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Production in knowledge and data‐intensive industries is powered by work that can, in theory, be done from anywhere, via cloudwork platforms. Cloudwork platforms govern data value chains in distinct ways to concentrate power and extract value at the global scale. We argue that unpaid labour is a systemic mechanism of accumulation in these digital value networks. In this paper we demonstrate how it is tied to platform business models and facilitated by elements of platform governance including monopsony power, a high degree of spatial flexibility in sourcing labour, regulatory unaccountability and digital enclosure. We draw on a survey of 699 workers on 14 platforms in 74 countries to show that unpaid labour is an engine of South–North value extraction, and workers in the global South perform more unpaid labour than counterparts in the global North. Our findings have important ramifications our understanding of the changing international division of labour and platform capitalism. [ABSTRACT FROM AUTHOR]

This paper applies insights from global value chains (GVC)/global production networks (GPN) frameworks to explore the economic geographies brought into being by digital labour platforms. In particular, these perspectives facilitate analyses of power imbalances and value extraction across territories—an under‐theorized aspect within platform studies. We theorize this dynamic by introducing the descriptor 'digital value network' (DVN): a digitally mediated nexus of platform operations that produce and distribute value between territories, on the basis of labour transactions. Empirically, we draw on a multi‐year action research project, assessing the operations of platforms and the experiences of platform workers in 54 countries. Our analysis highlights that platforms as lead firms extend GVC/GPN logics of coordination and drivenness in DVN to (i) optimize production capabilities while externalizing ownership and costs, (ii) accumulate both monetary and non‐monetary forms of value, and (iii) concentrate power at the global scale in both existing and new sectors. [ABSTRACT FROM AUTHOR]

Digital labour platforms have been widely promoted as a solution to the unemployment crisis sparked by the COVID‐19 pandemic. However, the pandemic has also highlighted the vulnerability of gig workers when cast as essential workers. This article examines the COVID‐19 policies of 191 platforms in 43 countries to understand how the crisis has shifted the conventions of the gig economy. Using a typology of "fair platform work", the authors identify areas of progress in worker protection but also significant shortfalls, including the entrenchment of precarious work as platforms leverage the opportunities arising from the crisis. [ABSTRACT FROM AUTHOR]

Résumé: Les plateformes de travail numériques ont souvent été présentées comme une solution au chômage engendré par la pandémie. Cependant, la crise a mis en lumière la vulnérabilité des collaborateurs des plateformes, notamment des travailleurs essentiels parmi eux. Les auteurs examinent le comportement de 191 plate‐formes de 43 pays pendant la pandémie pour savoir si celle‐ci a fait évoluer la branche. Sur la base de critères relatifs à l'équité au travail, ils repèrent certains progrès mais aussi des lacunes importantes en matière de protection et concluent à une précarisation du travail, alors même que les plateformes ont plutôt tiré profit de la crise. [ABSTRACT FROM AUTHOR]

Resumen: Las plataformas digitales de trabajo se promueven a gran escala como solución a la crisis de desempleo provocada por la pandemia de COVID‐19. Sin embargo, la pandemia también ha puesto de manifiesto la vulnerabilidad de quienes trabajan en ellas en tareas consideradas esenciales. Se examinan aquí las políticas de COVID‐19 de 191 plataformas en 43 países para entender cómo la crisis ha cambiado las convenciones de la economía de plataformas. Utilizando una tipología de «trabajo de plataforma justo», se identifican avances en la protección de las y los trabajadores, pero también problemas significativos, como el afianzamiento del trabajo precario a medida que las plataformas aprovechan las oportunidades derivadas de la crisis. [ABSTRACT FROM AUTHOR]

