• Comparative pharmacokinetic study of PEGylated gemcitabine and gemcitabine in rats by LC-MS/MS coupled with pre-column derivatization and MS technique

      Yin, Lei; Ren, Tianming; Zhao, Shiying; Shi, Meiyun; Gu, Jingkai; Univ Arizona, Coll Pharm (ELSEVIER, 2020-01-01)
      Gemcitabine is a small molecular antitumor compound used to treat many types of solid tumors. The clinical application of gemcitabine is limited by its short biological half-life, rapid metabolism and poor tumor tissue targeting. The covalent attachment of polyethylene glycol to gemcitabine is a promising technique to overcome these limitations. After PEGylation, PEGylated gemcitabine could be metabolized into gemcitabine and its metabolites in vivo. Due to the scale effect of PEGylated gemcitabine, the DMPK process of the original drug is greatly changed. Therefore, understanding the pharmacokinetic behavior of PEGylated gemcitabine, gemcitabine and the metabolite dFdU in vivo is really important to clarify the antitumoral activity of these compounds. It would also guide the development of other PEGylated drugs. Due to the complex structure and diverse physiochemical property of PEG, direct quantification analysis of PEGylated gemcitabine presented many challenges in terms of assay sensitivity, selectivity, and robustness. In this article, a data-independent acquisition method, MSALL-based approach using electrospray ionization (ESI) coupled quadrupole time of flight mass spectrometry (MS), was utilized for the determination of PEGylated gemcitabine in rat plasma. The technique consists of a Q1 mass window through all the precursor ions, fragmenting and recording all product ions. PEGylated gemcitabine underwent dissociation in collision cell to generate a series of PEG related ions at m/z 89.0604, 133.0868, 177.1129 of 2, 3, 4 repeating ethylene oxide subunits and PEGylated gemcitabine related ions at m/z 112.0514. PEGylated gemcitabine was detected by the high resolution extracted ions based on the specific compound. For gemcitabine and dFdU, the study used derivatization of these high polarity compounds with dansyl chloride to improve their chromatographic retention. This paper describes comparative pharmacokinetic study of PEGylated gemcitabine and gemcitabine in rats by LC-MS/MS coupled with pre-column derivatization and MSALL technique. The results show that PEGylation could reduce the drug clearance of the conjugated compounds and increase the drug plasma half-life. After administration of PEGylated gemcitabine, the exposure of the free gemcitabine in vivo is lower than administration of gemcitabine, which means that PEGylated gemcitabine possesses lower toxicity compared with gemcitabine.
    • Multiple reservoirs of volatiles in the Moon revealed by the isotopic composition of chlorine in lunar basalts

      Barnes, Jessica J.; Franchi, Ian A.; McCubbin, Francis M.; Anand, Mahesh; Univ Arizona, Lunar & Planetary Lab (PERGAMON-ELSEVIER SCIENCE LTD, 2019-12-01)
      The isotopes of chlorine (Cl-37 and Cl-35) are highly fractionated in lunar samples compared to most other Solar System materials. Recently, the chlorine isotope signatures of lunar rocks have been attributed to large-scale degassing processes that occurred during the existence of a magma ocean. In this study we investigated how well a suite of lunar basalts, most of which have not previously been analyzed, conform to previous models. The Cl isotope compositions (delta Cl-37 (parts per thousand) = [(Cl-37/Cl-35(sample)/Cl-37/Cl-35(SMOC)) - 1] x 1000, where SMOC refers to standard mean ocean chloride) recorded range from similar to+7 to +14 parts per thousand (Apollo 15), +10 to +19 parts per thousand (Apollo 12), +9 to +15 parts per thousand (70017), +4 to +8 parts per thousand (MIL 05035), and +15 to +22 parts per thousand (Kalahari 009). The Cl isotopic data from the present study support the mixing trends previously reported by Boyce et al. (2015) and Barnes et al. (2016), as the Cl isotopic composition of apatites are positively correlated with bulk-rock incompatible trace element abundances in the low-Ti basalts, inclusive of low-Ti and KREEP basalts. This trend has been interpreted as evidence that incompatible trace elements, including Cl, were concentrated in the urKREEP residual liquid of the lunar magma ocean, rather than the mantle cumulates, and that urKREEP Cl had a highly fractionated isotopic composition. The source regions for the basalts were thus created by variable mixing between the mantle (Cl-poor and relatively unfractionated) and urKREEP. The high-Ti basalts show much more variability in measured Cl isotope ratios and scatter around the trend formed by the low-Ti basalts. Most of the data for lunar meteorites also fits the mixing of volatiles in their sources, but Kalahari 009, which is highly depleted in incompatible trace elements, contains apatites with heavily fractionated Cl isotopic compositions. Given that Kalahari 009 is one of the oldest lunar basalts and ought to have been derived from very early-formed mantle cumulates, a heavy Cl isotopic signature is likely not related to its mantle source, but more likely to magmatic or secondary alteration processes, perhaps via impact-driven vapor metasomatism of the lunar crust. (C) 2019 The Authors. Published by Elsevier Ltd.
    • Differential resistance and resilience of functional groups to livestock grazing maintain ecosystem stability in an alpine steppe on the Qinghai-Tibetan Plateau

