As evidenced by isotope geochemistry, the persistence of primitive reservoirs indicates that the earth's lower mantle is likely to be heterogeneous. Such heterogeneity could be a legacy from magma-ocean (MO) solidification. The viscosity of MO is a key parameter to constrain the solidification type of MO. Here we directly measure the viscosity of peridotite (an analog of MO composition) melt at the pressure-temperature conditions of the deep mantle, using the in situ falling sphere method. The viscosity of peridotite melt along liquidus is in the range of 38-17 mPa s at pressures from 7 to 25 GPa, which is 0.9-0.4 times of the estimation based on the viscosity of endmember compositions. Low viscosity favors fractional solidification and chemically layering of the early mantle at least to the top lower mantle, which could be a source of heterogeneity for the present mantle.

We attempted to generate ultrahigh pressure and temperature simultaneously using a multi-anvil apparatus by combining the technologies of ultrahigh-pressure generation using sintered diamond (SD) anvils, which can reach 120 GPa, and ultrahigh-temperature generation using a boron-doped diamond (BDD) heater, which can reach 4000 K. Along with this strategy, we successfully generated a temperature of 3300 K and a pressure of above 50 GPa simultaneously. Although the high hardness of BDD significantly prevents high-pressure generation at low temperatures, its high-temperature softening allows for effective pressure generation at temperatures above 1200 K. High temperature also enhances high-pressure generation because of the thermal pressure. We expect to generate even higher pressure in the future by combining SD anvils and a BDD heater with advanced multi-anvil technology.

Titanium (Ti) isotopes are emerging as a power tool for studying magmatic processes on the Earth and other planets. Pioneering studies carried out bulk-rock Ti isotopic measurements by conventional solution nebulization multi-collector inductively coupled plasma mass spectrometry (SN-MC-ICP-MS) and in situ Ti isotopic analysis via secondary ionization mass spectrometry (SIMS), which sacrificed spatial resolution and had relatively low analytical precision, respectively. In this work, a novel and robust method for in situ Ti isotopic analysis of titanium-bearing minerals (i.e., rutile and ilmenite) was presented, based on a femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometer (fs-LA-MC-ICP-MS). Very stable isotopic signals can be ensured after careful optimization of the parameters of fs-LA (e.g., fluence, spot size, and frequency), and thus a high analytical precision has been obtained for Alfa-Ti (an ultrapure Ti metal rod) under a high spatial resolution of spot diameter = 30 mu m. The within run and external reproducibility for delta Ti-49/47 (Ti-49/Ti-47 isotopic ratio, reported as delta Ti-49/47 notation, in parts in 10(3)) measurement on Alfa-Ti are 0.05 parts per thousand (2SE, internal precision of within-spot analysis) and 0.07 parts per thousand (2SD, external reproducibility of spot-to-spot analysis), respectively. A series of titanium-bearing minerals, including five potential rutile U-Pb chronological standards and four potential ilmenite Fe isotope standards, were assessed for Ti isotopic homogeneity on a 30 mu m-scale and precision of the measurement. The most homogeneous minerals were subsequently used to comprehensively evaluate the analytical accuracy and potential matrix effect. Our results show that in situ Ti isotopic analysis is susceptible to matrix effects when using fs-LA and accurate delta Ti-49/47(OL-Ti) values (calibrated against the OL-Ti reference material developed in the Origins Laboratory of the University of Chicago) can be obtained when a matrix-matched reference material is used as a bracketing standard. Therefore, well characterized matrix-matched reference materials are necessary for in situ Ti isotopic analysis. KNW rutile and PZH12-15 ilmenite characterized in this study show potential as suitable reference materials for micro-beam Ti isotopic analysis.

For several decades, economists have been warning the academic community that graduate training has been too tightly focused on careers in higher education, using the apprenticeship model in which students are trained to become tenure-track faculty at research-focused institutions. These jobs are simply not growing at the same rate as graduate admissions. In biomedical research, the mismatch in supply and demand has now been widely recognized. Other disciplines have begun these discussions, but for smaller fields, employment trends are more difficult to identify because they are subsumed in aggregated national statistics. For non-biomedical biological fields in particular, such as ecology, using biology statistics may be inappropriate since trends within the field may be obscured by the strong signal from biomedical disciplines. Here, we use the 2013 Survey of Doctorate Recipients (SDR) to investigate career paths for ecology Ph.D. recipients in the United States, and present the first fine-scale national profile of careers in ecology. Our results demonstrate that while involuntary unemployment is low for ecology Ph.D. recipients (3.3%) and job satisfaction is high, the assumptions of the prevailing apprenticeship model are inappropriate: Less than 20% of employed recent ecology Ph.D. graduates are in tenure-track positions at a Ph.D.-granting university. Accordingly, proactive steps could be taken to create more realistic expectations about graduate training and preparation for diverse careers. Further, the SDR data provide demographic profiles for ecology. Ethnic diversity has remained low in ecology (7.5% non-Caucasian for Ph.D. recipients since 2000). Gender balance in career-track positions appears to have improved by multiple metrics. However, women are overrepresented in non-tenure-track academic positions, where access to resources that support professional advancement may be limited relative to tenure-track jobs, and salary disparities appear for women in private academic institutions. Thus, while there is much good news in these data, we suggest that ecology as a field would benefit from (1) a broad analysis of the training required to make Ph.D.s best prepared for jobs outside of the research-oriented tenure track and (2) continued attention to increasing diversity and equity.