Information‐technologies are essential for global capitalism to function at speed across scale, space and complexity. The importance of software and algorithms in the governance of these systems is reflected in the attention of scholars to the ways digital code and materiality (re)combine to create hybrid digital/material spaces of economic activity, movement and everyday life. This paper extends this work in two key ways: first by emphasising the relational aspect of these code/spaces, and second by showing how the digital algorithms of code/spaces are hackable rather than hegemonic. Using the case study of frequent flyer programmes we demonstrate how networked knowledge‐sharing reshapes code/spaces to provide unintended opportunities such as low‐cost travel and access to spaces normally only frequented by global elites. Although this case highlights vulnerabilities in the code of global capitalism, it is primarily only those with significant lifestyle privilege who are able to fully participate in these subversions. Moreover, while much of the value captured by “airline hackers” comes from airlines’ profit margins, the relationality of code/spaces can impact citizens and consumers not directly connected to or interested in airline travel. Ultimately, this paper demonstrates that in contrast to characterisations of omnipresence and hegemony, the information networks and algorithms of global capitalism contain moments of uneven porousness and selective hackability. [ABSTRACT FROM AUTHOR]

This article presents findings regarding collective organisation among online freelancers in middle‐income countries. Drawing on research in Southeast Asia and Sub‐Saharan Africa, we find that the specific nature of the online freelancing labour process gives rise to a distinctive form of organisation, in which social media groups play a central role in structuring communication and unions are absent. Previous research is limited to either conventional freelancers or ‘microworkers’ who do relatively low‐skilled tasks via online labour platforms. This study uses 107 interviews and a survey of 658 freelancers who obtain work via a variety of online platforms to highlight that Internet‐based communities play a vital role in their work experiences. Internet‐based communities enable workers to support each other and share information. This, in turn, increases their security and protection. However, these communities are fragmented by nationality, occupation and platform. [ABSTRACT FROM AUTHOR]

Henri Lefebvre talked of the 'right to the city' alongside a right to information. As the urban environment becomes increasingly layered by abstract digital representation, Lefebvre's broader theory warrants application to the digital age. Through considering what is entailed by the urbanization of information, this paper examines the problems and implications of any 'informational right to the city'. In directing Tony Benn's five questions of power towards Google, arguably the world's most powerful mediator of information, this paper exposes processes that occur when geographic information is mediated by powerful digital monopolies. We argue that Google currently occupies a dominant share of any informational right to the city. In the spirit of Benn's final question-'How do we get rid of you?'-the paper seeks to apply post-political theory in exploring a path to the possibility of more just information geographies. [ABSTRACT FROM AUTHOR]

Abstract: Corporations, development organisations and governments have launched ambitious programmes to ‘connect the unconnected’, reasoning that this creates economic growth and inclusive development. This paper contrasts these actors’ discourses with evidence from academic research. The evidence suggests a highly uneven economic impact of Internet connectivity across geographies and social strata. The analysed sources of discourse (African ICT policies and reports by international organisations) instead propose Grand Visions of connectivity, attributing a self‐evident positive, widespread, and transformational impact to the Internet. We discuss technological determinism, acontextual modernism, and optimistic simplism as underlying this contrast, calling for more reflexivity towards the opportunities of ‘digital development’. [ABSTRACT FROM AUTHOR]

Global production networks (GPNs) have become a key framework in conceptualizing linkages, power and structure in globalized production. However, this framework has been less successful in integrating the influence of digital information and ICTs in production, and this problematic in a world where relationships and power are increasingly mediated by digital information flows and resources. We thus look to adapt the GPN framework to allow more substantive analysis of 'the digital'. Primarily, this is done through a theoretical analysis of the three core categories of the GPN framework - embeddedness, value and networks - to highlight how these categories can better integrate a more dynamic and contested conceptualization of the digital. Illustrations from research on the digitalization of tea sector GPNs in East Africa highlight how these theoretical advances provide new insights on the digital and its expanding role in economic production. [ABSTRACT FROM AUTHOR]

