Reshaping and Enzymatic Activity allow Viruses to move through the Mucus

Filamentous viruses like influenza and torovirus often display systematic bends and arcs of mysterious physical origin. We propose that such viruses undergo an instability from a cylindrically symmetric to a toroidally curved state. This "toro-elastic" state emerges via a spontaneous symmetry breaking under prestress, induced via short range spike protein interactions and magnified by the filament's surface topography. Once surface stresses become sufficiently large, the filament buckles and the toroidal, curved state constitutes a soft mode that can propagate through the filament's material frame around a "mexican-hat" potential. In the mucus of our airways, glycan chains are omnipresent that influenza's spike proteins can bind to and cut. We show that when coupled to such a non-equilibrium chemical reaction, the curved toro-elastic state can attain a spontaneous rotation for sufficiently strong enzymatic activity, leading to a whole body reshaping propulsion similar to -- but different from -- eukaryotic flagella and spirochetes.Comment: 6 pages, Supplementary Info (PDF file in the source file

Charge fluctuations and electron-phonon interaction in the finite-UU Hubbard model

In this paper we employ a gaussian expansion within the finite-$U$ slave-bosons formalism to investigate the momentum structure of the electron-phonon vertex function in the Hubbard model as function of $U$ and $n$. The suppression of large momentum scattering and the onset a small-${\bf q}$ peak structure, parametrized by a cut-off $q_c$, are shown to be essentially ruled by the band narrowing factor $Z_{\rm MF}$ due to the electronic correlation. A phase diagram of $Z_{\rm MF}$ and $q_c$ in the whole $U$-$n$ space is presented. Our results are in more than qualitative agreement with a recent numerical analysis and permit to understand some anomalous features of the Quantum Monte Carlo data.Comment: 4 pages, eps figures include

Optical Properties of Heavy Fermion Systems with SDW Order

The dynamical conductivity $\sigma (\omega)$, reflectivity $R(\omega)$, and tunneling density of states $N(\omega)$ of strongly correlated systems (like heavy fermions) with a spin-density wave (SDW) magnetic order are studied as a function of impurity scattering rate and temperature. The theory is generalized to include strong coupling effects in the SDW order. The results are discussed in the light of optical experiments on heavy-fermion SDW materials. With some modifications the proposed theory is applicable also to heavy fermions with localized antiferromagnetic (LAF) order.Comment: 9 pages, 10 figure

Diffusion-limited loop formation of semiflexible polymers: Kramers theory and the intertwined time scales of chain relaxation and closing

We show that Kramers rate theory gives a straightforward, accurate estimate of the closing time $\tau_c$ of a semiflexible polymer that is valid in cases of physical interest. The calculation also reveals how the time scales of chain relaxation and closing are intertwined, illuminating an apparent conflict between two ways of calculating $\tau_c$ in the flexible limit.Comment: Europhys. Lett., 2003 (in press). 8 pages, 3 figures. See also, physics/0101087 for physicist's approach to and the importance of semiflexible polymer looping, in DNA replicatio

DNA Spools under Tension

DNA-spools, structures in which DNA is wrapped and helically coiled onto itself or onto a protein core are ubiquitous in nature. We develop a general theory describing the non-equilibrium behavior of DNA-spools under linear tension. Two puzzling and seemingly unrelated recent experimental findings, the sudden quantized unwrapping of nucleosomes and that of DNA toroidal condensates under tension are theoretically explained and shown to be of the same origin. The study provides new insights into nucleosome and chromatin fiber stability and dynamics

Anisotropic impurities in anisotropic superconductors

Physical properties of anisotropic superconductors like the critical temperature and others depend sensitively on the electron mean free path. The sensitivity to impurity scattering and the resulting anomalies are considered a characteristic feature of strongly anisotropic pairing. These anomalies are usually analyzed in terms of s-wave impurity scattering which leads to universal pair breaking effects depending on only two scattering parameters, the mean free path and the impurity cross section. We investigate here corrections coming from anisotropies in the scattering cross section, and find not only quantitative but also qualitative deviations from universal s-wave isotropic pairbreaking. The properties we study are the transition temperature, the density of states, quasiparticle bound states at impurities, and pinning of flux lines by impurities.Comment: 19 page

Ispitivanje povezanosti težine srca sa rupturom srca kod 119 slučajeva umrlih od akutnog infarkta miokarda

