21 research outputs found

    New measurement of charge asymmetry xF3x{F}_3 from HERA

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    After presenting the recent measurements of neutral current cross section in DIS at HERA, we explain the effect of the ő≥‚ąíZ0\gamma-Z_0 interference at the electro-weak scale, visible on these data. Then, the beam charge difference xF3x{F}_3 is measured and the interference itself is extracted. Results are discussed in the context of perturbative QCD.Comment: 4 pages, 3 figures, proceedings of the International Workshop on Positrons at Jefferson Lab (March 25-27, 2009), Thomas Jefferson National Accelerator Facility, Newport News, V

    GPDs and DVCS with Positrons

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    The beam charge asymmetry helps to isolate the real part of the deeply virtual Compton scattering (DVCS) amplitude. It is discussed what information can be gained both from the real and imaginary part of the DVCS amplitude.Comment: 5 pages, 2 figures, invited talk at `Workshop on Positrons at Jefferson Lab

    Two-photon exchange measurements with positrons and electrons

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    Two-photon exchange contributions have potentially broad ranging impact on several charged lepton scattering measurements. Previously believed to be extremely small, based in part on comparisons of positron scattering and electron scattering in the 1950s and 1960s, recent data suggest that the corrections may be larger than expected, in particular in kinematic regions that were inaccessible in these early positron scattering measurements. Additional measurements using positron beams at Jefferson Lab would allow for a detailed investigation of these contributions in a range of reactions and observables.Comment: 6 pages, proceedings from the International Workshop on Positrons at Jefferson Lab (JPOS09), Jefferson Lab, Newport News, VA, March 25-27, 200

    First radial velocity results from the MINiature Exoplanet Radial Velocity Array (MINERVA)

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    The MINiature Exoplanet Radial Velocity Array (MINERVA) is a dedicated observatory of four 0.7m robotic telescopes fiber-fed to a KiwiSpec spectrograph. The MINERVA mission is to discover super-Earths in the habitable zones of nearby stars. This can be accomplished with MINERVA's unique combination of high precision and high cadence over long time periods. In this work, we detail changes to the MINERVA facility that have occurred since our previous paper. We then describe MINERVA's robotic control software, the process by which we perform 1D spectral extraction, and our forward modeling Doppler pipeline. In the process of improving our forward modeling procedure, we found that our spectrograph's intrinsic instrumental profile is stable for at least nine months. Because of that, we characterized our instrumental profile with a time-independent, cubic spline function based on the profile in the cross dispersion direction, with which we achieved a radial velocity precision similar to using a conventional "sum-of-Gaussians" instrumental profile: 1.8 m s‚ąí1^{-1} over 1.5 months on the RV standard star HD 122064. Therefore, we conclude that the instrumental profile need not be perfectly accurate as long as it is stable. In addition, we observed 51 Peg and our results are consistent with the literature, confirming our spectrograph and Doppler pipeline are producing accurate and precise radial velocities.Comment: 22 pages, 9 figures, submitted to PASP, Peer-Reviewed and Accepte

    Global change effects on plant communities are magnified by time and the number of global change factors imposed

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    Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (‚Č•10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity‚Äďecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously

    Neuromatch Academy: a 3-week, online summer school in computational neuroscience

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    Neuromatch Academy: a 3-week, online summer school in computational neuroscience

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    Neuromatch Academy (https://academy.neuromatch.io; (van Viegen et al., 2021)) was designed as an online summer school to cover the basics of computational neuroscience in three weeks. The materials cover dominant and emerging computational neuroscience tools, how they complement one another, and specifically focus on how they can help us to better understand how the brain functions. An original component of the materials is its focus on modeling choices, i.e. how do we choose the right approach, how do we build models, and how can we evaluate models to determine if they provide real (meaningful) insight. This meta-modeling component of the instructional materials asks what questions can be answered by different techniques, and how to apply them meaningfully to get insight about brain function

    The ABC130 barrel module prototyping programme for the ATLAS strip tracker

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    For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100 % silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.Comment: 82 pages, 66 figure

    Taking the pulse of Earth's tropical forests using networks of highly distributed plots

