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Long-term atmospheric CO2 concentration records have suggested a reduction in the positive effect of warming on high-latitude carbon uptake since the 1990s. A variety of mechanisms have been proposed to explain the reduced net carbon sink of northern ecosystems with increased air temperature, including water stress on vegetation and increased respiration over recent decades. However, the lack of consistent long-term carbon flux and in situ soil moisture data has severely limited our ability to identify the mechanisms responsible for the recent reduced carbon sink strength. In this study, we used a record of nearly 100 site-years of eddy covariance data from 11 continuous permafrost tundra sites distributed across the circumpolar Arctic to test the temperature (expressed as growing degree days, GDD) responses of gross primary production (GPP), net ecosystem exchange (NEE), and ecosystem respiration (ER) at different periods of the summer (early, peak, and late summer) including dominant tundra vegetation classes (graminoids and mosses, and shrubs). We further tested GPP, NEE, and ER relationships with soil moisture and vapor pressure deficit to identify potential moisture limitations on plant productivity and net carbon exchange. Our results show a decrease in GPP with rising GDD during the peak summer (July) for both vegetation classes, and a significant relationship between the peak summer GPP and soil moisture after statistically controlling for GDD in a partial correlation analysis. These results suggest that tundra ecosystems might not benefit from increased temperature as much as suggested by several terrestrial biosphere models, if decreased soil moisture limits the peak summer plant productivity, reducing the ability of these ecosystems to sequester carbon during the summer.

Top-down estimates of CO2 fluxes are typically constrained by either surface-based or space-based CO2 observations. Both of these measurement types have spatial and temporal gaps in observational coverage that can lead to differences in inferred fluxes. Assimilating both surface-based and space-based measurements concurrently in a flux inversion framework improves observational coverage and reduces sampling related artifacts. This study examines the consistency of flux constraints provided by these different observations and the potential to combine them by performing a series of 6-year (2010?2015) CO2 flux inversions. Flux inversions are performed assimilating surface-based measurements from the in situ and flask network, measurements from the Total Carbon Column Observing Network (TCCON), and space-based measurements from the Greenhouse Gases Observing Satellite (GOSAT), or all three data sets combined. Combining the data sets results in more precise flux estimates for subcontinental regions relative to any of the data sets alone. Combining the data sets also improves the accuracy of the posterior fluxes, based on reduced root-mean-square differences between posterior flux-simulated CO2 and aircraft-based CO2 over midlatitude regions (0.33?0.56?ppm) in comparison to GOSAT (0.37?0.61?ppm), TCCON (0.50?0.68?ppm), or in situ and flask measurements (0.46?0.56?ppm) alone. These results suggest that surface-based and GOSAT measurements give complementary constraints on CO2 fluxes in the northern extratropics and can be combined in flux inversions to improve constraints on regional fluxes. This stands in contrast with many earlier attempts to combine these data sets and suggests that improvements in the NASA Atmospheric CO2 Observations from Space (ACOS) retrieval algorithm have significantly improved the consistency of space-based and surface-based flux constraints.

The springtime transition to regional-scale onset of photosynthesis and net ecosystem carbon uptake in boreal and tundra ecosystems are linked to the soil freeze-thaw state. We present evidence from diagnostic and inversion models constrained by satellite fluorescence and airborne CO2 from 2012 to 2014 indicating the timing and magnitude of spring carbon uptake in Alaska correlates with landscape thaw and ecoregion. Landscape thaw in boreal forests typically occurs in late April (DOY 111 ± 7) with a 29 ± 6 day lag until photosynthetic onset. North Slope tundra thaws 3 weeks later (DOY 133 ± 5) but experiences only a 20 ± 5 day lag until photosynthetic onset. These time lag differences reflect efficient cold season adaptation in tundra shrub and the longer dehardening period for boreal evergreens. Despite the short transition from thaw to photosynthetic onset in tundra, synchrony of tundra respiration with snow melt and landscape thaw delays the transition from net carbon loss (at photosynthetic onset) to net uptake by 13 ± 7 days, thus reducing the tundra net carbon uptake period. Two global CO2 inversions using a CASA-GFED model prior estimate earlier northern high latitude net carbon uptake compared to our regional inversion, which we attribute to (i) early photosynthetic-onset model prior bias, (ii) inverse method (scaling factor + optimization window), and (iii) sparsity of available Alaskan CO2 observations. Another global inversion with zero prior estimates the same timing for net carbon uptake as the regional model but smaller seasonal amplitude. The analysis of Alaskan eddy covariance observations confirms regional scale findings for tundra, but indicates that photosynthesis and net carbon uptake occur up to 1 month earlier in evergreens than captured by models or CO2 inversions, with better correlation to above-freezing air temperature than date of primary thaw. Further collection and analysis of boreal evergreen species over multiple years and at additional subarctic flux towers are critically needed.

