Diatoms are estimated to contribute 25 percent of the primary production on Earth and therefore they play a significant role in the global carbon cycle. Diatom blooms often terminate with the formation of aggregates that sink rapidly from surface waters, affecting the flux of organic carbon from the surface to deep waters and the sea floor. The role of carbon-rich transparent exopolymeric particles (TEP) in aggregate formation as ocean temperature increases has yet to investigated in continuous cultures. I hypothesize that temperature increase can influence the production of TEP, a fraction of total suspended exopolymers. To test the hypothesis, a laser in situ scattering and transmissometry instrument (LISST-100X, Sequoia Instruments) successfully counted and sized six individual diatom species in batch culture: Chaetoceros muelleri, Coscinodiscus wailesii, Thalassiosira weissflogii, Phaeodactylum tricornutum, Skeletonema costatum, and Skeletonema marinoi and successfully demonstrated its efficacy in detecting diatom aggregates using S. costatum. Four replicate continuous cultures were sampled for particle size distribution (PSD), nutrients, chlorophyll a, total carbohydrates, prokaryote concentration, and TEP at temperatures of 22.5, 27 and then 20 degrees C. While TEP particles were scarce, acid polysaccharide (APS)-coated C. muelleri cells were observed, forming dense webs on the filters. Both carbohydrate per cell and APS area per cell were found to significantly correlate with temperature (p<0.05) while significant difference between APS concentration at each temperature was only found between 27 and 22.5 or 20 degrees C (p<0.05). Net changes in PSDs with increasing temperature showed that distributions of relative volume concentration decreased in the smallest size bins and increased in the largest size bins. Our results show that increasing the temperatures of nitrogen-limited C. muelleri cultures did not cause increased TEP formation but instead resulted in increased cell-surface coating. Increasing concentration of cell coatings and TEP particles will cause diatoms to aggregate more readily, enhancing their sinking rate away from the ocean surface. Increased ocean temperature has great implications for diatom blooms and other microorganisms, causing greater export of carbon out of the surface waters and potentially altering the microbial loop.

Data warehouses contain data consolidated from several operational databases and provide the historical, and summarized data which is more appropriate for analysis than detail, individual records. On-Line Analytical Processing (OLAP) provides advanced analysis tools to extract information from data stored in a Data Warehouse. OLAP is designed to provide aggregate information that can be used to analyze the contents of databases and data warehouses. A range query applies an aggregation operation over all selected cells of an OLAP data cube where the selection is specified by providing ranges of values for numeric dimensions. Range sum queries are very useful in finding trends and in discovering relationships between attributes in the database. There is a method, prefix sum method, promises that any range sum query on a data cube can be answered in constant time by precomputing some auxiliary information. However, it is hampered by its update cost. For today's applications, interactive data analysis applications which provide current or "near current" information will require fast response time and have reasonable update time. Since the size of a data cube is exponential in the number of its dimensions, rebuilding the entire data cube can be very costly and is not realistic. To cope with this dynamic data cube problem, several strategies have been proposed. They all use specific data structures, which require extra storage cost, to response range sum query fast. For example, the double relative prefix sum method makes use of three components: a block prefix array, a relative overlay array and a relative prefix array to store auxiliary information. Although the double relative prefix sum method improves the update cost, it increases the query time. In the thesis, we present a method, called the recursive relative prefix sum method, which tries to provide a compromise between query and update cost. In the recursive relative prefix sum method with k levels, we use a relative prefix array and k relative overlay arrays. From our performance study, we show that the update cost of our method is always less than that of the prefix sum method. In most of cases, the update cost of our method is less than that of the relative prefix sum method. Moreover, in most of cases, the query cost of our method is less than that of the double relative prefix sum method. Compared with the dynamic data cube method, our method has lower storage cost and shorter query time. Consequently, our recursive relative prefix sum method has a reasonable response time for ad hoc range queries on the data cube, while at the same time, greatly reduces the update cost. In some applications, however, updating in some regions may happen more frequently than others. We also provide a solution, called the weighted relative prefix sum} method, for this situation. Therefore, this method can also provide a compromise between the range sum query cost and the update cost, when the update probabilities of different regions are considered.

