Bostonia. Volume 2

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

UV-light-driven prebiotic synthesis of iron–sulfur clusters

Iron–sulfur clusters are ancient cofactors that play a fundamental role in metabolism and may have impacted the prebiotic chemistry that led to life. However, it is unclear whether iron–sulfur clusters could have been synthesized on prebiotic Earth. Dissolved iron on early Earth was predominantly in the reduced ferrous state, but ferrous ions alone cannot form polynuclear iron–sulfur clusters. Similarly, free sulfide may not have been readily available. Here we show that UV light drives the synthesis of [2Fe–2S] and [4Fe–4S] clusters through the photooxidation of ferrous ions and the photolysis of organic thiols. Iron–sulfur clusters coordinate to and are stabilized by a wide range of cysteine-containing peptides and the assembly of iron–sulfur cluster-peptide complexes can take place within model protocells in a process that parallels extant pathways. Our experiments suggest that iron–sulfur clusters may have formed easily on early Earth, facilitating the emergence of an iron–sulfur-cluster-dependent metabolism

Studies of possible solid oxide fuel cell anode materials in the MgO:TiO2:ZrO2 ternary system

The MgO:TiO2 :ZrO2 ternary system was investigated as a possible novel anode material in a solid oxide fuel cell. Titanium-substituted yttria-stabilised zirconias have the necessary electrical conductivity properties for a ZrO2 -based fluorite electrode but problems have been encountered such as a decrease in unit-cell size upon reduction leading to mechanical failure. By incorporating magnesium into the titanium-stabilised zirconia structure, it was thought that the cubic-fluorite structure might be stabilised. A phase diagram study was made of the MgO:TiO2 : ZrO2 ternary system at 1500°C. Upon researching the literature phase diagram of the MgO:TiO2 :ZrO2 system, it was found that the authors had not studied the single-phase region in the ZrO2 -rich area extensively and did not use a consistent temperature for their analysis of samples. This has meant that the phase diagram has had to be reinvestigated. The results obtained at 1500°C are in disagreement with the previously published phase diagram. A large area bounded by single-phase cubic-fluorite was detected; however the central region of this domain contained both tetragonal and cubic-fluorite domains. This implies that for the central region of this phase area that the cubic- fluorite phase is not stable at 1500°C. Selected stabilised cubic-fluorite samples with ~ 10 atom% Mg were annealed at l000°C after preparation at 1500°C and it was found that due to the presence of other phases present at 1000°C, that the cubic-fluorite phase is thermodynamically unstable at lower temperatures. DTA analysis revealed that as the titanium content in the cubic-fluorite solid-solution increased, the phase transition from tetragonal phase (+ MgO) to cubic-fluorite phase decreased. These results were used to provide a basis for a temperature phase diagram showing the likely phase transitions that occur at a particular temperature range. The activation energy for conduction increased and ionic conductivity decreased with increasing titanium content in the solid solution, due to the effects of local distortions created by the smaller ionic radius of titanium when compared to zirconium

Bostonia. Volume 5

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Bostonia. Volume 6

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Bostonia. Volume 12

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Optimal joint production and emissions reduction strategies considering consumers\u27 environmental preferences: A manufacturer\u27s perspective

Carbon cap-and-trade mechanism is a government-mandated, market-based scheme to reduce emissions, which has a significant effect on manufacturers\u27 operation decisions. Based on the cap-and-trade mechanism, this paper studies the joint production and emission reduction problem of a manufacturer. The manufacturer faces emissions-sensitive demand impacted by consumers\u27 environmental preferences (CEP). An extended newsvendor model is used to find the optimal production quantity and emissions reduction quantity. We explore the impacts of market price of carbon credits, emission reduction investment coefficient and CEP on the optimal strategies. Numerical examples are provided to illustrate the theoretical results and orthogonal experimental design technique was applied to find robust system parameters. It is concluded that among all parameters, emissions cap has the greater impact on the expected profit, which is followed by than the market price of carbon credits. This means that the government plays a major role in economic development. The total carbon emissions are mainly affected by the carbon trading price and the product\u27s sale price, which indicates the carbon trading market and product market play a larger role in controlling environmental benefits. Several valuable managerial insights on helping governments and industries understand how market conditions change and make better long-term decisions are further concluded

Life Cycle-based Environmental Performance Indicator for the Coal-to-energy Supply Chain: A Chinese Case Application

Coal consumption and energy production (CCEP) has received increasing attention since coal-fired power plants play a dominant role in the power sector worldwide. In China, coal is expected to retain its primary energy position over the next few decades. However, a large share of CO2 emissions and other environmental hazards, such as SO2 and NOx, are attributed to coal consumption. Therefore, understanding the environmental implications of the life cycle of coal from its production in coal mines to its consumption at coal-fired power plants is an essential task. Evaluation of such environmental burdens can be conducted using the life cycle assessment (LCA) tool. The main issues with the traditional LCA results are the lack of a numerical magnitude associated with the performance level of the obtained environmental burden values and the inherent uncertainty associated with the output results. This issue was addressed in this research by integrating the traditional LCA methodology with a weighted fuzzy inference system model, which is applied to a Chinese coal-to-energy supply chain system to demonstrate its applicability and effectiveness. Regarding the coal-to-energy supply chain under investigation, the CCEP environmental performance has been determined as “medium performance”, with an indicator score of 39.15%. Accordingly, the decision makers suggested additional scenarios (redesign, equipment replacement, etc.) to improve the performance. A scenario-based analysis was designed to identify alternative paths to mitigate the environmental impact of the coal-to-energy supply chain. Finally, limitations and possible future work are discussed, and the conclusions are presented

Structure of the Global Plastic Waste Trade Network and the Impact of China's Import Ban

Millions of tonnes (teragrams) of plastic waste are traded around the world every year, which plays an important role in partially substituting virgin plastics as a source of raw materials in plastic product manufacturing. In this paper, global plastic waste trade networks (GPWTNs) from 1988 to 2017 are established using the UN-Comtrade database. The spatiotemporal evolution of the GPWTNs is analyzed. Attention is given to the country ranks, inter- and intra-continental trade flows, and geo-visual communities in the GPWTNs. We also evaluate the direct and indirect impacts of China’s plastic waste import ban on the GPWTNs. The results show that the GPWTNs have small-world and scale-free properties and a core-periphery structure. The geography of the plastic waste trade is structured by Asia as the dominant importer and North America and Europe as the largest sources of plastic waste. China is the unrivaled colossus in the global plastic waste trade. After China’s import ban, the plastic waste trade flows have been largely redirected to Southeast Asian countries. Compared with import countries, export countries are more important for the robustness of GPWTNs. Clearly, developed countries will not announce bans on plastic waste exports; these countries have strong motivation to continue to shift plastic waste to poorer countries. However, the import bans from developing countries will compel developed countries to build new disposal facilities and deal with their plastic waste domestically