Novel blood platelet diagnostic platform

This project involves the design and implementation of a platform to investigate the activation state of platelets. The �nal aim is to develop an assay to be used for diagnostic purposes. Blood platelets play a key role in the cardiovascular system. When the en- dothelium of the vessel wall is damaged platelets adhere and become activated, leading to platelet aggregation to maintain physiological haemostasis. Any abnormality in platelet functionality induces thrombus or atherosclerotic plaques leading to life-threatening consequences such as stroke. Recent reports suggest that the detection of activated platelets in the blood may be a useful indicator of the on-set of stroke and other cardiovascular abnormalities. Hence, the detection of the functional state of platelets is of huge clinical importance. A luminescence-based platelet bio-assay which uses high brightness silica nanoparticles (NPs) as super-bright labels is an innovative and promising tool for diagnostics. Compared to assays carried out using conventional single molecule dye labels, the usage of NPs makes it possible to enhance the detection e�ciency of the assay and to achieve a reduced limit-of-detection. In this work NPs doped with a near infra-red dye are synthesized and their interactions with the platelets are characterized. Protocols of conjugation of antibodies towards platelet surface antigens to NPs are tested. The second part of the work studies the activation state and the morphology of platelets in di�erent environments by using single molecule dye label assays and with AFM. The con�nement of platelets in micrometer sized area using a protein patterning technique makes the analysis innovative and potentially very useful

Discriminant analysis of solar bright points and faculae I. Classification method and center-to-limb distribution

While photospheric magnetic elements appear mainly as Bright Points (BPs) at the disk center and as faculae near the limb, high-resolution images reveal the coexistence of BPs and faculae over a range of heliocentric angles. This is not explained by a "hot wall" effect through vertical flux tubes, and suggests that the transition from BPs to faculae needs to be quantitatively investigated. To achieve this, we made the first recorded attempt to discriminate BPs and faculae, using a statistical classification approach based on Linear Discriminant Analysis(LDA). This paper gives a detailed description of our method, and shows its application on high-resolution images of active regions to retrieve a center-to-limb distribution of BPs and faculae. Bright "magnetic" features were detected at various disk positions by a segmentation algorithm using simultaneous G-band and continuum information. By using a selected sample of those features to represent BPs and faculae, suitable photometric parameters were identified in order to carry out LDA. We thus obtained a Center-to-Limb Variation (CLV) of the relative number of BPs and faculae, revealing the predominance of faculae at all disk positions except close to disk center (mu > 0.9). Although the present dataset suffers from limited statistics, our results are consistent with other observations of BPs and faculae at various disk positions. The retrieved CLV indicates that at high resolution, faculae are an essential constituent of active regions all across the solar disk. We speculate that the faculae near disk center as well as the BPs away from disk center are associated with inclined fields

