Probing the entanglement and locating knots in ring polymers: a comparative study of different arc closure schemes

The interplay between the topological and geometrical properties of a polymer ring can be clarified by establishing the entanglement trapped in any portion (arc) of the ring. The task requires to close the open arcs into a ring, and the resulting topological state may depend on the specific closure scheme that is followed. To understand the impact of this ambiguity in contexts of practical interest, such as knot localization in a ring with non trivial topology, we apply various closure schemes to model ring polymers. The rings have the same length and topological state (a trefoil knot) but have different degree of compactness. The comparison suggests that a novel method, termed the minimally-interfering closure, can be profitably used to characterize the arc entanglement in a robust and computationally-efficient way. This closure method is finally applied to the knot localization problem which is tackled using two different localization schemes based on top-down or bottom-up searches.Comment: 9 pages, 7 figures. Submitted to Progress of Theoretical Physic

Analysis of quantitative methods to evaluate resilience in a supply chain netwotk

openThis thesis, starting from an analysis of the existing literature, aims to identify and analyze a range of methods for the quantitative calculation of resilience in the supply chain with a focus in the event of disruption. With the development of globally distributed supply chains, the topic has been increasingly analyzed and various approaches and methodologies have been proposed in the literature to address the complex management, improvement techniques and study of possible dangers. In fact, the activities carried out in the distribution chain have an intrinsic risk of unforeseen interruptions due to factors such as an ever-increasing tendency to offer lean and just in time services, the deterioration rate in products and the uncertainty of demand that have reduced the time available to manage any unexpected events. The need to deal with unknown events has become even more evident with the recent Covid-19 pandemic, which has forced many companies to modify or completely suspend their processes temporarily due to unforeseen interruptions becasue of events like local quarantines and lock downs, also to drastic changes in procurement and means of distribution. What this thesis will therefore deal with are the quantitative methods that allow the numerical evaluation of the resilience of a supply chain, this kind of metods allows to take into consideration various aspects and characteristics of the supply chain, such as impact on performance, recovery time, economic damage and time of survival, to compare different chains and be able to evaluate the possible degree of improvement.This thesis, starting from an analysis of the existing literature, aims to identify and analyze a range of methods for the quantitative calculation of resilience in the supply chain with a focus in the event of disruption. With the development of globally distributed supply chains, the topic has been increasingly analyzed and various approaches and methodologies have been proposed in the literature to address the complex management, improvement techniques and study of possible dangers. In fact, the activities carried out in the distribution chain have an intrinsic risk of unforeseen interruptions due to factors such as an ever-increasing tendency to offer lean and just in time services, the deterioration rate in products and the uncertainty of demand that have reduced the time available to manage any unexpected events. The need to deal with unknown events has become even more evident with the recent Covid-19 pandemic, which has forced many companies to modify or completely suspend their processes temporarily due to unforeseen interruptions becasue of events like local quarantines and lock downs, also to drastic changes in procurement and means of distribution. What this thesis will therefore deal with are the quantitative methods that allow the numerical evaluation of the resilience of a supply chain, this kind of metods allows to take into consideration various aspects and characteristics of the supply chain, such as impact on performance, recovery time, economic damage and time of survival, to compare different chains and be able to evaluate the possible degree of improvement

Multiscale entanglement in ring polymers under spherical confinement

The interplay of geometrical and topological entanglement in semiflexible knotted polymer rings confined inside a spherical cavity is investigated using advanced numerical methods. By using stringent and robust algorithms for locating knots, we characterize how the knot length lk depends on the ring contour length, Lc and the radius of the confining sphere, Rc . In the no- and strong- confinement cases we observe weak knot localization and complete knot delocalization, respectively. We show that the complex interplay of lk, Lc and Rc that seamlessly bridges these two limits can be encompassed by a simple scaling argument based on deflection theory. The same argument is used to rationalize the multiscale character of the entanglement that emerges with increasing confinement.Comment: 9 pages 9 figure

Multiscale Entanglement in Spherically Confined DNA Rings

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Urban imperviousness effects on summer surface temperatures nearby residential buildings in different urban zones of Parma

