Classification of phase transitions in small systems

We present a classification scheme for phase transitions in finite systems like atomic and molecular clusters based on the Lee-Yang zeros in the complex temperature plane. In the limit of infinite particle numbers the scheme reduces to the Ehrenfest definition of phase transitions and gives the right critical indices. We apply this classification scheme to Bose-Einstein condensates in a harmonic trap as an example of a higher order phase transitions in a finite system and to small Ar clusters.Comment: 12 pages, 4 figures, accepted for publication in Phys. Rev. Let

Observations of meteoric material and implications for aerosol nucleation in the winter Arctic lower stratosphere derived from in situ particle measurements

Number concentrations of total and non-volatile aerosol particles with size diameters >0.01 μm as well as particle size distributions (0.4–23 μm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified FSSP 300 (Forward Scattering Spectrometer Probe). Around 18–20 km altitude typical total particle number concentrations nt range at 10–20 cm−3 (ambient conditions). Correlations with the trace gases nitrous oxide (N2O) and trichlorofluoromethane (CFC-11) are discussed. Inside the polar vortex the total number of particles >0.01 μm increases with potential temperature while N2O is decreasing which indicates a source of particles in the above polar stratosphere or mesosphere. A separate channel of the COPAS instrument measures the fraction of aerosol particles non-volatile at 250°C. Inside the polar vortex a much higher fraction of particles contained non-volatile residues than outside the vortex (~67% inside vortex, ~24% outside vortex). This is most likely due to a strongly increased fraction of meteoric material in the particles which is transported downward from the mesosphere inside the polar vortex. The high fraction of non-volatile residual particles gives therefore experimental evidence for downward transport of mesospheric air inside the polar vortex. It is also shown that the fraction of non-volatile residual particles serves directly as a suitable experimental vortex tracer. Nanometer-sized meteoric smoke particles may also serve as nuclei for the condensation of gaseous sulfuric acid and water in the polar vortex and these additional particles may be responsible for the increase in the observed particle concentration at low N2O. The number concentrations of particles >0.4 μm measured with the FSSP decrease markedly inside the polar vortex with increasing potential temperature, also a consequence of subsidence of air from higher altitudes inside the vortex. Another focus of the analysis was put on the particle measurements in the lowermost stratosphere. For the total particle density relatively high number concentrations of several hundred particles per cm3 at altitudes below ~14 km were observed in several flights. To investigate the origin of these high number concentrations we conducted air mass trajectory calculations and compared the particle measurements with other trace gas observations. The high number concentrations of total particles in the lowermost stratosphere are probably caused by transport of originally tropospheric air from lower latitudes and are potentially influenced by recent particle nucleation

Classification of the Nuclear Multifragmentation Phase Transition

Using a recently proposed classification scheme for phase transitions in finite systems [Phys.Rev.Lett.{\bf 84},3511 (2000)] we show that within the statistical standard model of nuclear multifragmentation the predicted phase transition is of first order.Comment: 5 pages, 4 eps figures, accepted for publication in Phys.Rev.C (in press

Integrating rules of modular coordination to improve model authoring in BIM

As the adoption of Building Information Modelling (BIM) becomes pervasive and its level of application matures, the need to incorporate domain-specific knowledge in BIM authoring tools is also increasing. Rule-based scripts that assist and guide the modeller in model authoring are needed to enhance the level of usage of BIM. The authors developed a framework for incorporation of rule-driven domain knowledge into BIM authoring tools. With the objective of customizing the modelling process using a set of rules, the approach presented in this paper combines rules of modular coordination in prefabricated building with BIM. Modular coordination, a dimensional coordination system for sizing and placing building elements within a three-dimensional (3D) reference system, is translated into rules that are incorporated into the BIM authoring tool through object-level and process-level interventions. The study explores various options of parametric modelling for integration of identified modular coordination rules. The aim of integrating modular coordination rules is to assist the user during the modelling process. The proposed approach has the potential of reducing inconsistencies and time spent in modelling and documentation allowing the designer to spend more effort on value-adding design tasks. With the help of a case study and an experiment, capabilities of the proposed framework are demonstrated and validated

