Folded network and structural transition in molten tin

The fundamental relationships between the structure and properties of liquids are far from being well understood. For instance, the structural origins of many liquid anomalies still remain unclear, but liquid-liquid transitions (LLT) are believed to hold a key. However, experimental demonstrations of LLTs have been rather challenging. Here, we report experimental and theoretical evidence of a second-order-like LLT in molten tin, one which favors a percolating covalent bond network at high temperatures. The observed structural transition originates from the fluctuating metallic/covalent behavior of atomic bonding, and consequently a new paradigm of liquid structure emerges. The liquid structure, described in the form of a folded network, bridges two well-established structural models for disordered systems, i.e., the random packing of hard-spheres and a continuous random network, offering a large structural midground for liquids and glasses. Our findings provide an unparalleled physical picture of the atomic arrangement for a plethora of liquids, shedding light on the thermodynamic and dynamic anomalies of liquids but also entailing far-reaching implications for studying liquid polyamorphism and dynamical transitions in liquids.

Resilience in the Context of Pandemics and Disasters: A Framework for Public Governance, Ecosystem Innovation, Co-creation, and Co-production

This article, through a literature review, explores evidence that public governance positively influences and stimulates the innovation ecosystem, the co-creation, and co-production of resilience in communities that are victims of disasters, shocks, and even pandemic disasters, such as COVID-19. Disaster scenarios of all kinds cause millions of damage to society. The negative impacts of these contexts disasters, shocks, catastrophes, even if pandemic, such as COVID-19, can be greater or lesser, depending on the dysfunctions of governance and the negative barriers to the creation of public policies consistent with the capacity for resilience. Thus, the possible solution to this scenario may be based on public governance, if the pubic governance is instituted in an organized, integrated, and articulated manner. For this purpose, a theoretical conceptual framework of value creation is proposed through public governance that values and stimulates the innovation ecosystem, the co-creation, co-production of value, and a static, hierarchical, and linear structural vision. There is theoretical evidence that public governance can promote resilience in communities that are victims of disasters, shocks, pandemics or disturbances, through an ecosystem of innovation, co-creation and co-production of value. In this regard, at the end of this article, a theoretical-conceptual framework for creating public value is proposed.

Function and Plasticity of Electrical Synapses in the Mammalian Brain: Role of Non-Junctional Mechanisms

Electrical transmission between neurons is largely mediated by gap junctions. These junctions allow the direct flow of electric current between neurons, and in mammals, they are mostly composed of the protein connexin36. Circuits of electrically coupled neurons are widespread in these animals. Plus, experimental and theoretical evidence supports the notion that, beyond synchronicity, these circuits are able to perform sophisticated operations such as lateral excitation and inhibition, noise reduction, as well as the ability to selectively respond upon coincident excitatory inputs. Although once considered stereotyped and unmodifiable, we now know that electrical synapses are subject to modulation and, by reconfiguring neural circuits, these modulations can alter relevant operations. The strength of electrical synapses depends on the gap junction resistance, as well as on its functional interaction with the electrophysiological properties of coupled neurons. In particular, voltage and ligand gated channels of the non-synaptic membrane critically determine the efficacy of transmission at these contacts. Consistently, modulatory actions on these channels have been shown to represent relevant mechanisms of plasticity of electrical synaptic transmission. Here, we review recent evidence on the regulation of electrical synapses of mammals, the underlying molecular mechanisms, and the possible ways in which they affect circuit function.

Function and Plasticity of Electrical Synapses in the Mammalian Brain: Role of Non-Junctional Mechanisms

Electrical transmission between neurons is largely mediated by gap junctions. These junctions allow the direct flow of electric current between neurons, and in mammals are mostly composed of the protein connexin (Cx)36. Circuits of electrically coupled neurons are widespread in these animals, plus, experimental and theoretical evidence supports the notion that, beyond synchronicity, these circuits are able to perform sophisticated operations like lateral excitation and inhibition, noise reduction, as well as the ability to selectively respond upon coincident excitatory inputs. Although once considered stereotyped and unmodifiable, we now know that electrical synapses are subject to modulation and, by reconfiguring neural circuits, these modulations can alter relevant operations. The strength of electrical synapses depends on gap junction conductance, as well as on its functional interaction with the electrophysiological properties of coupled neurons. In particular, voltage dependent channels of the non-synaptic membrane critically determine the efficacy of transmission at these contacts. Consistently, modulatory actions on these channels have been shown to represent relevant mechanisms of plasticity of electrical synaptic transmission. Here we review recent evidence on the regulation of electrical synapses of mammals, the underlying molecular mechanisms, and the possible ways in which they affect circuit function.