Recently, alterations in dopamine signaling have been implicated in Huntington's disease. In this work, dopamine release and uptake was measured in striatal slices from the R6/2 transgenic mouse model of Huntington's disease using fast-scan cyclic voltammetry at carbon-fiber microelectrodes. Dopamine release in brain slices from 6-week-old R6/2 mice is substantially reduced (53% of wild type), while dopamine uptake is unaffected. In agreement with this, R6/2 mice injected with the dopamine uptake inhibitor cocaine exhibited a blunted motor activity response (54% of wild type). At 10 weeks of age, an even more dramatic motor activity decrease in response to cocaine injection (21% of wild type) was observed. Moreover, the pre-drug activity of 10-week-old R6/2 mice was significantly reduced (by 37%) compared with 6-week-old R6/2 mice. Striatal dopamine release decreased with age, indicating that progressive alterations in dopaminergic pathways may affect motor activity. The inhibition constants of cocaine and methamphetamine (METH) determined in brain slices differed little between genotype or age group, suggesting that the decreased responses to cocaine and METH arise from compromised dopamine release rather than differences in uptake or drug action. Collectively, these data demonstrate (i) a reduction in the ability of dopamine terminals to release dopamine and (ii) the importance of this attenuation of release on the motor symptoms of Huntington's disease.

In today's chemical industry there is a great need to both improve the effectiveness of existing assets and generate new prospects for business renewal. In addition, the fast pace of the current ‘information age’ makes it necessary to bring about both of these in a rapid and responsive manner in order to be competitive. On-line spectroscopic techniques, which provide rapid and representative information on a chemical process, are inherently capable of facilitating both asset productivity and business renewal. Chemometric ‘tools’, in principle, are particularly well suited for improving the effectiveness of on-line spectroscopic techniques through two main functions: (1) extracting the wealth of useful, yet convoluted information that is available from such techniques; and (2) facilitating the automation of on-line analytical techniques, at a time when manufacturing plant support resources are being ‘cut back’. Multivariate calibration tools can be used to improve the performance of existing methods, as well as to prepare more stable methods for new applications. More ‘soft’ modeling tools, such as multivariate curve resolution, are particularly well suited for providing timely information during the early stages of new process development, where very little is known about the process chemistry and dynamics. In practice, however, there is a wide range of issues, both technical and non-technical, that limit and even prevent the successful application of chemometric techniques for on-line spectroscopy. This paper will illustrate both the means by which chemometric tools can make a difference in the chemical industry, and the issues that are preventing its successful implementation, using examples from actual process development projects and on-line measurements. Copyright © 2000 John Wiley & Sons, Ltd.

The ability of near-infrared (NIR) diffuse reflectance spectroscopy to characterize reaction-injection-molded (RIM) polyurethane elastomers is demonstrated. The advantage of NIR spectroscopy over other analytical methods is its ability to analyze samples without any preparation. In this work, the specific effects of composition, density, phase separation, and moisture content on the NIR spectra of the polymers are identified. In addition, the ability of NIR spectroscopy to make rapid assessments of physical properties, such as heat sag and flex modulus, is demonstrated. In order to perform these analyses, the multivariate statistical methods of principal components analysis (PCA) and partial least squares (PLS) are used.

The sections in this article are Introduction Hydrocarbons Saturated Hydrocarbons Unsaturated Hydrocarbons Aromatic Hydrocarbons Hydrocarbon Polymers Sample State Effects – Hydrocarbons Ketones, Esters, Ethers, and Peroxides Polymers with Ketone, Ester, and Ether Groups Sample State Effects – Ketones, Esters, Ethers, and Peroxides Alcohols and Organic Acids Sample State Effects – Alcohols and Organic Acids OH-Containing Polymers Nitrogen-Containing Compounds Sample State Effects – Nitrogen-Containing Compounds Halogenated Compounds Aqueous Systems Inorganic Materials Gases Acknowledgments

Somatogamy by rhizoidal anastomosis initiates sexual reproduction and resting body formation in Chytriomyces hyalinus Karling. At least two external factors influence somatogamy: the level of nutrients available and the chance association of rhizoids of young thalli (germlings). Syngamy and resting body development occurs in axenic culture when germlings are developing on a nutrient-depleted substrate and when the rhizoids of two germlings (contributing thalli) anastomose. After anastomosis, the contents of the two contributing thalli flow into a swelling (incipient fusion body) which develops near the point of anastomosis. Nuclear fusion occurs in the fusion body (incipient resting body). After nuclear fusion, the resting body continues to enlarge, its wall thickens, and lipoid inclusions coalesce to form a large refractile globule. This sexual process is better referred to as somatogamy rather than Siphonaria-type sexual reproduction.

