How Can We Provide Additively Manufactured Parts with a Fingerprint? A Review of Tagging Strategies in Additive Manufacturing

Additive manufacturing (AM) is rapidly evolving from “rapid prototyping” to “industrial production”. AM enables the fabrication of bespoke components with complicated geometries in the high-performance areas of aerospace, defence and biomedicine. Providing AM parts with a tagging feature that allows them to be identified like a fingerprint can be crucial for logistics, certification and anti-counterfeiting purposes. Whereas the implementation of an overarching strategy for the complete traceability of AM components downstream from designer to end user is, by nature, a cross-disciplinary task that involves legal, digital and technological issues, materials engineers are on the front line of research to understand what kind of tag is preferred for each kind of object and how existing materials and 3D printing hardware should be synergistically modified to create such tag. This review provides a critical analysis of the main requirements and properties of tagging features for authentication and identification of AM parts, of the strategies that have been put in place so far, and of the future challenges that are emerging to make these systems efficient and suitable for digitalisation. It is envisaged that this literature survey will help scientists and developers answer the challenging question: “How can we embed a tagging feature in an AM part?”.

Giving Mirrors to Female Prisoners in Alice Birch’s [BLANK]

The paper at hand attempts to interpret a contemporary British playwright’s theatrical artistic attempt to present a disturbing social issue and to suggest possible modes of help. In [BLANK], Alice Birch confronts the audience with the ugly cycle of women’s criminal conducts, female criminals’ offending and reoffending. The playwright employs the theater of the absurd as a theatrical medium through which she portrays the absurd reality of these female criminals and their families. To confront and shock the audience with the ugliness of these charterers’ reality, Birch uses In-Yer-Face theater. Birch suggests that the female criminal characters are victims who need proper psychological and medical rehabilitation services to break the ugly cycle of reoffending. The playwright implies a very challenging question for the audience: is it possible to break some patterns of some biological genetic behaviors? That is, can female criminals, in [BLANK], break away from their criminal behaviors that are biologically innate through the help of medicine and psychology not just through some practices of traditional stigmatizing forms of discipline and punishment in the justice system that are often proven to be unreliable means of constraint? By shocking and confronting society with the ugly reality of many female prisoners, in [BLANK], Birch is trying to give these pathetic female characters’ voices, mirrors, selves, forcing society to acknowledge them as human beings who have an essential role in society.

Dissecting cascade computational components in spiking neural networks

Finding out the physical structure of neuronal circuits that governs neuronal responses is an important goal for brain research. With fast advances for large-scale recording techniques, identification of a neuronal circuit with multiple neurons and stages or layers becomes possible and highly demanding. Although methods for mapping the connection structure of circuits have been greatly developed in recent years, they are mostly limited to simple scenarios of a few neurons in a pairwise fashion; and dissecting dynamical circuits, particularly mapping out a complete functional circuit that converges to a single neuron, is still a challenging question. Here, we show that a recent method, termed spike-triggered non-negative matrix factorization (STNMF), can address these issues. By simulating different scenarios of spiking neural networks with various connections between neurons and stages, we demonstrate that STNMF is a persuasive method to dissect functional connections within a circuit. Using spiking activities recorded at neurons of the output layer, STNMF can obtain a complete circuit consisting of all cascade computational components of presynaptic neurons, as well as their spiking activities. For simulated simple and complex cells of the primary visual cortex, STNMF allows us to dissect the pathway of visual computation. Taken together, these results suggest that STNMF could provide a useful approach for investigating neuronal systems leveraging recorded functional neuronal activity.