Novel system for measuring the scattering of the cornea and the lens

Pla de Doctorat Industrial de la Generalitat de CatalunyaSpatial vision features play a key role in human vision quality, which in turn depends on the retinal image quality and posterior neural processing. The retinal image is affected by three optical phenomena: diffraction, aberrations and scattering. Traditionally, visual impairment due to scattering has been evaluated using clinical psychophysical tests such as contrast sensitivity charts although specialized instruments to account for this are now commercially available such as the C-Quant (Oculus Optikgeräte GmbH, Germany). There are also methods that deal with the assessment of backscattered light such as the slit lamp and Scheimpflug cameras. However, this light never reaches the retina, and thus, it does not affect vision. Recently, robust techniques to measure the global intraocular scattering by means of forward scattering in an objective way have also been proposed. They are mainly based on the double-pass technique (HD Analyzer, Visiometrics S.L., Spain) and the reconstruction of the wide angle point spread function of the eye (Sigma, University of Murcia, Spain). Nevertheless, there is not yet any objective technique capable of measuring the intraocular scattering and determining from which part of the eye it is coming from, i. e., the cornea, anterior chamber, lens and vitreous. In this thesis we developed a novel technique based on the contrast of the third (P3) and the fourth (P4) Purkinje images for the objective and independent assessment of scattering caused by different parts of the eye. The hypothesis is that the P3 contrast is affected by the corneal scattering while the P4 contrast is additionally influenced by the light scattered in the lens. The technique was firstly validated using an experimental system in artificial eyes with different controlled levels of corneal and lens scattering. Results revealed that P3 and P4 contrasts decreased as the corneal scattering increased, and that the P4 contrast decreased as the lens scattering increased while the P3 contrast remained constant. The system was also used to assess corneal and lens scattering in a small group of subjects (13). A clinical prototype was also developed and a study was conducted to validate the proposed technique in a clinical environment including 46 eyes with cataracts and 11 eyes with corneal disorders. An additional study with healthy eyes wearing scatter-customized CLs was also carried out. P3 and P4 contrasts given by our system were compared with the scattering measured in terms of densitometry obtained with the Pentacam Scheimpflug camera, the OSI (Objective Scatter Index) from the HD Analyzer, and the Log(S) from the C-Quant. The results revealed that the technique was suitable to account for corneal and lens scattering separately but that, unexpectedly, some cataracts influenced the P3 contrast to some extent. In these cases, a Ghost Purkinje Image (GPI) appeared between the P3 and P4 images probably due to hypereflective lens areas with different refractive indexes. To overcome this limitation, a compensation of the P3 contrast was applied based on the maximum intensity of the GPI. It was shown that the new contrast, P3’, provided information about the corneal scattering independently of the lens scattering, while the P4 contrast had information about the lens and corneal scattering altogether. In summary, agreement between parameters demonstrated the ability of our novel method to assess scattering in patients with different levels of corneal and lens scattering.Les propietats de la visió espacial tenen un paper clau en la qualitat de la visió humana, que alhora depèn de la qualitat de la imatge retinal i del processament neural posterior. La imatge de la retina es veu afectada per tres fenòmens òptics: difracció, aberracions i difusió. Tradicionalment, l`afectació que la difusió te en la visió ha estat avaluada mitjançant proves psicofísiques, com ara test de sensibilitat al contrast, tot i que actualment també existeixen instruments comercials especialitzats, com per exemple el C-Quant (Oculus Optikgeräte GmbH, Alemanya). També hi ha mètodes que avaluen la llum retrodifosa, com el biomicroscopi i les càmeres de Scheimpflug. No obstant, aquesta llum mai arriba a la retina i, per tant, no afecta la visió. Recentment, s'han proposat tècniques més robustes i objectives per mesurar la difusió intraocular cap endavant que arriba a la retina. Es basen principalment en la tècnica de doble pass (HD Analyzer, Visiometrics S.L., Espanya) i variacions de la mateixa que permeten quantificar la llum difosa a angles més grans (Sigma, Universitat de Múrcia, Espanya). Tot i això, encara no hi ha cap tècnica objectiva capaç de mesurar la difusió intraocular i determinar de quina part de l'ull prové, és a dir, la còrnia, humor aquós, cristal·lí o vitri. En aquesta tesi s'ha desenvolupat una tècnica basada en el contrast de la tercera (P3) i la quarta (P4) imatges de Purkinje per a l'avaluació objectiva i independent de la difusió causada en diferents parts de l'ull. La hipòtesi és que el contrast de P3 es veu afectat per la difusió corneal mentre que el contrast de P4 també està influenciat per la llum difosa en el cristal·lí. En primer lloc, la tècnica es va validar mitjançant un sistema experimental en ulls artificials amb diferents nivells controlats de difusió a la còrnia i al cristal·lí. Els resultats van mostrar que els contrastos de P3 i P4 disminueixen a mesura que augmenta la difusió corneal, i que el contrast de P4 disminueix quan la difusió del cristal·lí augmenta mentre que el contrast de P3 es manté constant. El sistema també es va utilitzar per avaluar la difusió de la còrnia i del cristal·lí en 13 voluntaris. Per validar la tècnica proposada, també es va desenvolupar un prototip clínic i es va realitzar un estudi en un entorn clínic amb 46 ulls amb cataractes i 11 ulls amb alteracions a la còrnia. A més, es va dur a terme un altre estudi amb ulls sans amb lents de contacte difusores. Els contrastos de P3 i P4 del nostre sistema es van comparar amb la difusió mesurada en termes de densitometria obtinguda amb la càmera Scheimpflug Pentacam; l'OSI (Objective Scatter Index) del HD Analyzer i el Log(S) del C-Quant. Els resultats han mostrat que la tècnica és útil per determinar la difusió de la còrnia i del cristal·lí per separat però que algunes cataractes poden afectar el contrast de P3. En aquests casos, es va comprovar que apareix una imatge de Purkinje fantasma (GPI) addicional entre les imatges P3 i P4, probablement a causa de zones hiperreflectives del cristal·lí amb diferents índexs de refracció. Per superar aquesta limitació es va aplicar una compensació del contrast de P3 en funció de la intensitat màxima de la GPI. Es va demostrar que el nou contrast, P3', proporciona informació exclusiva de la difusió corneal, independentment de la difusió del cristal·lí, mentre que el contrast de P4 conté informació de la difusió del cristal·lí i de la còrnia. En resum, la concordança entre paràmetres demostra la capacitat del nou mètode per avaluar la difusió en pacients amb diferents nivells de difusió a la còrnia i al cristal·lí.Postprint (published version

