100,410 research outputs found
Spatial Distribution of the International Food Prices: Unexpected Heterogeneity and Randomness
No full textGlobalfoodpricesaretypicallyanalysedinatime-seriesframework.Wecomplementthisapproachbyfocusingonthespatialpricedispersionofthecountry-pairbilateraltradeintheinternationalfoodtradenetwork(IFTN),fortenrelevantcommodities.ThemainpurposesaretoverifyiftheLawofOnePrice(LOP)holdsandtoinvestigatetheemergenceofrandomnessintheprice-formationmechanism.Wedistinguishbetweenthe“internal”variance,whichindicatesthemagnitudeofpricediscrimination,andthe“external”variance,thatisameasureofpricedispersion.Wefindthat,forsomecommodities,spatialpricedispersionisremarkableandpersistentovertime(i.e.,failureoftheLOP)andthatthereexistsastrictcorrelationbetweenpricespikesandpeaksinspatialpricevariability.We test whether the price distribution can be replicated through a stochastic process of extraction.Surprisingly, the actual distribution of prices, for several commodities, is well described by a random dis-tribution.Then,theprocessofdataaggregationisnotneutralbecausetheinformationatthemicro-levelscalemightbelostatthemacro-scale,duetothecomplexityoftheIFTN.Finally,wediscusssomepossibleeconomicexplanationsoftheseoutcomesandthemainmethodological,environmental,andpolicyconsequences.1. IntroductionTheendofhungerandtheachievementoffoodsecurityareglobalkey issues explicitly included in the Sustainable Development Goalsagenda (UN, 2015). The interest of the international community isjustifiedbyacknowledgingthecomplexandinterrelatedenvironmentalandsocialdimensionslinkedtofoodmanagement,suchaswaterre-sources(Generoso,2015;DistefanoandKelly,2017;Distefanoetal.,2018b), energy and pollution (Carlsson-Kanyama et al., 2003;D’Odoricoetal.,2018),landuseanddeforestation(OdegardandVanderVoet,2014),andsocialsecurityandhealth(Bellemare,2015;Bush,2010).Thus,abetterunderstandingoffoodmarkets,especiallyinaneraofglobalisation(Duarteetal.,2014;Biewaldetal.,2014;Suweisetal.,2015),iscrucialtoprovidesolidbasesforfoodpoliciesandre-source management (Wang et al., 2016). This interest has been re-inforcedrecently–afterthetwowavesofworldfoodpricecrises(2008and2011)–whereeconomistsanalysedtheaftermathsofprice‘spikes'to assess the short-run effects (Piesse and Thirtle, 2009; Bellemare,2015)andthemaincausesoftemporalfoodpricevolatility(seeDíaz-Bonilla,2016,foradiscussion).Acommonassumptionbehindthesestudies,andusualamongagriculturaleconomists,istheso-calledLawofOnePrice(henceforthLOP):oncepricesareconvertedtoacommoncurrency (including transaction and transport costs), homogeneousgoods should be sold for the same price in different countries(Miljkovic,1999).1TheLOPshouldholdwhengoodsarehighlytraded,at least in spatially separated international markets (Baffes, 1991;GoldbergandVerboven,2005).Onthecontrary,pricedispersion–namely,ahomogeneousproductbeingsoldatdifferentpricesbydifferentexporters–canemerge,forseveralreasons,suchasentrybarriersandgeographicalseparationofmarkets(Krugman,1991;Yangetal.,2017),differentmarginalcosts(Crucini and Yilmazkuday, 2014; Yilmazkuday, 2016), variations inconsumer preferences (Grebitus et al., 2013), and monetary illusion(FehrandTyran,2001).2Followingthisbranchofliterature,weaimattestingthepresenceornotofLOPintheinternationalfoodtradenet-work(IFTN),extendingtheanalysistotheprice-formationmechanism.Theexistentliteratureempiricallyanalysedspatialfood-pricedisper-siononlyattheretaillevel(e.g.,AnaniaandNisticò,2014)but,toourhttps://doi.org/10.1016/j.ecolecon.2019.01.010Received30January2018;Receivedinrevisedform5November2018;Accepted8January2019*Correspondingauthor.E-mailaddress:[email protected](T.Distefano).1Ancillaryhypothesesarethoseconcerningperfectcompetition:agentsareprice-takers,perfectinformation,nofrictionsonfactormobility,individualrationality,andsoon.2Monetaryillusionindicatesthepsychologicaleffectofmakingmistakesduetotheuseofdifferentcurrencies.Ecological Economics 159 (2019) 122–132Available online 28 January 20190921-8009/ © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Fluctuating asymmetry, body size, reproductive period and life time mating success of males of Cercion lindeni (Odonata: Coenagrionidae)
