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Variations in neuronal connectivity occur widely in nervous systems from invertebrates to mammals. Yet, it is unclear how neuronal variability originates, to what extent and at what time scales it exists, and what functional consequences it might carry. To assess inter- and intraindividual neuronal variability, it would be ideal to analyze the same identified neuron across different brain hemispheres and individuals. Here, using genetic labeling and electron microscopy connectomics, we show that an identified inhibitory olfactory local interneuron, TC-LN, exhibits extraordinary variability in its glomerular innervation patterns. Moreover, TC-LN’s innervation of the VL2a glomerulus, which processes food signals and modulates mating behavior, is sexually dimorphic, is influenced by female’s courtship experience, and correlates with food intake in mated females. Mating also affects output connectivity of TC-LN to specific local interneurons. We propose that mating-associated variability of TC-LNs regulates how food odor is interpreted by an inhibitory network to modulate feeding.

Several large or mid-scale collections of Drosophila enhancer traps have been recently created to allow for genetic swapping of GAL4 coding sequences to versatile transcription activators or suppressors such as LexA, QF, split-GAL4 (GAL4-AD and GAL4-DBD), GAL80 and QS. Yet a systematic analysis of the feasibility and reproducibility of these tools is lacking. Here we focused on InSITE GAL4 drivers that specifically label different subpopulations of olfactory neurons, particularly local interneurons (LNs), and genetically swapped the GAL4 domain for LexA, GAL80 or QF at the same locus. We found that the major utility-limiting factor for these genetic swaps is that many do not fully reproduce the original GAL4 expression patterns. Different donors exhibit distinct efficacies for reproducing original GAL4 expression patterns. The successfully swapped lines reported here will serve as valuable reagents and expand the genetic toolkits of Drosophila olfactory circuit research.

Drosophila olfactory local interneurons (LNs) in the antennal lobe are highly diverse and variable. How and when distinct types of LNs emerge, differentiate, and integrate into the olfactory circuit is unknown. Through systematic developmental analyses, we found that LNs are recruited to the adult olfactory circuit in three groups. Group 1 LNs are residual larval LNs. Group 2 are adult-specific LNs that emerge before cognate sensory and projection neurons establish synaptic specificity, and Group 3 LNs emerge after synaptic specificity is established. Group 1 larval LNs are selectively reintegrated into the adult circuit through pruning and re-extension of processes to distinct regions of the antennal lobe, while others die during metamorphosis. Precise temporal control of this pruning and cell death shapes the global organization of the adult antennal lobe. Our findings provide a road map to understand how LNs develop and contribute to constructing the olfactory circuit., Local interneurons (LNs) in the Drosophila olfactory system are highly diverse. Here, the authors labeled different LN types and described how different LN subtypes are integrated into the developing circuit.

The Drosophila olfactory system is an attractive model for exploring the wiring logic of complex neural circuits. Remarkably, olfactory local interneurons exhibit high diversity and variability in their morphologies and intrinsic properties. Although olfactory sensory and projection neurons have been extensively studied of development and wiring; the development, mechanisms for establishing diversity, and integration of olfactory local interneurons into the developing circuit remain largely undescribed. In this review, we discuss some challenges and recent advances in the study of Drosophila olfactory interneurons.

Models show that to avert dangerous levels of climate change, global carbon dioxide emissions must fall to zero later this century. Most of these emissions arise from energy use. Davis et al. review what it would take to achieve decarbonization of the energy system. Some parts of the energy system are particularly difficult to decarbonize, including aviation, long-distance transport, steel and cement production, and provision of a reliable electricity supply. Current technologies and pathways show promise, but integration of now-discrete energy sectors and industrial processes is vital to achieve minimal emissions. Net emissions of CO2 by human activities - including not only energy services and industrial production but also land use and agriculture - must approach zero in order to stabilize global mean temperature. Energy services such as light-duty transportation, heating, cooling, and lighting may be relatively straightforward to decarbonize by electrifying and generating electricity from variable renewable energy sources (such as wind and solar) and dispatchable ("on-demand") nonrenewable sources (including nuclear energy and fossil fuels with carbon capture and storage). However, other energy services essential to modern civilization entail emissions that are likely to be more difficult to fully eliminate. These difficult-to-decarbonize energy services include aviation, long-distance transport, and shipping; production of carbon-intensive structural materials such as steel and cement; and provision of a reliable electricity supply that meets varying demand. Moreover, demand for such services and products is projected to increase substantially over this century. The long-lived infrastructure built today, for better or worse, will shape the future. Here, we review the special challenges associated with an energy system that does not add any CO2 to the atmosphere (a net-zero emissions energy system). We discuss prominent technological opportunities and barriers for eliminating and/or managing emissions related to the difficult-to-decarbonize services; pitfalls in which near-term actions may make it more difficult or costly to achieve the net-zero emissions goal; and critical areas for research, development, demonstration, and deployment. It may take decades to research, develop, and deploy these new technologies. DOI Link: https://doi.org/10.1126/science.aas9793