Magnetic impurity resonance states and symmetry of the superconducting order parameter in iron-based superconductors

We investigate the effect of magnetic impurities on the local quasiparticle density of states (LDOS) in iron-based superconductors. Employing the two-orbital model where 3$d$ electron and hole conduction bands are hybridizing with the localized $f$-orbital of the impurity spin, we investigate how various symmetries of the superconducting gap and its nodal structure influence the quasiparticle excitations and impurity bound states. We show that the bound states behave qualitatively different for each symmetry. Most importantly we find that the impurity-induced bound states can be used to identify the nodal structure of the extended s-wave symmetry ($S^{\pm}$) that is actively discussed in ferropnictides.Comment: 7 pages, 5 figures, theory part is extended, figures are replace

Deceptive signals of phase transitions in small magnetic clusters

We present an analysis of the thermodynamic properties of small transition metal clusters and show how the commonly used indicators of phase transitions like peaks in the specific heat or magnetic susceptibility can lead to deceptive interpretations of the underlying physics. The analysis of the distribution of zeros of the canonical partition function in the whole complex temperature plane reveals the nature of the transition. We show that signals in the magnetic susceptibility at positive temperatures have their origin at zeros lying at negative temperatures.Comment: 4 pages, 5 figures, revtex4, for further information see http://www.smallsystems.d

Order-disorder transition in nanoscopic semiconductor quantum rings

Using the path integral Monte Carlo technique we show that semiconductor quantum rings with up to six electrons exhibit a temperature, ring diameter, and particle number dependent transition between spin ordered and disordered Wigner crystals. Due to the small number of particles the transition extends over a broad temperature range and is clearly identifiable from the electron pair correlation functions.Comment: 4 pages, 5 figures, For recent information on physics of small systems see http://www.smallsystems.d

A BIM-Based Framework to Visually Evaluate Circularity and Life Cycle Cost of buildings

The Circular Economy paradigm seeks to shift products and systems from linear to “closed loop” life cycles applying specific business models and strategies to their designs and lifelines. The implementation of the circular economy in buildings depends on the efforts made by all the stakeholder involved in the life cycle of a building, where it can draw most of the benefits if the application of a circular business model is planned during the design phases. Building Information Modelling is an approach that helps designers in creating and managing semantically rich 3D-models describing the status of the building over its life cycle. In this paper, a BIM-based framework for evaluating the application of circular business models of buildings from the circularity and the life cycle cost points of views is proposed

Zur Polymorphie von TbCl3

3 different modifications of TbCl3 were synthesized. TbCl3 (UCl3type). probably in a metastable state, crystallizes in space group P63/m with a = 737.63(2) pm, c = 405.71(2) pm and Z = 2. TbCl3(PuBr3-type) crystallizes in space group Cmcm with a = 384.71(6) pm, b = 1177.37(7) pm, c = 851.77(4) pm and Z = 4. h-TbCl3, the high temperature phase being stable above 790 K, crystallizes in space group P42/mnm with a = 642.51(4) pm, c = 1177.14(18) pm and Z = 4. © 1988, Walter de Gruyter. All rights reserved

Classification of phase transitions of finite Bose-Einstein condensates in power law traps by Fisher zeros

We present a detailed description of a classification scheme for phase transitions in finite systems based on the distribution of Fisher zeros of the canonical partition function in the complex temperature plane. We apply this scheme to finite Bose-systems in power law traps within a semi-analytic approach with a continuous one-particle density of states $\Omega(E)\sim E^{d-1}$ for different values of $d$ and to a three dimensional harmonically confined ideal Bose-gas with discrete energy levels. Our results indicate that the order of the Bose-Einstein condensation phase transition sensitively depends on the confining potential.Comment: 7 pages, 9 eps-figures, For recent information on physics of small systems see "http://www.smallsystems.de