Factors Influencing Water Extractable Phosphorus Reduction in Poultry Litter by Chitosan Treatment

Phosphorus is known to be a chief factor in the eutrophication of freshwaters. Phosphorus in land applied poultry litter can runoff and pollute these freshwaters. Chitosan, the deacetylated form of the biopolymer chitin, has been shown to have an effect on reducing water extractable phosphorus (WEP) in poultry litter when applied as a powder. The intent of this study was to measure the effect that acetic acid and incubation time have on chitosan’s ability to reduce WEP in poultry litter. The results were that the presence of poultry litter treatment (PLT) in the litter inhibits chitosan’s ability reduce WEP. Chitosan dissolved in acetic acid does not decrease WEP after any amount of incubation time. Chitosan in a powder form reaches its full effectiveness after three weeks of incubation

Beaver Lake Numeric Chlorophyll-a and Secchi Transparency Standards, Phases II and III: Uncertainty and Trend Analysis

The objective of Phases II and III of this study were to 1) assess the variation in chl‐a and ST across multiple spatial and temporal scales in Beaver Lake in order to validate the assessment method, and 2) quantify trends in chl‐a, ST, and nutrient (total phosphorus and total nitrogen) concentrations in Beaver Lake and the major inflowing rivers to verify any potential water quality impairment

Engineering stochasticity in gene expression

Stochastic fluctuations (noise) in gene expression can cause members of otherwise genetically identical populations to display drastically different phenotypes. An understanding of the sources of noise and the strategies cells employ to function reliably despite noise is proving to be increasingly important in describing the behavior of natural organisms and will be essential for the engineering of synthetic biological systems. Here we describe the design of synthetic constructs, termed ribosome competing RNAs (rcRNAs), as a means to rationally perturb noise in cellular gene expression. We find that noise in gene expression increases in a manner proportional to the ability of an rcRNA to compete for the cellular ribosome pool. We then demonstrate that operons significantly buffer noise between coexpressed genes in a natural cellular background and can even reduce the level of rcRNA enhanced noise. These results demonstrate that synthetic genetic constructs can significantly affect the noise profile of a living cell and, importantly, that operons are a facile genetic strategy for buffering against noise

Advanced Materials for Energy Conversion and Storage: Low-Temperature, Solid-State Conversion Reactions of Cuprous Sulfide and the Stabilization and Application of Titanium Disilicide as a Lithium-Ion Battery Anode Material

Thesis advisor: Dunwei WangIn this work, we present our findings regarding the low-temperature, solid-state conversion of Cu₂S nanowires to Cu₂S/Cu₅FeS₄ rod-in-tube structures, Cu₂S/ZnS segmented nanowires, and a full conversion of Cu₂S nanowires to ZnS nanowires. These conversion reactions occur at temperatures as low as 105 degrees Celsius, a much lower temperature than those required for reported solid-state reactions. The key feature of the Cu₂S nanowires that enables such low conversion temperatures is the high ionic diffusivity of the Cu⁺ within a stable S sublattice. The second portion of this work will focus on the oxide-stabilization and utilization of TiSi₂ nanonets as a lithium-ion battery anode. This nanostructure, first synthesized in our lab, was previously demonstrated to possess a lithium storage capacity when cycled against a metallic Li electrode. However, with subsequent lithiation and delithiation cycles, the TiSi₂ nanonet structure was found to be unstable. By allowing a thin oxide layer to form on the surface of the nanonet, we were able to improve the capacity retention of the nanonets in a lithium-ion half-cell; 89.8% of the capacity of the oxide-coated TiSi₂ was retained after 300 cycles compared to 62.3% of the capacity of as-synthesized TiSi₂ nanonets after 300 cycles. The layered structure of C49 TiSi₂ exhibited in the nanonets allows for a specific capacity greater than 700 mAh g(-1), and the high electrical conductivity of the material in conjunction with the layered structure confer the ability to cycle the anode at rates of up to 6C, i.e., 10 minute charge and discharge cycles, while still maintaining more than 75% of the capacity at 1C, i.e., 1 hour charge and discharge cycles.Thesis (MS) — Boston College, 2013.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Chemistry

Phosphorus buffering in streams by benthic sediments : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

