A New Approach to Accessibility – Perceived accessibility versus objectively measured accessibility in daily travel

Accessibility has conventionally been measured and evaluated ignoring the user-perspective in favor for focus on travel time and distance to a number of pre-determined destinations. Acknowledging this gap, we recently developed a scale for perceived accessibility PAC (Lättman, Friman, & Olsson 2016) aimed at capturing the individual perspective of accessibility within a certain travel mode. In this paper, we 1) further develop the PAC measure of perceived accessibility in order to capture the perceived accessibility of the individuals’ actual daily travel 2) compare residents’ perceived accessibility to the objective accessibility level for the same residential area, and 3) compare levels of perceived accessibility between residential areas and main travel modes. Data from 2711 residents of Malmö, Sweden show that perceived accessibility is consistently higher than objective accessibility across 13 residential areas, with minor differences in levels of perceived accessibility between areas. Surprisingly, bicycle users rate their accessibility significantly higher than those who mainly use the car or public transport for daily travel, contrary to objective accessibility assumptions. These differences point at the importance of including perceived accessibility as a complementary tool when planning for and evaluating the transport systems.Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne

Vacuum fluctuations and the thermodynamics of chiral models

We consider the thermodynamics of chiral models in the mean-field approximation and discuss the relevance of the (frequently omitted) fermion vacuum loop. Within the chiral quark-meson model and its Polyakov loop extended version, we show that the fermion vacuum fluctuations can change the order of the phase transition in the chiral limit and strongly influence physical observables. We compute the temperature-dependent effective potential and baryon number susceptibilities in these models, with and without the vacuum term, and explore the cutoff and the pion mass dependence of the susceptibilities. Finally, in the renormalized model the divergent vacuum contribution is removed using the dimensional regularization.Comment: 9 pages, 5 figure

Vector meson spectral function and dilepton rate in an effective mean field model

We have studied the vector meson spectral function (VMSF) in a hot and dense medium within an effective QCD model namely the Nambu-Jona-Lasinio (NJL) and its Polyakov Loop extended version (PNJL) with and without the effect of isoscalar vector interaction (IVI). The effect of the IVI has been taken into account using the ring approximation. We obtained the dilepton production rate (DPR) using the VMSF and observed that at moderate temperature it is enhanced in the PNJL model as compared to the NJL and Born rate due to the suppression of color degrees of freedom.Comment: 5 pages, 7 figures, conference proceedings of the XXI DAE-BRNS HEP Symposium, IIT Guwahati, December 2014; to appear in 'Springer Proceedings in Physics Series

Imaginary polarization as a way to surmount the sign problem in ab initio calculations of spin-imbalanced Fermi gases

From ultracold atoms to quantum chromodynamics, reliable ab initio studies of strongly interacting fermions require numerical methods, typically in some form of quantum Monte Carlo calculation. Unfortunately, (non)relativistic systems at finite density (spin polarization) generally have a sign problem, such that those ab initio calculations are impractical. It is well-known, however, that in the relativistic case imaginary chemical potentials solve this problem, assuming the data can be analytically continued to the real axis. Is this feasible for nonrelativistic systems? Are the interesting features of the phase diagram accessible in this manner? By introducing complex chemical potentials, for real total particle number and imaginary polarization, the sign problem is avoided in the nonrelativistic case. To give a first answer to the above questions, we perform a mean-field study of the finite-temperature phase diagram of spin-1/2 fermions with imaginary polarization.Comment: 5 pages, 2 figures; published versio

Neutrino Emission from Superfluid Neutron-Star Cores: Various Types of Neutron Pairing

We calculate and provide analytic fits of the factors which describe the reduction of the neutrino emissivity of modified Urca and nucleon-nucleon bremsstrahlung processes by superfluidity of neutrons and protons in neutron-star cores. We consider $^1$S$_0$ pairing of protons and either $^1$S$_0$ or $^3$P$_2$ pairing of neutrons. We analyze two types of $^3$P$_2$ pairing: the familiar pairing with zero projection of the total angular momentum of neutron pairs onto quantization axis, $m_J=0$; and the pairing with $|m_J|=2$ which leads to the gap with nodes at the neutron Fermi surface. Combining the new data with those available in the literature we fully describe neutrino emission by nucleons from neutron star cores to be used in simulations of cooling of superfluid neutron stars.Comment: 14 pages, 6 figures, A&A, accepte

Mapping the phase diagram of strongly interacting matter

We employ a conformal mapping to explore the thermodynamics of strongly interacting matter at finite values of the baryon chemical potential $\mu$. This method allows us to identify the singularity corresponding to the critical point of a second-order phase transition at finite $\mu$, given information only at $\mu=0$. The scheme is potentially useful for computing thermodynamic properties of strongly interacting hot and dense matter in lattice gauge theory. The technique is illustrated by an application to a chiral effective model.Comment: 5 pages, 3 figures; published versio

Plant pathogenic bacterium Ralstonia solanacearum can rapidly evolve tolerance to antimicrobials produced by Pseudomonas biocontrol bacteria.

Soil-borne plant pathogens significantly threaten crop production due to lack of effective control methods. One alternative to traditional agrochemicals is microbial biocontrol, where pathogen growth is suppressed by naturally occurring bacteria that produce antimicrobial chemicals. However, it is still unclear if pathogenic bacteria can evolve tolerance to biocontrol antimicrobials and if this could constrain the long-term efficacy of biocontrol strategies. Here we used an in vitro experimental evolution approach to investigate if the phytopathogenic Ralstonia solanacearum bacterium, which causes bacterial wilt disease, can evolve tolerance to antimicrobials produced by Pseudomonas bacteria. We further asked if tolerance was specific to pairs of R. solanacearum and Pseudomonas strains and certain antimicrobial compounds produced by Pseudomonas. We found that while all R. solanacearum strains could initially be inhibited by Pseudomonas strains, this inhibition decreased following successive subculturing with or without Pseudomonas supernatants. Using separate tolerance assays, we show that the majority of R. solanacearum strains evolved increased tolerance to multiple Pseudomonas strains. Mechanistically, evolved tolerance was most likely linked to reduced susceptibility to orfamide lipopeptide antimicrobials secreted by Pseudomonas strains in our experimental conditions. Some levels of tolerance also evolved in the control treatments, which was likely correlated response due to adaptations to the culture media. Together, these results suggest that plant-pathogenic bacteria can rapidly evolve increased tolerance to bacterial antimicrobial compounds, which could reduce the long-term efficacy of microbial biocontrol. [Abstract copyright: © The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Evolutionary Biology.

Effective Nucleon-Nucleon Interaction and Fermi Liquid Theory

We present two novel relations between the quasiparticle interaction in nuclear matter and the unique low momentum nucleon-nucleon interaction in vacuum. These relations provide two independent constraints on the Fermi liquid parameters of nuclear matter. Moreover, the new constraints define two combinations of Fermi liquid parameters, which are invariant under the renormalization group flow in the particle-hole channels. Using empirical values for the spin-independent Fermi liquid parameters, we are able to compute the major spin-dependent ones by imposing the new constraints as well as the Pauli principle sum rules.Comment: 4 pages, 5 figures, in Proc. 11th International Conference on Recent Progress in Many-Body Theories, Manchester, UK, July 9-13, 200