      Ganjurjav, Hasbagan; Zhang, Yong; Gornish, Elise S; Hu, Guozheng; Li, Yue; Wan, Yunfan; Gao, Qingzhu; Univ Arizona, Sch Nat Resources & Environm (ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2019-12-01)
      Ecosystem stability is one of the main factors maintaining ecosystem functioning and is closely related to temporal variability in productivity. Resistance and resilience reflect tolerance and recovering ability, respectively, of a plant community under perturbation, which are important for maintaining the stability of ecosystems. Generally, heavy grazing reduces the stability of grassland ecosystems, causing grassland degradation. However, how livestock grazing affects ecosystem stability is unclear in alpine steppe ecosystems. We conducted a five-year grazing experiment with Tibetan sheep in a semi-arid alpine steppe on the Qinghai-Tibetan Plateau, China. The experimental treatments included no grazing (NG), light grazing (LG, 2.4 sheep per ha), moderate grazing (MG, 3.6 sheep per ha) and heavy grazing (HG, 6.0 sheep ha). We calculated resistance and resilience of three plant functional groups and ecosystem stability under the three grazing intensities using aboveground primary productivity. The results showed that with increasing grazing intensity, aboveground biomass of each functional group significantly decreased. As grazing intensity increased, the resistance of forbs first increased then decreased. The resilience of graminoids in HG was significantly lower than in LG plots, but the resilience of legumes in HG was higher than in LG and MG plots. The resilience of graminoids was significantly higher than legume and forbs under LG and MG treatments. In HG treatments, resilience of legumes was higher than graminoids and forbs. Ecosystem stability did not change under different grazing intensities, because of dissimilar performance of the resilience and resistance of functional groups. Our results highlight how the differential resistance and resilience of different function groups facilitate the tolerance of alpine steppe to grazing under even a heavy intensity. However, the degradation risk of alpine steppe under heavy grazing still needs to be considered in grassland management due to sharp decreases of productivity.
    • Host-free biofilm culture of “Candidatus Liberibacter asiaticus,” the bacterium associated with Huanglongbing

      Ha, Phuc T.; He, Ruifeng; Killiny, Nabil; Brown, Judith K.; Omsland, Anders; Gang, David R.; Beyenal, Haluk; Univ Arizona, Sch Plant Sci (Elsevier BV, 2019-12)
      Inability to culture the phloem-restricted alpha-proteobacterium “Candidatus Liberibacter asiaticus” (“Ca. L. asiaticus”) or the closely related species (“Candidatus Liberibacter americanus” and “Candidatus Liberibacter africanus”) that are associated with Huanglongbing (HLB) hampers the development of effective long-term control strategies for this devastating disease. Here we report successful establishment and long-term maintenance of host-free “Ca. L. asiaticus” cultures, with the bacterium growing within cultured biofilms derived from infected citrus tissue. The biofilms were grown in a newly designed growth medium under specific conditions. The initial biofilm-based culture has been successfully maintained for over two years and has undergone over a dozen subcultures. Multiple independent cultures have been established and maintained in a biofilm reactor system, opening the door to the development of pure culture of “Ca. L. asiaticus” and the use of genetics-based methods to understand and mitigate the spread of HLB.
    • Is greed contagious? Four experimental studies