The loss of phosphorus (P) to aquatic ecosystems accelerates eutrophication – a problem felt worldwide. Central to any effort to monitor and mitigate the effect of P in stream is knowing how inputs of P, whether point or diffuse, map to P transport downstream. However, the stream itself possesses several mechanisms to attenuate P inputs thus blurring the connection between P inputs and P availability in-stream. For example, various stream biota and geochemical processes may remove P from or even release P to the water column. In particular, benthic stream sediments have the capacity to sorb P to their surfaces which may later desorb back into solution. This P sorption means benthic sediments can behave much like a buffer for P: a transient store of P which may offset changes to P concentrations in the stream. The thesis of this work is that the benthic sediment-P buffer is a predominant control on P availability at baseflow in streams. In its five studies, I investigate sediment-P sorption in detail but also examine multiple alternative pathways for stream P retention. Special attention is given to the sediment equilibrium phosphate concentration at net zero sorption (EPC0), which is the dissolved reactive P (DRP) concentration towards which sediments buffer DRP concentrations in the solution (i.e., sediment porewater and, via hyporheic exchange, the water column) through sorption. A systematic review and meta-analysis of the EPC0 in streams at baseflow – covering 45 studies and 466 stream sites across the globe – found wide variability in the disparity between in-stream DRP concentrations and sediment EPC0 (termed as a potential for P exchange). This contrasts with previous views that P in sediments and streamwater is typically in an ‘equilibrium’. Further, this potential for P exchange was moderated by sediment and stream characteristics, including sorption affinity, pH, and sediment exchangeable P concentrations. For example, fine benthic sediments are often highly sorptive but may also restrict hydrological exchange between the water column and the hyporheic zone, leading to wider disparities. Methodological factors were also influential (e.g., choice of solution, sediment pre-treatment, equilibration time), indicating a need for research on unified EPC0 methodology. The second study established that drying sediments prior to analyses (either air- or freeze-drying) biases sediment P fractionation measurements and inflates the variance of EPC0. Such drying techniques may lyse microbial biomass P, alter organic P availability, and age metal oxides responsible for sorption, thus complicating the natural sediment P chemistry. Instead, analyzing stream sediments fresh (wet) is recommended. The third study surveyed a variety of stream waters and sediments from catchments draining three distinct lithologies (alluvium, sedimentary, and volcanic basic) to assess the likelihood of various geochemical controls on stream DRP concentrations. Geochemical equilibria in the water-column indicated no significant potential for the (co-)precipitation of minerals that could sequester P (e.g., calcite). However, the sediments stored large amounts of P in labile and redox-sensitive forms: indeed, this labile P correlated with stream DRP concentrations but only for streams with likely sufficient hyporheic exchange. Catchment geology and redox cycling in stream influence sediment reactivity for P and so are a major source of between-stream variability in DRP concentrations. The fourth study focused on a confounding factor when interpreting EPC0: is P sorption or microbial P cycling responsible for sediment P buffering? Unlike some previous work, this study found a minimal role for sediment microbes to alter sediment EPC0 values even with replete labile carbon and nitrogen sources available. Further, sediments sterilized via γ-irradiation did increase in EPC0, but this increase was attributed to lysis of the microbial biomass – an overlooked P stock in streams. The study highlights that the sediment P buffer, while largely abiotic in nature, may subsidize microbial P demand in sediment biofilms, thus influencing stream ecological function. The last study examined P uptake at the stream reach scale. Considering two contrasting but predominant controls on stream P uptake – periphyton P demand and sediment P sorption – a natural way to separate the two processes was to measure P uptake under light and dark conditions. Stream gross primary productivity (driven by periphyton) was high as expected for this open-canopy stream. However, this did not translate to an increase in stream P uptake when compared to dark conditions. Sediments were highly sorptive and their relatively low EPC0 suggested a potential for P removal throughout the experiment. Thus the sediment P buffer was likely most responsible for the measured stream P uptake although different stream conditions (e.g., greater nitrogen availability) could increase periphyton’s relevance and should be studied further. In summary, the benthic sediment P buffer can contribute to the regulation of P availability in many streams. Sediments may attenuate P inputs, thus dampening DRP variation at baseflow and prolonging the legacy of past P inputs in the catchment. Stream hydrology (e.g., hyporheic exchange), geochemistry (e.g. pH), and biota (e.g., sediment microbial P demand) are among the chief external factors that may moderate or interact with the sediment P buffer and deserve further study. Predicting P availability in streams remains a major challenge, but understanding the sediment P buffer will greatly improve our ability to prevent stream eutrophication

Trend Analysis of Water Quality in Northwest Arkansas Streams Reflects Changes in the Watershed

Watershed export of nutrients, sediments, and chemicals impacts receiving waters. Changes within the watershed (e.g., anthropogenic or climatic) can alter the transport of constituents in streams. Stream monitoring is crucial for understanding these effects. This study developed a potential improvement to flow-adjusting constituent concentrations in streams, an important step of analyzing monitoring data in lotic systems for trends. The method incorporates a K-fold cross-validation procedure to optimize a model explaining the relationship between the concentration and streamflow, thus providing a valuable tool to researchers in water quality. Additionally, two case studies were conducted on watersheds located in northwest Arkansas using monitoring data collected from 2009 to 2015. The first case study focused on phosphorus concentrations in the Illinois River watershed and illustrated significant decreases in soluble reactive phosphorus following reductions of effluent phosphorus from upstream wastewater treatment plants. However, no significant trends were found in total phosphorus at the most downstream site on the Illinois River, suggesting that there are legacy sources of phosphorus remaining in the watershed. The second case study focused on nitrogen and phosphorus in the three main inflows to Beaver Lake, where primary productivity will likely cause the lake to violate its water quality standard for chlorophyll-a concentration. Data collected at two sites in Beaver Lake showed elevated chlorophyll-a concentrations and one site near Lowell, Arkansas, the location of a major drinking water supply intake, showed increasing trends from 2001 to 2015 for total nitrogen as well as chlorophyll-a. Monitoring data of the inflows illustrated the variability in hydrological and climatic factors (e.g., drought), which affects nutrient delivery to Beaver Lake. Long-term monitoring of streams in both watersheds will be crucial for understanding the processes that affect water quality and will better inform watershed management