This paper analyses and compares two transformative moments of technologically mediated change in East Africa, the construction of the Uganda railway between Mombasa and Lake Victoria (1896-1903) and the introduction of fibre-optic cables that landed into the ports of Dar Es Salaam and Mombasa in 2009. The paper uses discourse analysis to examine how technologically mediated connectivity has been represented by political and economic actors during these transformative moments. In both cases we explore the origins of the expectations of connectivity and the hope and fear associated with them. Building on Massey's notion of power-geometry and Sheppard's concept of positionality, the paper focuses on power relationships in discussions of connectivity and asks how people understand the abilities of transformative technologies to modify positionalities and alter relational distance and proximity. Ultimately, by examining historical and contemporary expectations of connectivity in East Africa, this paper works towards more grounded and historicised understandings of the coming-together of technology and connectivity. [ABSTRACT FROM AUTHOR]

Information has always had geography. It is from somewhere; about somewhere; it evolves and is transformed somewhere; it is mediated by networks, infrastructures, and technologies: all of which exist in physical, material places. These geographies of information about places matter because they shape how we are able to find and understand different parts of the world. Places invisible or discounted in representations are invisible in practice to many people. In other words, geographic augmentations are much more than just representations of places: they are part of the place itself; they shape it rather than simply reflect it. This fusing of the spatial and informational augmentations that are immutable means that annotations of place emerge as sites of political contestation: with different groups of people trying to impose different narratives on informational augmentations. This paper therefore explores how information geographies have their own geographic distributions: geographies of access, of participation, and of representation. The paper offers a deliberately broad survey of a range of key platforms that mediate, host, and deliver different types of geographic information. It does so using a combination of existing statistics and bespoke data not previously mapped or analysed. Through this effort, the paper demonstrates that in addition to the geographies of uneven access to contemporary modes of communication, uneven geographies of participation and representation are also evident and in some cases are being amplified rather than alleviated. In other words, the paper comprehensively shows one important facet of contemporary information geographies: that geographic information itself is characterised by a host of uneven geographies. The paper concludes that there are few signs that global informational peripheries are achieving comparable levels of participation or representation with traditional information cores, despite the hopes that the fast‐paced spread of the internet to three billion people might change this pattern. [ABSTRACT FROM AUTHOR]

Several lines of evidence from a eutrophic lake show how polymixis enables phosphorus (P) released from anoxic, iron (Fe)-poor sediments to lower nitrogen-to-phosphorus (N : P) ratios and stimulate cyanobacterial blooms. Detailed sediment analyses revealed extensive formation of Fe sulfides, which suppressed porewater Fe levels and prevented sequestration of P in Fe minerals. Experimental additions of Fe significantly decreased the flux of dissolved P from warm, anoxic sediments, increasing N : P ratios in porewater and overlying water. The net midsummer effect of polymixis and P release from Fe-poor sediments quickly doubled the total P in the euphotic zone during a period of very low external P loading. This internal 'nutrient pump' decreased N : P in surface waters and led to a cyanobacterial bloom comprised primarily of diazotrophic Anabaena and Aphanizomenon spp. along with nonheterocystous and potentially toxic Microcystis icthyoblabe and Woronichinia naegelianum. Concentrations of the cyanotoxin, microcystin, in this lake were typically elevated during, or shortly after, episodes of internal P loading. Our study demonstrates an important mechanism underlying the increasing cyanobacterial dominance of weakly stratified eutrophic north temperate lakes, and warns of further increases under a warming climate. [ABSTRACT FROM AUTHOR]

With the increasing prevalence of both geographically referenced information and the code through which it is regulated, digital augmentations of place will become increasingly important in everyday, lived geographies. Through two detailed explorations of 'augmented realities', this paper provides a broad overview of not only the ways that those augmented realities matter, but also the complex and often duplicitous manner that code and content can congeal in our experiences of augmented places. Because the re-makings of our spatial experiences and interactions are increasingly influenced through the ways in which content and code are fixed, ordered, stabilised and contested, this paper places a focus on how power, as mediated through technological artefacts, code and content, helps to produce place. Specifically, it demonstrates there are four key ways in which power is manifested in augmented realities: two performed largely by social actors, distributed power and communication power; and two enacted primarily via software, code power and timeless power. The paper concludes by calling for redoubled attention to both the layerings of content and the duplicity and ephemerality of code in shaping the uneven and power-laden practices of representations and the experiences of place augmentations in urban places. [ABSTRACT FROM AUTHOR]