      Cardella, Eric; Kugler, Tamar; Anderson, Jennifer; Connolly, Terry; Univ Arizona, Eller Coll Management (WILEY, 2019-12)
      Do people become greedier when interacting with others they perceive to be greedy? It has been speculated that greed contagion exits and may have influenced the 2008 financial collapse. We examined this possibility in four experimental studies using a common pool resource dilemma. Specifically, whether participants' second-round (R2) withdrawal from the common pool was influenced (a) by their assessment of how greedy their opponents' first-round (R1) withdrawal was, (b) by R1 opponents' reputation for being greedy, (c) by observing past behavior of others in unrelated interactions, and (d) when R1 opponents directly confronted them with an assessment of their own greediness of their R1 withdrawal. In addition, Study 2 examined R2 interactions involving new opponents. Taken together, results suggest that there is contagion of greed. However, the connection appears to be driven by participants adjusting to their opponent's actual behavior, not by their evaluation of the greediness of such behavior. It seems that perceptions of greed do not mediate future behavior and, thus, are not necessarily contagious, but norms of selfish behavior are. In this sense, greed perceptions appear to by epiphenomenal in that they are an incidental by-product of the behavioral interaction. We discuss the implications of these findings and suggest directions for further research.
    • Provenance of invaders has scale-dependent impacts in a changing wetland ecosystem

      Amatangelo, Kathryn L.; Stevens, Lee; Wilcox, Douglas A.; Jackson, Stephen T.; Sax, Dov F.; Amatangelo, Kathryn L.; Stevens, Lee; Wilcox, Douglas A.; Jackson, Stephen T.; Sax, Dov F.; et al. (PENSOFT PUBL, 2019-11-19)
      Exotic species are associated with a variety of impacts on biodiversity, but it is unclear whether impacts of exotic specks differ from those of native species with similar growth forms or native species invading disturbed sites. We compared presence and abundance of native and exotic invaders with changes in wetland plant species diversity over a 28-year period by re-surveying 22 ponds to identify factors correlated with observed changes. We also compared communities found within dense patches of native and exotic emergent species with similar habits. Within patches, we found no categorical diversity differences between areas dominated by native or exotic emergent species. At the pond scale, the cover of the exotic grass Phragmites australis best predicted change in diversity and evenness over time, likely owing to its significant increase in coverage over the study period. These changes in diversity and evenness were strongest in younger, less successionally-advanced ponds. Changes associated with cover of P. australis in these ponds were not consistent with expected diversity decreases, but instead with a dampening of diversity gains, such that the least-invaded ponds increased in diversity the most over the study period. There were more mixed effects on evenness, ranging from a reduction in evenness gains to actual losses of evenness in the ponds with highest invader cover. In this wetland complex, the habit, origin and invasiveness of species contribute to diversity responses in a scale- and context-dependent fashion. Future efforts to preserve diversity should focus on preventing the arrival and spread of invaders that have the potential to cover large areas at high densities, regardless of their origin. Future studies should also investigate more thoroughly how changes in diversity associated with species invasions are impacted by other ongoing ecosystem changes.
    • Subsurface Cl-bearing salts as potential contributors to recurring slope lineae (RSL) on Mars

