25,088 research outputs found
Calculation of membrane bending rigidity using field-theoretic umbrella sampling
No full textThe free-energy change of membrane shape transformations can be small, e.g., as in the case of membrane bending. Therefore, the calculation of the free-energy difference between different membrane morphologies is a challenge. Here, we discuss a computational method - field-theoretic umbrella sampling - to compute the local chemical potential of a non-equilibrium configuration and illustrate how one can apply it to study free-energy changes of membrane transformations using simulations. Specifically, the chemical potential profile of the bent membrane and the bending rigidity of membrane are calculated for a soft, coarse-grained amphiphile model and the MARTINI model of a dioleoylphosphatidylcholine (DOPC) membrane. (C) 2015 AIP Publishing LLC.DFG [SFB-803, B03
How does curvature affect the free-energy barrier of stalk formation? Small vesicles vs apposing, planar membranes
No full textAbstract
Using molecular simulations of POPC lipids in conjunction with the calculation of the Minimum Free-Energy Path (MFEP), we study the effect of strong membrane curvature on the formation of the first fusion intermediate—the stalk between a vesicle and its periodic image. We find that the thermodynamic stability of this hourglass-shaped, hydrophobic connection between two vesicles is largely increased by the strong curvature of small vesicles, whereas the intrinsic barrier to form a stalk, i.e., associated with dimple formation and lipid tails protrusions, is similar to the case of two, apposing, planar membranes. A significant reduction of the barrier of stalk formation, however, stems from the lower dehydration free energy that is required to bring highly curved vesicle into a distance, at which stalk formation may occur, compared to the case of apposing, planar membranes.CRC 803 3187Projekt DEA
The generalized Liénard polynomial differential systems x'=y,y'= -g(x) - f (x)y with deg g = deg f 1 are not Liouvillian integrable
Get PDFAgraïments: The second author was supported by Portuguese National Funds through FCT - Fundação para a Ciência e a Tecnologia within the project PTDC/MAT/117106/2010 and by CAMGSD (PEst-OE/EEI/LA0009/2013)We prove the nonexistence of Liouvillian first integrals for the generalized Li\'enard polynomial differential systems of the form x' = y, y'=-g(x)-f(x)y, where g(x) and f(x) are arbitrary polynomials such that g = f 1
Pensar la violencia desde G. Deleuze
Get PDFEl artículo reflexiona sobre el fenómeno de la violencia en nuestras sociedades tardomodernas. En primer lugar, critica la concepción ilustrada de la violencia, según la cual ésta es siempre una desviación de la razón, es decir, una "sinrazón". En segundo lugar, el autor sostiene que la comprensión de la violencia debe hacerse desde el "pensamiento de la diferencia". Desde esta última perspectiva, la violencia es el resultado del imperio de la "lógica oposicional" o "lógica binaria", la cual sustituye a la relación diferencial de carácter rizomático. Se recurre, fundamentalmente, al pensamiento de G. Deleuze, matizando el fenómeno de la violencia como "necedad", "geometría de Estado" e "incapacidad para ser afectado".The article reflects on the phenomenon of violence in our late modern societies. First, criticizes the Enlightenment conception of violence, that it is always a deviation of reason, ie a "unreason". Secondly, the author argues that the understanding of violence must be from the "thought of difference". From the latter perspective, violence is the result of the rule of "oppositional logic" or "binary logic" which replaces the differential relation of rhizomatic character. It basically resorts to thoughts of G. Deleuze, qualifying the phenomenon of violence as "stupidity", "geometry of State" and "incapacity to be affected"
Cooling rates of neutron stars and the young neutron star in the Cassiopeia A supernova remnant
No full textWe explore the thermal state of the neutron star in the Cassiopeia A supernova remnant using the recent result of Ho & Heinke that the thermal radiation of this star is well described by a carbon atmosphere model and the emission comes from the entire stellar surface. Starting from neutron star cooling theory, we formulate a robust method to extract neutrino cooling rates of thermally relaxed stars at the neutrino cooling stage from observations of thermal surface radiation. We show how to compare these rates with the rates of standard candles – stars with non-superfluid nucleon cores cooling slowly via the modified Urca process. We find that the internal temperature of standard candles is a well-defined function of the stellar compactness parameter x=rg/R, irrespective of the equation of state of neutron star matter (R and rg are circumferential and gravitational radii, respectively). We demonstrate that the data on the Cassiopeia A neutron star can be explained in terms of three parameters: f?, the neutrino cooling efficiency with respect to the standard candle; the compactness x; and the amount of light elements in the heat-blanketing envelope. For an ordinary (iron) heat-blanketing envelope or a low-mass (? 10?13 M?) carbon envelope, we find the efficiency f?? 1 (standard cooling) for x? 0.5 and f?? 0.02 (slower cooling) for a maximum compactness x? 0.7. A heat blanket containing the maximum mass (?10?8 M?) of light elements increases f? by a factor of 50. We also examine the (unlikely) possibility that the star is still thermally non-relaxe
Overview of the Author Profiling Task at PAN 2013
Get PDF[EN] This overview presents the framework and results for the Author Profiling
task at PAN 2013. We describe in detail the corpus and its characteristics,
and the evaluation framework we used to measure the participants performance to
solve the problem of identifying age and gender from anonymous texts. Finally,