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    Tropical forests are the most diverse and productive ecosystems on Earth. While better understanding of these forests is critical for our collective future, until quite recently efforts to measure and monitor them have been largely disconnected. Networking is essential to discover the answers to questions that transcend borders and the horizons of funding agencies. Here we show how a global community is responding to the challenges of tropical ecosystem research with diverse teams measuring forests tree-by-tree in thousands of long-term plots. We review the major scientific discoveries of this work and show how this process is changing tropical forest science. Our core approach involves linking long-term grassroots initiatives with standardized protocols and data management to generate robust scaled-up results. By connecting tropical researchers and elevating their status, our Social Research Network model recognises the key role of the data originator in scientific discovery. Conceived in 1999 with RAINFOR (South America), our permanent plot networks have been adapted to Africa (AfriTRON) and Southeast Asia (T-FORCES) and widely emulated worldwide. Now these multiple initiatives are integrated via ForestPlots.net cyber-infrastructure, linking colleagues from 54 countries across 24 plot networks. Collectively these are transforming understanding of tropical forests and their biospheric role. Together we have discovered how, where and why forest carbon and biodiversity are responding to climate change, and how they feedback on it. This long-term pan-tropical collaboration has revealed a large long-term carbon sink and its trends, as well as making clear which drivers are most important, which forest processes are affected, where they are changing, what the lags are, and the likely future responses of tropical forests as the climate continues to change. By leveraging a remarkably old technology, plot networks are sparking a very modern revolution in tropical forest science. In the future, humanity can benefit greatly by nurturing the grassroots communities now collectively capable of generating unique, long-term understanding of Earth's most precious forests. Resumen Los bosques tropicales son los ecosistemas m√°s diversos y productivos del mundo y entender su funcionamiento es cr√≠tico para nuestro futuro colectivo. Sin embargo, hasta hace muy poco, los esfuerzos para medirlos y monitorearlos han estado muy desconectados. El trabajo en redes es esencial para descubrir las respuestas a preguntas que trascienden las fronteras y los plazos de las agencias de financiamiento. Aqu√≠ mostramos c√≥mo una comunidad global est√° respondiendo a los desaf√≠os de la investigaci√≥n en ecosistemas tropicales a trav√©s de diversos equipos realizando mediciones √°rbol por √°rbol en miles de parcelas permanentes de largo plazo. Revisamos los descubrimientos m√°s importantes de este trabajo y discutimos c√≥mo este proceso est√° cambiando la ciencia relacionada a los bosques tropicales. El enfoque central de nuestro esfuerzo implica la conexi√≥n de iniciativas locales de largo plazo con protocolos estandarizados y manejo de datos para producir resultados que se puedan trasladar a m√ļltiples escalas. Conectando investigadores tropicales, elevando su posici√≥n y estatus, nuestro modelo de Red Social de Investigaci√≥n reconoce el rol fundamental que tienen, para el descubrimiento cient√≠fico, quienes generan o producen los datos. Concebida en 1999 con RAINFOR (Suram√©rica), nuestras redes de parcelas permanentes han sido adaptadas en √Āfrica (AfriTRON) y el sureste asi√°tico (T-FORCES) y ampliamente replicadas en el mundo. Actualmente todas estas iniciativas est√°n integradas a trav√©s de la ciber-infraestructura de ForestPlots.net, conectando colegas de 54 pa√≠ses en 24 redes diferentes de parcelas. Colectivamente, estas redes est√°n transformando nuestro conocimiento sobre los bosques tropicales y el rol de √©stos en la bi√≥sfera. Juntos hemos descubierto c√≥mo, d√≥nde y porqu√© el carbono y la biodiversidad de los bosques tropicales est√° respondiendo al cambio clim√°tico y c√≥mo se retroalimentan. Esta colaboraci√≥n pan-tropical de largo plazo ha expuesto un gran sumidero de carbono