Issues in Distance Learning
This review of literature and research into the effectiveness of distance education systems deals with a number of factors which affect their success or failure. These include the influence of distance learning theory upon instructional design and delivery, redefining the roles of partners in distance education teams, media selection, technology adoption, change implementation, methods and strategies to increase interactivity, inquiry, and active learning, learner characteristics and modes of learning, teacher mediation and learner support, operational issues, policy and management issues, and cost/ benefit tradeoffs. It is intended as a companion piece to Sherry and Morse’s (1994) training needs assessment.
Cross-subsidization, Incentives, and Outcomes in Professional Team Sports Leagues
Professional team sports leagues provide insight into the problems facing the management of functioning cartels. This paper provides an analysis of the incentives and outcomes inherent in the management of professional team sports cartels. Except for revenue sharing and salary caps, league cartel management outcomes are consistent with league-wide revenue maximization and have no impact on competitive balance. However, there are predictable impacts on the profitability of strong- and weak-drawing teams within the league. While providing an analytical review of the literature, the work here also yields new results concerning salary caps, local TV revenue sharing, and the behavior of cartel managers in the face of rival leagues.
Visualizing the mechanical activation of Src
The mechanical environment crucially influences many cell functions. However, it remains largely mysterious how mechanical stimuli are transmitted into biochemical signals. Src is known to regulate the integrin–cytoskeleton interaction, which is essential for the transduction of mechanical stimuli. Using fluorescent resonance energy transfer (FRET), here we develop a genetically encoded Src reporter that enables the imaging and quantification of spatio-temporal activation of Src in live cells. We introduced a local mechanical stimulation to human umbilical vein endothelial cells (HUVECs) by applying laser-tweezer traction on fibronectin-coated beads adhering to the cells. Using the Src reporter, we observed a rapid distal Src activation and a slower directional wave propagation of Src activation along the plasma membrane. This wave propagated away from the stimulation site with a speed (mean ± s.e.m.) of 18.1 ± 1.7 nm s-1. This force-induced directional and long-range activation of Src was abolished by the disruption of actin filaments or microtubules. Our reporter has thus made it possible to monitor mechanotransduction in live cells with spatio-temporal characterization. We find that the transmission of mechanically induced Src activation is a dynamic process that directs signals via the cytoskeleton to spatial destinations.
Ras recruits Raf‐1 to the plasma membrane for activation by tyrosine phosphorylation.
A central feature of signal transduction downstream of both receptor and oncogenic tyrosine kinases is the Ras‐dependent activation of a protein kinase cascade consisting of Raf‐1, Mek (MAP kinase kinase) and ERKs (MAP kinases). To study the role of tyrosine kinase activity in the activation of Raf‐1, we have examined the properties of p74Raf‐1 and oncogenic Src that are necessary for activation of p74Raf‐1. We show that in mammalian cells activation of p74Raf‐1 by oncogenic Src requires pp60Src to be myristoylated and the ability of p74Raf‐1 to interact with p21Ras‐GTP. The Ras/Raf interaction is required for p21Ras‐GTP to bring p74Raf‐1 to the plasma membrane for phosphorylation at tyrosine 340 or 341, probably by membrane‐bound pp60Src. When oncogenic Src is expressed with Raf‐1, p74Raf‐1 is activated 5‐fold; however, when co‐expressed with oncogenic Ras and Src, Raf‐1 is activated 25‐fold and this is associated with a further 3‐fold increase in tyrosine phosphorylation. Thus, p21Ras‐GTP is the limiting component in bringing p74Raf‐1 to the plasma membrane for tyrosine phosphorylation. Using mutants of Raf‐1 at Tyr340/341, we show that in addition to tyrosine phosphorylation at these sites, there is an additional activation step resulting from p21Ras‐GTP recruiting p74Raf‐1 to the plasma membrane. Thus, the role of Ras in Raf‐1 activation is to bring p74Raf‐1 to the plasma membrane for at least two different activation steps.
