Cortical Magnification Neutralizes the Eccentricity Effect in Visual Search

AbstractWe report two visual search experiments that explain an eccentricity effect previously found: detection of both feature and conjunction targets becomes increasingly less efficient as the orientation target appears at more distant field eccentricities (Carrasco et al., 1995). By cortically magnifying the stimuli we flattened out this effect for both feature and conjunction tasks. We conclude that spatial resolution factors affect visual search findings that have hitherto been attributed to covert attention. We stress the importance of analyzing data by target position to minimize the confound of the set size effect and retinal/field eccentricity. An alternative theory of orientation asymmetries is offered. Copyright © 1996 Elsevier Science Ltd

0++0^{++} Resonances Observed at BES

In last 10 years, $0^{++}$ resonances have been observed and studied at BES in many processes, such as $J/\psi\to\gamma\pi^+\pi^-\pi^+\pi^-$, $\gamma\pi^+\pi^-$, $\gamma\pi^0\pi^0$, $\gamma K^+K^-$, $\gamma K_SK_S$, $\gamma\omega\phi$, $\omega\pi^+\pi^-$, $\omega K^+K^-$, $\phi\pi^+\pi^-$, $\phi K^+K^-$, $\psi(2S)\to J/\psi\pi^+\pi^-$, $\chi_{c0}\to\pi^+\pi^-K^+K^-$, $\pi^+\pi^-\pi^+\pi^-$ etc.. The results on $0^{++}$ resonances observed at BES are reviewed.Comment: Plenary talk at SCADRON70, Lisbon, Feb. 200

Abiotic methane synthesis and serpentinization in olivine-hosted fluid inclusions

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Proceedings of the National Academy of Sciences.of the United States of America 116(36), (2019): 17666-17672. doi:10.1073/pnas.1907871116.The conditions of methane (CH4) formation in olivine-hosted secondary fluid inclusions and their prevalence in peridotite and gabbroic rocks from a wide range of geological settings were assessed using confocal Raman spectroscopy, optical and scanning electron microscopy, electron microprobe analysis, and thermodynamic modeling. Detailed examination of 160 samples from ultraslow- to fast-spreading midocean ridges, subduction zones, and ophiolites revealed that hydrogen (H2) and CH4 formation linked to serpentinization within olivine-hosted secondary fluid inclusions is a widespread process. Fluid inclusion contents are dominated by serpentine, brucite, and magnetite, as well as CH4(g) and H2(g) in varying proportions, consistent with serpentinization under strongly reducing, closed-system conditions. Thermodynamic constraints indicate that aqueous fluids entering the upper mantle or lower oceanic crust are trapped in olivine as secondary fluid inclusions at temperatures higher than ∼400 °C. When temperatures decrease below ∼340 °C, serpentinization of olivine lining the walls of the fluid inclusions leads to a near-quantitative consumption of trapped liquid H2O. The generation of molecular H2 through precipitation of Fe(III)-rich daughter minerals results in conditions that are conducive to the reduction of inorganic carbon and the formation of CH4. Once formed, CH4(g) and H2(g) can be stored over geological timescales until extracted by dissolution or fracturing of the olivine host. Fluid inclusions represent a widespread and significant source of abiotic CH4 and H2 in submarine and subaerial vent systems on Earth, and possibly elsewhere in the solar system.We are indebted to J. Eckert for his support with FE-EMPA; to K. Aquinho and E. Codillo for providing samples from Zambales; to K. Aquinho for Raman analysis of some of the samples from Zambales and Mt. Dent; to H. Dick for providing access to his thin section collection; to the curators of the IODP core repositories for providing access to Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) samples; and to the captains and crews of the many cruises without whom the collection of these samples would not have been possible. Reviews by Peter Kelemen and an anonymous referee greatly improved this manuscript. This study is supported with funds provided by the National Science Foundation (NSF-OCE Award 1634032 to F.K. and J.S.S.).2020-02-1

D^+ \to K^- \p^+ \p^+ : the low-energy sector

An effective $SU(3)\times SU(3)$ chiral lagrangian, which includes scalar resonances, is used to describe the process D^+ \rar K^- \p^+ \p^+ at low-energies. Our main result is a set of five $S$-wave amplitudes, suited to be used in analyses of production data.Comment: Talk given at SCADRON 70 - Workshop on Scalar Mesons and Related Topics - Lisbon - February 200

Cystein-Mutanten der Cu,Zn-Superoxiddismutase und ihre Anwendung in Proteinelektroden für die Detektion von freien Sauerstoffradikalen