Les divisions nucleaires somatiques des plasmodes sporangiogenes de W.p. sont etudiees a l'aide de la microscopie electronique par transmission. Durant la metaphase chaque noyau presente une configuration cruciforme

Previous studies of coalition behaviour have failed to find any significant effects of monetary stakes. The study described here proposes a possible explanation for these previous failures and tests this explanation, along with the equal excess model of coalition formation, which makes specific predictions regarding the effects of stakes. Each of 288 four-person groups played one of two apex games, for either high ($30) or low ($3) monetary stakes. The two games were alike in that the pay-offs (values) per member were greater in the apex (AB, AC, AD) coalitions than the base (BCD) coalition, and the value of the AB coalition was greater than the values of the other apex coalitions. The games differed in that, compared to the AB coalition, the values of the other apex coalitions were greater in Game 1 than Game 2. Player A thus had better alternatives to the AB coalition in Game 1 than Game 2. As predicted by the equal excess model, in Game 1 the apex player (A) received a larger share of the pay-off in the AB coalition—but the AB coalition formed less frequently—under high stakes than under low stakes. Contrary to the predictions of the equal excess model, however, monetary stakes had no effect on coalition behaviour in Game 2. The findings suggest that the failure of previous studies to find significant effects for monetary stakes has probably been due to their use of weak stakes manipulations and/or their use of games such as Game 2, in which one of the coalitions has a value per member that is relatively large.

The problematic organism, Sporocarpon, was among the first fossil fungi to be described. The genus was actually a heterogeneous assemblage of fungal forms, and was eventually divided into several taxa including Sporocarpon, Dubiocarpon} and A{ycocarpon. In the present paper these organisms, as well as a similar, previously undescribed genus, Coleocarpon, are described from Lower Middle, and Upper Pennsylvanian strata in North America, and from Upper Carboniferous sediments in England. Although initially considered to be radiolarian-like protozoa, these structures show far more similarity to ascomycetous cleistothecia. All forms are ornamented, spherical bodies with a complex wall which encloses scattered asci and ascospores. Taxa are distinguished primarily by diffierences in the organization of the cleistothecial wall. Structurally similar organisms are found today among the Eurotiales. J7ossiles incertae sedis. This taxonomic organization has been consistently accepted to the present time (BaxterS 1960; Davis and Leisman, 1962; Tiffiney and Barghoorn, 1974). Fossil sporocarps were first reported from North America by Baxter (1960), who described Sporocarpon and Dubiocarpon from the Pennsylvanian of Kansas and Missouri. Shortly afterwards, Davis and Leisman (1962) described several species of Mycocarpon, Sporocarpon, and Dubiocarpon from the Middle Pennsylvanian of Kansas. These genera were not investigated further until Traquairia, a morphologically similar form, was described from several localities in the United States and Europe (Stubblefield and Taylor, 1983). Fungal sporocarps are far more abundant in North American coal ball floras than might be implied by their scarcity in paleobotanical literature. Recently, an investigation of North Amencan Traquairia has demonstrated its abundance and the value of scanning electron microscopy in documenting the structure of fossil cleistothecia (Stubblefield and Taylor, 1983). Further examination of North American coal balls has revealed representatives of Sporocarpons Dubiocarpons and Mycocarpon as well as an additionalS previously undescribed organism with a similar organization. In this paper representatives ofthese taxa from several North American coal ball localities are described and compared with their European IN THE LATE 1800 s, Williamson proposed the generic name Sporocarpon for several types of problematic microfossils from the Upper Carboniferous of England (Williamson, 1878 1880, 1883). Soon after the first of these, S. cellulosum, was described, Williamson proposed seven additional species: S. elegans, S. compactum, S. tabulatum (Williamson, 1878) S. pachyderma, S. asteroides, S. ornatum (Williamson, 1880), and S. anomalum (WilliamsonS 1883). At this point the genus was loosely defined and included a number of disparate forms. Although McLean (1912) recognized the heterogeneity ofthe assemblage, he chose only to divide the genus into five sections. Much later Hutchinson (1955) reexamined Williamson's original material and revised the genus retaining only S. cellulosum and S. asteroides in Sporocarpon, and erecting two new genera: Mycocarpon to include S. pachyderma, and Dubiocarpon to include S. compactum and S. tabulatum. He placed S. ornatum (which he regarded as a synonym of S. anomalum) in ' Received for publication 13 December 1982revision accepted 14 June 1983. The authors wish to thank Dr. Roland L. Seymour of The Ohio State University who generously participated in much thought-provoking discussion. We also appreciate the use of specimens loaned to us by Dr. Gilbert A. Leisman of Emporia State University and Dr. Gar W. Rothwell of Ohio University who loaned several of the specimens examined in this study.

