12 research outputs found
Basic Research of Material Properties of Mycelium-Based Composites
The subject of this research is growing mycelium-based composites and exploring their basic material properties. Since the building industry is responsible for a large amount of annual CO(2) emissions, rethinking building materials is an important task for future practices. Using such composites is a carbon-neutral strategy that offers alternatives to conventional building materials. Yet, in order to become competitive, their basic research is still needed. In order to create mycelium-based composites, it was necessary to establish a sterile work environment and develop shaping procedures for objects on a scale of architectural building elements. The composite material exhibited qualities that make it suitable for compression-only structures, temporary assemblies, and acoustic and thermal insulation. The methodology includes evaluating several substrates, focused on beech sawdust, with two mycelium strains (Pleurotus ostreatus and Ganoderma lucidum), density calculations, compression tests, three-point flexural tests and capillary water absorption. The results of this study are presented through graphical and numerical values comparing material and mechanical properties. This study established a database for succeeding investigations and for defining the potentials and limitations of this material. Furthermore, future applications and relevant examinations have been addressed
Revisiting Robustness in Graph Machine Learning
Many works show that node-level predictions of Graph Neural Networks (GNNs)
are unrobust to small, often termed adversarial, changes to the graph
structure. However, because manual inspection of a graph is difficult, it is
unclear if the studied perturbations always preserve a core assumption of
adversarial examples: that of unchanged semantic content. To address this
problem, we introduce a more principled notion of an adversarial graph, which
is aware of semantic content change. Using Contextual Stochastic Block Models
(CSBMs) and real-world graphs, our results uncover: for a majority of
nodes the prevalent perturbation models include a large fraction of perturbed
graphs violating the unchanged semantics assumption; surprisingly, all
assessed GNNs show over-robustness - that is robustness beyond the point of
semantic change. We find this to be a complementary phenomenon to adversarial
examples and show that including the label-structure of the training graph into
the inference process of GNNs significantly reduces over-robustness, while
having a positive effect on test accuracy and adversarial robustness.
Theoretically, leveraging our new semantics-aware notion of robustness, we
prove that there is no robustness-accuracy tradeoff for inductively classifying
a newly added node.Comment: Published as a conference paper at ICLR 2023. Preliminary version
accepted as an oral at the NeurIPS 2022 TSRML workshop and at the NeurIPS
2022 ML safety worksho
Expressivity of Graph Neural Networks Through the Lens of Adversarial Robustness
We perform the first adversarial robustness study into Graph Neural Networks
(GNNs) that are provably more powerful than traditional Message Passing Neural
Networks (MPNNs). In particular, we use adversarial robustness as a tool to
uncover a significant gap between their theoretically possible and empirically
achieved expressive power. To do so, we focus on the ability of GNNs to count
specific subgraph patterns, which is an established measure of expressivity,
and extend the concept of adversarial robustness to this task. Based on this,
we develop efficient adversarial attacks for subgraph counting and show that
more powerful GNNs fail to generalize even to small perturbations to the
graph's structure. Expanding on this, we show that such architectures also fail
to count substructures on out-of-distribution graphs.Comment: Published in AdvML Frontiers workshop at
International Conference on Machine Learnin
Assessing Robustness via Score-Based Adversarial Image Generation
Most adversarial attacks and defenses focus on perturbations within small
-norm constraints. However, threat models cannot capture all
relevant semantic-preserving perturbations, and hence, the scope of robustness
evaluations is limited. In this work, we introduce Score-Based Adversarial
Generation (ScoreAG), a novel framework that leverages the advancements in
score-based generative models to generate adversarial examples beyond
-norm constraints, so-called unrestricted adversarial examples,
overcoming their limitations. Unlike traditional methods, ScoreAG maintains the
core semantics of images while generating realistic adversarial examples,
either by transforming existing images or synthesizing new ones entirely from
scratch. We further exploit the generative capability of ScoreAG to purify
images, empirically enhancing the robustness of classifiers. Our extensive
empirical evaluation demonstrates that ScoreAG matches the performance of
state-of-the-art attacks and defenses across multiple benchmarks. This work
highlights the importance of investigating adversarial examples bounded by
semantics rather than -norm constraints. ScoreAG represents an
important step towards more encompassing robustness assessments
Great Cause—Small Effect: Undeclared Genetically Engineered Orange Petunias Harbor an Inefficient Dihydroflavonol 4-Reductase
