Tobias S. Schmidt

Is there a role for the Ca2+ influx during fertilization of the sea urchin egg?

Abstract Both isotopic and microelectrode studies reveal a significant Ca2+ influx at fertilization which if freely distributed in the cytoplasm would equal 1–2 × 10−5 M. The role, if any, of this influx is disputed. We have attempted to reevaluate contradictory findings by others on this role. Our results with Strongylocentrotus purpuratus and Lytechinus pictus eggs, assessing fertilization with acrosome-reacted sperm in EGTA-buffered media (free [Ca2+], 4.4 × 10−8 M) indicate that exogenous Ca2+ is not required for fertilization and subsequent cleavage. The contradictory findings by others may have resulted from reduced fertilizability in Ca2+-free seawater, which can be circumvented by higher sperm concentration and by a sensitivity to temperature in Ca2+-free medium, which can be bypassed by carrying out fertilization at lower temperature. Also consistent with the absence of a requirement for this Ca2+ influx, we found that Ca2+ uptake can be induced in eggs by depolarizing the membrane with high [K+], but there is no resultant activation of egg metabolism. Under our conditions for fertilization in Ca2+-free media, there is no effect on the block to polyspermy but the initiation of the cortical reaction may be delayed. The data support the hypothesis that sperm induce release of Ca2+ from intracellular stores, perhaps by affecting an equilibrium between Ca2+ sequestration and Ca2+ release.

The hierarchy of requirements for an elevated intracellular pH during early development of sea urchin embryos.

The intracellular pH (pHi) rises 0.3-0.5 units after fertilization of sea urchin eggs, and this and previous work show this pHi change is necessary for initiating the developmental processes leading to cell division. The experiments described here reveal that while the elevated pHi is permanently required for a normal early development, lowering pHi of embryos after fertilization affects different processes to different extents. Protein synthesis gradually becomes less sensitive to pHi. Karyokinesis proceeds to completion under a low pHi, but is retarded, while cytokinesis is always impaired. These results indicate a hierarchy of requirements for high pHi during early development of sea urchin embryos, with protein synthesis, karyokinesis, and cytokinesis showing, respectively, increasing requirements for an elevated pHi.

Composting projects under the Clean Development Mechanism: Sustainable contribution to mitigate climate change

The Clean Development Mechanism (CDM) of the Kyoto Protocol aims to reduce greenhouse gas emissions in developing countries and at the same time to assist these countries in sustainable development. While composting as a suitable mitigation option in the waste sector can clearly contribute to the former goal there are indications that high rents can also be achieved regarding the latter. In this article composting is compared with other CDM project types inside and outside the waste sector with regards to both project numbers and contribution to sustainable development. It is found that, despite the high number of waste projects, composting is underrepresented and a major reason for this fact is identified. Based on a multi-criteria analysis it is shown that composting has a higher potential for contribution to sustainable development than most other best in class projects. As these contributions can only be assured if certain requirements are followed, eight key obligations are presented.

Performance of renewable energy technologies under the CDM

While many different greenhouse gas (GHG) mitigation technologies can be implemented under the Clean Development Mechanism (CDM), renewable energy technologies (RETs), in particular, are often viewed as one of the key solutions for achieving the CDMs goals: host-country sustainable development and cost-efficient emissions reductions. However, the viability of emission reduction projects like RETs is technology- and country-specific. To improve the CDM with respect to the diffusion of RETs, it is crucial to understand the factors that ultimately drive or hinder investments in these technologies. This study develops a methodology based on project-level, regional and global variables that can systematically assess the financial and environmental performance of CDM projects in different country contexts. We quantitatively show how six RETs (PV, wind, hydro, biomass, sewage, landfill) are impacted differently by the CDM and how this impact depends on regional conditions. While sewage and landfill are strongly affected independently of their location; wind, hydro and biomass projects experience small to medium impacts through the carbon price, and strongly depend on regional conditions. PV depends more on regional conditions than on the carbon price but is always unprofitable. Furthermore, we determine the carbon prices necessary to push these six RETs to profitability under various regional conditions. Based on these results, we derive policy recommendations to advance the interplay between international and domestic climate policy to further incentivize GHG emission reductions from RETs.

How a Product's Design Hierarchy Shapes the Evolution of Technological Knowledge – Evidence from Patent-Citation Networks in Wind Power

We analyze how a products design hierarchy shapes the focus of inventive activity and the expansion of the underlying body of knowledge, building on the complex-system perspective on technological evolution. This perspective suggests that the design hierarchy of a product can have an ordering effect on the evolution of commercialized artifacts, in particular when product design decisions on high levels of the design hierarchy set the agenda for subsequent variation and experimentation on lower levels. We extend this literature by analyzing the design hierarchys effect on the evolution of the industrys knowledge base, using the case of wind turbine technology over the period 1973–2009. We assess the technological focus of patents along the core trajectory of knowledge generation, identified through a patent-citation network analysis, and link it to a classification of technological problems into different levels in the design hierarchy. Our analysis suggests that the evolution of an industrys knowledge base along a technological trajectory is not a unidirectional process of gradual refinement: the focus of knowledge generation shifts over time between different sub-systems in a highly sequential pattern, whose order is strongly influenced by the design hierarchy. Each of these shifts initiates the integration of new domains of industry-external knowledge into the knowledge base, thus opening windows of competitive opportunity for potential entrants with strong knowledge positions in the new focus of inventive activity. We discuss implications for the understanding of the competitive advantage of specific knowledge positions of firms and nations and technology policy for emerging technologies.