Introduction. Cardiovascular and blood vessel diseases are the most common cause of death, which is shown by data obtained in our and foreign authors' research, and acute myocardial infarction is the most common emergency in internal medicine and its mortality is very high, about one third of total mortality. The aim of this paper is to determine whether there is a statistically significant difference in heart weight in deceased patients with acute myocardial infarction (AMI) with heart rupture and with AMI without heart rupture. Methods. The research material is made up of 119 autopsied patients at the Institute of Pathology of the University of Kragujevac Medical Faculty and Clinical Center Kragujevac. The following pathological morphological research methods were applied: autopsy, macroscopic diagnostics and microscopic analysis. In addition, a statistical processing of results was performed, and the Pharmocologic Circulapon System Student's t-test statistical software package was used to test the significance of differences. A value of p lt 0.05 was considered as a statistically significant difference, and a value of p lt 0.01 as highly significant. Results and Discussion. Out of 119 cases of AMI deaths, of which 74 male and 45 female, heart rupture was found in 21 cases. Of the 74 men who died of AMI, 13 had a rupture, and of the 45 women who died of AMI, 8 had a rupture. The heart weight was measured in each respondent who died of AMI and the correlation between heart weight and rupture was investigated. The study showed that there was a statistically significant difference (p lt 0.05) in the average heart weight between the autopsied who had and those who did not have heart rupture, and that those who did not have heart rupture had significantly more heart weight. The study showed that there was a statistically significant difference (p lt 0.05) in the average heart weight between the autopsied men who had and those who did not have heart rupture. The heart of those men who did not have heart rupture had more weight. There were no statistically significant differences (p>0.05) in the mean heart weight between the autopsied women who had and those who did not have heart rupture. Conclusion. The study showed the difference in the heart weight of autopsied patients who had and those who did not have heart rupture, and that those who did not have heart rupture had significantly more heart weight. In relation to sex, the heart of those men who did not have heart rupture had more weight, while in women there are no statistically significant differences (p>0.05) in the average heart weight in those with and without rupture of the heart.Uvod. Bolesti srca i krvnih sudova predstavljaju najčešći uzrok smrti, što pokazuju podaci dobijeni u istraživanjima naših i stranih autora, a akutni infarkt miokarda je najčešće urgentno stanje u internoj medicini i mortalitet mu je veoma visok, jer od ukupnog mortaliteta jedna trećina otpada na infarkt miokarda. Cilj rada je bio da utvrdimo postoji li statistički značajna razlika u težini srca kod umrlih pacijenata sa akutnim infarktom miokarda (AIM) sa rupturom srca i sa AIM-om bez rupture srca. Metode. Istraživački materijal čini 119 obdukovanih pacijenata u Institutu za patologiju Medicinskog fakulteta u Kragujevcu i KBC Kragujevac. Primenjene su patološko morfološke metode istraživanja: obdukcija, makroskopska dijagnostika i mikroskopska analiza. Pored toga, vršena je statistička obrada rezultata, a za testiranje značajnosti razlika korišćen je Studentov test softverski paket statističkih testova Pharmocologic Circulapon Sistem. Kao statistički značajna smatrana je razlika ako je p lt 0,05 i visoko značajna ako je p lt 0,01. Rezultati i diskusija. Od 119 slučajeva umrlih od AIM-a, od čega je 74 muškarca i 45 žena, ruptura srca nađena je u 21 slučaju. Od 74 muškarca koji su umrli od AIM-a, 13 je imalo rupturu, a od 45 žena koje su umrle od AIM-a, osam je imalo rupturu. Merena je težina srca kod svakog ispitanika koji je umro od AIM-a i ispitivana povezanost težine srca sa rupturom. Ispitivanje je pokazalo da postoji statistički značajna razlika (p lt 0,05) u prosečnoj težini srca između obdukovanih koji su imali i onih koji nisu imali rupturu srca i da je značajno teže srce onih koji nisu imali rupturu srca. Ispitivanje je pokazalo da postoji statistički značajna razlika (p lt 0,05) u prosečnoj težini srca između obdukovanih muškaraca koji su imali i onih koji nisu imali rupturu srca. Značajno je teže srce onih muškaraca koji nisu imali rupturu srca. Nema statistički značajnih razlika (p>0,05) u prosečnoj težini srca između obdukovanih žena koje su imale i onih koje nisu imale rupturu srca. Zaključak. Ispitivanje je pokazalo razliku u težini srca između obdukovanih koji su imali i onih koji nisu imali rupturu srca i da je značajno teže srce onih koji nisu imali rupturu srca. U odnosu na pol značajno je teže srce onih muškaraca koji nisu imali rupturu srca, dok kod žena nema statistički značajnih razlika (p>0,05) u prosečnoj težini srca kod onih sa i bez rupture srca

Time of life as it is in LiFeAs

The time of life of fermionic quasiparticles, the distribution of which in the momentum-energy space can be measured by angle resolved photoemission (ARPES), is the first quantity to look for fingerprints of interaction responsible for the superconducting pairing. Such an approach has been recently used for superconducting cuprates, but its direct application to pnictides was not possible due to essential three-dimensionality of the electronic band structure and magnetic ordering. Here, we report the investigation of the quasiparticle lifetime in LiFeAs, a non-magnetic stoichiometric superconductor with a well separated two-dimensional band. We have found two energy scales: the lower one contains clear fingerprints of optical phonon modes while the higher scale indicates a presence of strong electron-electron interaction. The result suggests that LiFeAs is a phonon mediated superconductor with strongly enhanced electronic density of states at the Fermi level.Comment: reevaluated electron-phonon coupling strength, added reference

Nonadiabatic Superconductivity and Vertex Corrections in Uncorrelated Systems

We investigate the issue of the nonadiabatic superconductivity in uncorrelated systems. A local approximation is employed coherently with the weak dependence on the involved momenta. Our results show that nonadiabatic vertex corrections are never negligible, but lead to a strong suppression of $T_c$ with respect to the conventional theory. This feature is understood in terms of the momentum-frequency dependence of the vertex function. In contrast to strongly correlated systems, where the small ${\bf q}$-selection probes the positive part of vertex function, vertex corrections in uncorrelated systems are essentially negative resulting in an effective reduction of the superconducting pairing. Our analysis shows that vertex corrections in nonadiabatic regime can be never disregarded independently of the degree of electronic correlation in the system.Comment: 4 pages, 3 eps fig

Social Roles and Baseline Proxemic Preferences for a Domestic Service Robot

© The Author(s) 2014. This article is published with open access at Springerlink.com. This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. The work described in this paper was conducted within the EU Integrated Projects LIREC (LIving with Robots and intEractive Companions, funded by the European Commission under contract numbers FP7 215554, and partly funded by the ACCOMPANY project, a part of the European Union’s Seventh Framework Programme (FP7/2007–2013) under grant agreement n287624The goal of our research is to develop socially acceptable behavior for domestic robots in a setting where a user and the robot are sharing the same physical space and interact with each other in close proximity. Specifically, our research focuses on approach distances and directions in the context of a robot handing over an object to a userPeer reviewe