Marine deoxygenated areas are expanding, and more hypoxic zones emerge globally. Climate change induced warming and stratification can extrapolate the biological oxygen demand, more predominantly at coastal areas and reefs with dense vegetation and high metabolic activity. The diurnal oxygen fluctuation can reach a critically low oxygen level at nighttime, exposing aquatic organisms to severe hypoxia that could interfere with viable ecosystem functions. Little is known about the impact of hypoxia on marine primary producers macroalgae, mainly the physiological adaptation of the Red Sea macroalgae under climate change scenarios is understudied. Here we investigate hypoxia thresholds at night time for conspicuous Red Sea macroalgae species calcareous Halimeda opuntia and Padina boryana and noncalcifying brown algae Sargassum latifolium. We utilized a computer-based gas system to expose the samples to different oxygen treatments (normoxia, hypoxia, and severe hypoxia) that mimic in situ water chemistry at 32 °C. We monitored algal physiological response during 12 hours of exposure to different oxygen levels in the dark by measuring photochemical efficiency, respiration rates, and cellular viability. For the duration of our experiments (12h), we did not detect lethal thresholds. In all tested species, severe hypoxia significantly decreased photochemical efficiency, and hypoxia had a limited impact on photochemical efficiency. However, both low oxygen treatments significantly decreased respiration rates and induced changes in cellular activity. We concluded a sublethal O$_2$ thresholds SLC$_{(50)}$ of 1.2 ±0.1, 1.5 ±0.1, and 1.7 ±0.1 mg O$_2$ L$^{−1}$ ±SD for H. opuntia, P. boryana, and S. latifolium responses, respectively. We also found that during 12 hours of treatments, the median time to observe a 50% reduction in photochemical efficiency under severe hypoxia treatment relative to control was 6.3 ±1.4, 3.5 ±1.0, and 0.8 ±1.3 hours ±SD for H. opuntia, P. boryana, and S. latifolium responses, respectively. This study is the first assessment of Red Sea macroalgae response to hypoxia and the first dark nighttime algal adaptation of its kind for our proposed species. Further investigation is needed to assess daytime recovery, recurring dark hypoxia, and synergic or sequential effects of other environmental stressors on hypoxia thresholds.

Mountains play an important role in providing water resources from snow and ice to downstream urban population centers. In Utah, USA, nearly 86% of the state's population resides in the rapidly growing urban corridor along the Wasatch Front. Water along the Wasatch Front is stored in several deep reservoirs in the Provo River Watershed. Additions of nutrients, into these reservoirs, may stimulate the growth of primary producers (e.g., total phytoplankton and cyanobacteria) potentially attenuating water quality. To determine the influence of nutrients on primary producers in the Provo River's reservoirs, identify whether cyanobacteria are transported downstream, and quantify nutrient thresholds that regulate phytoplankton responses, we monitored and experimentally manipulated total phytoplankton and cyanobacteria in rivers and reservoirs. We found that total phytoplankton biomass (measured as chlorophyll a concentrations) was correlated with the total phosphorus (TP) in the Jordanelle Reservoir and the outflow from the Jordanelle Reservoir. Cyanobacteria biomass (measured as phycocyanin concentration) was correlated with dissolved inorganic N (DIN):SRP in the Deer Creek Reservoir and river sites below the Deer Creek Reservoir. Based on next generation sequencing 16S rDNA of all waters evaluated, the relative abundance of cyanobacteria within bacterial communities was extremely low, with the highest relative abundance of cyanobacteria present in the reservoirs being 10.7% for Deer Creek and 5.5% in Jordanelle during the late summer. Of the 25 genera of cyanobacteria that were found across all waters, five species have the ability to produce cyanotoxin: Microcystaceae; Aphanizomenon MDT14a; Aphanizominon NIES81; and Planktothrix NIVA-CYA. Season determined bacterial community composition in the river and reservoir over the almost two years of sampling with bacterial communities being distinct between the limnetic location in Deer Creek Reservoir to the outflow into the river immediately below the dam. We found no difference between the bacterial communities in the limnetic zone in Jordanelle and the river site directly below Jordanelle Dam. In the nutrient starvation bioassays, cyanobacteria and total phytoplankton responded to the nutrient additions, but there were no specific nutrient thresholds where pigment concentrations leveled out even as nutrient concentration increased. However, when P was added as SRP treatments both total phytoplankton and cyanobacteria concentrations increased, especially in the highest SRP treatment (0.08 mg/L) without any N addition. The addition of N alone did not influence total phytoplankton until there was at least 0.2 mg/L of P added. Further, cyanobacteria required at least 0.2 mg/L of SRP before responding to N levels above 0.8 mg/L. Thus, a nutrient threshold to maintain the reservoir at its current state would be 0.2 mg/L P and between 0.3 and 0.8 mg/L DIN. Our results identify that the water within the reservoirs and rivers are extremely clean and is in no immediate risk of extensive total phytoplankton or cyanobacterial blooms with P being the dominant driver of primary producer activity.

No description available.