Inactivity/sleep in two wild free-roaming African elephant matriarchs - Does large body size make elephants the shortest mammalian sleepers?

The current study provides details of sleep (or inactivity) in two wild, free-roaming African elephant matriarchs studied in their natural habitat with remote monitoring using an actiwatch subcutaneously implanted in the trunk, a standard elephant collar equipped with a GPS system and gyroscope, and a portable weather station. We found that these two elephants were polyphasic sleepers, had an average daily total sleep time of 2 h, mostly between 02:00 and 06:00, and displayed the shortest daily sleep time of any mammal recorded to date. Moreover, these two elephants exhibited both standing and recumbent sleep, but only exhibited recumbent sleep every third or fourth day, potentially limiting their ability to enter REM sleep on a daily basis. In addition, we observed on five occasions that the elephants went without sleep for up to 46 h and traversed around 30 km in 10 h, possibly due to disturbances such as potential predation or poaching events, or a bull elephant in musth. They exhibited no form of sleep rebound following a night without sleep. Environmental conditions, especially ambient air temperature and relative humidity, analysed as wet-bulb globe temperature, reliably predict sleep onset and offset times. The elephants selected novel sleep sites each night and the amount of activity between sleep periods did not affect the amount of sleep. A number of similarities and differences to studies of elephant sleep in captivity are noted, and specific factors shaping sleep architecture in elephants, on various temporal scales, are discussed

A Survey, Taxonomy, and Analysis of Network Security Visualization Techniques

Network security visualization is a relatively new field and is quickly gaining momentum. Network security visualization allows the display and projection of the network or system data, in hope to efficiently monitor and protect the system from any intrusions or possible attacks. Intrusions and attacks are constantly continuing to increase in number, size, and complexity. Textually reading through log files or other textual sources is currently insufficient to secure a network or system. Using graphical visualization, security information is presented visually, and not only by text. Without network security visualization, reading through log files or other textual sources is an endless and aggravating task for network security analysts. Visualization provides a method of displaying large volume of information in a relatively small space. It also makes patterns easier to detect, recognize, and analyze. This can help security experts to detect problems that may otherwise be missed in reading text based log files. Network security visualization has become an active research field in the past six years and a large number of visualization techniques have been proposed. A comprehensive analysis of the existing techniques is needed to help network security designers make informed decisions about the appropriate visualization techniques under various circumstances. Moreover, a taxonomy of the existing visualization techniques is needed to classify the existing network security visualization techniques and present a high level overview of the field. In this thesis, the author surveyed the field of network security visualization. Specifically, the author analyzed the network security visualization techniques from the perspective of data model, visual primitives, security analysis tasks, user interaction, and other design issues. Various statistics were generated from the literatures. Based on this analysis, the author has attempted to generate useful guidelines and principles for designing effective network security visualization techniques. The author also proposed a taxonomy for the security visualization techniques. To the author’s knowledge, this is the first attempt to generate a taxonomy for network security visualization. Finally, the author evaluated the existing network security visualization techniques and discussed their characteristics and limitations. For future research, the author also discussed some open research problems in this field. This research is a step towards a thorough analysis of the problem space and the solution space in network security visualization