A recall campaign for commercial, orange flowering petunia varieties in spring 2017 caused economic losses worldwide. The orange varieties were identified as undeclared genetically engineered (GE)-plants, harboring a maize dihydroflavonol 4-reductase (DFR, A1), which was used in former scientific transgenic breeding attempts to enable formation of orange pelargonidin derivatives from the precursor dihydrokaempferol (DHK) in petunia. How and when the A1 cDNA entered the commercial breeding process is unclear. We provide an in-depth analysis of three orange petunia varieties, released by breeders from three countries, with respect to their transgenic construct, transcriptomes, anthocyanin composition, and flavonoid metabolism at the level of selected enzymes and genes. The two possible sources of the A1 cDNA in the undeclared GE-petunia can be discriminated by PCR. A special version of the A1 gene, the A1 type 2 allele, is present, which includes, at the 3′-end, an additional 144 bp segment from the non-viral transposable Cin4-1 sequence, which does not add any functional advantage with respect to DFR activity. This unequivocally points at the first scientific GE-petunia from the 1980s as the A1 source, which is further underpinned e.g., by the presence of specific restriction sites, parts of the untranslated sequences, and the same arrangement of the building blocks of the transformation plasmid used. Surprisingly, however, the GE-petunia cannot be distinguished from native red and blue varieties by their ability to convert DHK in common in vitro enzyme assays, as DHK is an inadequate substrate for both the petunia and maize DFR. Recombinant maize DFR underpins the low DHK acceptance, and, thus, the strikingly limited suitability of the A1 protein for a transgenic approach for breeding pelargonidin-based flower color. The effect of single amino acid mutations on the substrate specificity of DFRs is demonstrated. Expression of the A1 gene is generally lower than the petunia DFR expression despite being under the control of the strong, constitutive p35S promoter. We show that a rare constellation in flavonoid metabolism—absence or strongly reduced activity of both flavonol synthase and B-ring hydroxylating enzymes—allows pelargonidin formation in the presence of DFRs with poor DHK acceptance.Peer Reviewe
Adversarial Training for Graph Neural Networks
Despite its success in the image domain, adversarial training does not (yet)
stand out as an effective defense for Graph Neural Networks (GNNs) against
graph structure perturbations. In the pursuit of fixing adversarial training
(1) we show and overcome fundamental theoretical as well as practical
limitations of the adopted graph learning setting in prior work; (2) we reveal
that more flexible GNNs based on learnable graph diffusion are able to adjust
to adversarial perturbations, while the learned message passing scheme is
naturally interpretable; (3) we introduce the first attack for structure
perturbations that, while targeting multiple nodes at once, is capable of
handling global (graph-level) as well as local (node-level) constraints.
Including these contributions, we demonstrate that adversarial training is a
state-of-the-art defense against adversarial structure perturbations
DataSheet1.docx
<p>A recall campaign for commercial, orange flowering petunia varieties in spring 2017 caused economic losses worldwide. The orange varieties were identified as undeclared genetically engineered (GE)-plants, harboring a maize dihydroflavonol 4-reductase (DFR, A<sub>1</sub>), which was used in former scientific transgenic breeding attempts to enable formation of orange pelargonidin derivatives from the precursor dihydrokaempferol (DHK) in petunia. How and when the A<sub>1</sub> cDNA entered the commercial breeding process is unclear. We provide an in-depth analysis of three orange petunia varieties, released by breeders from three countries, with respect to their transgenic construct, transcriptomes, anthocyanin composition, and flavonoid metabolism at the level of selected enzymes and genes. The two possible sources of the A<sub>1</sub> cDNA in the undeclared GE-petunia can be discriminated by PCR. A special version of the A<sub>1</sub> gene, the A<sub>1</sub> type 2 allele, is present, which includes, at the 3′-end, an additional 144 bp segment from the non-viral transposable Cin4-1 sequence, which does not add any functional advantage with respect to DFR activity. This unequivocally points at the first scientific GE-petunia from the 1980s as the A<sub>1</sub> source, which is further underpinned e.g., by the presence of specific restriction sites, parts of the untranslated sequences, and the same arrangement of the building blocks of the transformation plasmid used. Surprisingly, however, the GE-petunia cannot be distinguished from native red and blue varieties by their ability to convert DHK in common in vitro enzyme assays, as DHK is an inadequate substrate for both the petunia and maize DFR. Recombinant maize DFR underpins the low DHK acceptance, and, thus, the strikingly limited suitability of the A<sub>1</sub> protein for a transgenic approach for breeding pelargonidin-based flower color. The effect of single amino acid mutations on the substrate specificity of DFRs is demonstrated. Expression of the A<sub>1</sub> gene is generally lower than the petunia DFR expression despite being under the control of the strong, constitutive p35S promoter. We show that a rare constellation in flavonoid metabolism—absence or strongly reduced activity of both flavonol synthase and B-ring hydroxylating enzymes—allows pelargonidin formation in the presence of DFRs with poor DHK acceptance.</p