Full motion simulators are traditionally used in the flight industry to train pilots. They are used to add the sensation of acceleration in simulation to make it more "realistic". Clearly the motion envelop of the simulator is limited by physical constraints so the motion platform has to be stopped and returned to the center position after an acceleration cue, called washout. A key question is: which acceleration can a subject feel and which not, called the acceleration threshold. We are also interested in strength of accelerations for which a subject can detect the direction. Literature gives several results, but we found that some of these values seemed very low to us and the experiments were conducted on very specific groups of people like pilots, A.J.Benson and H.Vogel (1986), Schroeder (1999). Furthermore, we are simulating moving vehicles like a car or an air plane and are interested in the acceleration ranges in a noisy environment. Noisy, the noise is a result from the vibration of engines, rough roads and disturbances that are Gaussian. This thesis gives a literature review, implement the cueing procedure to make motion and vibration to do different experiment and analyze the results. / Thesis / Master of Computer Science (MCS)

No description available.

Integrating water-saving technologies with optimized nutrient management strategies provides opportunities for sustainable agriculture in the Mississippi Delta. Three studies were conducted to determine the effects of irrigation systems, row patterns, and nutrient management strategies on corn and soybeans. The first study determined the effects of irrigation, row pattern, and nitrogen (N) placement methods on corn (Zea mays L.) productivity and N use efficiency. The effects of N placement methods were only evident in 2021 when the rainfall events were more pronounced than in 2020. Regardless of the row pattern, placing N with one knife increased corn grain yield and the agronomic N use efficiency by 14.1% and 16.8%, respectively, when compared to the surface dribble method. The second study investigated the effects of irrigation systems and row patterns on grain yield, grain quality parameters, and irrigation water use efficiency (IWUE) on soybeans (Glycine max L.) grown on Sharkey clay. When irrigation was triggered at -80 kPa, furrow-irrigated soybeans produced 3.9% more grain yield compared to sprinkler-irrigated soybeans. The total amount of water applied by the sprinkler irrigation system represented 19-52% of the total amount applied by the furrow system. Narrow-row patterns achieved greater IWUE than single-row patterns. In the third study, we evaluated the effects of N and irrigation levels on grain quantity, quality, and plant growth on corn grown across different soil electrical conductivity (EC) levels and its implications for variable rate technology. Corn grain yields increased with the increase of N and irrigation levels but decreased as soil EC decreased. Overall, maintaining a sprinkler irrigation threshold between -40 and -70 kPa optimized corn yield. In addition, these results did not provide enough evidence to use variable rate irrigation or variable rate N application in the Mississippi Delta.

Yes / This paper presents a new analytical framework for the congestion control of Internet traffic using a queue threshold scheme. This framework includes two discrete-time analytical models for the performance evaluation of a threshold based congestion control mechanism and compares performance measurements through typical numerical results. To satisfy the low delay along with high throughput, model-I incorporates one threshold to make the arrival process step reduce from arrival rate ¿1 directly to ¿2 once the number of packets in the system has reached the threshold value L1. The source operates normally, otherwise. Model-II incorporates two thresholds to make the arrival rate linearly reduce from ¿1 to ¿2 with system contents when the number of packets in the system is between two thresholds L1 and L2. The source operates normally with arrival rate ¿1 before threshold L1, and with arrival rate ¿2 after the threshold L2. In both performance models, the mean packet delay W, probability of packet loss PL and throughput S have been found as functions of the thresholds and maximum drop probability. The performance comparison results for the two models have also been made through typical numerical results. The results clearly demonstrate how different load settings can provide different tradeoffs between throughput, loss probability and delay to suit different service requirements.

Estudamos a série de Mayer de um gás de Yukawa em duas dimensões. Introduzimos brevemente a noção de série de Mayer de um gás não-ideal através do uso de expansões em clusters e apresentamos motivações pelas quais o seu uso pode apresentar dificuldades. Introduzimos um formalismo algébrico que servirá de ferramenta alternativa para o estudo da convergência dessa série através do método dos majorantes via equações diferenciais parciais. Uma vez que o gás de Yukawa não é regular na origem, é preciso regulariza-lo para utilizar o método dos majorantes. Acredita-se que esta série (não regularizada) apresenta divergência do coeficiente de ordem 2k no regime de temperatura (recíproca) > k:= 8(2k-1)/2k por conta do colapso dos multipolos neutros contido nos clusters dessa ordem, e que neste regime, a retirada desses termos é suficiente para garantir a convergência da série remanescente. Por fim, estudamos a convergência da série de Mayer para um gás de Yukawa bidimensional quando a regularizacão é removida no intervalo < 16/3 e apresentamos uma extensão desse resultado para o regime < 6. Mostramos que haverá de fato divergência do coeficiente de ordem 2 da série, que pode ser regularizado enquanto < 6, garantindo a convergência da série com termo 2 omitido. / We study the Mayer series for the bidimensional Yukawa gas. We briefly introduce the notion of a Mayer series of a non-ideal gas using cluster expansions and present some motivations on the dificulties this formalism may present. An algebraic formalism is introduced in order to develop an alternative tool to study this series using a majorant method via partial diferential equations. As the Yukawa gas is not regular at the origin, it should be regularized for the majorant method to be applicable. It is believed that the non-regularized Yukawa series presents divergence on its coeficients of order 2k when the inverse temperature > k := 8(2k - 1)/2k due to the collapse of neutral multipoles belonging to clusters of this order and if we omit these coficients, the convergence is obtained. Finally we study the convergence of the Mayer series of a bidimensional Yukawa gas when the regularization is removed when < 16/3 and we extend these results to < 6. Its is shown explicitly that the coeficient of order 2 diverges but can be regularized if < 6, assuring the convergence of the remaining series when the coeficient of order 2 is omitted.

