A Permutation-Equivariant Neural Network Architecture For Auction Design

Designing an incentive compatible auction that maximizes expected revenue is a central problem in Auction Design. Theoretical approaches to the problem have hit some limits in the past decades and analytical solutions are known for only a few simple settings. Computational approaches to the problem through the use of LPs have their own set of limitations. Building on the success of deep learning, a new approach was recently proposed by Duetting et al. (2019) in which the auction is modeled by a feed-forward neural network and the design problem is framed as a learning problem. The neural architectures used in that work are general purpose and do not take advantage of any of the symmetries the problem could present, such as permutation equivariance. In this work, we consider auction design problems that have permutation-equivariant symmetry and construct a neural architecture that is capable of perfectly recovering the permutation-equivariant optimal mechanism, which we show is not possible with the previous architecture. We demonstrate that permutation-equivariant architectures are not only capable of recovering previous results, they also have better generalization properties

Reversible Covalent Binding of Desferrioxamine B (DFOB) to 2 Polystyrene Microspheres for the Chelation of Aqueous Iron Citrate

Desferrioxamine B (DFOB) was reversibly and covalently conjugated to polystyrene microspheres via N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) crosslinker. DFOB retained post-immobilization activity with at least 89% able to bind Fe(III)-citrate under pH 7.4 and a citrate:iron molar ratio = 100:1. Comparing iron capture by DFOB-activated beads and sulfhydryl (−SH) control beads demonstrated exclusive iron chelation by surface DFOB molecules. Support regeneration was achieved by cleaving the disulfide bonds linking the spent chelators to the surface with dithiothreitol (DTT) and then recoupling to fresh DFOB. This process did not significantly change iron uptake after two uses. The Langmuir isotherm described the adsorption data with maximum iron coverage of 3.7 × 10⁻³ mmolFe(III)/gadsorbent. DFOB immobilization significantly reduced the chelation rate; 30 and 180 min were required to reach equilibrium chelation levels with free and immobilized DFOB, respectively. The chelation rate decrease was attributed to a surface hindrance of DFOB’s iron complexation mechanism and the reduced access to the supernatant bulk. It is anticipated that future systems tailored for specific DFOB applications can utilize the developed reversible attachment for flexible chelator regeneration, in addition to support reusability and preservation

Intensification of Solvent Extraction in an Additively Manufactured Microfluidic Separator

Solvent extraction is an integral chemical and biochemical separation process that is drastically intensified in microfluidic systems. A novel high-throughput micro-separator was additively manufactured for the intensification of liquid–liquid separation. The micro-posts array within the flow plate generated a capillary pressure gradient on the non-wetting organic phase, enabling continuous, membrane-free, and density-independent phase separation. The device was integrated with an upstream micromixer for aqueous isobutanol extraction, allowing equilibrium extraction levels within 0.25 s. By capitalizing on the high depth-to-width aspect ratio of binder jetting, hydraulic pressure drops were substantially reduced, avoiding a detrimental effect on separation observed in current micro-separators. This novel architecture also enabled the rare ability to separate both “slug flow” and the highly effective but challenging “dispersed droplet flow”. Near-complete separation of the aqueous and organic phases was attained at flow rates up to 15 ml/min, under interfacial tensions of 48.9 and 10.9 mN/m, and aqueous:organic inlet flow ratios of 1:1 and 2:1. Separation performance deteriorated at 20 ml/min due to an increase of velocity gradients near the outlets, leading the wetting aqueous phase to exit from the organic outlet. Owing to its simplicity, manufacturing merits, and robust separation performance, this device addresses key requirements for achieving industrial-level throughputs using a “scale-up via number-up” approach

Tracking the international spread of SARS-CoV-2 lineages B.1.1.7 and B.1.351/501Y-V2

Publisher Copyright: © 2021 O'Toole Á et al.Late in 2020, two genetically-distinct clusters of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with mutations of biological concern were reported, one in the United Kingdom and one in South Africa. Using a combination of data from routine surveillance, genomic sequencing and international travel we track the international dispersal of lineages B.1.1.7 and B.1.351 (variant 501Y-V2). We account for potential biases in genomic surveillance efforts by including passenger volumes from location of where the lineage was first reported, London and South Africa respectively. Using the software tool grinch (global report investigating novel coronavirus haplotypes), we track the international spread of lineages of concern with automated daily reports, Further, we have built a custom tracking website (cov-lineages.org/global_report.html) which hosts this daily report and will continue to include novel SARS-CoV-2 lineages of concern as they are detected.Peer reviewe

A communal catalogue reveals Earth's multiscale microbial diversity

Our growing awareness of the microbial world's importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth's microbial diversity.Peer reviewe

A communal catalogue reveals Earth’s multiscale microbial diversity

Our growing awareness of the microbial world’s importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth’s microbial diversity

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good