Ras converting enzyme 1 (Rce1) is an integral membrane endoprotease localized to the endoplasmic reticulum that mediates the cleavage of the carboxyl-terminal three amino acids from CaaX proteins, whose members play important roles in cell signaling processes. Examples include the Ras family of small GTPases, the gamma-subunit of heterotrimeric GTPases, nuclear lamins, and protein kinases and phosphatases. CaaX proteins, especially Ras, have been implicated in cancer, and understanding the post-translational modifications of CaaX proteins would provide insight into their biological function and regulation. Many proteolytic mechanisms have been proposed for Rce1, but sequence alignment, mutational studies, topology, and recent crystallographic data point to a novel mechanism involving a glutamate-activated water and an oxyanion hole. Studies using in vivo and in vitro reporters of Rce1 activity have revealed that the enzyme cleaves only prenylated substrates and the identity of the a(2) amino residue in the Ca(1)a(2)X sequence is most critical for recognition, preferring Ile, Leu, or Val. Substrate mimetics can be somewhat effective inhibitors of Rce1 in vitro. Small-molecule inhibitor discovery is currently limited by the lack of structural information on a eukaryotic enzyme, but a set of 8-hydroxyquinoline derivatives has demonstrated an ability to mislocalize all three mammalian Ras isoforms, giving optimism that potent, selective inhibitors might be developed. Much remains to be discovered regarding cleavage specificity, the impact of chemical inhibition, and the potential of Rce1 as a therapeutic target, not only for cancer, but also for other diseases.

Elevated allochthonous inputs of organic matter are increasingly recognized as a driver of ecosystem change in lakes, particularly when concurrent with eutrophication. Evaluation of lakes in a nutrient-color paradigm (i.e., based on total phosphorus and true color) enables a more robust approach to research and management. To assess temporal and spatial patterns in nutrient-color status for U.S. lakes and associated food web attributes, we analyzed the U.S. Environmental Protection Agency's National Lakes Assessment (NLA) data. With 1000+ lakes sampled in 2007 and 2012 in a stratified random sampling design, the NLA enables rigorous assessment of lake condition across the continental U.S. We demonstrate that many U.S. lakes are simultaneously experiencing eutrophication and brownification to produce an abundance of "murky" lakes. Overall, "blue" lakes decreased by similar to 18% (46% of lakes in 2007 to 28% in 2012) while "murky" lakes increased by almost 12% (24% of lakes in 2007 to 35.4% in 2012). No statistical differences were observed in the proportions of "green" or "brown" lakes. Regionally, murky lakes significantly increased in the Northern Appalachian, Southern Plains, and Xeric ecoregions. Murky lakes exhibited the highest epilimnetic chlorophyll a concentrations, cyanobacterial densities, and microcystin concentrations. Total zooplankton biomass was also highest in murky lakes, primarily due to increased rotifer and copepod biomass. However, zooplankton : phytoplankton biomass ratios were low, suggesting reduced energy transfer to higher trophic levels. These results emphasize that many lakes in the U.S. are simultaneously "greening" and "browning", with potentially negative consequences for water quality and food web structure.

Winter is an important season for many limnological processes, which can range from biogeochemical transformations to ecological interactions. Interest in the structure and function of lake ecosystems under ice is on the rise. Although limnologists working at polar latitudes have a long history of winter work, the required knowledge to successfully sample under winter conditions is not widely available and relatively few limnologists receive formal training. In particular, the deployment and operation of equipment in below 0 degrees C temperatures pose considerable logistical and methodological challenges, as do the safety risks of sampling during the ice-covered period. Here, we consolidate information on winter lake sampling and describe effective methods to measure physical, chemical, and biological variables in and under ice. We describe variation in snow and ice conditions and discuss implications for sampling logistics and safety. We outline commonly encountered methodological challenges and make recommendations for best practices to maximize safety and efficiency when sampling through ice or deploying instruments in ice-covered lakes. Application of such practices over a broad range of ice-covered lakes will contribute to a better understanding of the factors that regulate lakes during winter and how winter conditions affect the subsequent ice-free period.