Das Enzym Superoxiddismutase (SOD) bietet wegen seiner hohen Reaktionsrate und seiner extrem hohen Substratspezifi tät große Vorteile für eine Anwendung als Superoxidbiosensor. In dieser Arbeit wurden durch molekularbiologische Methoden Mutanten der humanen Cu,Zn-SOD gewonnen, welche ein oder zwei zusätzliche Cystein-Reste enthielten, die eine einfache Immobilisierung des Proteins durch Bindung des Cystein-Schwefels auf Goldelektroden ermöglichten. Sechs solcher Mutanten wurden entworfen, exprimiert, aufgereinigt und elektrochemisch charakterisiert. Alle Mutanten konnten durch einen einfachen Inkubationsschritt auf Goldelektroden gebunden werden und zeigten ein quasi-reversibles elektrochemisches Ansprechen. Für eine Mutante wurde die Anwendung als Superoxidsensor genauer untersucht und für beide Teilreaktionen der Dismutation ein Ansprechen des Sensors auf das Radikal gefunden. Bei Verwendung einer Teilreaktion konnte die Empfindlichkeit herkömmlicher Monoschichtsensoren um etwa eine Größenordnung übertroffen werden

Thallium as a tracer of fluid–rock interaction in the shallow Mariana forearc

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 430 (2015): 416-426, doi:10.1016/j.epsl.2015.09.001.Fluids driven off the subducting Pacific plate infiltrate the shallow Mariana 26 forearc and lead to extensive serpentinization of mantle peridotite. However, the sources, pathways, and chemical modifications of ascending, slab-derived fluids remain poorly constrained and controversial. In this study, we use thallium (Tl) concentrations and isotopic ratios of serpentinized peridotite and rodingitized diabase from the South Chamorro and Conical Seamounts to discriminate between potential fluid sources with distinct Tl isotope compositions. Serpentinite samples from the Mariana forearc all display ε205Tl > - 0.5 (where ε205Tl = 10,000 x (205Tl/203Tlsample-205Tl/203TlSRM 997)/(205Tl/203TlSRM 997)), which is significantly enriched in 205Tl compared to the normal mantle (ε205Tl = -2). Given that high temperature hydrothermal processes do not impart significant Tl isotope fractionation, the isotope compositions of the serpentinites must reflect that of the serpentinizing fluid. Pelagic sediments are the only known slab component that consistently display ε205Tl > -0.5 and, therefore, we interpret the heavy Tl isotope signatures as signifying that the serpentinizing fluids were derived from subducting pelagic sediments. A rodingitized diabase from Conical Seamount was found to have an ε205Tl of 0.8, suggesting that sediment-sourced serpentinization fluids could also affect diabase and other mafic lithologies in the shallow Mariana forearc. Forearc rodingitization of diabase led to a strong depletion in Tl content and a virtually complete loss of K, Na and Rb. The chemical composition of hybrid fluids resulting from serpentinization of harzburgite with concomitant rodingitization of diabase can be highly alkaline, depleted in Si, yet enriched in Ca, Na, K, and Rb, which is consistent with the composition of fluids emanating from mud volcanoes in the Mariana forearc. Our study suggests that fluid-rock interactions between sedimentary, mafic, and ultramafic lithologies are strongly interconnected even in the shallowest parts of subduction zones. We conclude that transfer of fluids and dissolved elements at temperatures and pressures below 400°C and 1GPa, respectively, must be taken into account when elemental budgets and mass transfer between the subducting plate, the forearc, the deep mantle and the ocean are evaluated.This study was funded by NSF grants EAR-1119373 and -1427310 to SGN, NSF grant OCE-1059534 to FK and a grant from the WHOI Deep Ocean Exploration Institute to FK and SGN

Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McCollom, T. M., Klein, F., Moskowitz, B., Berquo, T. S., Bach, W., & Templeton, A. S. Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture. Geochimica Et Cosmochimica Acta, 282, (2020): 55-75, doi:10.1016/j.gca.2020.05.016.A series of laboratory experiments was conducted to investigate serpentinization of olivine–pyroxene mixtures at 230 °C, with the objective of evaluating the effect of mixed compositions on Fe partitioning among product minerals, H2 generation, and reaction rates. An initial experiment reacted a mixture of 86 wt.% olivine and 14 wt.% orthopyroxene (Opx) with the same initial grain size for 387 days. The experiment resulted in extensive reaction (∼53% conversion), and solids recovered at termination of the experiment were dominated by Fe-bearing chrysotile and relict olivine along with minor brucite and magnetite. Only limited amounts of H2 were generated during the first ∼100 days of the experiment, but the rate of H2 generation then increased sharply coincident with an increase in pH from mildly alkaline to strongly alkaline conditions. Two shorter term experiments with the same reactants (26 and 113 days) produced a mixture of lizardite and talc that formed a thin coating on relict olivine and Opx grains, with virtually no generation of H2. Comparison of the results with reaction path models indicates that the Opx reacted about two times faster than olivine, which contrasts with some previous studies that suggested olivine should react more rapidly than Opx at the experimental conditions. The models also indicate that the long-term experiment transitioned from producing serpentine ± talc early in the early stages to precipitation of serpentine plus magnetite, with brucite beginning to precipitate only late in the experiment as Opx was depleted. The results indicate that overall reaction of olivine and Opx was initially relatively slow, but reaction rates accelerated substantially when the pH transitioned to strongly alkaline conditions. Serpentine and brucite precipitated from the olivine-Opx mixture had higher Fe contents than observed in olivine-only experiments at mildly alkaline pH, but had comparable Fe contents to reaction of olivine at strongly alkaline pH implying that higher pH may favor greater partitioning of Fe into serpentine and brucite and less into magnetite. Despite the presence of brucite, dissolved silica activities during the long-term olivine-Opx experiment maintained levels well above serpentine-brucite equilibrium. Instead, silica activities converged on levels close to metastable equilibrium between brucite and olivine. It is proposed that silica levels during the experiment may have been regulated by exchange of SiO2 between the fluid and a silica-depleted, brucite-like surface layer on dissolving olivine.This research was supported by the U. S. National Science Foundation Marine Geology and Geophysics program through grant NSF-OCE 0927744 and by the NASA Astrobiology Institute through Cooperative Agreement NNA15BB02A. Additional support to TMM from the Hanse Wissenschaftskolleg (Delmenhorst, Germany) at an early stage of this project is gratefully acknowledged. FK acknowledges support through Grant NSF-OCE 1427274. The IRM is supported by the Instruments and Facilities Program of the NSF Division of Earth Science. This is IRM contribution 1711. We very much appreciate the comments of Fabrice Brunet, Gleb Pokrovski and an anonymous reviewer that helped us refine our interpretations and improve communication of the results

Training Curricula for Open Domain Answer Re-Ranking

In precision-oriented tasks like answer ranking, it is more important to rank many relevant answers highly than to retrieve all relevant answers. It follows that a good ranking strategy would be to learn how to identify the easiest correct answers first (i.e., assign a high ranking score to answers that have characteristics that usually indicate relevance, and a low ranking score to those with characteristics that do not), before incorporating more complex logic to handle difficult cases (e.g., semantic matching or reasoning). In this work, we apply this idea to the training of neural answer rankers using curriculum learning. We propose several heuristics to estimate the difficulty of a given training sample. We show that the proposed heuristics can be used to build a training curriculum that down-weights difficult samples early in the training process. As the training process progresses, our approach gradually shifts to weighting all samples equally, regardless of difficulty. We present a comprehensive evaluation of our proposed idea on three answer ranking datasets. Results show that our approach leads to superior performance of two leading neural ranking architectures, namely BERT and ConvKNRM, using both pointwise and pairwise losses. When applied to a BERT-based ranker, our method yields up to a 4% improvement in MRR and a 9% improvement in P@1 (compared to the model trained without a curriculum). This results in models that can achieve comparable performance to more expensive state-of-the-art techniques

Expansion via Prediction of Importance with Contextualization

The identification of relevance with little textual context is a primary challenge in passage retrieval. We address this problem with a representation-based ranking approach that: (1) explicitly models the importance of each term using a contextualized language model; (2) performs passage expansion by propagating the importance to similar terms; and (3) grounds the representations in the lexicon, making them interpretable. Passage representations can be pre-computed at index time to reduce query-time latency. We call our approach EPIC (Expansion via Prediction of Importance with Contextualization). We show that EPIC significantly outperforms prior importance-modeling and document expansion approaches. We also observe that the performance is additive with the current leading first-stage retrieval methods, further narrowing the gap between inexpensive and cost-prohibitive passage ranking approaches. Specifically, EPIC achieves a MRR@10 of 0.304 on the MS-MARCO passage ranking dataset with 78ms average query latency on commodity hardware. We also find that the latency is further reduced to 68ms by pruning document representations, with virtually no difference in effectiveness

Efficient Document Re-Ranking for Transformers by Precomputing Term Representations

Deep pretrained transformer networks are effective at various ranking tasks, such as question answering and ad-hoc document ranking. However, their computational expenses deem them cost-prohibitive in practice. Our proposed approach, called PreTTR (Precomputing Transformer Term Representations), considerably reduces the query-time latency of deep transformer networks (up to a 42x speedup on web document ranking) making these networks more practical to use in a real-time ranking scenario. Specifically, we precompute part of the document term representations at indexing time (without a query), and merge them with the query representation at query time to compute the final ranking score. Due to the large size of the token representations, we also propose an effective approach to reduce the storage requirement by training a compression layer to match attention scores. Our compression technique reduces the storage required up to 95% and it can be applied without a substantial degradation in ranking performance