Many of the ways in which we discuss, imagine and envision the internet rely on inaccurate and unhelpful spatial metaphors. This paper focuses on the usage of the 'cyberspace' metaphor and outlines why the reliance by contemporary policymakers on this inherently geographic metaphor matters. The metaphor constrains, enables and structures very distinct ways of imagining the interactions between people, information, code and machines through digital networks. These distinct imaginations, in turn, have real effects on how we enact politics and bring places into being. The paper broadly traces the history of 'cyberspace', explores the scope of its current usage and highlights the discursive power of its distinct way of shaping our spatial imagination of the internet. It then concludes by arguing that geographers should take the lead in employing alternate, nuanced and spatially grounded ways of envisioning the myriad ways in which the internet mediates social, economic and political experiences. [ABSTRACT FROM AUTHOR]

Abstract: This is a paper about expectations surrounding a potentially highly transformative moment in East Africa's history: the arrival of underwater fibre‐optic broadband communications cables into the Indian Ocean port of Mombasa. It combines a media content analysis with findings from interviews with business owners in Kenya's nascent business process outsourcing (BPO) and software development sectors in order to explore how such moments of technological ‘connectivity’ are imagined, marketed and enacted within economic development. It argues that connectivity is not just a matter of boosting physical/material capacity but also about redressing conceptual connectivity; bringing places ‘closer together’ involves rehabilitating the images of places in peoples’ minds and removing imagined senses of distance. As such, technologies of connectivity are marketed not just as tools of altered communications affordances, but more importantly, as momentary opportunities for revisiting the image of places from afar. Additionally, the cables reveal the importance of fostering internal linkages in order to better build international recognition and connections. ‘Moments of expectation’ that surround new ICT technologies reveal how discourse and representation play a strong role in enabling markets to form and change. The very idea of ‘connectivity’ itself is driving plans and policies throughout the region. [ABSTRACT FROM AUTHOR]

Medical Education 2011: 45: 946-957 CONTEXT Training future doctors to develop an appropriate professional persona is an important goal of medical student education and residency training. Most medical education research paradigms on professionalism have focused largely on lapses (e.g. yelling as an example of communication failure) and tend to emphasise behaviour that should be avoided. The assumption is that, if left unchecked, students will see these negative behaviours exhibited by their role models and possibly emulate them, allowing the potential reinforcement of the inappropriate behaviours. OBJECTIVES Identifying and characterising exemplary, or positive, behaviours can be similarly valuable to both medical students and residents as tangible examples of behaviours to strive towards. The goal of the present research was to determine and thematically define the exemplary professional actions that medical students observe in the intense and patient-focused environment of the operating room (OR). METHODS Using qualitative methodology of content analysis and theme identification, we systematically documented the type of exemplary professional behaviours reported by medical students ( n = 263) when observing health care teams on an anaesthesia rotation in the OR. RESULTS The analysis generated a taxonomy of exemplary OR behaviour that included six overarching themes (e.g. teamwork), 15 sub-themes (e.g. collegial) and numerous exemplars (e.g. showed mutual respect). These themes and sub-themes were then conceptually 'matched'- through the use of antonyms - to complement an existing framework focused on medical student reports of professional lapses witnessed during medical school. CONCLUSIONS Year 3 medical students in the USA reported observing very positive, exemplary health care provider interactions that were diverse in focus. Themes were identified regarding the OR team members' interactions with patients ( calm, communication, comforting), with one another ( teamwork, respect) and with the medical students ( teaching). This classification of exemplary OR behaviour contributes to our understanding of how professional behaviour is viewed and potentially emulated by medical students on surgical rotations. [ABSTRACT FROM AUTHOR]