Vegetative nuclear divisions in cystosoral plasmodia from the shoot system of Sorosphaera veronicae Schroeter were studied with standard transmission electron microscopy. Each metaphase nucleus forms a cruciform configuration as the persistent nucleolus elongates perpendicularly to chromatin aligned on the equatorial plate. The nuclear envelope remains intact during metaphase and anaphase. Each spindle pole consists of a fenestrated nuclear envelope with an exteriorly situated centriole and closely associated endoplasmic reticulum. Intranuclear membranous vesicles occur within metaphase and anaphase nuclei and are closely associated with chromatin and nuclear envelope. Microtubules pass from centrioles into the nucleus and are also attached to chromatin at kinetochores. THE UNIQUENESS of somatic nuclear divisions in aquatic zoosporous fungi comprising the Class Plasmodiophoromycetes has been recognized since Nawaschin (1899) reported his observations on plasmodial development in Plasmodiophora brassicae Woron. Additionally described taxa of these obligately parasitic, holocarpic fungi have this unique nuclear division, now commonly called cruciform (Karling, 1968; Miller, 1958). Cruciform division, occurring in sporangial and cystosoral plasmodial development, is characterized by a persistent nuclear envelope and a large persistent nucleolus. During metaphase the persistent nucleolus, which divides simultaneously with the chromatin, elongates in the direction of the poles and at right angle to the equatorial chromatin plate, forming a cruciform configuration.

Coalition formation in decision making of three-person group systems was studied using a coalition game. This was devised as an analogue for many situations in which groups make decisions, both in “real life” and in laboratory experiments. One of the important findings of the study was that in this game, unlike the games usually employed in coalition research, the “resources” that the triad members possessed had relatively little effect upon which members tended to enter into a coalition or upon which of the partners to a coalition tended to receive the larger payoff. Instead, the formation of coalitions tended to depend upon whether the payoff structure of the game made it possible for the partners in a particular coalition to reach an agreement giving both of them relatively large payoffs. The findings are discussed in relation to previous research on coalitions.

A B S T R A C T The nutrition and its influence on some morphological characteristics of one isolate of Chytriomyces aureus Karling and two isolates of C. hyalinus Karling, one with and one without resting bodies, was studied. All three isolates required exogenous thiamine for optimum growth. Glucose, fructose, mannose, maltose, cellobiose, and starch supported good or moderate amounts of growth of all the isolates. Galactose, arabinose, xylose, ribose, sucrose, lactose, and raffinose supported little or only trace amounts of growth of C. hyalinus, with resting bodies, but failed to produce any growth of C. aureus and C. hyalinus, without resting bodies. All isolates utilized ammonium [NH4NO3, (NH4)2S04, NH4Cl] as nitrogen sources but were unable to utilize nitrate (KN03) and nitrite (KNO2). All isolates were able to grow at pH ranges of 5-8; the optimum pH range was 6.5. Both isolates of C. hyalinus were able to grow at a temperature of 10-30 C, whereas C. aureus did not grow below 15 C or above 25 C. Sporangial size was influenced by varying temperature levels, pH ranges, vitamins, carbohydrates, and nitrogen sources, while the morphology and sizes of zoospores, lipoid globules, apophyses, and rhizoids were little affected. The similarity of response exhibited by both species of Chytriomyces to various nutrients may suggest that these are closely related taxa.