Estudamos a série de Mayer de um gás de Yukawa em duas dimensões. Introduzimos brevemente a noção de série de Mayer de um gás não-ideal através do uso de expansões em clusters e apresentamos motivações pelas quais o seu uso pode apresentar dificuldades. Introduzimos um formalismo algébrico que servirá de ferramenta alternativa para o estudo da convergência dessa série através do método dos majorantes via equações diferenciais parciais. Uma vez que o gás de Yukawa não é regular na origem, é preciso regulariza-lo para utilizar o método dos majorantes. Acredita-se que esta série (não regularizada) apresenta divergência do coeficiente de ordem 2k no regime de temperatura (recíproca) > k:= 8(2k-1)/2k por conta do colapso dos multipolos neutros contido nos clusters dessa ordem, e que neste regime, a retirada desses termos é suficiente para garantir a convergência da série remanescente. Por fim, estudamos a convergência da série de Mayer para um gás de Yukawa bidimensional quando a regularizacão é removida no intervalo < 16/3 e apresentamos uma extensão desse resultado para o regime < 6. Mostramos que haverá de fato divergência do coeficiente de ordem 2 da série, que pode ser regularizado enquanto < 6, garantindo a convergência da série com termo 2 omitido. / We study the Mayer series for the bidimensional Yukawa gas. We briefly introduce the notion of a Mayer series of a non-ideal gas using cluster expansions and present some motivations on the dificulties this formalism may present. An algebraic formalism is introduced in order to develop an alternative tool to study this series using a majorant method via partial diferential equations. As the Yukawa gas is not regular at the origin, it should be regularized for the majorant method to be applicable. It is believed that the non-regularized Yukawa series presents divergence on its coeficients of order 2k when the inverse temperature > k := 8(2k - 1)/2k due to the collapse of neutral multipoles belonging to clusters of this order and if we omit these coficients, the convergence is obtained. Finally we study the convergence of the Mayer series of a bidimensional Yukawa gas when the regularization is removed when < 16/3 and we extend these results to < 6. Its is shown explicitly that the coeficient of order 2 diverges but can be regularized if < 6, assuring the convergence of the remaining series when the coeficient of order 2 is omitted.

There has always been a need for objective tests that assess auditory function in infants, young children, and/or any patient whose development level precludes the use of behavioral audiometric techniques. Although the Auditory Brainstem Response (ABR) is seen as the ‘gold standard’ in the field of objective audiometry, it presents with its own set of limitations. The Auditory Steady State Response (ASSR) has gained considerable attention and is seen as a promising addition to the AEP ‘family’ to address some of the limitations of the ABR. The ASSR promises to estimate all categories of hearing loss (mild to profound) in a frequency specific manner. It also indicates to the possibility to validate hearing aid fittings by determining functional gain of hearing aids by determining unaided and aided ASSR thresholds. An exploratory research design was selected in order to compare unaided thresholds, obtained through the use of three different procedures – ABR, ASSR and behavioral thresholds. Aided thresholds were also obtained and compared with two procedures – the aided ASSR (measured and predicted) and aided behavioral threshold. The results indicated that both the ABR (tone burst and click) and ASSR provided a reasonable estimation of the subsequently obtained behavioral audiograms. The ASSR, however, approximated the behavioral thresholds closer than the ABR and were furthermore able to quantify hearing thresholds accurately for subjects with severe and profound hearing losses. The result indicated further that the ASSR can be instrumental in the validation process of hearing aid fittings in infants. These results demonstrated however, that the ASSR measured thresholds underestimate the aided behavioral thresholds and the aided ASSR predicted thresholds overestimate the aided behavioral thresholds. The research concluded that the ASSR is useful in estimating frequency-specific behavioral thresholds accurately in infants and validating hearing aid fittings. Until evidence is sufficient to recommend the ASSR as primary electrophysiological measure of hearing in infants, the ASSR should be used in conjunction with the ABR – following a test battery approach in the diagnostic process of hearing loss in infants. The ASSR further shows great promise in validating hearing aid fittings, but this specific application of the ASSR needs further research evidence on large groups to validate the procedure. / Dissertation (Master of Communication Pathology)--University of Pretoria, 2007. / Speech-Language Pathology and Audiology / unrestricted