CDLT: A Dataset with Concept Drift and Long-Tailed Distribution for Fine-Grained Visual Categorization

Data is the foundation for the development of computer vision, and the establishment of datasets plays an important role in advancing the techniques of fine-grained visual categorization~(FGVC). In the existing FGVC datasets used in computer vision, it is generally assumed that each collected instance has fixed characteristics and the distribution of different categories is relatively balanced. In contrast, the real world scenario reveals the fact that the characteristics of instances tend to vary with time and exhibit a long-tailed distribution. Hence, the collected datasets may mislead the optimization of the fine-grained classifiers, resulting in unpleasant performance in real applications. Starting from the real-world conditions and to promote the practical progress of fine-grained visual categorization, we present a Concept Drift and Long-Tailed Distribution dataset. Specifically, the dataset is collected by gathering 11195 images of 250 instances in different species for 47 consecutive months in their natural contexts. The collection process involves dozens of crowd workers for photographing and domain experts for labelling. Extensive baseline experiments using the state-of-the-art fine-grained classification models demonstrate the issues of concept drift and long-tailed distribution existed in the dataset, which require the attention of future researches

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Two-Step Thermal Transformation of Multilayer Graphene Using Polymeric Carbon Source Assisted by Physical Vapor Deposited Copper

Direct in situ growth of graphene on dielectric substrates is a reliable method for overcoming the challenges of complex physical transfer operations, graphene performance degradation, and compatibility with graphene-based semiconductor devices. A transfer-free graphene synthesis based on a controllable and low-cost polymeric carbon source is a promising approach for achieving this process. In this paper, we report a two-step thermal transformation method for the copper-assisted synthesis of transfer-free multilayer graphene. Firstly, we obtained high-quality polymethyl methacrylate (PMMA) film on a 300 nm SiO2/Si substrate using a well-established spin-coating process. The complete thermal decomposition loss of PMMA film was effectively avoided by introducing a copper clad layer. After the first thermal transformation process, flat, clean, and high-quality amorphous carbon films were obtained. Next, the in situ obtained amorphous carbon layer underwent a second copper sputtering and thermal transformation process, which resulted in the formation of a final, large-sized, and highly uniform transfer-free multilayer graphene film on the surface of the dielectric substrate. Multi-scale characterization results show that the specimens underwent different microstructural evolution processes based on different mechanisms during the two thermal transformations. The two-step thermal transformation method is compatible with the current semiconductor process and introduces a low-cost and structurally controllable polymeric carbon source into the production of transfer-free graphene. The catalytic protection of the copper layer provides a new direction for accelerating the application of graphene in the field of direct integration of semiconductor devices

Hybrid weakness in a rice interspecific hybrid is nitrogen-dependent, and accompanied by changes in gene expression at both total transcript level and parental allele partitioning

<div><p>Background</p><p>Hybrid weakness, a phenomenon opposite to heterosis, refers to inferior growth and development in a hybrid relative to its pure-line parents. Little attention has been paid to the phenomenological or mechanistic aspect of hybrid weakness, probably due to its rare occurrence.</p><p>Methodology/Principal findings</p><p>Here, using a set of interspecific triploid F1 hybrids between <i>Oryza sativa</i>, ssp. <i>japonica</i> (genome AA) and a tetraploid wild rice species, <i>O</i>. <i>alta</i> (genome, CCDD), we investigated the phenotypic and physiological differences between the F1 hybrids and their parents under normal and nitrogen-limiting conditions. We quantified the expression levels of 21 key genes involved in three important pathways pertinent to the assayed phenotypic and physiological traits by real-time qRT-PCR. Further, we assayed expression partitioning of parental alleles for eight genes in the F1 hybrids relative to the <i>in silico</i> “hybrids” (parental cDNA mixture) under both normal and N-limiting conditions by using locus-specific cDNA pyrosequencing.</p><p>Conclusions/Significance</p><p>We report that the F1 hybrids showed weakness in several phenotypic traits at the final seedling-stage compared with their corresponding mid-parent values (MPVs). Nine of the 21 studied genes showed contrasted expression levels between hybrids and parents (MPVs) under normal vs. N-limiting conditions. Interestingly, under N-limiting conditions, the overtly enhanced partitioning of maternal allele expression in the hybrids for eight assayed genes echo their attenuated hybrid weakness in phenotypes, an observation further bolstered by more resemblance of hybrids to the maternal parent under N-limiting conditions compared to normal conditions in a suite of measured physiological traits. Our observations suggest that both overall expression level and differential partitioning of parental alleles of critical genes contribute to condition-specific hybrid weakness.</p></div

Overall resemblance of the F1 hybrids to <i>O</i>. <i>sativa</i> (maternal) or <i>O</i>. <i>alta</i> (paternal) parents, in 18 measured physiological or morphological traits under normal and N-limiting conditions.

<p>(<b>A</b>) Bar charts represent physiological or morphological traits, including (a) Cl^- concentration, (b) the ratio of the concentration K⁺ and Na⁺, (c) Chl (a+b) content, (d) whole plant fresh weight, the blue bars represent normal conditions and the orange bars represent N-limiting conditions. Different letters under same conditions represent significant difference among the samples. Capital and small letters denote for normal and N-limiting conditions, respectively. * and ** above the orange column refer to significant (<i>P</i> < 0.05) or extremely significant (<i>P</i> < 0.01) differences (based on LSD test) between the two conditions for a given physiological trait of each sample (i.e., comparisons between each pair of blue and orange columns). Error bars indicate s.d., n (replicates) = 3. (<b>B</b>) The similarities were depicted based on quantification of each of the 18 physiological or morphological traits as described by the methods of Yang et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172919#pone.0172919.ref036" target="_blank">36</a>].</p

Cytology and typical phenotypes of the F1 triploid hybrid plants between <i>Oryza sativa</i> ssp. <i>japonica</i> (<i>2n</i> = 2x = 24, genome AA) and <i>O</i>. <i>alta</i> (<i>2n</i> = 4x = 48, genome, CCDD) under both normal and N-limiting conditions.

<p>(<b>A</b>) Diagrams showing genesis of the F1 triploid rice hybrids; (<b>B</b>) Typical chromosomal constitution of the triploid hybrids based on multicolor GISH analysis (Bar = 10 μm). The pink-colored chromosomes belong to the A genome, green-colored chromosomes are the C genome and blue-colored chromosomes are the D genome; (<b>C</b>) Whole plant dry weight of parental plants (MPVs) and F1 hybrids under normal and N-limiting conditions, WPDW stands for whole plant dry weight. Different letters among genotypes of the same treatment denote statistical differences (based on the least significant difference or LSD test, <i>P</i> < 0.05). The capital and small letters refer to corresponding indices of normal and N-limiting conditions, respectively, Error bars indicate s.d., n (replicates) = 3 to 4; (<b>D-G</b>) The growth rates and whole plant fresh weight of parental plants (MPVs) and F1 hybrids under normal and N-limiting conditions after the treatment for 4 weeks, the blue-dotted lines represent normal conditions and the yellow-dotted lines N-limiting conditions, WPFW stands for whole plant fresh weight, error bars indicate s.d., n (replicates) = 3 to 4; (<b>H</b>) Whole plant phenotypic differences between normal and N-limiting conditions at the final seedling stage (Bar = 10 cm).</p

Number and percentage (%) of genes showing various expression patterns under normal and N-limiting conditions.

<p>Number and percentage (%) of genes showing various expression patterns under normal and N-limiting conditions.</p