On the Window Size for Classification in Changing Environments

Classification in changing environments (commonly known as concept drift) requires adaptation of the classifier to accommodate the changes. One approach is to keep a moving window on the streaming data and constantly update the classifier on it. Here we consider an abrupt change scenario where one set of probability distributions of the classes is instantly replaced with another. For a fixed ‘transition period’ around the change, we derive a generic relationship between the size of the moving window and the classification error rate. We derive expressions for the error in the transition period and for the optimal window size for the case of two Gaussian classes where the concept change is a geometrical displacement of the whole class configuration in the space. A simple window resize strategy based on the derived relationship is proposed and compared with fixed-size windows on a real benchmark data set data set (Electricity Market)

Activation of KCNQ1 expression in HEK293 cells using inducible CRISPR-dCas9-VPR tripartite transcriptional activator domain

Mutations in the KCNQ1 gene have been implicated in the onset of hypopituitarism. Regulating KCNQ1 expression would therefore enable future clinical research on the mechanism of the disease. CRISPR offers a flexible toolset for controlling genetic expression via knockout, knock-in, knockdown, and gene activation. Of these approaches, CRISPR activation (CRISPRa) is distinguished by its ability to induce gene overexpression in a cell’s native context, making it a valuable tool in the interrogation of genetic disorder pathogenesis. This thesis therefore tested the efficacy of a CRISPRa subsystem in increasing KCNQ1 expression. The CRISPRa subsystem, VPR, was chosen because of its high activation efficiency and the ease of controlling the activation system of its doxycycline-inducible mode of action. The cell line used for the experiment, HEK293, was similarly chosen because of its ease of culture and transfection. To validate the proper functioning of the activation system, expression rates of the related genes ASCL1 and GHRH were measured as positive controls. The activation system successfully upregulated the expression rates of the two genes. As the dCas9-VPR system is dependent on the Tet-ON operator for inducing activation in a controllable manner, a test for dCas9 leakage was conducted. RT-qPCR analysis showed the upregulation of ASCL1 expression in the uninduced state of the system, confirming the presence of dCas9-VPR leakage. The dCas9-VPR system finally aimed to test the expression rate of KCNQ1. Although one novel guide RNA successfully upregulated KCNQ1 expression, it did so inefficiently and its success was not shared by any of the other tested guide RNAs. Altogether, the dCas9-VPR system was successfully established in HEK293 cells, and the leakage of the inducible system was confirmed, however, KCNQ1 activation by CRISPRa requires further optimization

EPITHERMAL GOLD MINERALIZATION IN THE KRASSEN DEPOSIT, PANAGYURISHTE ORE DISTRICT, BULGARIA

Gold mineralization in the Krassen high-sulphidation epithermal deposit, Panagyurishte ore district, Bulgaria, has been studied in respect to mineral assemblages, gold grain size, fineness and trace elements based on EPMA and LA-ICP-MS studies. Part of the gold in the early massive pyrite dominated ores is submicroscopic in size (< 0.1 µm) and could be attached to the so called “invisible” gold. Later fracturing of the early massive pyrite, followed the deposition of Cu-pyrite ore bodies enriched in chalcopyrite, enargite, bornite, galena and sphalerite accompanied by deformation and recrystallization is suggested as a reason for Au and Ag migration to cracks and gold grains coarsening. The electrum fineness in individual grains varies between 882 and 998 ‰. Most commonly observed trace elements in the native gold, electrum grains and gold hosting sulphide minerals are: Cu, Fe, Hg, Sb, Te, Bi, As and Se. The Au content in pyrite varies from 0.35 to 7.83 ppm and in chalcopyrite from 0.97 to 2.78 ppm. BiTe-Se and Ga-Ge-In trace elements signature is characteristic feature of the ore minerals and indicator for Au enrichment