y sus tendencias, mostrando claramente cu√°les son los factores m√°s importantes, qu√© procesos se ven afectados, d√≥nde ocurren los cambios, los tiempos de reacci√≥n y las probables respuestas futuras mientras el clima contin√ļa cambiando. Apalancando lo que realmente es una tecnolog√≠a antigua, las redes de parcelas est√°n generando una verdadera y moderna revoluci√≥n en la ciencia tropical. En el futuro, la humanidad puede beneficiarse enormemente si se nutren y cultivan comunidades de investigadores de base, actualmente con la capacidad de generar informaci√≥n √ļnica y de largo plazo para entender los que probablemente son los bosques m√°s preciados de la tierra. Resumo Florestas tropicais s√£o os ecossistemas mais diversos e produtivos da Terra. Embora uma boa compreens√£o destas florestas seja crucial para o nosso futuro coletivo, at√© muito recentemente os esfor√ßos de medi√ß√Ķes e monitoramento foram amplamente desconexos. √Č essencial formarmos redes para obtermos respostas que transcendem fronteiras e horizontes de ag√™ncias financiadoras. Neste estudo n√≥s mostramos como uma comunidade global est√° respondendo aos desafios da pesquisa de ecossistemas tropicais, com equipes diversas medindo florestas, √°rvore por √°rvore, em milhares de parcelas monitoradas √† longo prazo. N√≥s revisamos as maiores descobertas cient√≠ficas deste trabalho, e mostramos tamb√©m como este processo est√° mudando a ci√™ncia de florestas tropicais. Nossa abordagem principal envolve unir iniciativas de base a protocolos padronizados e gerenciamento de dados a fim de gerar resultados robustos em escalas ampliadas. Ao conectar pesquisadores tropicais e elevar seus status, nosso modelo de Rede de Pesquisa Social reconhece o papel-chave do produtor dos dados na descoberta cient√≠fica. Concebida em 1999 com o RAINFOR (Am√©rica do Sul), nossa rede de parcelas permanentes foi adaptada para √Āfrica (AfriTRON) e Sudeste asi√°tico (T-FORCES), e tem sido extensamente reproduzida em todo o mundo. Agora estas m√ļltiplas iniciativas est√£o integradas atrav√©s de uma infraestrutura cibern√©tica do ForestPlots.net, conectando colegas de 54 pa√≠ses de 24 redes de parcelas. Estas iniciativas est√£o transformando coletivamente o entendimento das florestas tropicais e seus pap√©is na biosfera. Juntos n√≥s descobrimos como, onde e por que o carbono e a biodiversidade da floresta est√£o respondendo √†s mudan√ßas clim√°ticas, e seus efeitos de retroalimenta√ß√£o. Esta duradoura colabora√ß√£o pantropical revelou um grande sumidouro de carbono persistente e suas tend√™ncias, assim como tem evidenciado quais direcionadores s√£o mais importantes, quais processos florestais s√£o mais afetados, onde eles est√£o mudando, seus atrasos no tempo de resposta, e as prov√°veis respostas das florestas tropicais conforme o clima continua a mudar. Dessa forma, aproveitando uma not√°vel tecnologia antiga, redes de parcelas acendem fa√≠scas de uma moderna revolu√ß√£o na ci√™ncia das florestas tropicais. No futuro a humanidade pode se beneficiar incentivando estas comunidades basais que agora s√£o coletivamente capazes de gerar conhecimentos √ļnicos e duradouros sobre as florestas mais preciosas da Terra. R√©sume Les for√™ts tropicales sont les √©cosyst√®mes les plus diversifi√©s et les plus productifs de la plan√®te. Si une meilleure compr√©hension de ces for√™ts est essentielle pour notre avenir collectif, jusqu'√† tout r√©cemment, les efforts d√©ploy√©s pour les mesurer et les surveiller ont √©t√© largement d√©connect√©s. La mise en r√©seau est essentielle pour d√©couvrir les r√©ponses √† des questions qui d√©passent les fronti√®res et les horizons des organismes de financement. Nous montrons ici comment une communaut√© mondiale rel√®ve les d√©fis de la recherche sur les √©cosyst√®mes tropicaux avec diverses √©quipes qui mesurent les for√™ts arbre apr√®s arbre dans de milliers de parcelles permanentes. Nous passons en revue les principales d√©couvertes scientifiques de ces travaux et montrons comment ce processus modifie la science des for√™ts tropicales. Notre approche principale consiste √† relier les initiatives de base √† long terme √† des protocoles standardis√©s et une gestion de donn√©es afin de g√©n√©rer des r√©sultats solides √† grande √©chelle. En reliant les