The aggregation-attachment-pheromone (AAP) of two geographic strains of the Gulf Coast tick, Amblyomma maculatum Koch, was investigated to evaluate practicality of using solid-phase-microextraction (SPME) in an AAP study of Gulf Coast tick. Solid-phase microextraction was used to compare the AAP production in two strains of fed male Gulf Coast tick and demonstrate and confirm the presence of AAP in bioassays. A solid-phase-microextraction (SPME) headspace collection technique was sufficient to capture volatile organic compounds produced by fed and unfed male Gulf Coast ticks. Gas chromatography analysis revealed three major volatile organic compounds were produced in significantly greater amounts (p < 0.05) by fed males than those produced by unfed males. These volatile compounds were produced in significantly higher amount by the third day of feeding by male ticks. However, two of these volatiles remained relatively constant in their production while the primary volatile compound increased in its production until the eighth day of feeding by male Gulf Coast ticks. Also, the relative abundances of these three volatile organic compounds were different between Oklahoma and Texas strains of Gulf Coast ticks. The activity of AAP from fed male Gulf Coast ticks was confirmed using two bioassay techniques. A petri dish bioassay revealed significantly higher numbers of female Gulf Coast ticks attracted to fed-males which also produced significantly greater amounts (p < 0.001) of volatile organic compounds detected by GC analysis. The Ytube olfactometer bioassay revealed that significantly higher numbers of females responded to fed-males or to CO2 when compared to purified air (p < 0.001), but the differences in female response to fed-males and CO2 were not significant (p < 0.391 in Oklahoma strain and p < 0.458 in Texas strain). However, female responses to stimuli containing both fed-males and CO2 were significantly higher when compared to either stimulus alone (p < 0.001).

Alzheimer’s disease (AD) is a neurodegenerative disorder that is one of such diseases associated with protein aggregation. A&#946; is the main protein component of senile plaques in AD, and is neurotoxic when aggregated. In particular, soluble oligomeric forms of A&#946; are closely related to neurotoxicity. In this dissertation, we examine the differences in A&#946; aggregation intermediates, and final structures formed when only a simple modification in A&#946; aggregation conditions is made, the presence or absence of mixing during aggregation. We show that intermediates in the aggregation pathway show significantly different structural rearrangements. The protein stabilities of &#913;&#946; species show that spherical aggregates corresponding to the most toxic &#913;&#946; species change their structure the most rapidly in denaturant, and that in general, increased toxicity correlated with decreased aggregate stability. In Alzheimer’s disease, even delaying A&#946; aggregation onset or slowing its progression might be therapeutically useful, as disease onset is late in life. Small heat shock proteins (sHsps) may be useful for prevention of &#913;&#946; aggregation, since sHsps can interact with partly folded intermediate states of proteins to prevent incorrect folding and aggregation. In this research, several small heat shock proteins (sHsps) are tested to prevent A&#946; aggregation and toxicity. sHsps used in this research are Hsp17.7, Hsp27, and Hsp20. All types of Hsp20, Hsp20-MBP, His-Hsp20 and His-Hsp20 without 11 residues in C-terminus, can prevent A&#946;1-40 aggregation. Hsp20 also prevents A&#946; toxicity in the same concentration ranges of it aggregation prevention activity. Hsp17.7 and Hsp27, however, can inhibit &#913;&#946;1-40 aggregation but not toxicity. A number of experiments to examine the mechanism of Hsp20 suggest that multivalent binding of sHsp to A&#946; is necessary for the toxicity prevention activity. Conclusively, different A&#946; incubation conditions in vitro can affect the rate of A&#946; fibril formation, the morphology, the toxicity and the conformation of intermediates in the aggregation pathway. Hsp20 rather than other sHsps may be a useful molecular model for the drug design of the next generation of A&#946; aggregation inhibitors to be used in the treatment of AD.

The emerging popularity and interest in Voice-over-IP (VoIP) has been accompanied by customer concerns about voice quality over these networks. The lack of an appropriate real-time capable infrastructure in packet networks along with the threats of denial-of service (DoS) attacks can deteriorate the service that these voice calls receive. And these conditions contribute to the decline in call quality in VoIP applications; therefore, error-correcting/concealing techniques remain the only alternative to provide a reasonable protection for VoIP calls against packet losses. Traditionally, each voice call employs its own end-to-end forward-error-correction (FEC) mechanisms. In this paper, we show that when VoIP calls are aggregated over a provider's link, with a suitable linear-time encoding for the aggregated voice traffic, considerable quality improvement can be achieved with little redundancy. We show that it is possible to achieve rates closer to channel capacity as more calls are combined with very small output loss rates even in the presence of significant packet loss rates in the network. The advantages of the proposed scheme far exceed similar or other coding techniques applied to individual voice calls.

