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RNA-triggered Cas12a3 cleaves tRNA tails to execute bacterial immunity
No full textIn all domains of life, tRNAs mediate the transfer of genetic information from mRNAs to proteins. As their depletion suppresses translation and, consequently, viral replication, tRNAs represent long-standing and increasingly recognized targets of innate immunity1,2,3,4,5. Here we report Cas12a3 effector nucleases from type V CRISPR–Cas adaptive immune systems in bacteria that preferentially cleave tRNAs after recognition of target RNA. Cas12a3 orthologues belong to one of two previously unreported nuclease clades that exhibit RNA-mediated cleavage of non-target RNA, and are distinct from all other known type V systems. Through cell-based and biochemical assays and direct RNA sequencing, we demonstrate that recognition of a complementary target RNA by the CRISPR RNA triggers Cas12a3 to cleave the conserved 5′-CCA-3′ tail of diverse tRNAs to drive growth arrest and anti-phage defence. Cryogenic electron microscopy structures further revealed a distinct tRNA-loading domain that positions the tRNA tail in the RuvC active site of the nuclease. By designing synthetic reporters that mimic the tRNA acceptor stem and tail, we expanded the capacity of current CRISPR-based diagnostics for multiplexed RNA detection. Overall, these findings reveal widespread tRNA inactivation as a previously unrecognized CRISPR-based immune strategy that broadens the application space of the existing CRISPR toolbox
Mixing of a binary passive particle system using smart active particles
No full textThe controlled activity of active entities interacting with a passive environment can generate emergent system-level phenomena, positioning such systems as promising platforms for potential downstream applications in targeted drug delivery, adaptive and reconfigurable materials, microfluidic transport, and related fields. The present work aims to realise an optimal mixing of two segregated species of passive particles by introducing a small fraction of active particles ( by composition) with adaptive and intelligent behaviour, directed by a trained Artificial Neural Network-based agent. While conventional run-and-tumble particles can induce mixing in the system, the smart active particles demonstrate enhanced performance, achieving faster and more efficient mixing. Interestingly, an optimal mixing strategy doesn’t involve a uniform dispersion of active particles in the domain, but rather limiting their motion to an eccentrically placed zone of activity, inducing a global rotational motion of the passive particles about the system centre. A transition in the directionality of the passive particles’ motion is observed along the radius towards the centre, likening the active particles’ motion to an ellipse-shaped void with a defined surface speed. Situated at the intersection of active matter and machine learning, this work highlights the potential of integrating adaptive learning frameworks into traditional models of active matter
The Effect of Guide Star Variability on PLATO Pointing Stability
No full textThe main science goal of the PLAnetary Transits and Oscillations of stars (PLATO) is to detect and characterize extrasolar planets, including terrestrial planets in the habitable zone (HZ) of their host stars. Detecting rocky planets in the HZ requires high photometric stability, which depends on the spacecraft’s pointing performance. PLATO’s pointing performance is managed by the Fine Guidance System (FGS), which utilizes a catalog of guide stars to determine the spacecraft’s attitude. The FGS compares the position of these guide stars within the telescope’s CCDs to their position in the sky to determine the spacecraft’s orientation. This is critical as PLATO’s science mission requires an extremely high level of pointing accuracy. High astrophysical variability in these guide stars can cause apparent shifts in their centroids in the presence of background stellar contaminants. If this happens during science operations, the apparent movement in the guide stars’ centroids will cause the spacecraft to move in an attempt to maintain pointing direction. This movement creates systematic bias in any photometric measurements taken by the spacecraft. The goal of this project is to quantify what, if any, effect astrophysical variability in guide stars will have on PLATO’s pointing stability. By correlating the impact on performance with variability indicators (like Flicker in the Power Domain), we find that the PLATO FGS is robust against stellar variability
Fichte's global material constitution
No full textThe article shows that Fichte's conception of human rights implies concrete guidelines for the economic organization of states and international relations. First, I elucidate Fichte's view on human rights at the domestic level. Fichte's complex theory of human rights consists in a meta-right to live in a state that secures at least two “original rights”: a right to bodily inviolability and a right to sufficient property. I focus on the latter. Due to Fichte's unorthodox view of property rights as rights to actions rather than objects, this amounts to a right to work. This right, according to Fichte, must be realized in a planned economy. Second, I focus on the global level. Fichte's right to sufficient (unorthodox) property has implications for three dimensions of global justice: cosmopolitan right, the right of nations and commercial relations. Third, I draw some insights from thinking through Fichte's global material constitution for long observed conceptual tensions regarding his political and legal philosophy, namely between freedom and security as well as cosmopolitanism and nationalism, and for current debates in politics and political theory
Untersuchungen über die Verwendbarkeit des Eukupin bihydrocloricum in der Veterinärchirurgie
No full textDigitalisat der Ausgabe von 1922, erschienen 202
Geometry of chiral temporal structures. I. Physical effects