NMDA Channel Regulation by Channel-Associated Protein Tyrosine Kinase Src
The N-methyl-D-aspartate (NMDA) receptor mediates synaptic transmission and plasticity in the central nervous system (CNS) and is regulated by tyrosine phosphorylation. In membrane patches excised from mammalian central neurons, the endogenous tyrosine kinase Src was shown to regulate the activity of NMDA channels. The action of Src required a sequence [Src(40–58)] within the noncatalytic, unique domain of Src. In addition, Src coprecipitated with NMDA receptor proteins. Finally, endogenous Src regulated the function of NMDA receptors at synapses. Thus, NMDA receptor regulation by Src may be important in development, plasticity, and pathology in the CNS.
SU6656, a Selective Src Family Kinase Inhibitor, Used To Probe Growth Factor Signaling
The use of small-molecule inhibitors to study molecular components of cellular signal transduction pathways provides a means of analysis complementary to currently used techniques, such as antisense, dominant-negative (interfering) mutants and constitutively activated mutants. We have identified and characterized a small-molecule inhibitor, SU6656, which exhibits selectivity for Src and other members of the Src family. A related inhibitor, SU6657, inhibits many kinases, including Src and the platelet-derived growth factor (PDGF) receptor. The use of SU6656 confirmed our previous findings that Src family kinases are required for both Myc induction and DNA synthesis in response to PDGF stimulation of NIH 3T3 fibroblasts. By comparing PDGF-stimulated tyrosine phosphorylation events in untreated and SU6656-treated cells, we found that some substrates (for example, c-Cbl, and protein kinase C δ) were Src family substrates whereas others (for example, phospholipase C-γ) were not. One protein, the adaptor Shc, was a substrate for both Src family kinases (on tyrosines 239 and 240) and a distinct tyrosine kinase (on tyrosine 317, which is perhaps phosphorylated by the PDGF receptor itself). Microinjection experiments demonstrated that a Shc molecule carrying mutations of tyrosines 239 and 240, in conjunction with an SH2 domain mutation, interfered with PDGF-stimulated DNA synthesis. Deletion of the phosphotyrosine-binding domain also inhibited synthesis. These inhibitions were overcome by heterologous expression of Myc, supporting the hypothesis that Shc functions in the Src pathway. SU6656 should prove a useful additional tool for further dissecting the role of Src kinases in this and other signal transduction pathways.
Structure and regulation of Src family kinases
Src family kinases are prototypical modular signaling proteins. Their conserved domain organization includes a myristoylated N-terminal segment followed by SH3, SH2, and tyrosine kinase domains, and a short C-terminal tail. Structural dissection of Src kinases has elucidated the canonical mechanisms of phosphotyrosine recognition by the SH2 domain and proline-motif recognition by the SH3 domain. Crystallographic analysis of nearly intact Src kinases in the autoinhibited state has shown that these protein interaction motifs turn inward and lock the kinase in an inactive conformation via intramolecular interactions. The autoinhibited Src kinase structures reveal a mode of domain assembly used by other tyrosine kinases outside the Src family, including Abl and likely Tec family kinases. Furthermore, they illustrate the underlying regulatory principles that have proven to be general among diverse modular signaling proteins. Although there is considerable structural information available for the autoinhibited conformation of Src kinases, how they may assemble into active signaling complexes with substrates and regulators remains largely unexplored.
Wireless multimedia sensor networks: A survey
In recent years, the growing interest in the wireless sensor network (WSN) has resulted in thousands of peer-reviewed publications. Most of this research is concerned with scalar sensor networks that measure physical phenomena, such as temperature, pressure, humidity, or location of objects that can be conveyed through low-bandwidth and delay-tolerant data streams. Recently, the focus is shifting toward research aimed at revisiting the sensor network paradigm to enable delivery of multimedia content, such as audio and video streams and still images, as well as scalar data. This effort will result in distributed, networked systems, referred to in this paper as wireless multimedia sensor networks (WMSNs). This article discusses the state of the art and the major research challenges in architectures, algorithms, and protocols for wireless multimedia sensor networks. Existing solutions at the physical, link, network, transport, and application layers of the communication protocol stack are investigated. Finally, fundamental open research issues are discussed, and future research trends in this area are outlined.
