Willingness to adopt improved shrimp aquaculture practices in Vietnam

The shrimp industry plays a leading role in aquaculture development in Vietnam. Currently, the government is running a credit subsidy program to support farmers investing in improved production methods. This paper aimed to investigate white-legged shrimp farmers’ willingness to invest in improved production methods and to examine whether the current government policy for the sector is in line with farmers’ preferences using a discrete choice experiment. The results show that farmers do not care about the environmental impacts but emphasize increased yields and more successful crops as the main drivers of their willingness to invest. There is a mismatch between the current subsidized interest rate and farmers’ required interest rate. These findings suggest that to promote better investment in improved production methods, the government should focus on the regulatory framework, monitoring and control of environmental impacts, and reevaluate the size of the credit subsidy.acceptedVersio

Triarylmethyl Cation Catalysis: A Tunable Lewis Acid Organocatalyst for the Synthesis of Bisindolylmethanes

Triarylmethyl cations serve as tunable organocatalysts for the synthesis of bisindolylmethanes. The catalyst structure can be modified to increase or decrease reactivity as needed to match the requirements of the substrate. High yields are achieved for a variety of substrates by using these green catalysts. Catalyst tuning allows for the use of less reactive electrophiles by increasing the reactivity of the catalyst. Acid-sensitive products can be isolated under these mild reaction conditions

Exploration of Carbonyl–Olefin Metathesis Reactions: Ring Opening, Ring Closing and Polymerization. Investigation of Cyclopropenimines for Carbon Dioxide Capture and Its Conjugate Acids for Per– and Polyfluoroalkyl Substances (PFAS) Remediation

The first part of this thesis describes the development of carbonyl–olefin metathesis reactions utilizing hydrazine catalysts. The second chapter presents the challenges at hand for enabling ring–opening carbonyl olefin metathesis (ROCOM) on norbornene substrates. Through a combinatory computational and empirical approach, bicyclic hydrazine [2.2.2] with facile cycloreversion was identified and demonstrated to enable catalytic ROCOM on norbornenes. In the course of the study, hydrolysis, was identified as a barrier for efficient catalyst turn–over.The third chapter describes the development of ring opening metathesis polymerization (ROMP) of cyclopropenes, with hydrazonium initiators. Taking advantage of COM capability of bicyclic hydrazonium, cyclopropane monomers were polymerized by series of [3+2] cycloaddition and cycloreversion reactions. Detailed optimization along with reaction kinetics investigation unveiled that there is a positive correlation between monomer to initiator ratio and degree of polymerization. The fourth chapter describes the development of ring–closing COM (RCCOM) to generate polycyclic aromatic compounds (PAC) bearing Lewis basic functionalities, which can strongly inhibit conventional Lewis acid methodologies. Using 5 mol% catalyst loadings, a variety of PAC structures can be synthesized from biaryl alkenyl aldehydes, which themselves are readily prepared by cross-coupling reactions. In the second part of this thesis, the fifth chapter describes the discovery of cyclopropenimines’ (CPI) capability of rapid CO2 sequestration at room temperature. Decarboxylation temperature was demonstrated to be 60 °C in vacuo. CPI demonstrated remarkable oxidative and hydrolytic stability in the temperature range required for adsorption and regeneration. In the last chapter, another application of cyclopropenimine hydrochloride (CPI·HCl) as per– and polyfluoroalkyl substances (PFAS) adsorbent is discussed. The mechanism of PFAS removal was hypothesized to be through the formation of insoluble CPI–PFAS aggregates, which were subsequently removed via a conventional filter membrane. Fast removal kinetics (≤ 10 second) were observed on both legacy and emerging anionic PFAS. Factors with potential impact on CPI·HCl performance such as salt content, pH level and natural organic content were investigated. A demonstrative practical PFAS removal was illustrated through purification of PFAS spiked potable tap water from Cornell University, NY, USA

Single Wire Power Monitoring Utilizing Non- Intrusive Current Measurement

In order to determine the power consumption of an unknown load circuit both its current and voltage must be determined, as well as any phase difference between them. The current measurement is made non-intrusively by using a Rogowski coil, which picks up the magnetic field created by the current through either the supply or the return wire. The coil outputs a voltage which is proportional to the rate of change of current through the wire. This voltage is integrated and sent to a PIC18 microcontroller for further processing and storage. The PIC also implements a voltmeter via the onboard A-D converter to determine the voltage dropped across the load. The current and voltage signals are analyzed to determine the phase difference, and the actual rms current, rms voltage, power factor, and average power are computed. These values are displayed in real-time on an LCD screen, and all data can be uploaded to a computer for graphical analysis