No full textIn nonrelativistic physics, the concepts of geometry and topology are usually applied to characterize spatial structures or structures in momentum space. We introduce the concept of temporal geometry, which encompasses the geometric and topological properties of temporal shapes, i.e., trajectories traced by the tip of a time-dependent vector. We apply it to electric field polarizations controlling ultrafast electron currents or induced polarization in chiral molecules. The central concepts of temporal geometry—Berry curvature and Berry connection—emerge as ubiquitous features of photoexcited, nonequilibrium, chiral electron dynamics. We demonstrate that the Berry curvature and Berry connection (1) rely on the polarization properties of light pulses, (2) can be introduced for multiphoton processes, and (3) control enantiosensitive geometric observables via nonequilibrium electronic dynamics excited by tailored laser fields. Our findings may open a way to ultrafast, topologically nontrivial, and enantiosensitive chemical dynamics
Exo-Geoscience Perspectives Beyond Habitability
No full textThis article reviews the emerging field of exo-geoscience, focusing on the geological and geophysical processes thought to influence the evolution and (eu)habitability of rocky exoplanets. We examine the possible roles of planetary interiors, tectonic regimes, continental coverage, volatile cycling, magnetic fields, and atmospheric composition and evolution in shaping long-term climate stability and biospheric potential. Comparisons with Earth and other planets in the Solar System highlight the diversity of planetary conditions and the rarity of conditions relevant to life. We also discuss contingency and convergence in planetary and biological evolution as they relate to the spread of life in the universe. The observational limits of current and planned missions are assessed, emphasizing the need for models that connect internal dynamics to detectable atmospheric and surface signatures as well as the need for laboratory measurements of planetary properties under a wide range of conditions. The large number of exoplanets promises opportunities for empirical and statistical studies of processes that may have occurred earlier in Earth’s history, as well as for the other pathways rocky planets and biospheres may take. Thus, exo-geoscience provides a framework for interpreting exoplanet diversity and refining strategies for detecting life beyond the Solar System
Spread of invasive algae unchecked by delayed reporting across South America
No full textContextualizing the lag between detection and publication of invasive species records is critical for management and communication. Using a literature review of records spanning 1963–2023 and complementary snapshot monitoring data (2012–2016), we quantify the lag time of reporting new records by researchers and illustrate the importance of timely and more reliable tracking of Ceratium spread, a genus of bloom-forming dinoflagellates with phytosanitary and ecological impacts. Our literature review indicates that records of C. furcoides and C. hirundinella (in South America) show considerable publication delays ( C. furcoides 4.3 ± 2.6 years and C. hirundinella 4.9 ± 3.9 years), limiting early control and informed water management decisions. Our mixed-effects model revealed that publication delays have significantly decreased over time, but remain longer in Brazilian records and in reservoir and river environments. From monitoring data, C. furcoides was found at 72 sites, 53 of which remain unpublished to date, spanning urban, peri-urban, and rural water bodies in São Paulo, South America’s most populous state. The species was absent from 225 sites, often associated with slightly higher water quality and preserved vegetation. More transparent and timely reporting, including absence data, is essential to enable risk modeling and preventive planning in a changing world. Once published, such data can offer valuable insights into species distributions, enabling reconstruction of invasion routes, estimation of spread rates, and identification of potential lag phases
Kernel density estimation under masking of geolocations with applications to DHS data
No full textThe availability of geocoordinates offers valuable insights into spatial patterns of economic, demographic and
health outcomes. However, disclosing the exact geolocation of statistical units to secondary analysts contravenes
the responsible use of data. To protect privacy, anonymisation methods are used. A commonly applied
anonymisation method is the one used by Demographic and Health Surveys (DHS). The DHS anonymisation
scheme works by first aggregating data at small spatial units followed by random (donut) displacement of the
geocoordinates. It is reasonable for secondary analysts to be concerned about the impact of anonymisation on
the analyses. In this paper, the DHS anonymisation scheme is used as a basis for studying how anonymisation
impacts on kernel density estimation. We propose methodology to account for the impact of the anonymisation
process on density estimation. The proposed methodology is based on deriving the distribution of the true
coordinates given the observed (anonymised) coordinates. Density estimation is then implemented by using the
theoretical distribution and an iterative algorithm that accounts for both aggregation and displacement. The
aim is to approximate the original population density using generated pseudo-coordinates under the assumption
that the anonymisation process is known. The proposed method is illustrated by using DHS data from the
Rajshahi Division in Bangladesh to estimate the density of households below the poverty line. The results show
that accounting for measurement error due to anonymisation leads to a more accurate picture of the spatial
distribution of poverty
Disputatio juridica inauguralis de iurisdictione
No full textDigitalisat der Ausgabe von 1644, erschienen 202