the approaches of the 21 participants and their results are described.The author profiling task @PAN-2013 was an activity of the WIQ-EI IRSES project (Grant No. 269180) within the FP 7 Marie Curie People Framework of the European Commission. We want to thank the Forensic Lab of the Universitat Pompeu Fabra Barcelona for sponsoring the award for the winner team. The work of the first author was partially funded by Autoritas Consulting SA and by Ministerio de Economía y Competitividad de España under grant ECOPORTUNITY IPT-2012-1220-430000. The work of the second author was in the framework the DIANA-APPLICATIONS-Finding Hidden Knowledge in Texts: Applications (TIN2012-38603-C02-01) project, and the VLC/CAMPUS Microcluster on Multimodal Interaction in Intelligent Systems. The work of fifth author was funded in part by the Swiss National Science Foundation (SNF) project "Mining Conversational Content for Topic Modelling and Author Identification (ChatMiner)" under grant number 200021_130208.Rangel, F.; Rosso, P.; Koppel, M.; Stamatatos, E.; Inches, G. (2013). Overview of the Author Profiling Task at PAN 2013. CLEF Conference on Multilingual and Multimodal Information Access Evaluation. 352-365. https://riunet.upv.es/handle/10251/46636S35236
G-Drazin inverse combined with inner inverse
Get PDF[EN] This article introduces new classes of generalized inverses for square matrices named GD1, and the dual, called 1GD inverse. In addition, we discuss a few characterizations and representations of these inverses. The explicit expressions of these inverses have been established via core-nilpotent decomposition. Further, we introduce a binary relation for GD1 inverse and 1GD inverse, along with a few derived properties.The second author is partially supported by the Science & Engineering Research Board (SERB),Govt. of India [grant ID SUR/2022/004357]. The third author was partially supported by the Universidad Nacional de Rio Cuarto [grant PPI 18/C559], Universidad Nacional de La Pampa, Facultadde Ingenieria [grant resol. nro. 135/19], Universidad Nacional del Sur [grant PGI 24/L108], and Ministerio de Economia, Industria y Competitividad (Spain) [grant red de excelencia RED2022-134176-T].Maharana, G.; Sahoo, JK.; Thome, N. (2024). G-Drazin inverse combined with inner inverse. Linear and Multilinear Algebra. https://doi.org/10.1080/03081087.2024.2316786
Matrices de Jacobi, fracciones continuas vectoriales y productos de Sobolev
No full textLa tesis doctoral se enmarca dentro de la teoría de la aproximación estudiándose tres problemas aparentemente disconexos: las matrices de Jacobi, las fracciones continuas y polinomios otorgonales respecto a productos de Sobolev. La memoria está dividida en tres partes. En la primera se estudia una extensión de un resultado sobre determinación de matrices (infinitas) de Jacobi reales al caso complejo y prueba un resultado similar al caso real. Así, en el capítulo 2 se prueba que si una matriz de Jacobi compleja G se puede escribir de la forma G= J+C, con J una matriz de Jacobi real y C una matriz con coeficientes complejos uniformemente acotados, entonces G es determinada si y sólo si J lo es, de donde además se induce que para la determinación de los matrices G= J+C en el caso complejo es necesario y suficiente que D(G) = D(G*), donde D(G) denota el dominio del operador asociado a G y G* el adjunto de G. De esta forma se tiene la existencia a C de una propiedad conocida en R. Esto además, tiene estrecha relación con la teoría de fracciones continuas que precisamente constituye el objetivo de la segunda parte de la tesis. La segunda parte de la tesis trata de la generalización de las S-fracciones de Stieltjes "escalares". Así, se definen y estudian las fracciones continuas vectoriales. Se dan, en particular, distintas condiciones necesarias y suficientes de convergencia de S-fracciones continuas vectoriales, muchas de ellas son extensiones "naturales" de las condiciones del caso clásico. Finalmente, en el capítulo 5 se estudia la ecuación de recurrencia yn + cnYn-1 + CnYn-2 = O, n - N que está ligada al problema de la convergencia de las fracciones vectoriales.La tercera y última parte de la tesis aborda el problema de la localización de ceros de los polinomios ortogonales respecto a un producto escalar de Sobolev (.,.)S, entonces el soporte de la medida u asociada a (.,.)S es compacto
The generalized Liénard polynomial differential systems x'=y,y'= -g(x) - f (x)y with deg g = deg f 1 are not Liouvillian integrable
No full textAgraïments: The second author was supported by Portuguese National Funds through FCT - Fundação para a Ciência e a Tecnologia within the project PTDC/MAT/117106/2010 and by CAMGSD (PEst-OE/EEI/LA0009/2013)We prove the nonexistence of Liouvillian first integrals for the generalized Li\'enard polynomial differential systems of the form x' = y, y'=-g(x)-f(x)y, where g(x) and f(x) are arbitrary polynomials such that g = f 1
High-resolution numerical analysis of turbulent flow in straight open ducts with rectangular cross-section
No full textTurbulent secondary flow in straight open ducts with rectangular cross-section are studied numerically by means of pseudo- spectral direct numerical simulation (DNS). Similarly to the corresponding closed duct flows, the mean streamwise vorticity pattern in turbulent open duct flows were found to be the statistical footprint of the most probable locations of the quasi-streamwise vortices. A major difference between the two configurations was found in the vicinity of mixed-boundary corners where noticeably persistent vortical structures exist.Turbulent secondary flow in straight open ducts with rectangular cross-section are studied numerically by means of pseudo- spectral direct numerical simulation (DNS). Similarly to the corresponding closed duct flows, the mean streamwise vorticity pattern in turbulent open duct flows were found to be the statistical footprint of the most probable locations of the quasi-streamwise vortices. A major difference between the two configurations was found in the vicinity of mixed-boundary corners where noticeably persistent vortical structures exist
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