A kernel is simply a similarity measure that can be applied to input data in the original representation; for example if the data is originally represented as numbers, then the absolute value of the ...difference between two numbers can be used as a kernel function. However the learning algorithm itself this algorithm is the kernel machine 4 - never sees the data in its original form. Instead, the algorithm only sees the values of various kernel functions that have been applied to the original data. This decouples the data representation from the learning algorithm itself, and thus allows the same machine learning principles to be applied to a wide variety of data types. The advent of kernel machines 2, 3 greatly simplified learning problems where the input data comes in the form strings. String kernels, which are just similarity measures on strings, can be used to train a kernel machine on string data, simply by replacing its existing kernel function with a string kernel function. There are numerous string kernels, but the emphasis is on efficiency. For example, the well-known Levenshtein distance (a.k.a. the edit-distance between two strings) could be used as the basis of a string kernel, but usually this is not done because the edit distance takes quadratic time to compute. One way to construct linear-time string kernels is to use suffix trees 1, which can be used to obtain measures like the longest common substring of two strings, or to get a measure that is close to the number of common substrings.
Secure information distribution is a strategic capability as significant as weapons systems and tactics to military operations. The Department of Defense has recognized the importance of establishing ...and maintaining secure distributed file systems and explores the practicality and applicability of one such system, Trusted Ficus File System (TRUFFLES), in the DoD infrastructure. Integrated into this research are discussions of Privacy Enhanced Mail (PEM), which is currently an integral part of the TRUFFLES implementation. This thesis concludes with a discussion of the actual installation of a PEM reference implementation, and future requirements for the TRUFFLES installation at the Naval Postgraduate School.
The role of self-antigen recognition in the development of T and B cells of the adaptive immune system has been studied in several different ways. We have shown that CD4 T cells are selected on ...selfpeptide:self-MHC class II ligands, and in the periphery, they are sustained by contact with the same or similar ligands. We have also observed that B cells are positively selected on unknown and presumed self-ligands. We have used this information to explore autoimmune diseases as well. Finally, we have recently identified the innate immune system as playing a crucial role in regulating expression of costimulatory molecules that are required for induction of adaptive immune responses.PUBLICATION ABSTRACT
Mike Kane is a cognitive psychologist who studies the dynamic interaction between attention and memory. Mike has Tourette's Syndrome (TS), a disorder characterized by multiple motor tics and at least ...one vocal tic. His first professional paper, while still a graduate student in psychology, was an introspective case study of his own experience of TS tics. Whereas the tics that characterize TS have typically been thought to be involuntary, Kane's observations and the work of others have suggested that TS tics tend to be compulsory, perhaps emitted in response to a subjective tactile/kinesthetic/sensory experience. Kane observed in himself, as have others, that tics are preceded by premonitory sensations:These sensations are not mere precursors to tics; they precipitate tics. … I experience the TS state as one of keen bodily awareness, or a continual consciousness of muscle, joint, and skin sensations. For example when sitting in a chair, I do not lose awareness of the tactile sensation of the seat against my body, nor can I ignore the deeper somatic sensations of what my back and legs feel like.The TS state is omnipresent with few exceptions (e.g., during intense concentration or attentional focus, such as in lecturing), but it is not constant in bodily location or intensity.…If a tic is temporarily stopped, its respective bodily location becomes less ignorable. If all tics are suppressed, virtually all of my joints and muscles begin to demand my attention. The TS state heightens to a stiffening feeling, such that my skin feels like a hardened casing and my joints feel as though they are becoming rigid. …
An investigation of DNA-protein interactions by capillary electrophoresis (CE) with laser fluorometric detection is performed that combines the rapid and minimal sample consumption methods of CE with ...the selective separation influence of mobility shift assays. An inspection of the well characterized interaction between the
trp repressor of
Escherichia coli and the
trp operator (DNA) is the basis of the assay. The use of fluorescently tagged operator not only lends itself to laser-induced fluorescence detection but also the use of radiolabeled detection. It is demonstrated that composition and pH of the running buffer are critical for maximized efficiency and resolution of operator from the repressor-operator complex. Quantitative studies showed reaction of repressor with operator resulted in the diminishing of free operator signal and the simultaneous creation of the repressor-operator peak that is well resolved from the free operator. Also examined was the ability to perform qualitative studies involving non-specific interactions between the operator and a complex protein sample. It is shown that the specificity of operator for repressor can be used to selectively the repressor from a complex sample that includes non-specific proteins.
Purpose: To evaluate the efficacy of macular grid photocoagulation in preserving or improving central visual acuity in eyes with macular edema due to central vein occlusion (CVO) and best-corrected ...visual acuity of 20/50 or poorer.
Methods: Patients with angiographically documented macular edema due to CVO were entered into a multicenter randomized controlled clinical trial supported by the National Eye Institute. Eligibility was determined based on both clinical examination findings and photographic documentation evaluated at a photograph reading center. Eyes were assigned randomly to macular grid photocoagulation (77 eyes) or no treatment (78 eyes). Patients were followed every 4 months for 3 years or until the end of the study. The outcome measure was visual acuity.
Results: The study population consisted of 155 eyes in 155 patients. There was no difference between treated and untreated eyes in visual acuity at any point during the follow-up period. Initial median visual acuity was 20/160 in treated eyes and 20/ 125 in control eyes. Final median visual acuity was 20/200 in treated eyes and 20/160 in control eyes. However, treatment clearly reduced angiographic evidence of macular edema.
Conclusion: The results of this study do not support a recommendation for macular grid photocoagulation for the population meeting the Central Vein Occlusion Study macular edema group eligibility criteria.
We used a stepwise approach to identify, design, synthesize, and test new high atomic number particulate contrast agents that would be especially well suited for use with computed tomography (CT). ...Our goal was to produce extremely radiopaque compounds with highly selective biodistribution to the normal liver. In this way, dose requirements could be lessened and toxicity minimized. Suspensions of cerium, gadolinium, and dysprosium oxide particles and silver iodide colloid were tested and compared with standard agents. All four experimental agents were selectively concentrated in the reticuloendothelial systems of rats and rabbits. These compounds produced greater and longer opacification of normal livers and larger liver-to-tumor differences in rabbits with hepatic tumors than did equivalent amounts of standard, iodinated agents. Lesions as small as 5 mm were visible with CT. These experimental materials have favorable characteristics as hepatic contrast agents, but their toxicity and long term retention may limit clinical use.
Silver iodide colloid was used as a model of a particulate hepatic contrast agent for computed tomography (CT). Following intravenous administration to rabbits, approximately 90% of the injected dose ...was phagocytized by the liver's reticuloendothelial system, resulting in a four- to five-fold increase in the liver CT number. Suspensions of CeO2, Dy2O3, and Gd2O3 were prepared using stabilizers to prevent clumping. Particles of appropriate size for reticuloendothelial cell uptake were selected by centrifugation. Intravenous injections of the three suspensions increased the CT number of rabbit liver by approximately 30 Hounsfield units (HU: 1,000 scale) for each experimental contrast agent resulted in a minimum addition of 250 HU to the liver CT number. A linear relationship was found between the CT number and its contrast material concentration. This relationship was also tested in vitro by ashing samples of livers containing various amounts of contrast material. Standard curves of CT number versus contrast material concentration in the liver were plotted, which predicted the amount of liver enhancement obtained after contrast material injection. There may be a use for heavy metal-containing particulate materials as hepatic contrast agents, since they opacify the liver more selectively, to a higher degree, and for longer periods than the conventional biliary and urographic iodinated contrast materials.
