COVID-19 has created global upheaval in a way not seen since the Second World War. Among the sectors hardest hit has been education, with modes of teaching and research, a long-term trajectory of internationalisation and multiple revenue streams for universities disrupted in ways unthinkable twelve months ago. This final session of the Redux Online looks at the potential impacts on university presses of an altered landscape. Leaders from the library and university press worlds will examine how previous strategic priorities and practices have changed and will change for some of the key stakeholders in scholarly publishing. Recording of a live webinar held on 30 July 2020 as part of the Redux Online series.
Chemical sensing properties of single wire and mat form sensor structures fabricated from the same carbon nanotube (CNT) materials have been compared. Sensing properties of CNT sensors were evaluated upon electrical response in the presence of five vapours as acetone, acetic acid, ethanol, toluene, and water. Diverse behaviour of single wire CNT sensors was found, while the mat structures showed similar response for all the applied vapours. This indicates that the sensing mechanism of random CNT networks cannot be interpreted as a simple summation of the constituting individual CNT effects, but is associated to another robust phenomenon, localized presumably at CNT-CNT junctions, must be supposed.
AbstractMittels des COND‐Berechnungsalgorithmus können eindimensionale Konstruktionsaufbauten hinsichtlich des hygrothermischen Verhaltens in der Kondensationsperiode bewertet werden. In Ergänzung zum Standardverfahren (Glaser) nach DIN 4108‐3 berücksichtigt COND den kapillaren Transport von Kondensat. Damit lässt sich der Feuchteschutznachweis auch für moderne praxisbewährte Innendämmsysteme führen, die nach Glaser nicht nachweisfähig sind. Der Berechnungsalgorithmus wird in der überarbeiteten, allgemeingültigen Form detailliert und vollständig dargestellt und beschrieben. Das Materialmodell und eingeführte Vereinfachungen werden diskutiert. Abschließend werden Einsatzbereiche und Grenzen des Verfahrens erläutert.With the COND algorithm architects and engineers may evaluate one‐dimensional constructions with respect to their hygrothermal behavior within a condensation period. COND considers, in contrast to the standard method (Glaser‐method) according to DIN 4108‐3, the capillary transport of interstitial condensate. The method allows hygrothermal verification of constructions, including modern internal insulation systems. Such systems, proven to be effective in practice but not verifiable with the Glaser method, may be analyzed and certified with the COND method. The article includes a full and detailed description of this computational algorithm. The paper discusses the material model and introduced simplifications, and concludes with a review on application fields and limits of the method.
We demonstrate that recent experimental data (E. Castel et al J.Phys. Cond. Mat. {\bf 21} (2009), 452201) on tungsten bronze compound (TBC) Ba$_2$Pr$_x$Nd$_{1-x}$FeNb$_4$O$_{15}$ can be well explained in our model predicting a crossover from ferroelectric ($x=0$) to orientational (dipole) glass ($x=1$), rather then relaxor, behavior. We show, that since a "classical" perovskite relaxor like Pb(Mn$_{1/3}$ Nb$_{2/3}$)O$_3$ is never a ferroelectric, the presence of ferroelectric hysteresis loops in TBC shows that this substance actually transits from ferroelectric to orientational glass phase with $x$ growth. To describe the above crossover theoretically, we use the simple replica-symmetric solution for disordered Ising model.
The objections raised by Vilar and Rubi [cond-mat arXiv:0707.3802v1] against the definition of the thermodynamical work appearing in Jarzynski's equality are shown to be misleading and inconsistent.
In a recent publication [Phys. Rev. Lett. 97, 227402 (2006), cond-mat/0611411], it has been demonstrated numerically that a long-range disorder potential in semiconductor quantum wells can be reconstructed reliably via single-photon interferometry of spontaneously emitted light. In the present paper, a simplified analytical model of independent two-level systems is presented in order to study the reconstruction procedure in more detail. With the help of this model, the measured photon correlations can be calculated analytically and the influence of parameters such as the disorder length scale, the wavelength of the used light, or the spotsize can be investigated systematically. Furthermore, the relation between the proposed angle-resolved single-photon correlations and the disorder potential can be understood and the measured signal is expected to be closely related to the characteristic strength and length scale of the disorder.
Two preceding parts of a paper (cond-mat/0508457, cond-mat/0508460) considered the heuristic values of recent experiments pointing to the nearly universal occurrence of photovoltages across solid surfaces under short-circuit conditions. These voltages arise by virtue of a variety of spectrally-dependent mechanisms activated by incident photons. For the visible range, the photovoltages are obliged to the photodetachment of ions which leave the surface charged. In an attempt to learn more, we now study short-circuit photovoltages in well-defined materials including high-Tc superconductors within a broad temperature range down to liquid nitrogen. We believe our data provide a new insight into the process.
The topological term in the effective action for the electrically neutral BCS system is discussed. It is applied for the calculation of the transverse force acting on a vortex in the limit of a smooth vortex core and vanishing interlevel distance in the vortex core. The controversy between the topological terms in the articles by I. J. R. Aitchison et al., Phys. Rev. B 51, 6531 (1995) and A. van Otterlo et al., cond-mat/9703124 is resolved.