UbiCrawler: a scalable fully distributed Web crawler
We report our experience in implementing UbiCrawler, a scalable distributed Web crawler, using the Java programming language. The main features of UbiCrawler are platform independence, linear scalability, graceful degradation in the presence of faults, a very effective assignment function (based on consistent hashing) for partitioning the domain to crawl, and more in general the complete decentralization of every task. The necessity of handling very large sets of data has highlighted some limitations of the Java APIs, which prompted the authors to partially reimplement them. Copyright © 2004 John Wiley & Sons, Ltd.
Proline‐rich (PxxP) motifs in HIV‐1 Nef bind to SH3 domains of a subset of Src kinases and are required for the enhanced growth of Nef+ viruses but not for down‐regulation of CD4.
Human immunodeficiency virus (HIV) and simian immunodeficiency virus Nef proteins contain a conserved motif with the minimal consensus (PxxP) site for Src homology region 3 (SH3)‐mediated protein‐protein interactions. Nef PxxP motifs show specific binding to biotinylated SH3 domains of Hck and Lyn, but not to those of other tested Src family kinases or less related proteins. A unique cooperative role of a distant proline is also observed. Endogenous Hck of monocytic U937 cells can be specifically precipitated by matrix‐bound HIV‐1 Nef, but not by mutant protein lacking PxxP. Intact Nef PxxP motifs are dispensable for Nef‐induced CD4 down‐regulation, but are required for the higher in vitro replicative potential of Nef+ viruses. Thus, CD4 down‐regulation and promotion of viral growth are two distinct functions of Nef, and the latter is mediated via SH3 binding.
Robust sparse coding for face recognition
Recently the sparse representation (or coding) based classification (SRC) has been successfully used in face recognition. In SRC, the testing image is represented as a sparse linear combination of the training samples, and the representation fidelity is measured by the l2-norm or l1-norm of coding residual. Such a sparse coding model actually assumes that the coding residual follows Gaussian or Laplacian distribution, which may not be accurate enough to describe the coding errors in practice. In this paper, we propose a new scheme, namely the robust sparse coding (RSC), by modeling the sparse coding as a sparsity-constrained robust regression problem. The RSC seeks for the MLE (maximum likelihood estimation) solution of the sparse coding problem, and it is much more robust to outliers (e.g., occlusions, corruptions, etc.) than SRC. An efficient iteratively reweighted sparse coding algorithm is proposed to solve the RSC model. Extensive experiments on representative face databases demonstrate that the RSC scheme is much more effective than state-of-the-art methods in dealing with face occlusion, corruption, lighting and expression changes, etc.
A review of studies on central receiver solar thermal power plants
The use of central receiver system (CRS) for electricity production promises to be one of the most viable options to replace fossil fuel power plants. Indeed, research and development activities on its basic subsystems have been booming rapidly since 1980s. This paper reviews the most important studies on the major components of central receiver solar thermal power plants including the heliostat field, the solar receiver and the power conversion system. After an overview of Concentrating Solar Power (CSP) technology, current status and applications of the CRSs are highlighted. Next, a detailed literature survey of existing design comprising optical, thermal and thermodynamic analysis, and techniques used to assess components have been arranged. This is followed by experimental investigations in which design concepts are established. The last section contains recent subsequent improvement of such key components as heliostat, receiver and hybrid solar gas turbine that are boosting in many R&D activities merging international collaboration during the past 30 years.
Extended SRC: Undersampled Face Recognition via Intraclass Variant Dictionary
Sparse Representation-Based Classification (SRC) is a face recognition breakthrough in recent years which has successfully addressed the recognition problem with sufficient training images of each gallery subject. In this paper, we extend SRC to applications where there are very few, or even a single, training images per subject. Assuming that the intraclass variations of one subject can be approximated by a sparse linear combination of those of other subjects, Extended Sparse Representation-Based Classifier (ESRC) applies an auxiliary intraclass variant dictionary to represent the possible variation between the training and testing images. The dictionary atoms typically represent intraclass sample differences computed from either the gallery faces themselves or the generic faces that are outside the gallery. Experimental results on the AR and FERET databases show that ESRC has better generalization ability than SRC for undersampled face recognition under variable expressions, illuminations, disguises, and ages. The superior results of ESRC suggest that if the dictionary is properly constructed, SRC algorithms can generalize well to the large-scale face recognition problem, even with a single training image per class.
