217 research outputs found
Tensor Renormalization Group: Local Magnetizations, Correlation Functions, and Phase Diagrams of Systems with Quenched Randomness
The tensor renormalization-group method, developed by Levin and Nave, brings
systematic improvability to the position-space renormalization-group method and
yields essentially exact results for phase diagrams and entire thermodynamic
functions. The method, previously used on systems with no quenched randomness,
is extended in this study to systems with quenched randomness. Local
magnetizations and correlation functions as a function of spin separation are
calculated as tensor products subject to renormalization-group transformation.
Phase diagrams are extracted from the long-distance behavior of the correlation
functions. The approach is illustrated with the quenched bond-diluted Ising
model on the triangular lattice. An accurate phase diagram is obtained in
temperature and bond-dilution probability, for the entire temperature range
down to the percolation threshold at zero temperature.Comment: Added comment. Published version. 8 pages, 7 figures, 1 tabl
Directed Cell Migration: From Single Cells to Collectively Moving Cell Groups
Unlike molecules, which are driven thermally by Brownian motion, eukaryotic cells move in a particular direction to accomplish designated tasks that are involved in diverse biological processes such as organ development and tumor progression. In this dissertation, I present experiments, analysis, and modeling of directed individual and collective cell migration. At subcellular scale, the migration of cells can be guided via the interaction of the cell cytoskeleton with the surrounding nanotopographic elements. I show that mechanical waves of actin polymerization are involved in this guidance–known as contact guidance–as dynamic sensors of surface nanotopography. The dynamics of guided actin waves were measured to build and test predictive models of contact guidance. The distributions of actin-wave propagation speed and direction were obtained from experimental observations of cell migration on nanotopographic surfaces as a function of the spacing between adjacent features (varying between 0.8 and 5 microns). I show that actin polymerization is preferentially localized to nanoscale features for a range of spacings. Additionally, the velocity of actin polymerization waves moving parallel to the direction of nanoridges depends on the nanoridge spacing. A model of actin polymerization dynamics in which nanoridges modify the distribution of the nucleation promoting factors captures these key observations. For individual cells, the question is how the intracellular processes result in directed migration of cells. I introduce a coarse-grained model for cell migration to connect contact guidance to intrinsic cellular oscillations.
The guidance of collective cell migration can be dictated via intercellular communication, which is facilitated by biochemical signals. I present a coarse-grained stochastic model for the influence of signal relay on the collective behavior of migrating Dictyostelium discoideum cells. In the experiment cells display a range of collective migration patterns including uncorrelated motion, formation of partially localized streams, and clumping, depending on the type of cell and the strength of the external concentration gradient of the signaling molecule cyclic adenosine monophosphate (cAMP). The collective migration model shows that the pattern of migration can be quantitatively described by considering the competition of two processes, the secretion of cAMP by the cells and the degradation of cAMP in the gradient chamber. With degradation, the model secreting cells form streams and efficiently traverse the gradient, but without degradation the model secreting cells form clumps without streaming. This observation indicates that streaming requires not only signal relay but also degradation of the signal. In addition, I show how this model can be extended to other eukaryotic systems that exhibit more complex cell-cell communication, in which the impact on collective migration is more subtle
Civil War and Power: A Theoretical Inquiry
This dissertation is a theoretical project that explores the conceptual nexus between civil war and power. It maps out a lineage of thought which posits civil war as a framework for explicating politics, not as a pre-political stage of savagery or a deteriorated condition of the socio-political order. Starting with Michel Foucaultâs radical yet short-lived civil war thesis, which situates civil war as the matrix of relations of power, this investigation traverses the work of several theorists and philosophers who have drawn on, or departed from, this line of thought. It critically evaluates Giorgio Agambenâs use of the concept of civil war as the fundamental threshold of (bio)politics in an epoch marked by the 9/11 attacks and the âwar on terrorâ. Then it gives an account of Michael Hardt & Antonio Negriâs and Eric Alliez & Maurizio Lazzaratoâs differing perspectives on the question of how civil war relates to contemporary capitalism. A central theme of the dissertation is the unresolved tension between the productive and repressive sides of power inherent in Foucaultâs formulation of civil war, the way subsequent theorists position themselves in relation to this aporia, and the success or failure of their attempts to resolve this tension. As an alternative, I draw from Baruch Spinozaâs political philosophy to generate a perspective that prioritizes the uncertain and volatile nature of the relationship between civil war and power. I contend that such a perspective could address the strange overlap between the contemporary modalities of diffused political violence and decentralized regimes of power characterizing our present and provide us a theoretical account on the relationship between power and civil war that does not culminate in a ratification of domination and sovereignty
Underfilled blood tube containing EDTA: Is it an inappropriate sample for HbA1c assay?
IntroductionBlood samples having inappropriate volume are a substantial part of preanalytical errors. Inadequate sample volume for glycated haemoglobin (HbA1c) test may be a common problem of patients with diabetes mellitus having vascular changes. In this study, we compared HbA1c concentrations of underfilled and appropriately filled blood collection tubes.
Materials and methodsTo compare HbA1c concentrations, blood samples were collected into 2 mL tubes containing K3-EDTA from 109 subjects. Two blood samples (underfilled and appropriately filled) were drawn from a patient by the same personnel and materials. HbA1c measurements were assayed on a Cobas 6000 analyser module c 501 (Roche Diagnostics, Mannheim, Germany). The HbA1c% results were compared by t-test and Wilcoxonâs signed-rank statistical methods (SPSS Inc., Chicago, USA). Bias analysis was performed using Microsoft Excel 4.0.
