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Thesis (Ph.D.)--University of Central Florida, 2008. / Adviser: Stacey Tantleff Dunn. Includes bibliographical references (p. 122-137).

abstract: The unpleasant bitter taste found in many nutritious vegetables may deter their consumption. While bitterness suppression by prototypical tastants is well-studied in the chemical and pharmacological fields, mechanisms to reduce the bitterness of foods such as vegetables remain to be elucidated. Here tastants representing the taste primaries of salty and sweet were investigated as potential bitterness suppressors of three types of Brassicaceae vegetables. The secondary aim of these studies was to determine whether the bitter masking agents were differentially effective for bitter-sensitive and bitter-insensitive individuals. In all experiments, participants rated vegetables plain and with the addition of tastants. In Experiments 1-3, sucrose and NNS suppressed the bitterness of broccoli, Brussels sprouts, and cauliflower, whereas NaCl did not. Varying concentrations of NaCl and sucrose were introduced in Experiment 4 to assess the dose-dependency of the effects. While sucrose was a robust bitterness suppressor, NaCl suppressed bitterness only for participants who perceived the plain Brussels sprouts as highly bitter. Experiment 5, through the implementation of a rigorous control condition, determined that some but not all of this effect can be accounted for by regression to the mean. Individual variability in taste perception as determined by sampling of aqueous bitter, salty, and sweet solutions did not influence the degree of suppression by NaCl or sucrose. Consumption of vegetables is deterred by their bitter taste. Utilizing tastants to mask bitterness, a technique that preserves endogenous nutrients, can circumvent this issue. Sucrose is a robust bitter suppressor whereas the efficacy of NaCl is dependent upon bitterness perception of the plain vegetables. / Dissertation/Thesis / Doctoral Dissertation Psychology 2014

Abstract Spread spectrum communication systems may be affected by other types of signals called outliers. These coexisting signals are typically narrow (or concentrated) in the considered domain. This thesis considers two areas of outlier detection, namely the concentrated interference suppression (IS) and concentrated signal detection. The focus is on concentrated signal extraction using blind, iterative and low-complex consecutive mean excision (CME) -based algorithms that can be applied to both IS and detection. A summary of results obtained from studying the performance of the existing IS methods, namely the CME, the forward CME (FCME) and the transform selective IS algorithms (TSISA), is presented. Accurate threshold parameter values for the FCME algorithm are defined. These accurate values are able to control the false alarm rate. The signal detection capability of the CME algorithms is studied and analyzed. It is noticed that the CME algorithms are able to detect signals, but they are not able to estimate signal parameters such as the bandwidth. The presented generic shape-based analysis leads to the limits of detection in which the concentrated signals can be detected. These limits enable checking fast whether the signal is detectable or not without time consuming computer simulations. The performance of the TSISA method is evaluated. Simulation results demonstrate that the TSISA method is able to suppress several types of concentrated interfering signals with a reasonable computational complexity. Finally, new CME-based methods are proposed and evaluated. The proposed methods are the extended TSISA method for IS and the localization algorithm based on double-thresholding (LAD), LAD with normalized thresholds (LAD NT), LAD with adjacent cluster combining (LAD ACC) and two-dimensional (2-D) LAD methods for detection. The simulations indicate that the extended TSISA method has a good performance against several types of concentrated interfering signals. The narrowband signal detection capability of the LAD methods is studied. Numerical results show that the proposed LAD methods are able to detect and localize signals in their domain, and they are able to estimate the number of narrowband signals and their parameters, including, for example, bandwidths and signal-to-noise ratio (SNR) values. The simulations show that the LAD methods outperform the CME algorithms, and ACC and 2-D LAD methods outperform the original LAD method. The LAD methods are also proposed to be used for spectrum sensing purposes in cognitive radios.