Src protein-tyrosine kinase structure and regulation.
Src and Src-family protein kinases are proto-oncogenes that play key roles in cell morphology, motility, proliferation, and survival. v-Src (a viral protein) is encoded by the chicken oncogene of Rous sarcoma virus, and Src (the cellular homologue) is encoded by a physiological gene, the first of the proto-oncogenes. From the N- to C-terminus, Src contains an N-terminal 14-carbon myristoyl group, a unique segment, an SH3 domain, an SH2 domain, a protein-tyrosine kinase domain, and a C-terminal regulatory tail. The chief phosphorylation sites of Src include tyrosine 416 that results in activation from autophosphorylation and tyrosine 527 that results in inhibition from phosphorylation by C-terminal Src kinase. In the restrained state, the SH2 domain forms a salt bridge with phosphotyrosine 527, and the SH3 domain binds to the kinase domain via a polyproline type II left-handed helix. The SH2 and SH3 domains occur on the backside of the kinase domain away from the active site where they stabilize a dormant enzyme conformation. Protein-tyrosine phosphatases such as PTPalpha displace phosphotyrosine 527 from the Src SH2 domain and mediate its dephosphorylation leading to Src kinase activation. C-terminal Src kinase consists of an SH3, SH2, and kinase domain; it lacks an N-terminal myristoyl group and a C-terminal regulatory tail. Its X-ray structure has been determined, and the SH2 lobe occupies a position that is entirely different from that of Src. Unlike Src, the C-terminal Src kinase SH2 and SH3 domains stabilize an active enzyme conformation. Amino acid residues in the alphaD helix near the catalytic loop in the large lobe of C-terminal Src kinase serve as a docking site for the physiological substrate (Src) but not for an artificial substrate (polyGlu(4)Tyr).
Primitive human hematopoietic cells are enriched in cord blood compared with adult bone marrow or mobilized peripheral blood as measured by the quantitative in vivo SCID-repopulating cell assay.
We have previously reported the development of in vivo functional assays for primitive human hematopoietic cells based on their ability to repopulate the bone marrow (BM) of severe combined immunodeficient (SCID) and nonobese diabetic/SCID (NOD/SCID) mice following intravenous transplantation. Accumulated data from gene marking and cell purification experiments indicate that the engrafting cells (defined as SCID-repopulating cells or SRC) are biologically distinct from and more primitive than most cells that can be assayed in vitro. Here we demonstrate through limiting dilution analysis that the NOD/SCID xenotransplant model provides a quantitative assay for SRC. Using this assay, the frequency of SRC in cord blood (CB) was found to be 1 in 9.3 x 10(5) cells. This was significantly higher than the frequency of 1 SRC in 3.0 x 10(6) adult BM cells or 1 in 6.0 x 10(6) mobilized peripheral blood (PB) cells from normal donors. Mice transplanted with limiting numbers of SRC were engrafted with both lymphoid and multilineage myeloid human cells. This functional assay is currently the only available method for quantitative analysis of human hematopoietic cells with repopulating capacity. Both CB and mobilized PB are increasingly being used as alternative sources of hematopoietic stem cells in allogeneic transplantation. Thus, the findings reported here will have important clinical as well as biologic implications.
