Abstract Purpose To investigate flow characteristics of the choriocapillaris using optical coherence tomography angiography. Design Retrospective observational case series. Methods Visualization of ...flow in individual choriocapillary vessels is below the current resolution limit of optical coherence tomography angiography instruments, but areas of absent flow signal, called flow voids, are resolvable. The central macula was imaged with the Optovue RTVue XR Avanti using a 10 micron slab thickness in 104 eyes of 80 patients who ranged in age from 24 to 99 years of age. Automatic local thresholding of the resultant raw data with the Phansalkar method was analyzed with generalized estimating equations. Results The distribution of flow voids versus size of the voids was highly skewed. The data showed a linear log-log plot and goodness of fit methods showed the data followed a power law distribution over the relevant range. A slope intercept relationship was also evaluated for the log transform and significant predictors for variables included age, hypertension, pseudodrusen, and the presence of late age-related macular degeneration (AMD) in the fellow eye. Conclusions The pattern of flow voids form a scale invariant pattern in the choriocapillaris starting in a size much smaller than a choroidal lobule. Age and hypertension affect the choriocapillaris, a flat layer of capillaries that may serve as an observable surrogate for the neural or systemic microvasculature. Significant alterations detectable in the flow pattern in eyes with pseudodrusen and in eyes with late AMD in the fellow eye offer diagnostic possibilities and impact theories of disease pathogenesis.
Starting with the dynamical picture of the exotic cc¯-containing states XYZ as the confinement-induced hadronization of a rapidly separating pair of a compact diquark and antidiquark, we describe the ...pentaquark candidates Pc+(4380) and Pc+(4450) in terms of a confined but rapidly separating color-antitriplet diquark cu and color-triplet “triquark” c¯(ud). This separation explains the relatively small Pc+ widths, despite these 5-quark systems lying far above both the J/ψp and ΛcD¯(⁎)0 thresholds. The Pc+ states are predicted to form isospin doublets with neutral partners Pc0.
Modular Brain Networks Sporns, Olaf; Betzel, Richard F
Annual review of psychology,
01/2016, Letnik:
67, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The development of new technologies for mapping structural and functional brain connectivity has led to the creation of comprehensive network maps of neuronal circuits and systems. The architecture ...of these brain networks can be examined and analyzed with a large variety of graph theory tools. Methods for detecting modules, or network communities, are of particular interest because they uncover major building blocks or subnetworks that are particularly densely connected, often corresponding to specialized functional components. A large number of methods for community detection have become available and are now widely applied in network neuroscience. This article first surveys a number of these methods, with an emphasis on their advantages and shortcomings; then it summarizes major findings on the existence of modules in both structural and functional brain networks and briefly considers their potential functional roles in brain evolution, wiring minimization, and the emergence of functional specialization and complex dynamics.
Research summary: U- and inverted U-shaped relationships are increasingly explored in strategy research, with 11 percent of all articles published in Strategic Management Journal (SMJ) in 2008-2012 ...investigating such quadratic relationships. Moreover, a movement towards introducing moderation to quadratic relationships has emerged. By reviewing 110 articles published in SMJ from 1980 to 2012, we identify several critical issues in theorizing and testing of these relationships for which current practice falls short. These include insufficient causal argumentation, incorrect testing, mixing up two different types of moderation, and not realizing that the curve can flip completely. For these and other issues, a guideline is provided which, when followed, may bring clarity to theoretical motivation and rigor to empirical testing. Managerial summary: Too much can be as bad as too little. Many relationships in strategic management follow an inverted U-shaped pattern, where moderate levels of a strategy lead to optimal performance. To gain deeper insights into the conventional wisdom that too much of a good thing can be harmful to performance, we discuss how such relationships can be better theorized and tested based on a review of articles exploring U-shaped relationships in Strategic Management Journal during 1980-2012. We identify several critical issues that require close attention and provide a guideline to further develop and validate this important managerial intuition.
Purpose To investigate the vascular appearance of choroidal neovascularization (CNV) treated with recurrent intravitreous anti–vascular endothelial growth factor (VEGF) injections, which have been ...proposed to cause transient vascular normalization along with decreased vascularity and leakage. Design Retrospective case series with perspective on the topic. Methods Patients with treated CNV secondary to age-related macular degeneration from a community-based retinal referral practice were evaluated with optical coherence tomography angiography employing split-spectrum amplitude decorrelation. The choroidal neovascular morphology of the 17 eyes of 14 consecutive patients was described. Results The mean age of the patients, 8 men and 6 women, was 78.4 (standard deviation ± 9.3) years. The mean greatest linear dimension of the lesion was 3600 μm. The mean number of anti-VEGF injections was 47 (±21). The vascular diameter of the vessels in the CNV appeared large even in small lesions, with feeder vessels approaching the size of the major arcade vessels of the retina. The vessels had few branch points and many vascular anastomotic connections among larger vessels. There was a paucity of capillaries visualized within the lesions. Conclusions The findings of this study do not support the hypothesis of vascular normalization in eyes receiving recurrent periodic antiangiogenic treatment. The observed “abnormalization” of the vessels may be explained by periodic pruning of angiogenic vascular sprouts by VEGF withdrawal in the face of unimpeded arteriogenesis. As the eye is a readily accessible VEGF laboratory, features expressed therein may also apply to neovascularization elsewhere in the body, such as in tumors.