      Wang, Alian; Ling, Zongcheng; Yan, Yuanchao; McEwen, Alfred S.; Mellon, Michael T.; Smith, Michael D.; Jolliff, Bradley L.; Head, James; Univ Arizona, Lunar & Planetary Lab (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2019-11-15)
      We report laboratory experimental results that support a brine-related hypothesis for the recurring slope lineae (RSL) on Mars in which the subsurface Cl-salts, i.e., hydrous chlorides and oxychlorine salts (HyCOS) are the potential source materials. Our experiments revealed that within the observed RSL temperature window T-RSL (250-300 K), the deliquescence of HyCOS could occur in relative humidity ranges (RH >= 22%-46%) much lower than those for hydrous (Mg, Fe)-sulfates (RH >= 75%-96%). In addition, we demonstrated that the RH values kept by common HyCOS and hydrous sulfates in enclosures have a general trend as RHsulfates > RHperchlorates > RHchlorides (with same type of cation) in wide T range. It means that the required RH range for a Cl-bearing salt to deliquescence can be satisfied by a co-existing salt of different type, e.g., in the subsurface layers of mixed salts on Mars. Furthermore, we found a strong temperature dependence of the deliquescence rates for all tested HyCOS, e.g., a duration of 1-5 sols for all HyCOS at the high end (300 K) of T-RSL, and of 20-70 sols for all tested HyCOS (except NaClO4 center dot H2O) at the low end (250 K) of T-RSL, which is consistent with the observed seasonal behavior of RSL on Mars. From a mass-balance point of view, the currently observed evidences on Mars do not support a fully-brine-wetted track model, thus we suggest a brine-triggered granular-flow model for the most RSL. Considering the recurrence of RSL in consecutive martian years, our experimental results support the rehydration of remnant HyCOS layers during a martian cold season through H2O vapor-to-salt direct interaction. We found that the evidences of HyCOS rehydration under Mars relevant P-T-RH conditions are detectable in a few minutes by in situ Raman spectroscopy. This rehydration would facilitate the recharge of H2O back into subsurface HyCOS, which could serve as the source material to trigger RSL in a subsequent warm season. The major limiting factor for this rehydration is the H2O supply, i.e., the H2O vapor density carried by current Mars atmospheric circulation and the diffusion rate of H2O vapor into the salt-rich subsurface in a cold season. In a worst-case scenario, these H2O supplies can support a maximum increase of hydration degrees of two for totally dehydrated HyCOS, whereas the full rehydration of subsurface HyCOS layers can be easily reached during a > 30 degrees obliquity period that has H2O vapor density 10 x to 20 x times the value of current obliquity. Overall, our results imply the existence of a large amount of Cl-bearing salts in the subsurface at RSL sites.
    • Multiscale formulation of pore-scale compressible Darcy-Stokes flow

      Guo, Bo; Mehmani, Yashar; Tchelepi, Hamdi A.; Univ Arizona, Dept Hydrol & Atmospher Sci (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2019-11-15)
      Direct numerical simulation (DNS) of fluid dynamics in digital images of porous materials is challenging due to the cut-off length issue where interstitial voids below the resolution of the imaging instrument cannot be resolved. Such subresolution microporosity can be critical for flow and transport because they could provide important flow pathways. A micro-continuum framework can be used to address this problem, which applies to the entire domain a single momentum equation, i.e., Darcy-Brinkman-Stokes (DBS) equation, that recovers Stokes equation in the resolved void space (i.e., macropores) and Darcy equation in the microporous regions. However, the DBS-based micro-continuum framework is computationally demanding. Here, we develop an efficient multiscale method for the compressible Darcy-Stokes flow arising from the micro-continuum approach. The method decomposes the domain into subdomains that either belong to the macropores or the microporous regions, on which Stokes or Darcy problems are solved locally, only once, to build basis functions. The nonlinearity from compressible flow is accounted for in a local correction problem on each subdomain. A global interface problem is solved to couple the local bases and correction functions to obtain an approximate global multiscale solution, which is in excellent agreement with the reference single-scale solution. The multiscale solution can be improved through an iterative strategy that guarantees convergence to the single-scale solution. The method is computationally efficient and well-suited for parallelization to simulate fluid dynamics in large high-resolution digital images of porous materials. (C) 2019 Elsevier Inc. All rights reserved.
    • Global characteristics of gravity waves in the upper atmosphere of Mars as measured by MAVEN/NGIMS

      Siddle, A.G.; Mueller-Wodarg, I.C.F.; Stone, S.W.; Yelle, R.V.; Univ Arizona, Lunar & Planetary Lab (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2019-11-15)
      We present an analysis of gravity waves in Mars' upper atmosphere above 120 km. Using in-situ data from NGIMS onboard MAVEN we have been able to characterise waves from nearly 4000 orbits. We have used temperature and density profiles to extract perturbations and interpret these as vertically propagating gravity waves which we characterise by their amplitude and wavelength. In this region of the atmosphere gravity waves have amplitudes of around 10%. Vertical wavelengths are found to be around 10-30 km. We observe an increase in gravity wave amplitudes with increasing solar zenith angle. Gravity wave amplitudes appear invariant in altitude on the dayside, however increase with altitude on the nightside.
    • Origin and abundances of H2O in the terrestrial planets, Moon, and asteroids

