Who Will Retweet This? Automatically Identifying and Engaging Strangers on Twitter to Spread Information

There has been much effort on studying how social media sites, such as Twitter, help propagate information in different situations, including spreading alerts and SOS messages in an emergency. However, existing work has not addressed how to actively identify and engage the right strangers at the right time on social media to help effectively propagate intended information within a desired time frame. To address this problem, we have developed two models: (i) a feature-based model that leverages peoples' exhibited social behavior, including the content of their tweets and social interactions, to characterize their willingness and readiness to propagate information on Twitter via the act of retweeting; and (ii) a wait-time model based on a user's previous retweeting wait times to predict her next retweeting time when asked. Based on these two models, we build a recommender system that predicts the likelihood of a stranger to retweet information when asked, within a specific time window, and recommends the top-N qualified strangers to engage with. Our experiments, including live studies in the real world, demonstrate the effectiveness of our work

High throughput sequencing analysis of RNA libraries reveals the influences of initial library and PCR methods on SELEX efficiency.

The systemic evolution of ligands by exponential enrichment (SELEX) technique is a powerful and effective aptamer-selection procedure. However, modifications to the process can dramatically improve selection efficiency and aptamer performance. For example, droplet digital PCR (ddPCR) has been recently incorporated into SELEX selection protocols to putatively reduce the propagation of byproducts and avoid selection bias that result from differences in PCR efficiency of sequences within the random library. However, a detailed, parallel comparison of the efficacy of conventional solution PCR versus the ddPCR modification in the RNA aptamer-selection process is needed to understand effects on overall SELEX performance. In the present study, we took advantage of powerful high throughput sequencing technology and bioinformatics analysis coupled with SELEX (HT-SELEX) to thoroughly investigate the effects of initial library and PCR methods in the RNA aptamer identification. Our analysis revealed that distinct "biased sequences" and nucleotide composition existed in the initial, unselected libraries purchased from two different manufacturers and that the fate of the "biased sequences" was target-dependent during selection. Our comparison of solution PCR- and ddPCR-driven HT-SELEX demonstrated that PCR method affected not only the nucleotide composition of the enriched sequences, but also the overall SELEX efficiency and aptamer efficacy

Finding the ideal: Single-cell cloning and seamless media transitions

Please click Additional Files below to see the full abstract

Dynamic Patterns of Transcript Abundance of Transposable Element Families in Maize.

Transposable Elements (TEs) are mobile elements that contribute the majority of DNA sequences in the maize genome. Due to their repetitive nature, genomic studies of TEs are complicated by the difficulty of properly attributing multi-mapped short reads to specific genomic loci. Here, we utilize a method to attribute RNA-seq reads to TE families rather than particular loci in order to characterize transcript abundance for TE families in the maize genome. We applied this method to assess per-family expression of transposable elements in >800 published RNA-seq libraries representing a range of maize development, genotypes, and hybrids. While a relatively small proportion of TE families are transcribed, expression is highly dynamic with most families exhibiting tissue-specific expression. A large number of TE families were specifically detected in pollen and endosperm, consistent with reproductive dynamics that maintain silencing of TEs in the germ line. We find that B73 transcript abundance is a poor predictor of TE expression in other genotypes and that transcript levels can differ even for shared TEs. Finally, by assessing recombinant inbred line and hybrid transcriptomes, complex patterns of TE transcript abundance across genotypes emerged. Taken together, this study reveals a dynamic contribution of TEs to maize transcriptomes

Imaging moving targets through scattering media

Imaging in turbid media such as biological tissue is challenging primarily due to light scattering, which degrades resolution and limits the depths at which we can reliably image objects. There are two main approaches for realizing non-destructive optical imaging through scattering tissue: gated approaches, which serve to distinguish and reject the multiply scattered photons; and non-gated approaches, which detect both the unscattered and scattered light contributions, and leverage the information from the scattering process in order to image the object1. In terms of non-gated approaches, both wavefront shaping (WFS) and speckle-correlation-based imaging (SCI) techniques can achieve high-resolution imaging of objects hidden within scattering media1,2. WFS techniques exploit the principles of time-reversal to undo the effects of scattering, whereas SCI methods exploit the angular correlations inherent within the scattering process to reconstruct the hidden object. In contrast with WFS approaches, SCI methods do not need long acquisition times or the presence of a guide star2. However, SCI methods are currently limited to imaging sparsely tagged objects in a dark-field scenario, and are strongly impacted by noise from other sources.2 In this work, we establish a technique that allows SCI to image obscured objects in a bright-field scenario.3 Our technique leverages the temporal correlations inherent in the scattering process to distinguish the object signal from the remaining, undesired ‘background’ light contributions. By using a deterministic phase modulator to generate a spatially incoherent light source, the background light contribution is kept constant between different acquisitions and can subsequently be subtracted out. As long as the object moves between acquisitions, the signal from the object can be isolated. The object can be reconstructed from this signal with high fidelity. Using this technique, we experimentally demonstrate successful reconstruction of moving objects hidden behind and between optically translucent materials. Due to the ability to effectively isolate the object signal, our work is not limited to imaging objects in the dark-field case, but also works in bright-field scenarios, with non-emitting objects. This ability opens up many potential applications for imaging in scattering media, such as through turbulent atmosphere or biological tissue, and makes this work relevant to the technical session on ‘Biophotonics in scattering tissue.’ References 1 R. Horstmeyer et al, “Guidestar-assisted wavefront-shaping methods for focusing light into biological tissue,” Nat. Photon. 9, 563-571 (2015). 2O. Katz et al, “Non-invasive single-shot imaging through scattering layers and around corners via speckle correlations,” Nat. Photon. 8, 784-790 (2014). 3M.Cua et al, “Imaging moving targets through scattering media,” O.E. 25(4), 3935-3945 (2017) Please click Additional Files below to see the full abstract