No full textMating success is linked to reproductive success in males, but parameters influencing it are poorly known. The relationships between lifetime mating success (LMS), fluctuating asymmetry (FA), body size (SIZE), reproductive period (RP) and emergence date (MD) of males of Cercion lindeni were investigated. Males were marked and photographed in their pre-reproductive period. and their matings monitored. RP was assumed to be the period between the MD and the last sighting cf each individual. Three different FA measures and the size of each individual were determined. The results showed that the individuals not present at the pond during the reproductive period had a higher FA (but not for meristic characters) than those present. For those individuals actually involved in reproductive activity, LMS was only positively correlated with RP, which was negatively related with MD, and this with SIZE
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Pelevin’s Trinity in the novel “t”: author – protagonist – reader
No full textThe article attempts to interpret Pelevin's artistic strategy in the novel "T" by exploring its subject organization and addressing the key problems of the author, the protagonist, and the reader as they are seen by the researcher. The article analyzes the peculiarities of constructing the narrative reality in the novel "T", and goes on to discuss Pelevin's philosophic models of the development of the humankind, and the emergence of his new anthropology
Predicting susceptibility and resilience in an animal model of post-traumatic stress disorder (PTSD)
No full textPost-Traumatic Stress Disorder (PTSD) is a psychiatric disorder whose pathogenesis relies on a maladaptive expression of the memory for a life-threatening experience, characterized by over-consolidation, generalization and impaired extinction, which are responsible of dramatic changes in arousal, mood, anxiety and social behavior. Even if subjects experiencing a traumatic event during lifetime all show an acute response to the trauma, only a subset of them (susceptible) ultimately develops PTSD, meanwhile the others (resilient) fully recover after the first acute response. However, the dynamic relationships between the interacting brain circuits that might potentially link trauma-related experiences to the emergence of susceptible and resilient PTSD phenotypes in individuals is not well understood. Toward the first step to reach this goal, we have implemented our experimental PTSD model previously developed, making it suitable to differentiate between susceptible (high responders, HR) and resilient (low responders, LR) rats in terms of over-consolidation, impaired extinction, and social impairment long after trauma. Rats were exposed to five footshocks paired with social isolation. One week after trauma but before extinction, animals were tested in the Open Field and Social Interaction tasks for the identification of a predictive variable to identify susceptible and resilient animals before the possible appearance of a PTSD-like phenotype. Our findings show that exploratory activity after trauma in a novel environment is a very robust variable to predict susceptibility towards a PTSD-like phenotype. This experimental model is thus able to screen and differentiate, before extinction learning and potential therapeutic intervention, susceptible and resilient PTSD-like rats
Frequency dependence in made simple using a multipole approximation
No full textIn the approximation, the screened interaction is a nonlocal and dynamical potential that usually has a complex frequency dependence. A full description of such a dependence is possible but often computationally demanding. For this reason, it is still common practice to approximate using a plasmon pole (PP) model. Such an approach, however, may deliver an accuracy limited by its simplistic description of the frequency dependence of the polarizability, i.e., of . In this work, we explore a multipole approach (MPA) and develop an effective representation of the frequency dependence of . We show that an appropriate sampling of the polarizability in the frequency complex plane and a multipole interpolation can lead to a level of accuracy comparable with full-frequency methods at a much lower computational cost. Moreover, both accuracy and cost are controllable by the number of poles used in MPA. Eventually, we validate the MPA approach in selected prototype systems, showing that full-frequency quality results can be obtained with a limited number of poles
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