China has made improving the thermal efficiencies of its coal-fired power plants a national priority. Official data show that the average thermal efficiency was enhanced from 31.3% in 2000 to 33.2% in 2005 and 36.9% in 2010. This paper aims to assess the validity of China's claimed improvement, examine major responsible factors, and identify future improvement opportunities. Recognizable factors can account for about 80% of the reported progress in the 10th Five-Year Plan (2001–2005) and about 85% in the 11th (2006–2010) to largely verify the reported progress. Engineering approaches—especially replacing inefficient power units with more efficient ones—are the largest contributing factors, while optimization approaches—particularly electricity dispatch—remains inefficient in China. In 2010, the explainable efficiency improvement might have avoided around 500 million tons of CO2 emissions. In comparison, although the United States was fairly static with most of its coal-fired power plants seriously outdated, it has more efficient electricity dispatch. In China's ongoing 12th Five-Year Plan (2011–2015), better dispatch patterns could be more important as opportunities for improvement through engineering approaches have been largely exhausted.

Since China decontrolled coal prices, its coal price has risen steadily and been unusually volatile. In 2011 in particular, high coal prices and capped electricity prices in China discouraged coal-fired power generation, triggering widespread power shortages. We suggest that these coal-price disturbances could be symptomatic of a major change in pricing dynamics of global fossil-fuel markets, with increasing correspondence between coal and oil prices globally. Historically, global coal prices have been more stable and lower than oil and natural gas prices on a per-heat basis. In recent years, however, coal prices have been increasingly volatile worldwide and have tracked other fossil fuel prices more closely. Meanwhile, the recent development of unconventional gas has substantially decoupled US natural gas and oil prices. Technically, low US natural gas prices, with potential fuel switching, could drive US domestic coal prices lower. However, this effect is unlikely to counteract the overall trend in increasing coal consumption globally. China’s market size and unique, partially-controlled energy system make its reform agenda a key force in the global economy. Policymakers in the US, E.U. and elsewhere should monitor China’s economic reform agenda to anticipate and respond to changes accompanying China’s increasing importance in the global energy economy.

For more than a decade, Nobel laureate George Olah and coworkers have advocated the Methanol Economy – replacing petroleum-based fuels and chemicals with methanol and methanol-derivatives – as a path to sustainable development. A first step to this vision appears to be occurring in China. In the past five years, China has quickly built an industry of coal-based methanol and dimethyl ether (DME) that is competitive in price with petroleum-based fuels. Methanol fuels offer many advantages, including a high octane rating and cleaner-burning properties than gasoline. Methanol also has some disadvantages. A coal-based Methanol Economy could enhance water shortages in China, increase net carbon dioxide emissions, and add volatility to regional and global coal prices. China’s rapidly expanding Methanol Economy provides an interesting experiment for what could happen elsewhere if methanol is widely adopted, as proposed by Olah and researchers before him.

In 2013, China׳s national government abandoned its previous cautious policy and started to promote large-scale deployment of coal-based synthetic natural gas (SNG). Coal-based SNG is both carbon-intensive and very water-intensive. Driven by a smog crisis and the recession of coal industry, China׳s 2013 policy change is major setback in its long-term efforts in carbon mitigation and water conservation. The government of China made the policy change before the commercial commencement of China׳s first SNG demonstration plant. Since the commencement of China׳s SNG demonstration plant, many problems have started to appear. In this article, I discuss the nature of demonstration project and explain the danger in starting a crash program without evaluating the demonstration comprehensively and transparently.

China is quickly building up its nuclear power capacity while the hailed nuclear renaissance in the United States has been largely stagnant. The political and industrial structures explain the divergent paths. This paper draws lessons from the French experiences in deploying nuclear power and uses the lessons in comparing Chinese and U.S. policies. An authoritative political system and state-owned utility industry allow China to emulate the French approaches such as government-backed financing and broad-scale deployment with standardized design. The democratic political system and fragmented utility industry, and the laissez-faire ideology in the United States, on the other hand, are unfavorable to a nuclear renaissance. The prospect of a nuclear revival in the United States remains highly uncertain. As China builds up its nuclear industry, it will be able to reduce carbon emissions without a carbon price through a national plan to deploy low-carbon nuclear electricity, while the United States cannot implement a climate policy without a carbon price. American politicians should stop using China's lack of carbon cap as an excuse for postponing the legislation of a carbon price.

The global demand for platinum has consistently outgrown supply in the past decade. This trend likely will continue and the imbalance may possibly escalate into a crisis. Platinum plays pivotal roles in both conventional automobile emissions control and the envisioned hydrogen economy. A platinum crisis would have profound implications on energy and environment. On the one hand, inadequate platinum supply will prevent widespread commercialization of hydrogen fuel-cell vehicles. On the other hand, expensive platinum may enhance the competitiveness of hybrid, plug-in hybrid, and battery-powered electric cars. Policymakers should weigh the potential impacts of a platinum crisis in energy policy.

