of refractive index of hemoglobin in the visible/NIR spectral range

This study is focused on the measurements of the refractive index of hemoglobin solutions in the visible/near-infrared (NIR) spectral range at room temperature for characteristic laser wavelengths: 480, 486, 546, 589, 644, 656, 680, 930, 1100, 1300, and 1550 nm. Measurements were performed using the multiwavelength Abbe refractometer. Aqua hemoglobin solutions of different concentrations obtained from human whole blood were investigated. The specific increment of refractive index on hemoglobin concentration and the Sellmeier coefficients were calculated

A Quantitative Theory of Mechanical Unfolding of a Homopolymer Globule

We propose the quantitative mean-field theory of mechanical unfolding of a globule formed by long flexible homopolymer chain collapsed in poor solvent and subjected to extensional deformation. We demonstrate that depending on the degree of polymerization and solvent quality (quantified by the Flory-Huggins $\chi$ parameter) the mechanical unfolding of the collapsed chain may either occur continuously (by passing a sequence of uniformly elongated configurations) or involves intra-molecular micro-phase coexistence of a collapsed and a stretched segment followed by an abrupt unraveling transition. The force-extension curves are obtained and quantitatively compared to our recent results of numerical self-consistent field (SCF) simulations. The phase diagrams for extended homopolymer chains in poor solvent comprising one- and two-phase regions are calculated for different chain length or/and solvent quality.Comment: 24 pages, 18 figure

Gene Algebra from a Genetic Code Algebraic Structure

The biological distinction between the base positions in the codon, the chemical types of bases (purine and pyrimidine) and their hydrogen bond number have been the most relevant codon properties used in the genetic code analysis. Now, these properties have allowed us to build a Genetic Code ring isomorphic to the ring (Z64, +,*) of the integer module 64. On the Z64-algebra of the set of 64^N codon sequences of length N, gene mutations are described by means of endomorphisms F: (Z64)^N->(Z64)^N. Endomorphisms and automorphisms helped us describe the gene mutation pathways. For instance, 77.7% mutations in 749 HIV protease gene sequences correspond to unique diagonal endomorphisms of the wild type strain HXB2. In particular, most of the reported mutations that confer drug resistance to the HIV protease gene correspond to diagonal automorphisms of the wild type. What is more, in the human beta-globin gene a similar situation appears where most of the single codon mutations correspond to automorphisms. Hence, in the analyses of molecular evolution process on the DNA sequence set of length N, the Z64-algebra will help us explain the quantitative relationships between genes.Comment: 27 pages, without figure

Phänomenologie und Bekämpfung von "Cyberpiraterie" : eine kriminologische und kriminalpolitische Analyse

Illegale Beschaffung und Distribution von Schutzgegenständen geistigen Eigentums über das Internet haben sich spätestens seit dem Siegeszug der sogenannten Online-Tauschbörsen (P2P-Filesharing-Systeme) zu einem regelrechten Massenphänomen entwickelt. Die vorliegende Arbeit untersucht die vielfältigen Tatbegehungsmodalitäten, die Täterstruktur und -motivation, die Auswirkungen von Cyberpiraterie sowie Bekämpfungs- und Überwachungsstrategien bezüglich des Problems. Neben einer kritischen Beurteilung der strafrechtlichen Situation enthält die Arbeit auch eigene Lösungsvorschläge.Die Dissertation gliedert sich in drei Teile: Der erste Teil enthält eine Einführung, in der auch die wichtigsten technischen Zusammenhänge erläutert werden. Teil 2 beschäftigt sich mit der ältesten Form digitaler Piraterie, der Softwarepiraterie (auch: ‘Warez-Szene’). Teil 3 schließlich behandelt das recht neue Phänomen der Online-Musikpiraterie (‘MP3-Szene’).Angesichts der starken Dynamik des Themenkreises ist bei der Wahl der Bekämpfungsstrategien stets die aktuelle digitale Realität zu berücksichtigen. Der Wahlspruch der Verwertungsgesellschaften, wonach ‘das Schützbare zu schützen und das Nicht-Schützbare zu vergüten’ ist, scheidet in diesem Zusammenhang die Geister. Während die Vertreter der Unterhaltungsindustrie sämtliche digitalen Werke für schützbar erklären, zeigt die vorliegende Arbeit exemplarisch auf, dass ein umfassender Schutz digitaler Inhalte im Internet zur Zeit weder rechtlich noch technisch durchsetzbar ist. Nicht nur aus diesem Grund sondern auch aus rechtspolitischen und kriminologischen Erwägungen ist es dringend geboten, zivilrechtliche Alternativen zu dem derzeit eingeschlagenen, strafrechtlichen Weg zu etablieren