Objective: We examine the concept of translational research from the perspective of evaluators charged with assessing translational efforts. One of the major tasks for evaluators involved in translational research is to help assess efforts that aim to reduce the time it takes to move research to practice and health impacts. Another is to assess efforts that are intended to increase the rate and volume of translation. Methods: We offer an alternative to the dominant contemporary tendency to define translational research in terms of a series of discrete 'phases.' Results: We contend that this phased approach has been confusing and that it is insufficient as a basis for evaluation. Instead, we argue for the identification of key operational and measurable markers along a generalized process pathway from research to practice. Conclusions: This model provides a foundation for the evaluation of interventions designed to improve translational research and the integration of these findings into a field of translational studies. Clin Trans Sci 2011; Volume 4: 153-162 [ABSTRACT FROM AUTHOR]

Places have always been palimpsests. The contemporary is constantly being constructed upon the foundations of the old. Yet only recently has place begun to take on an entirely new dimension. Millions of places are being represented in cyberspace by a labour force of hundreds of thousands of writers, cartographers and artists. This paper traces the history and geography of virtual places. The virtual Earth is not a simple mirror of its physical counterpart, but is instead characterised by both black holes of information and hubs of rich description and detail. The tens of millions of places represented virtually are part of a worldwide engineering project that is unprecedented in scale or scope and made possible by contemporary Web 2.0 technologies. The virtual Earth that has been constructed is more than just a collection of digital maps, images and articles that have been uploaded into Web 2.0 cyberspaces; it is instead a fluid and malleable alternate dimension that both influences and is influenced by the physical world. [ABSTRACT FROM AUTHOR]

Twenty lakes recovering from a century of atmospheric acid deposition over Northeastern Ontario were resurveyed for phytoplankton following a 20-year period and were compared with a 23-year study of an experimentally acidified lake, L302S (Experimental Lakes Area, ON, Canada). Phytoplankton species significantly tracked abiotic changes during both acidification and chemical recovery in all lakes based on concordance testing. However, ordination analyses showed that many phytoplankton communities had not returned to their preacidification state. Significant explanatory variables of taxonomic responses were pH, dissolved organic carbon (DOC), and inorganic nutrients (N, P), based on canonical correspondence analysis (CCA). Increases in DOC and pH influenced a significant taxonomic shift from acid-tolerant dinoflagellates to a diverse assemblage of cyanobacteria, chlorophytes, and diatoms. Declining nitrogen levels defined a secondary environmental gradient, which was characterized by a decrease in filamentous green algal abundance. L302S remained remote in ordination space from the more chronically and heavily polluted lakes in Northeastern Ontario, indicating that experimental acidification provided a conservative estimate of the true damage to atmospherically polluted lakes. However, L302S did increasingly resemble lakes in Northeastern Ontario, suggesting that experimental acidification simulated the impacts of moderate levels of atmospheric pollution. Our findings demonstrate the importance of ecological history in understanding the responses by boreal lake ecosystems to environmental change. [ABSTRACT FROM AUTHOR]

It often goes unmentioned that one of the primary purposes of the famous circumnavigation of H.M.S. Beagle was foreign missions. Charles Darwin, the voyage's most famous participant, was at best noncommittal about the missionary activity surrounding him for most of the trip. He emerged from the voyage, however, as an enthusiastic and outspoken proponent of missions. The British missions at Tahiti prompted him to change his view. Sailing to Tahiti, he read several accounts about the South Sea missions, and had already begun making arrangements to publish his “Diary” as a travel journal. Darwin became convinced that missionaries helped “advance” the natives toward “civilization” and thereafter enthusiastically defended missionaries in an ongoing public debate. [ABSTRACT FROM AUTHOR]