      McCubbin, Francis M.; Barnes, Jessica J.; Univ Arizona, Lunar & Planetary Lab (ELSEVIER, 2019-11-15)
      The presence of H2O within differentiated terrestrial bodies in the inner Solar System is well established; however, the source(s) of this H2O and the time of its arrival to the inner Solar System is an area of active study. At present, the prevailing model for the origin of inner Solar System H2O calls upon carbonaceous chondrites as the source. This is largely based on reported observations that H- and N-isotopic compositions of differentiated planetary bodies are largely the same and within a range of values that overlaps with carbonaceous chondrites as opposed to comets or the Sun. In this contribution, we evaluate the efficacy of this model and other models for the origin of inner Solar System H2O by considering geochronological constraints on early Solar System history, constraints on primary building blocks of differentiated bodies based on nucleosynthetic isotope anomalies, and constraints from dynamical models of planet formation. In addition to H- and N-isotopic data, these constraints indicate that an interstellar source of H2O was present in the inner Solar System within the first 4 Ma of CAI formation. Furthermore, the most H2O-rich carbonaceous chondrites are unlikely to be the source of H2O for the earliest-formed differentiated bodies based on their minimally overlapping primary accretion windows and the separation of their respective isotopic reservoirs by Jupiter in the timespan of about 1-4 Ma after CAI formation. The presence of deuterium-rich, non-nebular H2O sources in the inner Solar System prior to the formation of carbonaceous chondrites or comets implies early contributions of interstellar ices to both the inner and outer Solar System portions of the protoplanetary disk. Evidence for this interstellar ice component in the inner Solar System may be preserved in LL chondrites and in the mantle of Mars. In contrast to the earlier-formed bodies within the inner Solar System, Earth's protracted accretion window may have facilitated incorporation of H2O in its interior from both the inner and outer Solar System, helping the Earth to become a habitable planet. Published by Elsevier B.V.
    • An in situ investigation on the origins and processing of circumstellar oxide and silicate grains in carbonaceous chondrites

      Zega, Thomas J.; Haenecour, Pierre; Floss, Christine; Univ Arizona, Lunar & Planetary Lab; Univ Arizona, Dept Mat Sci & Engn (WILEY, 2019-11-13)
      We report on the isotopic, chemical, and structural properties of four O-rich presolar grains identified in situ in the Adelaide ungrouped C2, LaPaZ Icefield (LAP) 031117 CO3.0, and Dominion Range (DOM) 08006 CO3.0 chondrites. All four grains have oxygen-isotopic compositions consistent with origins in the circumstellar envelopes (CSE) of low-mass O-rich stars evolved along the red-giant and asymptotic-giant branch (RGB, AGB, respectively) of stellar evolution. Transmission electron microscope (TEM) analyses, enabled by focused-ion-beam scanning electron microscope extraction, show that the grain from Adelaide is a single-crystal Mg-Al spinel, and comparison with equilibrium thermodynamic predictions constrains its condensation to 1500 K assuming a total pressure <= 10(-3) atm in its host CSE. In comparison, TEM analysis of two grains identified in the LAP 031117 chondrite exhibits different microstructures. Grain LAP-81 is composed of olivine containing a Ca-rich and a Ca-poor domain, both of which show distinct orientations, suggesting changing thermodynamic conditions in the host CSE that cannot be precisely constrained. LAP-104 contains a polycrystalline assemblage of ferromagnesian silicates similar to previous reports of nanocrystalline presolar Fe-rich silicates that formed under nonequilibrium conditions. Lastly, TEM shows that the grain extracted from DOM 08006 is a polycrystalline assemblage of Cr-bearing spinel. The grains occur in different orientations, likely reflecting mechanical assembly in their host CSE. The O-isotopic and Cr-rich compositions appear to point toward nonequilibrium condensation. The spinel is surrounded by an isotopically solar pyroxene lacking long-range atomic order and could have served as a nucleation site for its condensation in the interstellar medium or the inner solar protoplanetary disk.
    • Mountain‐Block Recharge: A Review of Current Understanding