On the Temperature of SAT Formulas

The remarkable advances in SAT solving achieved in the last years have allowed to use this technology in many real-world applications of Artificial Intelligence, such as planning, formal verification, and scheduling, among others. Interestingly, these industrial SAT problems are commonly believed to be easier than classical random SAT formulas, but estimating their actual hardness is still a very challenging question, which in some cases even requires to solve them. In this context, realistic pseudo-industrial random SAT generators have emerged with the aim of reproducing the main features shared by the majority of these application problems. The study of these models may help to better understand the success of those SAT solving techniques and possibly improve them. In this work, we present a model to estimate the temperature of real-world SAT instances. This temperature represents the degree of distortion into the expected structure of the formula, from highly structured benchmarks (more similar to real-world SAT instances) to the complete absence of structure (observed in the classical random SAT model). Our solution is based on the Popularity-Similarity (PS) random model for SAT, which has been recently presented to reproduce two crucial features of application SAT benchmarks: scale-free and community structures. The PS model is able to control the hardness of the generated formula by introducing some randomizations in the expected structure. Our solution is a first step towards a hardness oracle based on the temperature of SAT formulas, which may be able to estimate the cost of solving real-world SAT instances without solving them.

Tubular microdomains of Rab7-endosomes retrieve TrkA, a mechanism disrupted in Charcot-Marie-Tooth 2B

Axonal survival and growth requires signalling from tropomyosin receptor kinases (Trks). To transmit their signals, receptor-ligand complexes are endocytosed and retrogradely trafficked to the soma where downstream signalling occurs. Vesicles transporting neurotrophic receptors to the soma are reported to be Rab7-positive late endosomes/multi vesicular bodies where receptors localize within so-called intraluminal vesicles. Therefore, one challenging question is how downstream signalling is possible given the insulating properties of intraluminal vesicles. In this study, we report that Rab7-endosomes/multi vesicular bodies retrieve TrkA through tubular microdomains. Interestingly, this phenotype is absent for the EGF-receptor. Further, we found that EndophilinA1, EndophilinA2 and EndophilinA3 together with WASH1 are involved in the tubulation process. In Charcot-Marie-Tooth 2B, a neuropathy of the peripheral nervous system, this tubulating mechanism is disrupted. In addition, the ability to tubulate correlates with the phosphorylation levels of TrkA as well as with neurite length in neuronal cultures from dorsal root ganglia. In all, we report a new retrieval mechanism of late Rab7-endosomes, which enables TrkA signalling and sheds new light onto how neurotrophic signalling is disrupted in CMT2B.

Free-choice Nets with Home Clusters are Lucent

A marked Petri net is lucent if there are no two different reachable markings enabling the same set of transitions, i.e., states are fully characterized by the transitions they enable. Characterizing the class of systems that are lucent is a foundational and also challenging question. However, little research has been done on the topic. In this paper, it is shown that all free-choice nets having a home cluster are lucent. These nets have a so-called home marking such that it is always possible to reach this marking again. Such a home marking can serve as a regeneration point or as an end-point. The result is highly relevant because in many applications, we want the system to be lucent and many “well-behaved” process models fall into the class identified in this paper. Unlike previous work, we do not require the marked Petri net to be live and stronglyconnected. Most of the analysis techniques for free-choice nets are tailored towards well-formed nets. The approach presented in this paper provides a novel perspective enabling new analysis techniques for free-choice nets that do not need to be well-formed. Therefore, we can also model systems and processes that are terminating and/or have an initialization phase.

The dorsal blastopore lip is a source of signals inducing PCP in the Xenopus neural plate

Coordinated polarization of cells in the tissue plane, known as planar cell polarity (PCP), is associated with a signaling pathway critical for the control of morphogenetic processes. Although the segregation of PCP components to opposite cell borders is believed to play a critical role in this pathway, whether PCP derives from egg polarity or preexistent long-range gradient, or forms in response to a localized cue remains a challenging question. Here we investigate the Xenopus neural plate, a tissue that has been previously shown to exhibit PCP. By imaging Vangl2 and Prickle3, we show that PCP is progressively acquired in the neural plate and requires a signal from the posterior region of the embryo. Tissue transplantations indicated that PCP is triggered in the neural plate by a planar cue from the dorsal blastopore lip. The PCP cue did not depend on the orientation of the graft and was distinct from neural inducers. These observations suggest that neuroectodermal PCP is not instructed by a preexisting molecular gradient, but induced by a signal from the dorsal blastopore lip.