Recently S.Galam and A.Mauger [Phys.Rev.E 56, 322 (1997); cond-mat/9706304 ] proposed an approximant which relates the bond and the site percolation threshold for a particular lattice. Their formula is based on a fit to exact and simulation results obtained earlier for different periodic and aperiodic lattices. However, the numerical result for an aperiodic dodecagonal lattice does not agree well with the proposed formula. I present here new and more precise data for this and other aperiodic lattices. The previously published value for the dodecagonal lattice is confirmed. The reason for the deviation from the Galam and Mauger approximant is discussed.
In a recent letter [Phys. Rev. Lett. 78, 515 (1997); cond-mat/9612034] Roemer and Schreiber report on numerical calculations that led them to conclude that the previously observed enhancement of the localization length $L_2$ of two interacting particles (TIP) vanishes in the thermodynamic limit. We point out that such a claim (i) is in conflict with the scaling theory of localization, (ii) ignores a consistent picture from a wealth of published numerical data and analytical investigations, and (iii) directly contradicts new numerical results obtained with a Green function method that is well adapted to the problem under study. The claim of Roemer and Schreiber is based on extrapolating from L<360 to infinity. Our data clearly shows the two particle localization length $L_2$ to be significantly enhanced and independent of system size between L=100 and L=1000, as expected on physical grounds.
There has been a corporative absence of understanding of Hall anomaly data in the mixed state in terms of vortex many-body effect and pinning, because of the dominant theoretical influence. Now D'Anna et al. [ Phys. Rev. Lett. 81, 2530 (1998) (cond-mat/9808164)] are brave enough to announce the prominent role played by vortex many-body effect and pinning in their interpretation of their own data. Here I wish to point out: (1) Indeed the data of D'Anna et al. can be explained within an existing Hall anomaly theory based on vortex many-body considerations; (2) It is not surprising that their data are not consistent with available microscopic Hall anomaly theories, because those theories are mathematically incorrect; and (3) The courage of D'Anna et al. should be appreciated.
We reply to the comment on our published paper `` Universal Fluctuations in Correlated Systems'',Phys. Rev. Lett. Vol; 84, p3744 (2000), by B. Zheng and S. Trimper, cond-mat/0109003. We argue that their results confirm our conjecture, that the probability distribution for order parameter fluctuations in the 2D and 3D Ising models at a temperature $T^{\ast}(L)$ slightly below $T_C$ for the infinite, system approximates the universal functional form of the 2D-XY model in its low temperature phase. We discuss the relevance of the temperature interval $T_C-T^{\ast}$, considered to be large by Zheng and Trimper and explain why the observed phenomena is a critical phenomena.
We show that the arguments in the posting cond-mat/0607432 by Flatte and Hall are flawed and untenable. Their spin based transistor cannot work as claimed because of fundamental scientific barriers, which cannot be overcome now, or ever. Their device is not likely to work as a transistor at room temperature, let alone outperform the traditional MOSFET, as claimed.
It was recently claimed that on d-dimensional small-world networks with a density p of shortcuts, the typical separation s(p) ~ p^{-1/d} between shortcut-ends is a characteristic length for shortest-paths{cond-mat/9904419}. This contradicts an earlier argument suggesting that no finite characteristic length can be defined for bilocal observables on these systems {cont-mat/9903426}. We show analytically, and confirm by numerical simulation, that shortest-path lengths \ell(r) behave as \ell(r) ~ r for r r_c, where r is the Euclidean separation between two points and r_c(p,L) = p^{-1/d} log(L^dp) is a characteristic length. This shows that the mean separation s between shortcut-ends is not a relevant length-scale for shortest-paths. The true characteristic length r_c(p,L) diverges with system size L no matter the value of p. Therefore no finite characteristic length can be defined for small-world networks in the thermodynamic limit.
The renormalization factor, dubbed "quasiparticle charge" Z e , of the coupling between the supercurrent and quasiparticles was analyzed in the context of high temperature cuprates in a recent paper by Ioffe and Millis [cond-mat/0112509 (unpublished)]. They observed that Z e in cuprates deviates from the BCS value (Z e = 1), which was interpreted as the proximity effect near a Mott insulator. Here we show that the deviation from Z e = I can occur, in general, even in the absence of quasiparticle interactions, when the superconducting order coexists with another order parameter with the same internal symmetry. As an example, we compute the coefficient of the linear temperature dependence of the superfluid density when the d-wave superconducting state coexists with the orbital antiferromagnetic state (d-density wave), and find that Z e varies from 1/√2 to 1.
We discuss a simple method of constructing correlated random networks, which was recently proposed by M. Bogu~n'a and R. Pastor-Satorras (cond-mat/0306072). The result of this construction procedure is a sparse network whose degree--degree distribution asymptotically approaches a given function at large degrees. We argue that this convergence is possible if the desired function is sufficiently slowly decreasing.