      Markovich, Katherine H.; Manning, Andrew H.; Condon, Laura E.; McIntosh, Jennifer C.; Univ Arizona, Dept Hydrol & Atmospher Sci (American Geophysical Union (AGU), 2019-11-11)
      Mountain‐block recharge (MBR) is the subsurface inflow of groundwater to lowland aquifers from adjacent mountains. MBR can be a major component of recharge but remains difficult to characterize and quantify due to limited hydrogeologic, climatic, and other data in the mountain block and at the mountain front. The number of MBR‐related studies has increased dramatically in the 15 years since the last review of the topic was conducted by Wilson and Guan (2004), generating important advancements. We review this recent body of literature, summarize current understanding of factors controlling MBR, and provide recommendations for future research priorities. Prior to 2004, most MBR studies were performed in the southwestern United States. Since then, numerous studies have detected and quantified MBR in basins around the world, typically estimating MBR to be 5–50% of basin‐fill aquifer recharge. Theoretical studies using generic numerical modeling domains have revealed fundamental hydrogeologic and topographic controls on the amount of MBR and where it originates within the mountain block. Several mountain‐focused hydrogeologic studies have confirmed the widespread existence of mountain bedrock aquifers hosting considerable groundwater flow and, in some cases, identified the occurrence of interbasin flow leaving headwater catchments in the subsurface—both of which are required for MBR to occur. Future MBR research should focus on the collection of high‐priority data (e.g., subsurface data near the mountain front and within the mountain block) and the development of sophisticated coupled models calibrated to multiple data types to best constrain MBR and predict how it may change in response to climate warming.
    • The Bolsonaro Election, Antiblackness, and Changing Race Relations in Brazil

      da Silva, Antonio José Bacelar; Larkins, Erika Robb; Univ Arizona (WILEY, 2019-11-11)
      We apply the concept of antiblackness and a Deleuzian approach to sociopolitical events to analyze Jair Bolsonaro's 2018 election in Brazil. Historically, Brazilians turned from overt expressions of antiblackness to subtler forms of racial prejudice, what Sergio Buarque de Holanda (1956) called the "cordial man" who practiced a "gentlemanly" form of white supremacy. Recently, however, cordial racism has eroded in favor of more virulent and explosive manifestations of antiblackness that fueled the sociopolitical climate that enabled Bolsonaro's rise to power. We examine the antiblack backlash against race-conscious laws and policies implemented during the Workers' Party era (2002-16), showing a gradual shift toward more overt expressions of antiblackness that Bolsonaro wielded to political effect in his 2018 campaign.
    • Search for a right-handed gauge boson decaying into a high-momentum heavy neutrino and a charged lepton in pp collisions with the ATLAS detector at root s=13 TeV

      Berlendis, S.; Cheu, E.; Delitzsch, C.M.; Johns, K.A.; Jones, S.; Lampl, W.; LeBlanc, M.; Leone, R.; Loch, P.; Rutherfoord, J.P.; et al. (ELSEVIER, 2019-11-10)
      A search for a right-handed gauge boson W-R, decaying into a boosted right-handed heavy neutrino N-R, in the framework of Left-Right Symmetric Models is presented. It is based on data from proton-proton collisions with a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015, 2016 and 2017, corresponding to an integrated luminosity of 80 fb(-1). The search is performed separately for electrons and muons in the final state. A distinguishing feature of the search is the use of large-radius jets containing electrons. Selections based on the signal topology result in smaller background compared to the expected signal. No significant deviation from the Standard Model prediction is observed and lower limits are set in the W-R and N-R mass plane. Mass values of the W-R smaller than 3.8-5 TeV are excluded for N-R in the mass range 0.1-1.8 TeV. (C) 2019 The Author. Published by Elsevier B.V.
    • The nutritional landscape of host plants for a specialist insect herbivore