chercheurs tropicaux et en √©levant leur statut, notre mod√®le de r√©seau de recherche sociale reconna√ģt le r√īle cl√© de l'auteur des donn√©es dans la d√©couverte scientifique. Con√ßus en 1999 avec RAINFOR (Am√©rique du Sud), nos r√©seaux de parcelles permanentes ont √©t√© adapt√©s √† l'Afrique (AfriTRON) et √† l'Asie du Sud-Est (T-FORCES) et largement imit√©s dans le monde entier. Ces multiples initiatives sont d√©sormais int√©gr√©es via l'infrastructure ForestPlots.net, qui relie des coll√®gues de 54 pays √† travers 24 r√©seaux de parcelles. Ensemble, elles transforment la compr√©hension des for√™ts tropicales et de leur r√īle biosph√©rique. Ensemble, nous avons d√©couvert comment, o√Ļ et pourquoi le carbone forestier et la biodiversit√© r√©agissent au changement climatique, et comment ils y r√©agissent. Cette collaboration pan-tropicale √† long terme a r√©v√©l√© un important puits de carbone √† long terme et ses tendances, tout en mettant en √©vidence les facteurs les plus importants, les processus forestiers qui sont affect√©s, les endroits o√Ļ ils changent, les d√©calages et les r√©actions futures probables des for√™ts tropicales √† mesure que le climat continue de changer. En tirant parti d'une technologie remarquablement ancienne, les r√©seaux de parcelles d√©clenchent une r√©volution tr√®s moderne dans la science des for√™ts tropicales. √Ä l'avenir, l'humanit√© pourra grandement b√©n√©ficier du soutien des communaut√©s de base qui sont maintenant collectivement capables de g√©n√©rer une compr√©hension unique et √† long terme des for√™ts les plus pr√©cieuses de la Terre. Abstrak Hutan tropika adalah di antara ekosistem yang paling produktif dan mempunyai kepelbagaian biodiversiti yang tinggi di seluruh dunia. Walaupun pemahaman mengenai hutan tropika amat penting untuk masa depan kita, usaha-usaha untuk mengkaji dan mengawas hutah-hutan tersebut baru sekarang menjadi lebih diperhubungkan. Perangkaian adalah sangat penting untuk mencari jawapan kepada soalan-soalan yang menjangkaui sempadan dan batasan agensi pendanaan. Di sini kami menunjukkan bagaimana sebuah komuniti global bertindak balas terhadap cabaran penyelidikan ekosistem tropika melalui penglibatan pelbagai kumpulan yang mengukur hutan secara pokok demi pokok dalam beribu-ribu plot jangka panjang. Kami meninjau semula penemuan saintifik utama daripada kerja ini dan menunjukkan bagaimana proses ini sedang mengubah bidang sains hutan tropika. Teras pendekatan kami memberi tumpuan terhadap penghubungan inisiatif akar umbi jangka panjang dengan protokol standar serta pengurusan data untuk mendapatkan hasil skala besar yang kukuh. Dengan menghubungkan penyelidik-penyelidik tropika dan meningkatkan status mereka, model Rangkaian Penyelidikan Sosial kami mengiktiraf kepentingan peranan pengasas data dalam penemuan saintifik. Bermula dengan pengasasan RAINFOR (Amerika Selatan) pada tahun 1999, rangkaian-rangkaian plot kekal kami kemudian disesuaikan untuk Afrika (AfriTRON) dan Asia Tenggara (T-FORCES) dan selanjutnya telah banyak dicontohi di seluruh dunia. Kini, inisiatif-inisiatif tersebut disepadukan melalui infrastruktur siber ForestPlots.net yang menghubungkan rakan sekerja dari 54 negara di 24 buah rangkaian plot. Secara kolektif, rangkaian ini sedang mengubah pemahaman tentang hutan tropika dan peranannya dalam biosfera. Kami telah bekerjasama untuk menemukan bagaimana, di mana dan mengapa karbon serta biodiversiti hutan bertindak balas terhadap perubahan iklim dan juga bagaimana mereka saling bermaklum balas. Kolaborasi pan-tropika jangka panjang ini telah mendedahkan sebuah sinki karbon jangka panjang serta arah alirannya dan juga menjelaskan pemandu-pemandu perubahan yang terpenting, di mana dan bagaimana proses hutan terjejas, masa susul yang ada dan kemungkinan tindakbalas hutan tropika pada perubahan iklim secara berterusan di masa depan. Dengan memanfaatkan pendekatan lama, rangkaian plot sedang menyalakan revolusi yang amat moden dalam sains hutan tropika. Pada masa akan datang, manusia sejagat akan banyak mendapat manfaat jika memupuk komuniti-komuniti akar umbi yang kini berkemampuan secara kolektif menghasilkan pemahaman unik dan jangka panjang mengenai hutan-hutan yang paling berharga di dunia
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