Theoretical Studies of Quantum Interference in Electronic Transport Through Carbon Nanotubes

We performed studies of coherent electronic transport through a single walled carbon nanotube. In the calculations multiple scattering on the contacts and interference processes were taken into account. Conductance is a composition of contributions from different channels. We studied also spin--dependent transport in the system with ferromagnetic electrodes. The magnetoresistance is large and shows large oscillations, it can be even negative in some cases.Comment: 6 pages, 4 figures, oral presentation at the XXXI International School on the Physics of Semiconducting Coumpounds, Jaszowiec 2002, to appear in the Acta Physica Polonic

Job Creation, Destruction and Transition in Poland, 1988-1998: Panel Evidence

Longitudinal data from interviews with Poles of working age conducted in 1988, 1993 and 1998 present a detailed view of the transition from a state dominated to a market economy. Job loss in state firms and job creation in new private firms are the dominant employment change, other than retirements from the labor force. In the Polish case, a significant proportion of this movement over the 1988 to 1998 period involves a period of unemployment or exit from the labor force before obtaining a private sector job. A second feature of the Polish transition is considerable job competition between workers leaving the state sector and those who were out of the labor force at the beginning of the transition. The likelihood of moving to the private sector was higher for the better educated and for residents of regions with a robust de novo economy, suggesting that the supply of jobs in the private sector combined with higher levels of human capital lead to faster and smoother transitions. Lastly, wage differences between the state sector and the de novo sector appear to have little association with mobility, suggesting that movement is not strongly related to the opportunity to find a higher paying job.http://deepblue.lib.umich.edu/bitstream/2027.42/39887/3/wp502.pd

Politicians in times of transformation: "Transformational correctness" or genuine differences in perception?

The paper presents selected results of the 1996 study of top Polish politicians-members of the 1993-97 Parliament and leaders of those important political parties which failed to get into this Parliament. Presented results pertain to five aspects of politicians' attitudes: (1) opinions on qualities of persons who should be vs. actually are involved in politics, (2) normatively accepted definitions of politics, (3) visions of the good state, (4) visions of democracy, and (5) opinions on what defines political views as being either on the left or on the right. As a result, consistently found across all five domains, there is a strong attitudinal similarity among politicians of differing political parties and of divergent political orientations. This finding is interpreted as reflection of a fundamental track similarity in the way in which Polish politicians perceive the most important tasks confronting the whole political class in times of systemic transformation. Transformational correctness - believing that in such times politicians should have (or at least should display) certain views - might be a strong force behind this similarity. --

Soliton creation during a Bose-Einstein condensation

We use stochastic Gross-Pitaevskii equation to study dynamics of Bose-Einstein condensation. We show that cooling into a Bose-Einstein condensate (BEC) can create solitons with density given by the cooling rate and by the critical exponents of the transition. Thus, counting solitons left in its wake should allow one to determine the critical exponents z and nu for a BEC phase transition. The same information can be extracted from two-point correlation functions.Comment: 4 pages, 3 figures, improved version to appear in PRL: scalings discussed more extensively, fitting scheme for determination of z and nu critical exponents is explaine

Solar cycle variation in Sun-as-a-star Ca II 854.2 nm bisectors

The bisector of the strong chromospheric Ca II 854.2 nm line has an inverse-C shape the cause of which is not yet fully understood. We show that the amplitude of the bisector in Sun-as-a-star observations exhibits a solar cycle variation with smaller amplitudes during highest activity. The line core intensity is lower during solar minima while the part of the bisector most sensitive to the line core shows no systematic change with activity. Our results support the use of Ca II 854.2 nm bisectors in studying the relationship between convection and magnetic fields, not only in the Sun but in other stars as well.Comment: Accepted to Ap

Magnetic Instability in Strongly Correlated Superconductors

Recently a new phenomenological Hamiltonian has been proposed to describe the superconducting cuprates. This so-called Gossamer Hamiltonian is an apt model for a superconductor with strong on-site Coulomb repulsion betweenthe electrons. It is shown that as one approaches half-filling the Gossamer superconductor, and hence the superconducting state, with strong repulsion is unstable toward an antiferromagnetic insulator an can undergo a quantum phase transition to such an insulator if one increases the on-site Coulomb repulsion

Politicians in times of transformation: "transformational correctness" or genuine differences in perception?