Global Positioning Systems (GPS) and Microtechnology Sensors in Team Sports: A Systematic Review
BackgroundUse of Global positioning system (GPS) technology in team sport permits measurement of player position, velocity, and movement patterns. GPS provides scope for better understanding of the specific and positional physiological demands of team sport and can be used to design training programs that adequately prepare athletes for competition with the aim of optimizing on-field performance.ObjectiveThe objective of this study was to conduct a systematic review of the depth and scope of reported GPS and microtechnology measures used within individual sports in order to present the contemporary and emerging themes of GPS application within team sports.MethodsA systematic review of the application of GPS technology in team sports was conducted. We systematically searched electronic databases from earliest record to June 2012. Permutations of key words included GPS; male and female; age 12–50 years; able-bodied; and recreational to elite competitive team sports.ResultsThe 35 manuscripts meeting the eligibility criteria included 1,276 participants (age 11.2–31.5 years; 95 % males; 53.8 % elite adult athletes). The majority of manuscripts reported on GPS use in various football codes: Australian football league (AFL; n = 8), soccer (n = 7), rugby union (n = 6), and rugby league (n = 6), with limited representation in other team sports: cricket (n = 3), hockey (n = 3), lacrosse (n = 1), and netball (n = 1). Of the included manuscripts, 34 (97 %) detailed work rate patterns such as distance, relative distance, speed, and accelerations, with only five (14.3 %) reporting on impact variables. Activity profiles characterizing positional play and competitive levels were also described. Work rate patterns were typically categoriszed into six speed zones, ranging from 0 to 36.0 km·h−1, with descriptors ranging from walking to sprinting used to identify the type of activity mainly performed in each zone. With the exception of cricket, no standardized speed zones or definitions were observed within or between sports. Furthermore, speed zone criteria often varied widely within (e.g. zone 3 of AFL ranged from 7 to 16 km·h−1) and between sports (e.g. zone 3 of soccer ranged from 3.0 to <13 km·h−1 code). Activity descriptors for a zone also varied widely between sports (e.g. zone 4 definitions ranged from jog, run, high velocity, to high-intensity run). Most manuscripts focused on the demands of higher intensity efforts (running and sprint) required by players. Body loads and impacts, also summarized into six zones, showed small variations in descriptions, with zone criteria based upon grading systems provided by GPS manufacturers.ConclusionThis systematic review highlights that GPS technology has been used more often across a range of football codes than across other team sports. Work rate pattern activities are most often reported, whilst impact data, which require the use of microtechnology sensors such as accelerometers, are least reported. There is a lack of consistency in the definition of speed zones and activity descriptors, both within and across team sports, thus underscoring the difficulties encountered in meaningful comparisons of the physiological demands both within and between team sports. A consensus on definitions of speed zones and activity descriptors within sports would facilitate direct comparison of the demands within the same sport. Meta-analysis from systematic review would also be supported. Standardization of speed zones between sports may not be feasible due to disparities in work rate pattern activities.
Activating SRC mutation in a subset of advanced human colon cancers
The discovery of Rous sarcoma virus (RSV) led to the identification of cellular Src (c–Src), a non-receptor tyrosine kinase, which has since been implicated in the development of numerous human cancers. c-Src has been found to be highly activated in colon cancers, particularly in those metastatic to the liver. Studies of the mechanism of c-Src regulation have suggested that c-Src kinase activity is downregulated by phosphorylation of a critical carboxy-terminal tyrosine (Tyr 530 in human c-Src, equivalent to Tyr 527 in chicken Src) and have implied the existence of activating mutations in this C-terminal regulatory region. We report here the identification of a truncating mutation in SRC at codon 531 in 12% of cases of advanced human colon cancer tested and demonstrate that the mutation is activating, transforming, tumorigenic and promotes metastasis. These results provide, for the first time, genetic evidence that activating SRC mutations may have a role in the malignant progression of human colon cancer.
Volumetric receivers in Solar Thermal Power Plants with Central Receiver System technology: A review
Deployment of the first generation of grid-connected plants for electricity production, based on Solar Thermal Power Plants with Central Receiver System technology using large heliostat fields and a solar receiver placed on the top of a tower, is currently being boosted by the first commercial plants in Spain, PS10, PS20, and Gemasolar. Therefore one of the main goals of solar technology research is the study of existing receivers and development of new designs to minimize heat losses. In this context, volumetric receivers appear to be the best alternative to tube receivers, mainly due to their functionality and geometric configuration. They consist of a porous material that absorbs concentrated radiation inside the volume of a structure and transfers the absorbed heat to a fluid passing through the structure. Solar radiation is first converted into thermal energy or chemical potential, and then at a later stage, into electricity. This volumetric receiver technology has been under development since the early 1990s in various research and development projects. This paper is a chronological review of the volumetric receivers of most interest for electricity production, identifying their different configurations, materials and real and expected results, and pointing out their main advantages and conclusions based on the multitude of international and national projects reports and references. This study also deals with other important issues surrounding the volumetric receiver, such as the basic plant configuration, flow stability phenomenon and the main problems of a windowed design for pressurized receivers.