The number of combinations of anthropogenic stressors affecting global change is increasing; however, few studies have empirically tested for their interactive effects on ecosystems. Most importantly, interactions among ecological stressors generate nonadditive effects that cannot be easily predicted based on single-stressor studies. Here, we corroborate findings from an in situ mesocosm experiment with evidence from a whole-ecosystem manipulation to demonstrate for the first time that interactions between climate and acidification determine their cumulative impact on the food-web structure of coldwater lakes. Interactions among warming, drought, and acidification, rather than the sum of their individual effects, best explained significant changes in planktonic consumer and producer biomass over a 23-year period. Further, these stressors interactively exerted significant synergistic and antagonistic effects on consumers and producers, respectively. The observed prevalence of long- and short-term ecological surprises involving the cumulative impacts of multiple anthropogenic stressors highlights the high degree of uncertainty surrounding current forecasts of the consequences of global change. [ABSTRACT FROM AUTHOR]

ATM kinase plays a central role in signaling DNA double-strand breaks to cell cycle checkpoints and to the DNA repair machinery. Although the exact mechanism of ATM activation remains unknown, efficient activation requires the Mre11 complex, autophosphorylation on S1981 and the involvement of protein phosphatases and acetylases. We report here the identification of several additional phosphorylation sites on ATM in response to DNA damage, including autophosphorylation on pS367 and pS1893. ATM autophosphorylates all these sites in vitro in response to DNA damage. Antibodies against phosphoserine 1893 revealed rapid and persistent phosphorylation at this site after in vivo activation of ATM kinase by ionizing radiation, paralleling that observed for S1981 phosphorylation. Phosphorylation was dependent on functional ATM and on the Mre11 complex. All three autophosphorylation sites are physiologically important parts of the DNA damage response, as phosphorylation site mutants (S367A, S1893A and S1981A) were each defective in ATM signaling in vivo and each failed to correct radiosensitivity, genome instability and cell cycle checkpoint defects in ataxia-telangiectasia cells. We conclude that there are at least three functionally important radiation-induced autophosphorylation events in ATM. [ABSTRACT FROM AUTHOR]

The process of metabolic coupling has been described as a means of providing additional fuel for neurons during periods of intense activity. This process has been suggested to occur in the mammalian retina, but whether retinal neurons can metabolise glial-derived monocarboxylates remains uncertain. The present study therefore sought to define the preferred energy substrates for maintenance of different retinal cells in culture, in order to clarify whether metabolic coupling can potentially occur in this tissue. All cells in rat retinal cultures were detrimentally affected by glucose deprivation. The effect on some neurons, however, could be partially reversed by 5 mmpyruvate or lactate. Furthermore, the glycolytic inhibitor, iodoacetic acid, caused a dose-dependent loss of all retinal cells in culture, whereas the mitochondrial inhibitor, 2,4-dinitrophenol, only led to a decrease in the number of neurons. Finally, inhibition of transporters for glucose or monocarboxylates caused the respective loss of glia or neurons from cultures. These data together demonstrate that, although cells do preferentially metabolise glucose, monocarboxylates such as lactate or pyruvate do play an important role in neuronal maintenance. These data therefore give partial support to the notion that metabolic coupling may occur in the retina. [ABSTRACT FROM AUTHOR]

The rate-limiting enzyme in catecholamine synthesis is tyrosine hydroxylase. It is phosphorylated at serine (Ser) residues Ser8, Ser19, Ser31 and Ser40in vitro,in situandin vivo. A range of protein kinases and protein phosphatases are able to phosphorylate or dephosphorylate these sitesin vitro. Some of these enzymes are able to regulate tyrosine hydroxylase phosphorylationin situandin vivobut the identity of the kinases and phosphatases is incomplete, especially for physiologically relevant stimuli. The stoichiometry of tyrosine hydroxylase phosphorylationin situandin vivois low. The phosphorylation of tyrosine hydroxylase at Ser40 increases the enzyme's activityin vitro,in situandin vivo. Phosphorylation at Ser31 also increases the activity but to a much lesser extent than for Ser40 phosphorylation. The phosphorylation of tyrosine hydroxylase at Ser19 or Ser8 has no direct effect on tyrosine hydroxylase activity. Hierarchical phosphorylation of tyrosine hydroxylase occurs bothin vitroandin situ, whereby the phosphorylation at Ser19 increases the rate of Ser40 phosphorylation leading to an increase in enzyme activity. Hierarchical phosphorylation depends on the state of the substrate providing a novel form of control of tyrosine hydroxylase activation. [ABSTRACT FROM AUTHOR]

