Place-cell capacity and volatility with grid-like inputs

What factors constrain the arrangement of the multiple fields of a place cell? By modeling place cells as perceptrons that act on multiscale periodic grid-cell inputs, we analytically enumerate a place cell's repertoire - how many field arrangements it can realize without external cues while its grid inputs are unique; and derive its capacity - the spatial range over which it can achieve any field arrangement. We show that the repertoire is very large and relatively noise-robust. However, the repertoire is a vanishing fraction of all arrangements, while capacity scales only as the sum of the grid periods so field arrangements are constrained over larger distances. Thus, grid-driven place field arrangements define a large response scaffold that is strongly constrained by its structured inputs. Finally, we show that altering grid-place weights to generate an arbitrary new place field strongly affects existing arrangements, which could explain the volatility of the place code.

Discovering antiviral restriction factors and pathways using genetic screens

Viral infections activate the powerful interferon (IFN) response that induces the expression of several hundred IFN stimulated genes (ISGs). The principal role of this extensive response is to create an unfavourable environment for virus replication and to limit spread; however, untangling the biological consequences of this large response is complicated. In addition to a seemingly high degree of redundancy, several ISGs are usually required in combination to limit infection as individual ISGs often have low to moderate antiviral activity. Furthermore, what ISG or combination of ISGs are antiviral for a given virus is usually not known. For these reasons, and since the function(s) of many ISGs remains unexplored, genome-wide approaches are well placed to investigate what aspects of this response result in an appropriate, virus-specific phenotype. This review discusses the advances screening approaches have provided for the study of host defence mechanisms, including clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (CRISPR/Cas9), ISG expression libraries and RNA interference (RNAi) technologies.

The allosteric activation of α7 nAChR by α-conotoxin MrIC is modified by mutations at the vestibular site

α-conotoxins are 13-19 amino acid toxin peptides that bind various nicotinic acetylcholine receptor (nAChR) subtypes. α-conotoxin Mr1.7c (MrIC) is a 17 amino acid peptide that targets α7 nAChR. Although MrIC has no activating effect on α7 nAChR when applied by itself, it evokes a large response when co-applied with the type II positive allosteric modulator PNU-120596, which potentiates α7 nAChR response by recovering it from a desensitized state. Lack of standalone activity despite activation upon co-application with a positive allosteric modulator was previously observed for molecules that bind to an extracellular domain allosteric activation (AA) site at the vestibule of the receptor. We hypothesized that MrIC may activate α7 nAChR allosterically through this site. We ran voltage-clamp electrophysiology experiments and in silico peptide docking calculations to gather evidence in support of α7 nAChR activation by MrIC through the AA site. The experiments with the wild-type α7 nAChR supported an allosteric mode of action, which was confirmed by the increased MrIC + PNU-120596 responses of three α7 nAChR AA site mutants that were designed in silico to improve MrIC binding. Overall, our results shed light on allosteric activation of α7 nAChR by MrIC and suggest involvement of the AA site.

Equality, Diversity, and Inclusion in Geoscience (EDIG) initiative: A time to listen, learn, and act.

<p>The Equality, Diversity, and Inclusion in Geoscience (EDIG) initiative was created to better understand the experiences of the geoscience community with respect to prejudice, inequity, bias, exclusion, sexism, and discrimination. EDIG aims to provide a platform for learning for the wider geoscience community and promote progressive action to make geoscience more inclusive and equitable.</p><p>As part of our initiatives, we organised the virtual EDIG conference in December 2020 entitled: A time to listen, learn, and act. This virtual event aimed to facilitate learning on equality, diversity, and inclusion related topics relevant to the geosciences. It hosted sessions on where we have come from, where we are now, and where we are going. The conference especially focused on raising awareness around the challenges experienced by minoritized geoscientists, helping to involve more people in these conversations. The conference hosted 17 speakers on a range of different topics, from the history of diversity in geoscience, to how we can become more inclusive, to how we can move forward together, as well as a workshop on unconscious bias sponsored by the Institute of Geologists of Ireland (IGI) and the Irish Centre for Research in Applied Geology (iCRAG).</p><p>Prior to the EDIG conference, we launched a global survey to carry out research on equality, diversity, and inclusion in the geosciences. The survey asked people about their own experiences (or lack of) around EDI related topics. The survey received a large response, with 708 participants from 58 countries. The main themes from the survey data were used to structure our conference programme.</p><p>We will present the results of this survey, and our experiences of the EDIG conference. With these and future events we hope to bring together several online initiatives, establish a community of support and learning, and to help us all come together to make the geosciences more welcoming, accessible, inclusive, and equitable.</p>

Competing magnetic phases and fluctuation-driven scalar spin chirality in the kagome metal YMn6Sn6

Identification, understanding, and manipulation of novel magnetic textures are essential for the discovery of new quantum materials for future spin-based electronic devices. In particular, materials that manifest a large response to external stimuli such as a magnetic field are subject to intense investigation. Here, we study the kagome-net magnet YMn6Sn6 by magnetometry, transport, and neutron diffraction measurements combined with first-principles calculations. We identify a number of nontrivial magnetic phases, explain their microscopic nature, and demonstrate that one of them hosts a large topological Hall effect (THE). We propose a previously unidentified fluctuation-driven mechanism, which leads to the THE at elevated temperatures. This interesting physics comes from parametrically frustrated interplanar exchange interactions that trigger strong magnetic fluctuations. Our results pave a path to chiral spin textures, promising for novel spintronics.

Impact of the Sensor Temperature on Low Acetone Concentration Detection Using AlGaN/GaN HEMTs

In this work, we report on AlGaN/GaN HEMT sensors for acetone concentration below 100ppm and in a broad range of the sensor temperature varying from RT to 300 ∘C. At RT, in the presence of acetone, a smooth and monotonic decrease of the current is observed with a rather large response of 15A/ppm and with a large response time (several minutes) and memory effect. At a high temperature (300 ∘C), a current decrease is first observed just after the acetone injection, then followed by an increase, which saturates and stabilizes at a constant value. In order to clarify this unexpected behaviour, a detailed study of the sensor response versus the temperature and acetone injection flow is carried out. The outcome of this investigation is that a competition between the current variations induced by both the sensor and gas flow temperature difference from one side and the acetone dipolar moment from the other side can explain this transient. Our study highlights that AlGaN/GaN HEMT-based sensors allow for very sensitive acetone detection at both room and high temperatures. Nevertheless, care must be taken during the characterization and operation of such sensors especially at high operating temperatures. On the other hand, the high temperature operation helps to improve the sensor response and suppress the memory effect.

Accelerator or Brake? Cash for Clunkers, Household Liquidity, and Aggregate Demand

This paper evaluates the Car Allowance Rebate System (CARS ) by comparing the vehicle purchases and disposals of households with eligible “clunkers” to those of households with similar but ineligible vehicles. CARS caused roughly 500,000 purchases during the program period. The provision of liquidity, through a rebate usable as a down payment, was critical in generating this large response. Participation was rare among households that owned clunkers with outstanding loans, which required loan repayment. This decline in participation is attributed to households’ preference for lower down payments and distinguished from the effects of income, other indebtedness, and the program subsidy. (JEL E23, E62, G51, H24, H31)