Since wireless network virtualization enables abstraction and sharing of infrastructure and radio spectrum resources, the overall expenses of wireless network deployment and operation can be reduced ...significantly. Moreover, wireless network virtualization can provide easier migration to newer products or technologies by isolating part of the network. Despite the potential vision of wireless network virtualization, several significant research challenges remain to be addressed before widespread deployment of wireless network virtualization, including isolation, control signaling, resource discovery and allocation, mobility management, network management and operation, and security as well as non-technical issues such as governance regulations, etc. In this paper, we provide a brief survey on some of the works that have already been done to achieve wireless network virtualization, and discuss some research issues and challenges. We identify several important aspects of wireless network virtualization: overview, motivations, framework, performance metrics, enabling technologies, and challenges. Finally, we explore some broader perspectives in realizing wireless network virtualization.
The integrin family of cell adhesion receptors plays a major role in mediating interactions between cells and the extracellular matrix. Normal adult articular chondrocytes express α1β1, α3β1, α5β1, ...α10β1, αVβ1, αVβ3, and αVβ5 integrins, while chondrocytes from osteoarthritic tissue also express α2β1, α4β1, α6β1. These integrins bind a host of cartilage extracellular matrix (ECM) proteins, most notably fibronectin and collagen types II and VI, which provide signals that regulate cell proliferation, survival, differentiation, and matrix remodeling. By initiating signals in response to mechanical forces, chondrocyte integrins also serve as mechanotransducers. When the cartilage matrix is damaged in osteoarthritis, fragments of fibronectin are generated that signal through the α5β1 integrin to activate a pro-inflammatory and pro-catabolic response which, if left unchecked, could contribute to progressive matrix degradation. The cell signaling pathways activated in response to excessive mechanical signals and to fibronectin fragments are being unraveled and may represent useful therapeutic targets for slowing or stopping progressive matrix destruction in arthritis.
In recent years, with the rapid development of current Internet and mobile communication technologies, the infrastructure, devices and resources in networking systems are becoming more complex and ...heterogeneous. In order to efficiently organize, manage, maintain and optimize networking systems, more intelligence needs to be deployed. However, due to the inherently distributed feature of traditional networks, machine learning techniques are hard to be applied and deployed to control and operate networks. Software defined networking (SDN) brings us new chances to provide intelligence inside the networks. The capabilities of SDN (e.g., logically centralized control, global view of the network, software-based traffic analysis, and dynamic updating of forwarding rules) make it easier to apply machine learning techniques. In this paper, we provide a comprehensive survey on the literature involving machine learning algorithms applied to SDN. First, the related works and background knowledge are introduced. Then, we present an overview of machine learning algorithms. In addition, we review how machine learning algorithms are applied in the realm of SDN, from the perspective of traffic classification, routing optimization, quality of service/quality of experience prediction, resource management and security. Finally, challenges and broader perspectives are discussed.
: Retinal vascular disease has the potential to affect hundreds of millions of people, with the inherent risk of vision loss related to cystoid macular edema. Although there have been histologic ...evaluation of eyes having cystoid macular edema, the most recent paper was published more than 30 years ago. In retinal vascular cystoid macular edema fluorescein angiography, a modality that images the superficial vascular plexus, shows increased leakage. Optical coherence tomography angiography has provided unprecedented resolution of retinal vascular flow in a depth resolved manner and demonstrates areas of decreased or absent flow in the deep vascular plexus colocalizing with the cystoid spaces. There has been a large amount of research on fluid management and edema in the brain, much of which may have analogues in the eye. Interstitial flow of fluid as managed by Müller cells may occur in the retina, comparable in some ways to the bulk flow in brain parenchyma, which is managed by astrocytes. Absent blood flow in the deep retinal plexus may restrict fluid management strategies in the retina, to include transport of excess fluid out of the retina into the blood by Müller cells. Application of this theory may help in increasing understanding of the pathophysiology of retinal vascular cystoid macular edema and may lead to new therapeutic approaches.
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