      Wilson, Jerome Keaton; Ruiz, Laura; Duarte, Jesse; Davidowitz, Goggy; Univ Arizona, Sch Nat Resources & Environm; Univ Arizona, Neurosci & Cognit Sci; Univ Arizona, Dept Entomol; Univ Arizona, Ecol & Evolutionary Biol (WILEY, 2019-11-08)
      Nutrition has far-reaching effects on both the ecology and evolution of species. A substantial body of work has examined the role of host plant quality on insect herbivores, with a particular focus on specialist-generalist dynamics, the interaction of growth and other physiological attributes on fitness and tritrophic effects. Measures of plant quality usually involve one or two axes of nutritional space: typically secondary metabolites or elemental proxies (N and C) of protein and carbohydrates, respectively. Here, we describe the nutrient space of seven host plants of the specialist insect herbivore, Manduca sexta, using an approach that measures physiologically relevant sources of nutrition, soluble protein and digestible carbohydrates. We show that plant species differ markedly in their nutrient content, offering developing insect herbivores a range of available nutrient spaces that also depend on the age of the leaves being consumed. The majority of host-plant species produce diets that are suboptimal to the herbivore, likely resulting in varying levels of compensatory feeding for M. sexta to reach target levels of protein to ensure successful growth and development. Low-quality diets can also impact immune function leading to complex patterns of optimization of plant resources that maximizes both growth and the ability to defend from parasitoids and pathogens. This study is the first to quantify the nutrient space of a suite of host plants used by an insect herbivore using physiologically relevant measures of nutrition.
    • Coupled Modes of North Atlantic Ocean‐Atmosphere Variability and the Onset of the Little Ice Age

      Anchukaitis, Kevin J.; Cook, Edward R.; Cook, Benjamin I.; Pearl, Jessie; D'Arrigo, Rosanne; Wilson, Rob; Univ Arizona, Dept Geosci; Univ Arizona, Lab Tree Ring Res; Univ Arizona, Sch Geog & Dev (AMER GEOPHYSICAL UNION, 2019-11-07)
      Hydroclimate extremes in North America, Europe, and the Mediterranean are linked to ocean and atmospheric circulation anomalies in the Atlantic, but the limited length of the instrumental record prevents complete identification and characterization of these patterns of covariability especially at decadal to centennial time scales. Here we analyze the coupled patterns of drought variability on either sides of the North Atlantic Ocean basin using independent climate field reconstructions spanning the last millennium in order to detect and attribute epochs of coherent basin‐wide moisture anomalies to ocean and atmosphere processes. A leading mode of broad‐scale moisture variability is characterized by distinct patterns of North Atlantic atmosphere circulation and sea surface temperatures. We infer a negative phase of the North Atlantic Oscillation and colder Atlantic sea surface temperatures in the middle of the fifteenth century, coincident with weaker solar irradiance and prior to strong volcanic forcing associated with the early Little Ice Age.
    • California's methane super-emitters

      Duren, Riley M; Thorpe, Andrew K; Foster, Kelsey T; Rafiq, Talha; Hopkins, Francesca M; Yadav, Vineet; Bue, Brian D; Thompson, David R; Conley, Stephen; Colombi, Nadia K; et al. (NATURE PUBLISHING GROUP, 2019-11-07)
      Methane is a powerful greenhouse gas and is targeted for emissions mitigation by the US state of California and other jurisdictions worldwide1,2. Unique opportunities for mitigation are presented by point-source emitters-surface features or infrastructure components that are typically less than 10 metres in diameter and emit plumes of highly concentrated methane3. However, data on point-source emissions are sparse and typically lack sufficient spatial and temporal resolution to guide their mitigation and to accurately assess their magnitude4. Here we survey more than 272,000 infrastructure elements in California using an airborne imaging spectrometer that can rapidly map methane plumes5-7. We conduct five campaigns over several months from 2016 to 2018, spanning the oil and gas, manure-management and waste-management sectors, resulting in the detection, geolocation and quantification of emissions from 564 strong methane point sources. Our remote sensing approach enables the rapid and repeated assessment of large areas at high spatial resolution for a poorly characterized population of methane emitters that often appear intermittently and stochastically. We estimate net methane point-source emissions in California to be 0.618 teragrams per year (95 per cent confidence interval 0.523-0.725), equivalent to 34-46 per cent of the state's methane inventory8 for 2016. Methane 'super-emitter' activity occurs in every sector surveyed, with 10 per cent of point sources contributing roughly 60 per cent of point-source emissions-consistent with a study of the US Four Corners region that had a different sectoral mix9. The largest methane emitters in California are a subset of landfills, which exhibit persistent anomalous activity. Methane point-source emissions in California are dominated by landfills (41 per cent), followed by dairies (26 per cent) and the oil and gas sector (26 per cent). Our data have enabled the identification of the 0.2 per cent of California's infrastructure that is responsible for these emissions. Sharing these data with collaborating infrastructure operators has led to the mitigation of anomalous methane-emission activity10.
    • A Modality-Independent Network Underlies the Retrieval of Large-Scale Spatial Environments in the Human Brain