Evidence that abrasion can govern snow kinetic friction

The long-accepted theory to explain why snow is slippery postulates self-lubrication: frictional heat from sliding melts and thereby lubricates the contacting snow grains. We recently published micro-scale interface observations that contradicted this explanation: contacting snow grains abraded and did not melt under a polyethylene slider, despite low friction values. Here we provide additional observational and theoretical evidence that abrasion can govern snow kinetic friction. We obtained coordinated infrared, visible-light and scanning-electron micrographs that confirm that the evolving shapes observed during our tribometer tests are contacting snow grains polished by abrasion, and that the wear particles can sinter together and fill the adjacent pore spaces. Furthermore, dry-contact abrasive wear reasonably predicts the evolution of snow-slider contact area and sliding-heat-source theory confirms that contact temperatures would not reach 0°C during our tribometer tests. Importantly, published measurements of interface temperatures also indicate that melting did not occur during field tests on sleds and skis. Although prevailing theory anticipates a transition from dry to lubricated contact along a slider, we suggest that dry-contact abrasion and heat flow can prevent this transition from occurring for snow-friction scenarios of practical interest.

The Number of Unanimous Witnesses who Identify a Suspect from a Lineup Influences Mock Jurors

<p>During a criminal proceeding, jurors need to weigh up the presented evidence and determine a verdict. Research has shown that witness identification evidence is compelling to jurors, despite the fact that it can be unreliable. How reliable are the combined lineup decisions gathered from multiple witnesses? Generally, the more witnesses who identify the same person from a lineup, the more likely that person is guilty. But recent theoretical evidence suggests that a greater number of witnesses identifying the same person from a biased lineup can indicate that person is actually less likely to be guilty than if there were a smaller number of witnesses identifying that person (Gunn et al., 2016). As the number of agreeing witnesses increases, the more likely that agreement is caused by the lineup bias, rather than consistent witness memories of the crime. In this thesis, I examined how unanimity and lineup bias influenced jurors’ perceptions of guilt. Subjects who saw a biased lineup gave lower ratings of guilt compared to subjects that were shown a lineup that had no obvious bias. In addition, warning subjects that a lineup was biased led them to give lower guilt ratings than subjects who did not receive a warning. Subjects who were told there were two witnesses who identified the police suspect gave higher guilt ratings than subjects who were told there was one witness who identified the police suspect, but only when the lineup was clearly not biased. Subjects’ guilt ratings were not significantly greater in conditions with more than two unanimous witnesses identifying the police suspect. It seems subjects had a limit of certainty based on changes in witness numbers alone. We also found that the way in which witness numbers were presented to subjects influenced guilt ratings. When we presented witnesses coming forward in different groups and on different days, subjects shifted their guilt ratings upwards. When the number of witnesses decreased during the experiment, subjects did not decrease their guilt ratings to the same extent as those subjects in conditions in which the number of witnesses increased by the same magnitude. This finding is consistent with the literature on confirmation bias and the story model of juror decision-making—subjects likely formed an initial belief that the identified suspect was guilty and subsequent evidence was evaluated against that belief (Nickerson, 1988; Pennington & Hastie, 1993). The finding that presenting witnesses coming forward in separate groups increased subjects’ guilt ratings adds to the literature showing that jurors are influenced by irrelevant information presented to them during a proceeding. This research also demonstrates that future research should examine strength of evidence manipulations over multiple levels—rather than as dichotomous “strong” and “weak” extremes.</p>