Solving Electrical Engineering Puzzles Using Spatial Reasoning

The precursor of any problem-solving strategy is the visualization of the problem at hand. When dealing with problems pertaining to STEM (science, technology, engineering, and mathematics) areas, visualization plays a very significant role in addressing the same. Several initiatives are being taken to improve the visualization skills of the students and spatial reasoning techniques have proved to be one of the most widely accepted tools for addressing the problems in the STEM field. In this paper, we specifically address the use of spatial reasoning to solve problems in the form of puzzles taken from electrical engineering and analyze the fruitfulness of employing such a strategy. The puzzles are hosted in an online interactive framework called UNTANGLED and classified into different categories on the basis of the nature of the puzzles and their difficulties. The results indicate that spatial reasoning technique indeed helped the players to successfully complete the puzzles. The interpretation of the data led to the conclusion that spatial reasoning techniques are imperative when it comes to discerning and resolving a problem, especially in the STEM domain

Talk That Counts: Participation in Practicums and Student Success in Civil Engineering

[EN] Engineering courses across the globe include practical components generally undertaken in small groups. This study aims to determine whether the quantity and quality of students’ participation in these group-based practicums could be correlated with their academic performance. A first year course in Concrete Technology was selected, and groups of students were filmed as they undertook a practicum that required them to mix, test, cast and crush concrete cubes as per the guidelines of two established procedures. Approximately four hours of film was then time-coded according to student activity. The resulting transcripts were analysed quantitatively in terms of total time spent on specific activities, and qualitatively in terms of the nature of student engagement with those activities. The results show that group discussion may have a greater impact on student learning than time spent on the task itself. However, this depends on the specific nature of this talk. Implications of the study include the fact that attention needs to be given to designing group tasks in such a way that they facilitate group interaction, and the fact that tutors and lecturers should promote group discussion and be aware of interactional dynamics that act to the detriment of student learning.Simpson, Z.; Bester, J. (2015). Talk That Counts: Participation in Practicums and Student Success in Civil Engineering. En 1ST INTERNATIONAL CONFERENCE ON HIGHER EDUCATION ADVANCES (HEAD' 15). Editorial Universitat Politècnica de València. 378-384. https://doi.org/10.4995/HEAd15.2015.396OCS37838

Reducing water extractable phosphorus in poultry litter using chitosan treatment

Phosphorus (P) is an important factor in the eutrophication of freshwater, and watershed sources include effluent discharges and the landscape. Poultry litter applied to the landscape can be a potential source of P, which is dependent on rainfall, runoff and dissolution. Chitosan, the deacetylated form of the biopolymer chitin, has been shown to have an effect on reducing water extractable phosphorus (WEP) in poultry litter when applied as a powder. The intent of this study was to measure the effect that poultry litter treatment (PLT), acetic acid and incubation time have on chitosan’s ability to reduce WEP in poultry litter. The results were that (1) the presence of PLT in the litter inhibits chitosan’s ability to reduce WEP; (2) chitosan dissolved in acetic acid (0.005, 0.01, 0.02, and 0.05 g mL-1) does not decrease WEP at any point during a 7 week incubation period; and (3) chitosan in a powder form reaches its full effectiveness after three weeks of incubation. Chitosan could be an effective coamendment to poultry litter with other treatments in order to reduce WEP

Antibody Dependent Enhancement of Infectious Bronchitis Virus in Poultry

Avian infectious bronchitis (IB) is a coronavirus infection of chickens that causes respiratory disease and reproductive problems in chickens. Currently, there are vaccines that are effective against IB. However, new variants and strains of avian infectious bronchitis virus (IBV) routinely emerge. A vaccine that is not the same strain as the virus is not completely effective in protecting against other variants because the vaccine will not allow the host antibodies to completely neutralize the strain. This is a problem because it makes IB difficult to control and diagnose. Antibody-dependent enhancement (ADE) is a phenomenon whereby non-neutralizing antibodies, or low levels of neutralizing antibodies, facilitate access into the host cell and allows either an enhanced viral infection or an increase in the severity of the clinical disease. This means the virus may create more variants that render current vaccines ineffective, created problems in diagnoses and may lead to more severity clinical disease. ADE has been found to occur with dengue virus and other viruses including some coronaviruses. This is a concern because COVID-19 is a human coronavirus and many vaccines have been developed, but variants routinely arise. ADE is thought to be a very important factor for developing new vaccines because vaccines that are not specific for a serotype could enhance viral infections. This would be the first work of looking at ADE on IBV to determine if ADE is occurring