4,845 research outputs found
Quantum corrections to the mass of self-dual vortices
The mass shift induced by one-loop quantum fluctuations on self-dual ANO
vortices is computed using heat kernel/generalized zeta function regularization
methods.Comment: 4 pages RevTex, version to appear in Physical Review
One-loop mass shift formula for kinks and self-dual vortices
A formula is derived that allows us to compute one-loop mass shifts for kinks
and self-dual Abrikosov-Nielsen-Olesen vortices. The procedure is based in
canonical quantization and heat kernel/zeta function regularization methods.Comment: LaTex file, 8 pages, 1 figure . Based on a talk given by J. M. G. at
the 7th Workshop on Quantum Field Theory under the Influence of External
Conditions (QFEXT05), Barcelona, Spain. Minor corrections. Version to appear
in Journal of Physics
Quantum fluctuations around low-dimensional topological defects
In these Lectures a method is described to analyze the effect of quantum
fluctuations on topological defect backgrounds up to the one-loop level. The
method is based on the spectral heat kernel/zeta function regularization
procedure, and it is first applied to various types of kinks arising in several
deformed linear and non-linear sigma models with different numbers of scalar
fields. In the second part, the same conceptual framework is constructed for
the topological solitons of the planar semilocal Abelian Higgs model, built
from a doublet of complex scalar fields and one U(1) gauge field.Comment: 63 pages, 14 figures, expanded version of two lectures given by
J.M.G. in 5th International School on Field Theory and Gravitation, Cuiaba,
Brazi
Existence of an information unit as a postulate of quantum theory
Does information play a significant role in the foundations of physics?
Information is the abstraction that allows us to refer to the states of systems
when we choose to ignore the systems themselves. This is only possible in very
particular frameworks, like in classical or quantum theory, or more generally,
whenever there exists an information unit such that the state of any system can
be reversibly encoded in a sufficient number of such units. In this work we
show how the abstract formalism of quantum theory can be deduced solely from
the existence of an information unit with suitable properties, together with
two further natural assumptions: the continuity and reversibility of dynamics,
and the possibility of characterizing the state of a composite system by local
measurements. This constitutes a new set of postulates for quantum theory with
a simple and direct physical meaning, like the ones of special relativity or
thermodynamics, and it articulates a strong connection between physics and
information.Comment: Published version - 6 pages, 3 appendices, 3 figure
Quantum oscillations of self-dual Abrikosov-Nielsen-Olesen vortices
The mass shift induced by one-loop quantum fluctuations on self-dual ANO
vortices is computed using heat kernel/generalized zeta function regularization
methods. The quantum masses of super-imposed multi-vortices with vorticity
lower than five are given. The case of two separate vortices with a quantum of
magnetic flux is also discussed.Comment: RevTex, 13 pages, 4 figures, 7 tables. Minor corrections. Version to
appear in Physical Review
Lamellar Structures of MUC2-Rich Mucin: A Potential Role in Governing the Barrier and Lubricating Functions of Intestinal Mucus
Mucus is a ubiquitous feature of mammalian wet epithelial surfaces, where it lubricates and forms a selective barrier that excludes a range of particulates, including pathogens, while hosting a diverse commensal microflora. The major polymeric component of mucus is mucin, a large glycoprotein formed by several MUC gene products, with MUC2 expression dominating intestinal mucus. A satisfactory answer to the question of how these molecules build a dynamic structure capable of playing such a complex role has yet to be found, as recent reports of distinct layers of chemically identical mucin in the colon and anomalously rapid transport of nanoparticles through mucus have emphasized. Here we use atomic force microscopy (AFM) to image a MUC2-rich mucus fraction isolated from pig jejunum. In the freshly isolated mucin fraction, we find direct evidence for trigonally linked structures, and their assembly into lamellar networks with a distribution of pore sizes from 20 to 200 nm. The networks are two-dimensional, with little interaction between lamellae. The existence of persistent cross-links between individual mucin polypeptides is consistent with a non-self-interacting lamellar model for intestinal mucus structure, rather than a physically entangled polymer network. We only observe collapsed entangled structures in purified mucin that has been stored in nonphysiological conditions
Polymeric endovascular strut and lumen detection algorithm for intracoronary optical coherence tomography images
Polymeric endovascular implants are the next step in minimally invasive vascular interventions. As an alternative to traditional metallic drug-eluting stents, these often-erodible scaffolds present opportunities and challenges for patients and clinicians. Theoretically, as they resorb and are absorbed over time, they obviate the long-term complications of permanent implants, but in the short-term visualization and therefore positioning is problematic. Polymeric scaffolds can only be fully imaged using optical coherence tomography (OCT) imagingâthey are relatively invisible via angiographyâand segmentation of polymeric struts in OCT images is performed manually, a laborious and intractable procedure for large datasets. Traditional lumen detection methods using implant struts as boundary limits fail in images with polymeric implants. Therefore, it is necessary to develop an automated method to detect polymeric struts and luminal borders in OCT images; we present such a fully automated algorithm. Accuracy was validated using expert annotations on 1140 OCT images with a positive predictive value of 0.93 for strut detection and an R^2 correlation coefficient of 0.94 between detected and expert-annotated lumen areas. The proposed algorithm allows for rapid, accurate, and automated detection of polymeric struts and the luminal border in OCT images
A New Wireless Biosensor for Intra-Vaginal Temperature Monitoring
Wireless Body Sensors for medical purposes offer valuable contributions to improve patientsâ healthcare, including diagnosis and/or therapeutics monitoring. Body temperature is a crucial parameter in healthcare diagnosis. In gynecology and obstetrics it is measured at the skinâs surface, which is very influenced by the environment. This paper proposes a new intra-body sensor for long-term intra-vaginal temperature collection. The embedded IEEE 802.15.4 communication module allows the integration of this sensor in a Wireless Sensor Network (WSN) for remote data access and monitoring. We present the sensor architecture, the construction of the corresponding testbed, and its performance evaluation. This sensor may be used in different medical applications, including preterm labor prevention and fertility and ovulation period detection. The features of the constructed testbed were validated in laboratory tests verifying its accuracy and performance
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