Marine aggregates are an important means of carbon transfers downwards to the deep ocean as well as an important nutritional source for benthic organism communities that are the ultimate recipients of the flux. During these last 10 years, data on size distribution of particulate matter have been collected in different oceanic provinces using an Underwater Video Profiler. The cruise data include simultaneous analyses of particle size distributions as well as additional physical and biological measurements of water properties through the water column. First, size distributions of large aggregates have been compared to simultaneous measurements of particle flux observed in sediment traps. We related sediment trap compositional data to particle size (d) distributions to estimate their vertical fluxes (F) using simple power relationships (F=Ad^b). The spatial resolution of sedimentation processes allowed by the use of in situ particle sizing instruments lead to a more detailed study of the role of physical processes in vertical flux. Second, evolution of the aggregate size distributions with depth was related to overlying primary production and phytoplankton size-distributions on a global scale. A new clustering technique was developed to partition the profiles of aggregate size distributions. Six clusters were isolated. Profiles with a high proportion of large aggregates were found in high-productivity waters while profiles with a high proportion of small aggregates were located in low-productivity waters. The aggregate size and mass flux in the mesopelagic layer were correlated to the nature of primary producers (micro-, nano-, picophytoplankton fractions) and to the amount of integrated chlorophyll a in the euphotic layer using a multiple regression technique on principal components. Finally, a mesoscale area in the North Atlantic Ocean was studied to emphasize the importance of the physical structure of the water column on the horizontal and vertical distribution of particulate matter. The seasonal change in the abundance of aggregates in the upper 1000 m was consistent with changes in the composition and intensity of the particulate flux recorded in sediment traps. In an area dominated by eddies, surface accumulation of aggregates and export down to 1000 m occured at mesoscale distances (<100 km).

New technologies are expected to play a major role for wireless cellular systems beyond the existing 4G paradigm. The need for several orders of magnitude increase in system capacity has led to the proliferation of low-powered cellular layers overlaid on the existing macrocell layer. This type of network consisting of different cellular layers, each with their unique characteristics including transmission power and frequency of operation among others is termed as a heterogeneous network (HetNet). The emergence of HetNets leads to several research challenges and calls for a profound rethinking of several existing approaches for mobility management and interference management among other issues.

The accumulation of the microtubule associated protein tau has been implicated in several neurological disorders; however, its interaction with chaperones along its normal degradation pathway remains largely uncharacterized at single residue resolution. In this study, nuclear magnetic resonance (NMR) spectroscopy was used to probe the interaction between tau, the molecular chaperone Hsp90, and the immunophilin FKBP51. Resonance intensity changes were observed for specific residues in the heteronuclear single quantum coherence (HSQC) spectra of 15N-labeled tau in the presence of Hsp90 and/or FKBP51. Analysis of the HSQC spectra identified the two hydrophobic hexapeptide motifs located at residues V275 - K280 and V306 - K311 in tau's C-terminal assembly domain as the sites of an interaction with both Hsp90 and FKBP51. Resonances that show reduced intensities did not experience line broadening, which suggests that slow chemical exchange is occurring with a bound conformation that is not observable due to the molecular weight of the complex. We have also investigated the role of the PPIase domain alone in binding to tau and found that specific residues within the PPIase active site experience significant reductions in intensity upon addition of tau. The experimental data is collectively used to propose a structural model for ternary complex formation between tau, Hsp90, and FKBP51.

It has been theorized that most proteins are under selection pressure to be soluble in crowded cellular spaces. To maintain solubility a proteins’ aggregation propensity should be inversely proportional to their maximum likely concentration. This theory was examined by comparing the proteome of the model organism S. cerevisiae, which has previously undergone a Whole Genome Duplication (WGD) event to the proteome of the closely related yeast K. waltii, which has not undergone WGD. This comparison revealed the following: 1) Predicted aggregation propensities are higher in S. cerevisiae than K. waltii. 2) Aggregation propensity does not predict which genes reverted to a single copy after WGD. 3) In genes which were retained as duplicates in S. cerevisiae after WGD, aggregation propensities rose from the inferred common ancestral protein. 4) Genes retained as duplicates showed less of an increase relative to their homologues in K. waltii than genes which were not retained as duplicates. 5) The relationship between the log predicted aggregation propensity and log mRNA expression level or log protein abundance was not linear as previously predicted. These results suggest that while there is broad selection pressure for reduced aggregation pressure for genes which have been duplicated, the precise relationship between aggregation propensity and gene expression is more complicated than previously predicted. These results also allow speculation that the whole genome duplication in S.cerevisiae may have been made possible by a general relaxation of aggregation-related selection pressure. / text

How to properly aggregate indirect information is more and more important. In this dissertation, we will present two aspects of the issue: indirect comparison of treatment effects and aggregation of ordered-based rank data. / Statistics