3,031 research outputs found
Profile measurements of plasma columns using microwave resonant cavities
Microwave resonant cavity measurements of radial electron density profile of positive column of gas discharg
Inverted neutrino mass hierarchies from U(1) symmetries
Motivated by effective low energy models of string origin, we discuss the
neutrino masses and mixing within the context of the Minimal Supersymmetric
Standard Model supplemented by a U(1) anomalous family symmetry and additional
Higgs singlet fields charged under this extra U(1). In particular, we interpret
the solar and atmospheric neutrino data assuming that there are only three
left-handed neutrinos which acquire Majorana masses via a lepton number
violating dimension-five operator. We derive the general form of the charged
lepton and neutrino mass matrices when two different pairs of singlet Higgs
fields develop non--zero vacuum expectation values and show how the resulting
neutrino textures are related to approximate lepton flavor symmetries. We
perform a numerical analysis for one particular case and obtain solutions for
masses and mixing angles, consistent with experimental data.Comment: 15 pages, 4 figure
Synchronization in Complex Systems Following the Decision Based Queuing Process: The Rhythmic Applause as a Test Case
Living communities can be considered as complex systems, thus a fertile
ground for studies related to their statistics and dynamics. In this study we
revisit the case of the rhythmic applause by utilizing the model proposed by
V\'azquez et al. [A. V\'azquez et al., Phys. Rev. E 73, 036127 (2006)]
augmented with two contradicted {\it driving forces}, namely: {\it
Individuality} and {\it Companionship}. To that extend, after performing
computer simulations with a large number of oscillators we propose an
explanation on the following open questions (a) why synchronization occurs
suddenly, and b) why synchronization is observed when the clapping period
() is ( is the mean self period
of the spectators) and is lost after a time. Moreover, based on the model, a
weak preferential attachment principle is proposed which can produce complex
networks obeying power law in the distribution of number edges per node with
exponent greater than 3.Comment: 16 pages, 5 figure
Three-Dimensional Microfluidic Tumor Vascular Model for Investigating Breast Cancer Metastasis
Metastasis is one of the primary reasons for the high mortality rates in female patients diagnosed with breast cancer. It involves the migration of cancer cells into the circulatory system allowing for the dissemination of cancer cells in distal tissues. Understanding the major processes that occur in cells and tissues during metastasis can help improve currently existing therapeutic methods. In order to understand such mechanisms, developing physiologically relevant tissue models is crucial. Advancements in microfluidics have led to the fabrication of 3D culture models with shear stress gradients and flow control that can recapitulate aspects of the tumor microenvironment in vitro. However, most of these 3D culture models were fabricated using photolithography techniques performed in a clean room, which requires extensive training and can be cost prohibitive. Other studies have used more accessible techniques such as mold casting to construct a vessel-like microchannel. The main drawback of this method is that it limits the usage of high magnification objective lenses. Here, we propose a simple, high-fidelity and cost-effective approach in fabricating in vitro tissue platforms using a 3D printer that is optimal for live-cell imaging. To demonstrate proof-of-concept, we imaged endothelial and fibroblast cells cultured inside the 3D microfluidic collagen hydrogel, which was compared with the control group cultured in the 2D platform. The integrity of the microchannel fabricated inside the collagen hydrogel was imaged by using confocal reflectance microscopy. This feature has broader implications to bioengineered tissue fabrication and should be further explored in depth in the future
Initial Conditions for Supersymmetric Inflation
We perform a numerical investigation of the fields evolution in the
supersymmetric inflationary model based on radiative corrections. Supergravity
corrections are also included. We find that, out of all the examined initial
data, only about 10% give an adequate amount of inflation and can be considered
as ''natural''. Moreover, these successful initial conditions appear scattered
and more or less isolated.Comment: 15 pages RevTeX 4 eps figure
Willmore Surfaces of Constant Moebius Curvature
We study Willmore surfaces of constant Moebius curvature in . It is
proved that such a surface in must be part of a minimal surface in
or the Clifford torus. Another result in this paper is that an isotropic
surface (hence also Willmore) in of constant could only be part of a
complex curve in or the Veronese 2-sphere in . It is
conjectured that they are the only examples possible. The main ingredients of
the proofs are over-determined systems and isoparametric functions.Comment: 16 pages. Mistakes occured in the proof to the main theorem (Thm 3.6)
has been correcte
Characterization of Left-Ventricular Thrombus Formation Using High Frequency Ultrasound
Heart failure is a leading cause of death in the United States, and cardiac thrombus, a common morbidity associated with heart failure, significantly increases a patient’s risk of embolic events. The objective of this project is to characterize left-ventricular (LV) thrombus development using high frequency ultrasound imaging in a murine model. C57BL/6J wild-type mice (n=6) were injected intraperitoneally with iron dextran five times a week for six weeks to increase oxidative stress in the heart. Granulocyte-colony stimulating factor (G-CSF) was subcutaneously injected daily during the second week to initiate stem cell migration and stimulate endothelial cell activation, thus increasing the hypercoagulability state of the blood. A high-frequency, small animal ultrasound system (Vevo2100, VisualSonics FUJIFILM Inc.) and a 40 MHz central frequency transducer were used to track LV thrombus progression and evaluate LV function weekly. Four out of six mice developed thrombus, but no significant differences in LV performance were observed when compared to mice that did not form a thrombus. Further investigation is necessary to study the role of attenuated heart function on thrombus formation. Future work will incorporate a murine model of myocardial infarction to investigate if a severely compromised heart increases the risk of or accelerates LV thrombus formation. This study will aid in identifying patients who are predisposed to thrombus formation following a heart attack, leading to more effective prevention and treatment methods
Individual-Based Modelling of Bacterial Ecologies and Evolution
This paper presents two approaches to the individual-based modelling of bacterial
ecologies and evolution using computational tools. The first approach is a fine-grained
model that is based on networks of interactivity between computational objects
representing genes and proteins. The second approach is a coarser-grained, agent-based
model, which is designed to explore the evolvability of adaptive behavioural
strategies in artificial bacteria represented by learning classifier systems. The
structure and implementation of these computational models is discussed, and some
results from simulation experiments are presented. Finally, the potential applications
of the proposed models to the solution of real-world computational problems, and
their use in improving our understanding of the mechanisms of evolution, are briefly
outlined
Temperature Homogeneity under Selective and Localized Microwave Heating in Structured Flow Reactors
Selective heating of different phases of multiphase systems via microwaves can result in energy savings and suppression of side reactions. However, materials properties and operating conditions that maximize temperature gradients are poorly understood. Here we utilize computational fluid dynamics (CFD) computations and temperature measurements in structured flow reactors (monoliths) in a monomodal microwave cavity to assess the temperature difference between the walls and the fluid and develop a simple lumped model to estimate when temperature gradients exist. We also explore the material's thermal and electrical properties of structured reactors for isothermal catalyst conditions. We propose that CFD simulations can be used as a nonintrusive, predictive tool of temperature homogeneity. Importantly, we demonstrate that localized heating in the bed under several conditions rather than selective heating is responsible for the selectivity enhancement. Our results indicate that structured beds made of high thermal conductivity materials avoid arcing and enable temperature homogeneity and low electrical conductivity materials allow microwaves to penetrate the domain
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