Climate change is a chronic yet unprecedented threat to civilization. Large scale abatement of greenhouse-gas emissions would require not only replacing carbon-intensive fuels (like coal and oil) with low-emission or carbon-free energy alternatives, but also replacing much of the infrastructure that uses primary and secondary energy. As a political issue, the scale of the problem makes carbon mitigation unique and difficult to resolve. Its chronic nature is another obstacle to implementation of policy in the near term. It would take decades to displace fossil fuels even if the technologies to do so were available. Furthermore, disagreement has arisen on whether currently available technologies are sufficient to significantly reduce emissions over the next several decades (Pacala and Socolow 2004; Hoffert et al. 2002). The notion of developing new technologies before mandating emissions reductions has gained currency in response to these complexities. The Bush Administration climate policy favors this line of thinking, rejecting any Kyoto-style arrangement involving mandatory targets and proposing the development of new technologies as an alternative (Bush 2005). Here we argue that such approaches are based on the misconception that innovations needed for carbon mitigation can be effectively and efficiently developed without carbon regulations. One concrete version of the “technology first” view has been expressed almost daily by scientists, political leaders, and others: Global warming problem can be solved in a timely fashion only through a crash research and development program similar to the Manhattan Project (Clinton 2005; Friedman 2005) or Apollo Project (See http://www.appolloalliance. org). The target of a “Manhattan Project” on Climate Change would be low-carbon technologies for energy generation and use. A common rationale for this approach is that the fossil-fueled greenhouse effect cannot be regulated away, an assertion that ignores the potential affect of regulation on innovation. Climatic Change (2007) 80:199–204 DOI 10.1007/s10584-006-9202-7

T United States and China are pursuing different choices of hydrocarbon feedstock for making chemicals. While the U.S. chemical industry is increasingly utilizing shale gas as feedstock to produce olefins and methanol, China is developing coal-to-olefins and coal-to-methanol. Shale gas chemicals are cheaper and cleaner than coal-based ones. By replacing those high-carbon coal-to-chemicals, the U.S. export of shale gas chemicals will be both profitable and environmentally beneficial. Ethylene, propylene, and methanol are the three most important building blocks in the chemical industry. In 2014, the world consumed about 160 million metric tons of ethylene, 90 million metric tons of propylene, and about 70 million metric tons of methanol. Ethylene and propylene are often grouped together with other alkenes and referred to as olefins. Olefins are made from steam cracking of hydrocarbons, with naphtha as the most common feedstock, followed by ethane and propane. Since the shale revolution, surplus of ethane and propane has triggered an investment boom in ethane crackers and exponential growth of propane/propylene exports. The announced projects are expected to increase the U.S. olefins production capacities by 14 million metric tons by 2020. The cheap and abundant ethane and propane provide the U.S. chemical industries with several competitive advantages. Manufacturing olefins from ethane and propane is cheaper, simpler, consume less energy, and less polluting than naphtha cracking. Meanwhile, China is pursuing the development of coal-toolefins (CTO). China’s 12th five-year plan (2011 to 2015) for olefins industry listed the development of CTO as a top priority. With favorable policies, China’s CTO production capacities have grown from 1.1 million metric tons per year in 2010 to 6.5 in 2014, and are expected to reach 12.4 by 2016. Coal-to-olefins requires high capital investment, complex processes, high energy consumption (therefore high carbon dioxide (CO2) emissions), and high water consumption. Despite the technical disadvantages, China is quickly building a coal-to-olefins industry with favorable government policies. For each metric ton of olefins output, ethane-to-olefins emit about 0.8 t of CO2, naphtha-to-olefins emit about 0.9 t, 1 whereas coal-to-olefins emit about 5.8 t. Similar dichotomy appears in the feedstock choice for methanol in the United States and China. While the U.S. companies are aggressively expanding methanol production from natural gas, China is building coal-to-methanol capacities. In the United States, the announced methanol projects are expected to increase the nationwide methanol production capacity from 1.6 million metric tons in 2013 to over 12 million metric tons per year by 2018, and nearly 30 million metric tons per year by the early 2020s. Because the U.S. domestic consumption of methanol has remained relatively stable at about 6 million metric tons per year, the expansion will transform the United States from a net importer to a major exporter. China is the world’s largest methanol consumer and the major target for U.S. methanol export. In 2014, China consumed about 41 million metric tons of methanol, which account for 55% of global demand. Meanwhile, China has been building a unique coal-tomethanol industry. Many coal-producing regions encourage investments in coal conversion to boost demand for coal. China has already more than enough methanol production capacities to meet its demand, yet it continues to build more. Coal-tomethanol is carbon intensive. Making a metric ton of methanol from coal emits roughly 5.3 t of CO2, while making the same amount from natural gas emits only 1.7 t. The capital investment for a coal-to-methanol plant is roughly twice as much as a methane-to-methanol plant of comparable capacity, while the feedstock costs are comparable. The capital cost of coal-to-olefins is nearly four times of that of an ethane steam cracker, with comparable feedstock costs. In terms of operation and maintenance (O&M) costs, such as catalysts, water, energy, and pollution treatment, coal-tochemicals are all much more expensive than shale gas chemicals (Figure 1). Due to great cost advantage, aggressive expansion of U.S. shale gas chemicals could eventually force some of the Chinese coal-to-chemicals producers out of business, and contribute to carbon mitigation by replacing the high-carbon coal-tochemicals.