Rapid and unplanned urban growth is responsible for the continuous conversion of green or generally natural spaces into artificial surfaces. The high degree of imperviousness modifies the urban microclimate and no studies have quantified its influence on the surface temperature (ST) nearby residential building. This topic represents the aim of this study carried out during summer in different urban zones (densely urbanized or park/rural areas) of Parma (Northern Italy). Daytime and nighttime ASTER images, the local urban cartography and the Italian imperviousness databases were used. A reproducible/replicable framework was implemented named "Building Thermal Functional Area" (BTFA) useful to lead building-proxy thermal analyses by using remote sensing data. For each residential building (n = 8898), the BTFA was assessed and the correspondent ASTER-LST value (ST_BTFA) and the imperviousness density were calculated. Both daytime and nighttime ST_BTFA significantly (p < 0.001) increased when high levels of imperviousness density surrounded the residential buildings. These relationships were mostly consistent during daytime and in densely urbanized areas. ST_BTFA differences between urban and park/rural areas were higher during nighttime (above 1 °C) than daytime (about 0.5 °C). These results could help to identify "urban thermal Hot-Spots" that would benefit most from mitigation actions

KymoKnot: A web server and software package to identify and locate knots in trajectories of linear or circular polymers

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Thigh Pain Occurrence Rate in a Short, Tapered, Porous, Proximally-Coated Cementless Femoral Stem - Clinical and Radiological Results at 2-Year Follow-Up

Abstract Introduction: Short stems have been designed with the purpose of preserving bone tissue, decreasing the incidence of thigh pain and facilitating surgical techniques. The aim of our study was to assess whether a shortened tapered conventional stem was able to reduce the incidence of thigh pain.Methods:Between March 2010 and December 2012, 200 patients were enrolled in the study. Visual analogue scale (VAS) that included mapping of the pain, Harris Hip Score (HHS), Short Form-12 (SF-12) and radiographic outcomes were evaluated prior to surgery as well as at 6, 12 and 24 months post-operatively.Results: After 6 months, 6 patients (3%) had thigh pain. After 12 months, 3 patients (1.5%) complained about thigh pain. After 2 years, 2 patients (1%) had thigh pain. There was no correlation between pain and clinical, radiological, or demographic variables.Conclusion:The shortened tapered conventional stem resulted in a lower incidence of thigh pain for up to 2-years following surgery, compared with conventional or other short stems

Dynamic and Facilitated Binding of Topoisomerase Accelerates Topological Relaxation

: How type 2 Topoisomerase (TopoII) proteins relax and simplify the topology of DNA molecules is one of the most intriguing open questions in genome and DNA biophysics. Most of the existing models neglect the dynamics of TopoII which is expected of proteins searching their targets via facilitated diffusion. Here, we show that dynamic binding of TopoII speeds up the topological relaxation of knotted substrates by enhancing the search of the knotted arc. Intriguingly, this in turn implies that the timescale of topological relaxation is virtually independent of the substrate length. We then discover that considering binding biases due to facilitated diffusion on looped substrates steers the sampling of the topological space closer to the boundaries between different topoisomers yielding an optimally fast topological relaxation. We discuss our findings in the context of topological simplification in vitro and in vivo

Dynamic and Facilitated Binding of Topoisomerase Accelerates Topological Relaxation

How type 2 Topoisomerase (TopoII) proteins relax and simplify the topology of DNA molecules is one of the most intriguing open questions in biophysics. Most of the existing models neglect the dynamics of TopoII which is characteristics for proteins searching their targets via facilitated diffusion. Here, we show that dynamic binding of TopoII speeds up the topological relaxation of knotted substrates by enhancing the search of the knotted arc. Intriguingly, this in turn implies that the timescale of topological relaxation is virtually independent of the substrate length. We then discover that considering binding biases due to facilitated diffusion on looped substrates steers the sampling of the topological space closer to the boundaries between different topoisomers yielding an optimally fast topological relaxation. We discuss our findings in the context of topological simplification in vitro and in vivo

Dirac Equation-Based Formulation for the Quantum Conductivity in 2D-Nanomaterials

bstract: Starting from the four component-Dirac equation for free, ballistic electrons with finite mass, driven by a constant d.c. field, we derive a basic model of scalar quantum conductivity, capable of yielding simple analytic forms, also in the presence of magnetic and polarization effects. The classical Drude conductivity is recovered as a limit case. A quantum-mechanical evaluation is provided for parabolic and linear dispersion, as in graphene, recovering currently used expressions as particular cases. Numerical values are compared with the ones from the literature in the case of graphene under d.c. applied field