Abstract The performance of conventional receivers for wireless communications may severely deteriorate in the presence of unaccounted interference. The effectiveness of methods for mitigating these effects greatly depends on the knowledge that is available about the interference and signal-of-interest (SOI), therefore making the design of robust receivers a great challenge. This thesis focuses on receiver structures for channel coded systems that exploit different levels of knowledge about the SOI and interference in an iterative fashion. This achieves both robustness and overall performance improvement compared to non-iterative receivers. Code division multiple access (CDMA) and spatial division multiple access (SDMA) systems are considered. The overlay of a turbo coded direct-sequence spread-spectrum (DS-SS) system and strong digitally modulated tone interference is studied. An iterative receiver, which is capable of blind cancellation of both wideband and narrowband interference is proposed based on the adaptive self-reconfigurable -filter scheme. Asymptotic performance analysis of the iterative receiver shows that significant iteration gains are possible if the signal-to-interference-plus-noise-ratio (SINR) is relatively large and the processing gain (PG) of the SOI is relatively small. Robust diversity detection in turbo-coded DS-SS system with statistically modeled interference is studied. A non-parametric type-based iterative receiver that estimates the probability density function (PDF) of interference-plus-noise is proposed. Its performance is shown to be rather robust to the number of interferers and their distances from the victim receiver and very similar to the performance of a clairvoyant receiver. Amazingly, this is achievable with no prior knowledge about the interference parameters. Furthermore, iteration gain is shown to significantly reduce the length of the pilot sequence needed for the PDF estimation. A family of iterative minimum-mean-squared-error (MMSE) and maximum-likelihood (ML) receivers for convolutionally and space-time coded SDMA systems is proposed. Joint iterative multiuser-detection (MUD), equalization and interference suppression are proposed to jointly combat co-channel interference (CCI), inter-symbol-interference (ISI) and unknown CCI (UCCI) in broadband single-carrier systems. It is shown that both in convolutional and space-time coded systems the ISI and CCI interference can be completely eliminated if UCCI is absent. This is achievable with a number of receive antennas equal to the number of users of interest and not to the total number of transmit antennas. In case UCCI is present, the effectiveness of CCI and ISI cancellation and UCCI suppression depends on the effective degrees of freedom of the receiver. Receiver robustness can be significantly preserved by using hybrid MMSE/ML detection for the signals of interest, or by using estimation of the PDF of the UCCI-plus-noise. A low complexity hybrid MMSE/ML iterative receiver for SDMA is proposed. It is shown that its performance is not significantly degraded compared to the optimal ML receiver. Its sensitivity to spatial correlation and a timing offset is assessed by using field measurement data. It was shown that the hybrid MMSE/ML receiver is robust against spatial correlation. The sensitivity to the timing offset is significantly reduced if the receiver performs UCCI suppression.

Background Since 2010, adult studies and clinical concerns about stavudine (d4T) toxicity had led to the phasing out of d4T from many antiretroviral treatment (ART) guidelines globally with substitution by abacavir. Recent studies, within Southern Africa, however have shown poorer virological suppression with abacavir (ABC) compared to d4T at their respective centres. Methods A retrospective study of HIV-positive children, who had been initiated on ART from 2005 to 2017, was conducted at an ART unit at New Somerset hospital, Western Cape, South Africa. Data was extracted from clinical notes and electronic medical records and virological suppression reviewed in those started on ABC and d4T based regimes. Results A total of 672 children were included in the study with a median age of 8.9 months (interquartile range (IQR) 4.1- 24.1 months) in the d4T based group and 11 months (IQR 3.5 - 29.9 months) in the ABC group. 64 of the 437 patients in the d4T containing group were transferred out, 15 reported to have died, and 49 were lost to follow up within the first 6months on treatment. Of the 181 ABC containing regimen group, 1 was transferred out to another care facility, 1 reported death within 6months of treatment and 2 children were lost to follow up. There was a noted increased risk of being virologically unsuppressed at 6months while taking ABC containing regimen compared to a d4T containing regimen. . The relative risk of being virologically unsuppressed at 6 months while taking abacavir/lopinavir (LPV/r) was 1.39 (95% confidence interval 1.03 to 1.88, p=0.04) compared to stavudine/LPV/r. The relative risk of being virologically unsuppressed at 6 months while taking abacavir/efavirenz (EFV) was 1.82 (95% confidence interval 0.98 to 3.37, p=0.054) compared to stavudine/EFV. Conclusion Our analysis again raises concerns about virological suppression in the abacavir era of paediatric ART, compared to the previous stavudine era, particularly in combination with LPV/r in the younger, more vulnerable children. Whether this is because of intrinsic properties of the different medications or is a marker of the evolving complexity of the South African ART rollout, may never be resolved. However, this is of concern as abacavir and LPV/r appear to be entrenched as first-line paediatric ART in a setting where attrition is high, many children are lost to follow up and virologic surveillance is not always optimal. Clinicians need to optimize retention strategies, especially of young infants, to ensure that children are retained in care, have viral load testing timeously, so that those virologically unsuppressed can be detected and treated early and appropriately.