High hydrostatic pressure and the dissection of fertilization responses: I. The relationship between cortical granule exocytosis and proton efflux during fertilization of the sea urchin egg☆

High hydrostatic pressure applied between sperm attachment and the onset of cortical granule exocytosis will inhibit this exocytotic event in sea urchin eggs. Such pressure-treated zygotes, nevertheless, are activated and capable of development. Thus, this technique can be used as a tool to study the relationship between cortical granule breakdown and other fertilization-related responses. We have studied whether the exocytosis of cortical granules is necessary for proton efflux (acid release) to occur. Our results indicate that although Ca2+ is released while the eggs are under pressure (a prerequisite for the following events to take place), cortical granule exocytosis and acid release are pressure-sensitive and completely inhibited at pressures above 400 atm (6000 psi) and 275 atm (4000 psi), respectively. However, upon decompression, acid release is initiated which amounts to 65-70% of that seen in the unpressurized controls, suggesting that the efflux mechanism does not require cortical granule exocytosis and must result from some modification of the original plasma membrane of the egg. The remaining 30-35% of the acid release is related to cortical granule exocytosis, since it can be obtained upon induction of the cortical granule fusion 30 min later under atmospheric pressure. The initiation of acid release after decompression indicates that the efflux mechanism is not transiently turned on at fertilization, but undergoing long-term modification; the recovery of the ability to induce cortical granule fusion after fertilization under pressure suggests a refilling of cytoplasmic Ca2+ stores within this time course.

Climate policy for short- and long-lived pollutants

The current focus on the long-term global warming potential in climate policy-making runs the risk of mitigation options for short-lived climate pollutants being ignored, and tipping points being crossed. We outline how a more balanced perspective on long- and short-lived climate pollutants could become politically feasible.

LCA of key technologies for future electricity supply—68th LCA forum, Swiss Federal Institute of Technology, Zurich, 16 April, 2018

The 68th LCA forum was held on 16 April, 2018, to discuss current and future developments in the electricity network as well as recent life cycle assessment work on key technologies, such as batteries, photovoltaic panels and geothermal power plants. Several countries adjusted their energy policy after the three core meltdowns in Fukushima Daiichi, Japan, in March 2011 and are redefining their climate policy as a consequence of the Paris Agreement in 2015. Method: During the one-day workshop, the current state of the Swiss energy and climate policy and key technologies suited to support the shift towards a renewable electricity mix were explored. Photovoltaics are considered a key technology for power generation in the Swiss electricity mix. It was shown how much an increase in PV production entails investments in the electricity networks and how such investments can be minimised. Batteries were named as one promising option. Several presentations showed the environmental footprints of current and future battery technologies and manufacturing. Recent LCA work on batteries using industry data showed that in the past; the environmental impacts of lithium-ion battery manufacture were often underestimated. However, the potential to reduce its current environmental footprint is rather huge and achievable with only a few measures. The day was concluded with presentations on the LCA of geothermal power production. This technology is particularly of interest as it delivers base load electricity. While the environmental footprint of geothermal power is comparable to hydroelectric and wind power, seismic risks and earthquakes may cause damage to buildings and infrastructure which are non-negligible. Results: The day revealed the following three key insights: (1) The Swiss (and other nations’) climate policy measures are not sufficient for reaching the 2 °C target of the Paris Agreement; (2) photovoltaic electricity combinedwith battery storage is one solution to increase the share of renewables in the grid. Like with any self-sufficiency measures, this comes along with significant additional environmental impacts; (3) more and more companies are starting to green their supply chains. Conclusion: National governments are encouraged to significantly strengthen their climate policy. Households should carefully evaluate the optimal level of self-sufficiency, taking into account the environmental impacts of storage facilities. Companies should invest in and use renewable energy, such

A Heuristic for Technology Strategies in Post-Kyoto Bottom-Up Climate Policy

The recent UNFCCC conferences starting with Bali in 2007 until Lima in 2014 have paved the way for the integration of nationally determined initiatives into the global climate governance architecture. National ‘green growth’ strategies have become a new paradigm for policymakers and executives. Designed with the aim of decoupling economic development from adverse environmental impacts, these bottom-up policies hold the promise of overcoming the gridlock in international climate negotiations. Building on the literature on innovation research, this paper contributes to the understanding of technology strategies in the context of nationally appropriate mitigation actions (NAMAs) under the UNFCCC. It is evident that NAMAs aiming to create domestic industries by leveraging technological innovation must consider the characteristics of the targeted technology. Working from this notion, this paper proposes a heuristic to differentiate between four distinct types of technologies. Each type features specific forms of technological learning, value chain constellations and modes of technology transfer. We illustrate the four types using the cases of small hydro, wind turbines, electric vehicles and solar cells and discuss methodologies to classify further technologies ex-ante. We argue that the heuristic captures essential technological characteristics that NAMAs and international support mechanisms need to consider. The different forms of technological learning and value chain constellations are relevant for a country’s choice of technological priorities, while the modes of technology transfer can inform strategies for implementation and international cooperation. We discuss technology-specific strategies for developing countries at different stages of development and international institutions such as the Green Climate Fund and the new Technology Mechanisms under the UNFCCC.