Transforming growth factor (TGF)-β1 is a major mediator of liver fibrosis. Connective tissue growth factor (CTGF) mediates TGF-β1 pro-fibrogenic effects in vitro, but its in vivo role is unknown. Both TGF-β1 and CTGF are overexpressed in hepatic stellate cells during liver fibrosis. We have used antisense oligonucleotides to examine the role of CTGF in carbon tetrachloride-induced liver fibrosis in mice. Mice received carbon tetrachloride together with CTGF or TGF-β1 antisense oligonucleotides for 2 weeks (preventive model), or carbon tetrachloride for 2 weeks followed by carbon tetrachloride and oligonucleotides for 2 more weeks (curative model). In both models, CTGF and TGF-β1 oligonucleotides decreased by more than 50 percent the mRNA expression of their targets. Type I collagen mRNA was also decreased by about 40 percent in the preventive experiment. Tissue inhibitor of matrix metalloproteinase-1 mRNA expression and fibrotic deposition evaluated by Sirius red staining were not modified in any group. In summary, our results suggest that hepatic stellate cells can be targeted in vivo with oligonucleotides, and that reducing CTGF levels can lead to a decrease in fibrogenesis as shown by the reduction in type I collagen expression. The lack of effect on fibrosis may be due to the persistence of high tissue inhibitor of matrix metalloproteinase-1 expression. [ABSTRACT FROM AUTHOR]

The method for the synthesis of 1,5-disubstituted triazolones involves the reaction of dilithiated Boc-hydrazines with substrates (I) or (IV). [ABSTRACT FROM AUTHOR]

An abstract of the article "Improving clinical supervision through formal incident reporting," by Gavin Thoms, Rebecca Ellis, Gbenga Afolabi and Mark Graham is presented.

Climate warming has been shown to increase the frequency of extreme weather effects on small lakes by increasing the variability of terrigenic inputs and surface water temperatures. We hypothesized that the effect of thermal variability on boreal plankton depends on dissolved terrigenic matter (i.e., temperature-terrigenic interaction). A two-factor mesocosm (1500-L capacity) experiment consisting of three terrigenic treatment levels (control, [-] runoff, [+] runoff) and three temperature treatment levels (control, warm, and cold) was conducted in triplicate for a total of 27 mesocosms deployed in Lake 302S of the Experimental Lakes Area in Canada. The warming treatment amplified the positive effect of terrigenic amendment on total phytoplankton biomass by stimulating large (>35-µm Greatest Axial Linear Dimension; GALD) taxa during the 50-d experiment. In comparison, removal of terrigenic matter increased the abundance of smaller (<35-µm GALD) phytoplankton along with copepods and cladocerans under cold and warm conditions, respectively. We also attempted to corroborate our experimental findings by comparing planktonic communities collected from reference Lake 239 during climatically contrasting summers between 1970 and 2001. Although planktonic communities in Lake 239 also differed significantly between years characterized by cold, wet vs. warm, dry ice-free conditions, their responses ran opposite to those detected during the experiment, highlighting the potential overriding importance of other scale-dependent factors (e.g., fish predation, vertical migration) mediating the effects of climate on lake communities. [ABSTRACT FROM AUTHOR]