Gabor Feature Based Sparse Representation for Face Recognition with Gabor Occlusion Dictionary
By coding the input testing image as a sparse linear combination of the training samples via l1-norm minimization, sparse representation based classification (SRC) has been recently successfully used for face recognition (FR). Particularly, by introducing an identity occlusion dictionary to sparsely code the occluded portions in face images, SRC can lead to robust FR results against occlusion. However, the large amount of atoms in the occlusion dictionary makes the sparse coding computationally very expensive. In this paper, the image Gabor-features are used for SRC. The use of Gabor kernels makes the occlusion dictionary compressible, and a Gabor occlusion dictionary computing algorithm is then presented. The number of atoms is significantly reduced in the computed Gabor occlusion dictionary, which greatly reduces the computational cost in coding the occluded face images while improving greatly the SRC accuracy. Experiments on representative face databases with variations of lighting, expression, pose and occlusion demonstrated the effectiveness of the proposed Gabor-feature based SRC (GSRC) scheme.
Endothelial barrier disruption by VEGF-mediated Src activity potentiates tumor cell extravasation and metastasis
VEGF is unique among angiogenic growth factors because it disrupts endothelial barrier function. Therefore, we considered whether this property of VEGF might contribute to tumor cell extravasation and metastasis. To test this, mice lacking the Src family kinases Src or Yes, which maintain endothelial barrier function in the presence of VEGF, were injected intravenously with VEGF-expressing tumor cells. We found a dramatic reduction in tumor cell extravasation in lungs or livers of mice lacking Src or Yes. At the molecular level, VEGF compromises the endothelial barrier by disrupting a VE-cadherin–β-catenin complex in lung endothelium from wild-type, but not Yes-deficient, mice. Disrupting the endothelial barrier directly with anti–VE-cadherin both amplifies metastasis in normal mice and overcomes the genetic resistance in Yes-deficient mice. Pharmacological blockade of VEGF, VEGFR-2, or Src stabilizes endothelial barrier function and suppresses tumor cell extravasation in vivo. Therefore, disrupting Src signaling preserves host endothelial barrier function providing a novel host-targeted approach to control metastatic disease.
sensor network wireless sensor network wireless sensor power plant wireless network face recognition breast cancer wireless lan sensor datum thermal power sparse representation systematic review wireless system thermal power plant amino acid solar thermal wireless multimedia cancer cell multimedia sensor network wireless multimedia sensor multimedia sensor multi-user mimo generation wireles based classification transcription factor representation based cell line behavior model generation wireless network solar thermal power behavior modeling based face recognition sparse representation based tumor cell receiver system robust face recognition amino acid sequence frog leaping algorithm frog leaping theory of planned growth factor signal transduction leaping algorithm scalable distributed planned behavior collaborative representation central receiver suspended sediment optical parameter team sport face recognition problem bone marrow protein domain generation wireless system cell growth representation based classification peripheral blood sparse representation-based cell proliferation professional sport protein kinase short rotation sparse representation-based classification revenue sharing signal transduction pathway cell adhesion myeloid leukemia central receiver system sparse coding model body tissue phage display generation wireless lan growth factor receptor sports league cell nucleu tyrosine kinase tumor progression cell activation solar thermal central competitive balance thermal central receiver human colon cell invasion real-world face recognition sparse representation-based classifier professional team biological signaling enhancing feature protein tyrosine scalar sensor datum focal adhesion protein protein interaction activation action dna, complementary interleukin receptor common gamma subunit adaptor proteins, signal transducing 1-phosphatidylinositol 3-kinase immunologic deficiency syndrome blood platelet sh3 domain myeloid leukemia, chronic protein tyrosine phosphatase erbb receptor fyn gene abl oncogene tyrosine phosphorylation proline-rich domain src gene tyrosine kinase domain src-family kinase v-src protein intracellular signal transduction lyn gene review [publication type] transcription, genetic homologous gene ligand binding domain tissue membrane staphylococcal protein a leukemia, b-cell kinase activity protein tyrosine kinase united state