      Huffman, Derek J; Ekstrom, Arne D; Univ Arizona, Psychol Dept (CELL PRESS, 2019-11-06)
      In humans, the extent to which body-based cues, such as vestibular, somatosensory, and motoric cues, are necessary for normal expression of spatial representations remains unclear. Recent breakthroughs in immersive virtual reality technology allowed us to test how body-based cues influence spatial representations of large-scale environments in humans. Specifically, we manipulated the availability of body-based cues during navigation using an omnidirectional treadmill and a head-mounted display, investigating brain differences in levels of activation (i.e., univariate analysis), patterns of activity (i.e., multivariate pattern analysis), and putative network interactions between spatial retrieval tasks using fMRI. Our behavioral and neuroimaging results support the idea that there is a core, modality-independent network supporting spatial memory retrieval in the human brain. Thus, for well-learned spatial environments, at least in humans, primarily visual input may be sufficient for expression of complex representations of spatial environments.
    • Biologically‐Relevant Trends in Springtime Temperatures Across the United States

      Crimmins, Theresa M.; Crimmins, Michael A.; Univ Arizona, Dept Environm Sci; Univ Arizona, Sch Nat Resources & Environm (AMER GEOPHYSICAL UNION, 2019-11-06)
      Long‐term trends in temperature—a primary driver of phenology—are typically evaluated using monthly or seasonal averages. However, accumulated warmth, rather than average temperature, cues phenological events; further, the amount of heat necessary to trigger activity is species‐specific. We evaluated trends in the timing of three heat accumulation thresholds encompassing spring‐season biological activity in the conterminous United States over a 70‐year period to document changes from a biologically relevant perspective. The Southwest, Northeast, and Northwest regions exhibit the strongest advancements. Rates of change vary among thresholds within many regions, resulting in temporal compression and lengthening within the season. Further, in the Eastern United States, the days between when a single threshold is met in the south and north are decreasing; in the West, the opposite pattern is occurring. These trends generally match long‐term observations of species' phenology, underscoring the value of this approach for documenting biologically relevant changes in temperature.
    • Water splitting promoted by electronically conducting interlayer material in bipolar membranes

      Chen, Yingying; Martínez, Rodrigo J.; Gervasio, Don; Baygents, James C.; Farrell, James; Univ Arizona, Dept Chem & Environm Engn (SPRINGER, 2019-11-06)
      Bipolar membranes are used in a variety of industrial applications to split water into hydronium and hydroxide ions. This research investigated the hypothesis that an electronically conducting material between the anion and cation exchange membranes can increase the rate of water splitting by increasing the electric field intensity in the mobile ion depleted region. Bipolar membranes were constructed with electronically conducting (graphene and carbon nanotubes) and electronically insulating (graphene oxide) interlayer materials of varying thickness. All three interlayer materials decreased the voltage required for water splitting compared to a bipolar membrane with no interlayer material. Quantum chemistry simulations were used to determine the catalytic effect of proton accepting and proton releasing sites on the three interlayer materials. Neither graphene nor carbon nanotubes had catalytic sites for water splitting. Thicker layers of graphene oxide resulted in decreased rates of water splitting at each applied potential. This effect can be attributed to a diminished electric field in the mobile ion depleted region with increasing catalyst layer thickness. In contrast, membrane performance with the electronically conducting graphene and carbon nanotube interlayers was independent of the interlayer thickness. An electrostatic model was used to show that interlayer electronic conductance can increase the electric field intensity in the mobile ion depleted region as compared to an electronically insulating material. Thus, including electronically conducting material in addition to a traditional catalyst may be a viable strategy for improving the performance of bipolar membranes.