"The paper presents selected results of the 1996 study of top Polish politicians members of the 1993-97 Parliament and leaders of those important political parties which failed to get into this Parliament. Presented results pertain to five aspects of politicians' attitudes: (1) opinions on qualities of persons who should be vs. actually are involved in politics, (2) normatively accepted definitions of politics, (3) visions of the 'good state', (4) visions of democracy, and (5) opinions on what defines political views as being either on the 'left' or on the 'right.' As a result, consistently found across all five domains, there is a strong attitudinal similarity among politicians of differing political parties and of divergent political orientations. This finding is interpreted as reflection of a fundamental 'track similarity' in the way in which Polish politicians perceive the most important tasks confronting the whole political class in times of systemic transformation. 'Transformational correctness' - believing that in such times politicians should have (or at least should display) certain views - might be a strong force behind this similarity." (author's abstract)Es werden ausgewählte Ergebnisse einer größeren Untersuchung maßgeblicher polnischer Politiker präsentiert, und zwar von Mitgliedern des Parlaments von 1993 bis 1997 und Führern von wichtigeren politischen Parteien, die den Einzug in dieses Parlament nicht schafften. Die Untersuchung bezieht sich auf fünf Aspekte der Einstellungen der Politiker: (1) Meinungen über die Eigenschaften von Personen, die in der Politik tätig sein sollten oder es tatsächlich sind; (2) normativ akzeptierte Definitionen von Politik; (3) Vorstellungen vom "guten Staat"; (4) Vorstellungen von Demokratie; (5) Meinungen über die Einstufung politischer Anschauungen als eher "rechts" oder eher "links". Als Gesamtergebnis stellt sich, und zwar konsistent auf sämtlichen fünf Fragegebieten, eine starke Ähnlichkeit in den Einstellungen von Politikern heraus - über unterschiedliche politische Parteien und divergierende politische Orientierungen hinweg. Die Autoren finden hierin eine grundlegende "Verlaufsähnlichkeit" dahingehend widergespiegelt, wie polnische Politiker die wichtigsten Aufgaben wahrnehmen, die der Politik in Zeiten systemischer Transformation gestellt sind. Als starke Kraft hinter dieser Ähnlichkeit wird ein Phänomen "transformationeller Korrektheit" gesehen - die Überzeugung, daß in derartigen Veränderungszeiten ein Politiker bestimmte Auffassungen haben (oder sie zumindest zum Ausdruck bringen) sollte. (HH

Feshbach Resonance Cooling of Trapped Atom Pairs

Spectroscopic studies of few-body systems at ultracold temperatures provide valuable information that often cannot be extracted in a hot environment. Considering a pair of atoms, we propose a cooling mechanism that makes use of a scattering Feshbach resonance. Application of a series of time-dependent magnetic field ramps results in the situation in which either zero, one, or two atoms remain trapped. If two atoms remain in the trap after the field ramps are completed, then they have been cooled. Application of the proposed cooling mechanism to optical traps or lattices is considered.Comment: 5 pages, 3 figures; v.2: major conceptual change

Multiphase change materials for energy storage application in buildings

Experimental study has been carried out towards the development of a multiphase change material (MCM) by combining two fabricated microencapsulated phase change materials (MEPCM-oct and MEPCM-eic) samples. The study also covered the characterization of the developed samples for their thermal properties. For the purpose of validation the thermal properties of the developed MCM sample were compared with that of the core components. The developed MCM sample achieved a combined energy storage capacity of 186 kJ/kg with two melting temperatures of 23.4oC and 34.5oC. Even though the two melting temperatures of the MCM were slightly reduced by 0.18℃ and 0.48℃ in comparison with the MEPCM-oct and MEPCM-eic respectively, their mean energy storage capacities were in perfect agreement. The study has therefore shown that it is possible to overcome some of the scientific barriers towards the development of multiphase change materials but further investigations are needed to enhance overall thermal response