MILLER, CHARLES E. (A. and M. College of Texas, College Station.) Studies on the life cycle and taxonomy of Ligniera verrucosa. Amer. Jour. Bot. 46(10): 725-729. Illus. 1959.-A study of the roots of Veronica persica Poir. and V. hederaefolia L. plants infected with Sorosphaera veronicae Schroeter revealed intracellular cystosori and zoosporangial sori of Ligniera verrucosa. The zoosporangial phase of this species has been heretofore unknown. The plasmodia of L. verrucosa occur in root hairs, and other epidermal and sub-epidermal cells of the roots. Zoosporangial and cystosoral plasmodia are indistinguishable until cleavage has started. It is thought that plasmodia produced during early infection develop into zoosporangia, while those produced later develop into resting spores. Zoospores discharged from zoosporangia may reinfect host cells developing there into zoosporangial or cystosoral plasmodia. No evidence for any sexual process was observed. The spherical zoosporangia making up a single zoosporangial sorus may be interconnected; a single discharge pore may serve to liberate zoospores from different zoosporangia. In the Plasmodiophorales the classical basis for generic distinction has been the arrangement of the resting spores in the sorus. Ligniera, because of the supposedly uncharacteristic nature of its cystosori, has been suggested as a host-variety of Sorosphaera. A comparative study of the cystosori and zoosporangia of Ligniera and Sorosphaera growing in a single host has led to the conclusion that these genera should be considered distinct. WHILE SURVEYING the roots of Veronica persica Poir. and V. hederaefolia L., host plants of Sorosphaera veronicae Schroeter heavily infected with cystosori which commonly occur in enlargements of theshoot system,the writer (1958b) foundcystosori and zoosporangial sori of the genus Ligniera Maire and Tison (1911). Further studies indicated that it was L. verrucosa Maire and Tison, a species in which the zoosporangial phase has not previously been found. Because of this, and also since the validity of the species and the genus has been questioned (Palm and Burk, 1933), it seemed opportune to make a study of this parasite. DEVELOPMENT OF THE PARASITE.-The following description of L. verrucosa is made from living and preserved material of the parasite in the roots of Veronica persica and V. hederaefolia. Prior to this report, the species was described as a parasite of the root hairs and roots of V. arvensis L., Beta vulgaris L., Chenopodium album L., Bromus L., and Festuca L.3 The parasite apparently completes its life cycle in the root hairs, other epidermal cells and sub-epidermal cells of the roots of the host (fig. 1, 3, 8). As is typical of Ligniera, no hypertrophy of the host cells occurs. The zoospore after penetrating the root cell develops into a multinucleate plasmodium which may fill the host cell (fig. 2, 21). No empty cysts are found after the zoospores penetrate the host cells. Zoosporangial and cystosoral plasmodia are in1 Received for publication May 2, 1959. 2 Initial studies forming a basis for this paper comprised a part of a Ph.D. dissertation submitted to the Faculty of the University of North Carolina. The author is grateful to Dr. John N. Couch for his guidance. The completion of these studies was supported by a grant from the McCandless Fund of Emory University. 3See J. S. Karling, 1942, The Plasmodiophorales, p. 62. distinguishable until sometime after cleavage has started. It is possible that a situation similar to that described by Couch et al. (1939) for Octomyxa achlyae Couch, Leitner, Whiffen occurs. These workers found that the early-formed plasmodia may develop into zoosporangia, while those formed later become cystosori. The protoplasm of the zoosporangial plasmodium after cleavage into the spherical zoosporangia, which are surrounded by a delicate cell wall, has a lumpy aspect (fig. 7, 11). The protoplasm gradually becomes more granular, and a central vacuole forms which separates the protoplasm into the zoospore initials (fig. 10, 18). The zoosporangia in a sorus may be interconnected (fig. 5, 17, 19). Consequently a single discharge pore may serve to liberate the zoospores from several zoosporangia. A similar condition has been described for the zoosporangia of other genera of the Plasmodiophorales (Couch et al., 1939; Goldie-Smith, 1951; Miller, 1958a,b, 1959). The walls of the zoosporangia are very thin, and they may collapse soon after the zoospores discharge (fig. 3, 5, 8, 17, 20). Figure 20 illustrates zoosporangia which have discharged their zoospores within the host cells. The zoospores lost their flagella and became slightly amoeboid after 2 hr. They were not seen to fuse or to develop further. Perhaps this was because of the poor environmental conditions which necessarily existed. Zoosporangia measured 4-9M (most 6.6,u) in diameter. Zoospores from zoosporangia of Ligniera junci (Schwartz) Maire and Tison have been reported as being uniflagellate by Cook (1928, 1933). However, in the light of Ledingham's (1934, 1935, 1939) discoveries of biflagellate heterokontean zoospores in Plasmodiophora Woronin, Spongospora Brunchorst and Polymyxa Ledingham and the subsequent dis

The urinary excretion of two persons contaminated by Sr/sup 90/ was followed for 34 weeks. The excretion curve of one of these persons, whose contamination ceased 940 days before the beginning of the analyses, and which corresponds to a period of slow elimination, indicates a half-time value of 2502 days. The curve of the other one, which has been taken just after contamination ceased and which corresponds therefore to a period of more rapid elimination, indicates a half-time value of 337 days.

Etude detaillee avec determination des constantes cinetiques, identification des produits et mecanisme reactionnel