Due to its ability to esterify cholesterol in hepatocytes and enterocytes, ACAT2 is believed to promote atherosclerosis by driving both cholesterol absorption in the intestine and promoting packaging cholesterol into VLDL in the liver. The purpose of these studies was determine how liver-specific depletion of ACAT2 via in vivo antisense oligonucleotide (ASO)-mediated inhibition alters hepatic cholesterol and lipoprotein metabolism in a hyperlipidemic mouse model. Liver-specific depletion (>85%) of ACAT2 resulted in a dramatic reduction the packaging of cholesterol into apoB-containing lipoproteins (VLDL, IDL, and LDL), while HDL cholesterol levels were not affected. In liver of ACAT2-ASO treated mice, total (TC), esterified (CE), free (FC) cholesterol and triglyceride (TG) concentrations all were decreased when compared to control mice. Furthermore, cholesterol, phospholipid, and bile acid concentrations in gall bladder bile were not altered in ACAT2-ASO treated mice. Interestingly, during isolated liver perfusion, ACAT2-ASO treated livers had augmented perfusate accumulation rates of FC and phospholipid (PL). Collectively, these studies provide the first insight into the hepatic itinerary of cholesterol, when cholesterol esterification is specifically inhibited within the liver. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms are a regular feature of lakes in central North America, but little is known of their importance to the nitrogen (N) cycle and nutrition of aquatic food webs. We hypothesized that N2-fixing cyanobacteria constitute a significant source of N to prairie lakes, that fixed N is effectively transferred to primary and secondary consumers, and that the importance of fixed N is structured on a landscape scale due to spatial gradients of lake chemistry and catchment characteristics. These hypotheses were tested using stable isotope analyses and mass budgets in six chained lakes of the northern Great Plains that were sampled biweekly during summers of 1994-2004. Mean annual N isotope signatures of particulate organic matter (d15N-POM) were highly correlated to the abundance of N2-fixing cyanobacteria (r² = 0.75, p , 0.001), but exhibited no marked spatial organization. Instead, the temporal variability of δ15N-POM was greatest in downstream lakes where N2-fixing cyanobacteria were abundant. Furthermore, seasonal declines in δ15N-POM were correlated with reductions in δ15N of individual zooplankton taxa (Daphnia spp., Diacyclops thomasi, Leptodiaptomus siciloides, Leptodora kindtii), especially in downstream eastern lakes. N mass balances revealed that the importance of biological N2 fixation relative to total N inputs (up to 77%) and initial N standing stock (up to 201%) were significantly linearly correlated with landscape position (0.59 ≤ r² ≤ 0.83, p ≤ 0.07) and effective drainage area (0.61 ≤ rsup2; ≤ 0.98, p ≤ 0.07), as were volumetric and areal estimates of N2 fixation during summer (r² ≥ 0.87, p ≤ 0.007). These patterns demonstrate that fixed N is spatially structured, highly predictable based on landscape position, and readily assimilated into aquatic food webs. [ABSTRACT FROM AUTHOR]

Conifer pollen deposition is a visually striking spring event in boreal lakes, representing a potentially major allochthonous input of limiting nutrients. We conducted a lake survey and mesocosm experiment at the Experimental Lakes Area in northwestern Ontario to test the hypothesis that jack pine (Pinus banksiana) pollen inputs subsidize littoral nutrient levels and stimulate algal growth and zooplankton abundance. A series of floating litterfall collectors were deployed along transects that span a 0.27-km² headwater lake (Lake 373) and monitored after ice-out to quantify pollen deposition over a 45-d period. Lake 373 (L373) received 11-56 µmol P m-2 d-1 from pollen, or an annual total of about 10 kg of P. These data were used to determine pollen amendment levels (ambient, 3x, 10x) for an experiment involving 18, 1-m³ littoral mesocosms distributed over three lakes (L239, L373, and L442). Pollen amendments significantly increased total phytoplankton and herbivorous zooplankton biomass, resulting in greater abundance of inedible filamentous green algae and large diatoms. Pollen also exerted a positive lake-specific effect. Periphyton biomass also increased in response to pollen additions, especially filamentous green algae and diatoms in L239 and L442. Conifer pollen subsidizes nutrient levels and promotes production in small boreal lakes. [ABSTRACT FROM AUTHOR]