ResultsUnderfilled samples were classified three groups (group 1, N = 44; group 2, N = 36; and group 3, N = 29) according to the filling ratio of the samples; 0.5 mL and below ( 50%), respectively. When we compared underfilled tubes with pairing filled tubes, there was a statistically significant difference only with tubes filled less than 25% (P = 0.030). Furthermore, we have done bias analysis between paired tubes according to the diagnostic cut-off value of 6.5%. The bias was more prominent in up to 50% underfilled blood tubes (1.1%), when HbA1c concentrations were below the diagnostic cut-off of 6.5%.
ConclusionsWe suggest that the blood tubes with EDTA for HbA1c measurement should be filled with at least 50% to avoid clinical variations
Microcirculation: Physiology, pathophysiology, and clinical application
This paper briefly reviews the physiological components of the microcirculation, focusing on its function in homeostasis and its central function in the realization of oxygen transport to tissue cells. Its pivotal role in the understanding of circulatory compromise in states of shock and renal compromise is discussed. Our introduction of hand-held vital microscopes (HVM) to clinical medicine has revealed the importance of the microcirculation as a central target organ in states of critical illness and inadequate response to therapy. Technical and methodological developments have been made in hardware and in software including our recent introduction and validation of automatic analysis software called MicroTools, which now allows point-of-care use of HVM imaging at the bedside for instant availability of functional microcirculatory parameters needed for microcirculatory targeted resuscitation procedures to be a reality
Effects of Two Fluoride Varnishes and One Fluoride/Chlorhexidine Varnish on Streptococcus mutans and Streptococcus sobrinus Biofilm Formation in Vitro
Aims: The aim of this study was to evaluate and to compare the effect of two fluoride varnishes and one fluoride/chlorhexidine varnish on Streptococcus mutans and Streptococcus sobrinus biofilm formation, in vitro
Helfrich-Canham bending energy as a constrained non-linear sigma model
The Helfrich-Canham bending energy is identified with a non-linear sigma
model for a unit vector. The identification, however, is dependent on one
additional constraint: that the unit vector be constrained to lie orthogonal to
the surface. The presence of this constraint adds a source to the divergence of
the stress tensor for this vector so that it is not conserved. The stress
tensor which is conserved is identified and its conservation shown to reproduce
the correct shape equation.Comment: 5 page
Morphologic Mapping of the Sublingual Microcirculation in Healthy Volunteers
PURPOSE
Monitoring the sublingual and oral microcirculation (SM-OM) using hand-held vital microscopes (HVMs) has provided valuable insight into the (patho)physiology of diseases. However, the microvascular anatomy in a healthy population has not been adequately described yet.
METHODS
Incident dark field-based HVM imaging was used to visualize the SM-OM. First, the SM was divided into four different fields; Field-a (between incisors-lingua), Field-b (between the canine-first premolar-lingua), Field-c (between the first-second premolar-lingua), Field-d (between the second molar-wisdom teeth-lingua). Second, we investigated the buccal area, lower and upper lip. Total/functional vessel density (TVD/FCD), focus depth (FD), small vessel mean diameters (SVMDs), and capillary tortuosity score (CTS) were compared between the areas.
RESULTS
Fifteen volunteers with a mean age of 29 ± 6 years were enrolled. No statistical difference was found between the sublingual fields in terms of TVD (p = 0.30), FCD (p = 0.38), and FD (p = 0.09). SVMD was similar in Field-a, Field-b, and Field-c (p = 0.20-0.30), and larger in Field-d (p < 0.01, p = 0.015). The CTS of the buccal area was higher than in the lips.
CONCLUSION
The sublingual area has a homogenous distribution in TVD, FCD, FD, and SVMD. This study can be a description of the normal microvascular anatomy for future researches regarding microcirculatory assessment
Lipid membranes with an edge
Consider a lipid membrane with a free exposed edge. The energy describing
this membrane is quadratic in the extrinsic curvature of its geometry; that
describing the edge is proportional to its length. In this note we determine
the boundary conditions satisfied by the equilibria of the membrane on this
edge, exploiting variational principles. The derivation is free of any
assumptions on the symmetry of the membrane geometry. With respect to earlier
work for axially symmetric configurations, we discover the existence of an
additional boundary condition which is identically satisfied in that limit. By
considering the balance of the forces operating at the edge, we provide a
physical interpretation for the boundary conditions. We end with a discussion
of the effect of the addition of a Gaussian rigidity term for the membrane.Comment: 8 page
Retinal Nerve Fiber Layer Thickness in Women with Polycystic Ovary Syndrome
Aim. To compare the retinal nerve fiber layer (RNFL) thickness between women with polycystic ovary syndrome (PCOS) and healthy women. Materials and Methods. The study included 88 eyes of 44 women (group 1) with PCOS and 84 eyes of 42 healthy women (group 2). In all subjects, the RNFL and ganglion cell complex (GCC) thicknesses were measured by optical coherence tomography (OCT). In addition, visual acuity (VA), intraocular pressure (IOP), refractive errors, central macular thickness (CMT), central corneal thickness (CCT), and excavation of optic disc were evaluated in all subjects. Results. Mean values of GCC, IOP, VA, CMT, CCT, and refractive errors were similar between the 2 groups. The average RNFL, superior average RNFL, and inferior average RNFL thicknesses were higher in subjects with PCOS than in healthy subjects (P=0.003, P=0.012, and P=0.009), respectively. Conclusion. The average RNFL, superior average RNFL, and inferior average RNFL thicknesses in women with PCOS were significantly higher than in healthy women
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