This study assessed whether civil society organizations in Zimbabwe that have previously been suppressed by the state, currently experience any change in their relations with the state under the Mnangagwa Presidency. I adopted a case study approach to comparatively assess the experiences of two civil society organizations relations with the state over a two- year period. The two case studies are of the Zimbabwe Congress of Trade Unions (ZCTU) and the Amalgamated Rural Teachers Union of Zimbabwe (ARTUZ). Selected media sources, including the organizations' social media (i.e., Facebook, websites, and Twitter) and non-state news media, were used to obtain mainly qualitative data and basic numerical information. Gramsci's theory of hegemony and Foucault's concept of ‘panoptic surveillance' informed my analytical framework. The findings show that state suppression is at the core of the relations between state and civil society organizations that are critical of the state in Zimbabwe. The recurring forms of suppression include arrests, detention, assaults, abduction, torture, raids, theft, surveillance, judicial harassment, cyber-attacks/smear campaigns, travel bans, salary cessation and abuse. The findings suggest that ongoing state suppression is worse than during the latter part of Mugabe's Presidency. Selective suppression of targeted civil society organizations that are critical of the state also reflects diminishing democracy in Zimbabwe. This appears to be a general pattern in the region and one possible reason why bodies such as African Union and the Southern African Development Community are reluctant to discipline member states, including Zimbabwe, for human rights violations or state repression of critics.

Behavioral contrast has been interpreted as a function of either (1) the reduction of frequency of reinforcement in one component of a multiple schedule or (2) the suppression of responses in one component regardless of reinforcement frequency. These explanations are discussed in terms of their adequacy in accounting for several recent experimental results. Two alternative explanations are considered. First, contrast is interpreted as a function of the relative summation of excitatory and inhibitory effects of stimuli. Second, contrast is discussed as a possible function of a switch from a response-reinforcer contingency to a stimulus-reinforcer contingency as seen in auto-pecking. Both avenues are considered promising in terms of accounting for behavioral contrast.

Cover crops play a part in improving sustainability by reducing negative environmental impacts such as soil erosion and nutrient runoff. Energycane could benefit from cover crops due to its row spacing. This study was conducted at the Bearden Dairy Research Center to determine differences in nitrogen accumulation, weed suppression, and energycane yield among treatments. Four cool-season species (planted in the fall of 2020 and 2021) [balansa clover (Trifolium michelianum), hairy vetch (Vicia villosa), white clover (T. repens) and winter pea (Pisum sativum subsp. arvense)], and four warm-season species (planted in the spring of 2021 and 2022 [alfalfa (Medicago sativa), alyceclover (Alysicarpus vaginalis), soybean (Glycine max), and sunnhemp (Crotalaria juncea)] plus negative and positive controls (0 and 168 kg N ha-1) were used. Regarding cool-season cover crops, significant differences were seen in all previously mentioned metrics. Warm-season cover crops only showed differences regarding nitrogen accumulation and weed suppression abilities.

In the absence of canopy-opening disturbances, upland oak forests in the eastern United States are shifting to shade-tolerant, fire-sensitive tree species (i.e. mesophytes) via a hypothesized positive feedback loop of less flammable, self-promoting conditions, termed mesophication. To evaluate species-specific impacts on mesophication, I quantified canopy, bark, and leaf litter traits of five hypothesized mesophytes [red maple (Acer rubrum), sugar maple (A. saccharum), American beech (Fagus grandifolia), hickory (Carya spp.), and tulip poplar (Liriodendron tulipifera)] and four upland oaks [black oak (Quercus velutina), chestnut oak (Q. montana), scarlet oak (Q. coccinea), and white oak (Q. alba)] in central Kentucky. Red maple, sugar maple, and American beech had increased canopy depth with stem size, smoother bark, and small, thin leaves when compared to oaks. My findings suggest that some mesophytes, such as red maple, sugar maple, and American beech, may decrease future forest flammability by reducing understory light and increasing fuel moisture.