Single Wire Power Monitoring Utilizing Non- Intrusive Current Measurement

In order to determine the power consumption of an unknown load circuit both its current and voltage must be determined, as well as any phase difference between them. The current measurement is made non-intrusively by using a Rogowski coil, which picks up the magnetic field created by the current through either the supply or the return wire. The coil outputs a voltage which is proportional to the rate of change of current through the wire. This voltage is integrated and sent to a PIC18 microcontroller for further processing and storage. The PIC also implements a voltmeter via the onboard A-D converter to determine the voltage dropped across the load. The current and voltage signals are analyzed to determine the phase difference, and the actual rms current, rms voltage, power factor, and average power are computed. These values are displayed in real-time on an LCD screen, and all data can be uploaded to a computer for graphical analysis

A case for true morphological crypsis: Pacific Dasya anastomosans and Atlantic D. cryptica sp. nov. (Dasyaceae, Rhodophyta)

With the advent of regular genetic bar coding for taxonomic distinction a decade ago, descriptions of morphologically cryptic species have exploded in the macroalgal literature. A review of this literature is provided. Produced by either convergence of morphological characteristics by geographically distant species or divergence of species from a common ancestor, cryptic species can often be distinguished by subtle anatomical or reproductive features. Some species pairs, however, remain indistinguishable with overlapping characteristics even upon close inspection. Such a case is demonstrated for two species differentiated by sequences of a portion of the rbcL chloroplast gene: Dasya anastomosans from the Indo-Pacific and D. cryptica sp. nov. from the western Atlantic. After assembling morphological and anatomical data for the two species, no significant differences were detected between them, thus affording the usage of the epithet for the new species from an ocean basin more distant than its congener

Metal–Free Ring–Opening Metathesis Polymerization with Hydrazonium Initiators

A new strategy for the ring–opening metathesis polymerization (ROMP) of cycloalkenes using hydrazonium initiators is described. The initiators, which are formed by the condensation of 2,3-diazabicyclo[2.2.2]octane and an aldehyde, polymerize cyclopropene monomers by a sequence of [3+2] cycloaddition and cycloreversion reactions. This process generates short chain polyolefins (Mn ≤ 9.4 kg/mol) with relatively low dispersities (Đ ≤ 1.4). The optimized conditions showed efficiency comparable to that achieved with Grubbs’ catalyst. A positive correlation between monomer to initiator ratio and degree of polymerization was revealed through NMR spectroscopy

Ring-Opening Carbonyl-Olefin Metathesis of Norbornenes

A computational and experimental study of the hydrazine-catalyzed ring-opening carbonyl-olefin metathesis of norbornenes is described. Detailed theoretical investigation of the energetic landscape for the full reaction pathway with six different hydrazines revealed several crucial aspects for the design of next-generation hydrazine catalysts. This study indicated that a [2.2.2]-bicyclic hydrazine should offer substantially increased reactivity versus the previously reported [2.2.1]-hydrazine due to a lowered activation barrier for the rate-determining cycloreversion step, a prediction which was verified experimentally. Optimized conditions for both cycloaddition and cycloreversion steps were identified, and a brief substrate scope study for each was conducted. A complication for catalysis was found to be the slow hydrolysis of the ring-opened hydrazonium intermediates, which were shown to suffer from a competitive and irreversible cycloaddition with a second equivalent of norbornene. This problem was overcome by the strategic incorporation of a bridgehead methyl group on the norbornene ring, leading to the first demonstrated catalytic carbonyl-olefin metathesis of norbornene rings. </div

Co-culture of microalgae-activated sludge for wastewater treatment and biomass production: Exploring their role under different inoculation ratios

In this study, mixed culture (microalgae:activated sludge) of a photobioreactor (PBR) were investigated at different inoculation ratios (1:0, 9:1, 3:1, 1:1, 0:1 wt/wt). This work was not only to determine the optimal ratio for pollutant remediation and biomass production but also to explore the role of microorganisms in the co-culture system. The results showed high total biomass concentrations were obtained from 1:0 and 3:1 ratio being values of 1.06, 1.12 g L-1, respectively. Microalgae played a dominant role in nitrogen removal via biological assimilation while activated sludge was responsible for improving COD removal. Compared with the single culture of microalgae, the symbiosis between microalgae and bacteria occurred at 3:1 and 1:1 ratio facilitated a higher COD removal by 37.5-45.7 %. In general, combined assessment based on treatment performance and biomass productivity facilitated to select an optimal ratio of 3:1 for the operation of the co-culture PBR