Search

In this paper we present an infrared laser pointer, consisting of a vertical-cavity surface-emitting laser (VCSEL) and a diffractive optical element (DOE), encapsulated into a scleral contact lens (SCL). The VCSEL is powered remotely by inductive coupling from a primary antenna embedded into an eyewear frame. The DOE is used either to collimate the laser beam or to project a pattern image at a chosen distance in front of the eye. We detail the different SCL constitutive blocks, how they are manufactured and assembled. We particularly emphasize the various technological challenges related to their encapsulation in the reduced volume of the SCL, while keeping the pupil free. Finally, we describe how the laser pointer operates, what are its performances (e.g. collimation, image formation) and how it can be used efficiently in various application fields such as visual assistance and augmented reality. [ABSTRACT FROM AUTHOR]

Partitioning of active gene loci to the nuclear envelope (NE) is a mechanism by which organisms increase the speed of adaptation and metabolic robustness to fluctuating resources in the environment. In the yeast Saccharomyces cerevisiae, adaptation to nutrient depletion or other stresses, manifests as relocalization of active gene loci from nucleoplasm to the NE, resulting in more efficient transport and translation of mRNA. The mechanism by which this partitioning occurs remains a mystery. Here, we demonstrate that the yeast inositol depletion-responsive gene locus INO1 partitions to the nuclear envelope, driven by local histone acetylation-induced polymer-polymer phase separation from the nucleoplasmic phase. This demixing is consistent with recent evidence for chromatin phase separation by acetylation-mediated dissolution of multivalent histone association and fits a physical model where increased bending stiffness of acetylated chromatin polymer causes its phase separation from de-acetylated chromatin. Increased chromatin spring stiffness could explain nucleation of transcriptional machinery at active gene loci. Partitioning of active genes to the nuclear periphery is commonly observed but not understood. Here, the authors show that this process occurs by phase separation of transcriptionally active chromatin providing for efficient mRNA transport and memory. [ABSTRACT FROM AUTHOR]

The Peer Review file and Supplementary Information file have been corrected. Correction to: I Nature Communications i https://doi.org/10.1038/s41467-023-36391-6, published online 28 February 2023 The original version of this article contained formatting errors in the Peer Review file and the Supplementary Information. [Extracted from the article]

Recent experimental and computational work revealed that transcriptional terminators in Saccharomyces cerevisiae can terminate transcription coming from both directions. This mechanism helps budding yeast cope with the pervasive nature of transcription by limiting aberrant transcription from invading neighboring genes. [ABSTRACT FROM AUTHOR]

Mediator is an essential, broadly used eukaryotic transcriptional coactivator. How and what Mediator communicates from activators to RNA polymerase II (RNAPII) remains an open question. Here we performed genome-wide location profiling of Saccharomyces cerevisiae Mediator subunits. Mediator is not found at core promoters but rather occupies the upstream activating sequence, upstream of the pre-initiation complex. In the absence of Kin28 (CDK7) kinase activity or in cells in which the RNAPII C-terminal domain is mutated to replace Ser5 with alanine, however, Mediator accumulates at core promoters together with RNAPII. We propose that Mediator is released quickly from promoters after phosphorylation of Ser5 by Kin28 (CDK7), which also allows for RNAPII to escape from the promoter. [ABSTRACT FROM AUTHOR]

Phosphorylation of histone H2AX is an early response to DNA damage in eukaryotes. In Saccharomyces cerevisiae, DNA damage or replication-fork stalling results in phosphorylation of histone H2A yielding γ-H2A (yeast γ-H2AX) in a Mec1 (ATR)- and Tel1 (ATM)-dependent manner. Here, we describe the genome-wide location analysis of γ-H2A as a strategy to identify loci prone to engaging the Mec1 and Tel1 pathways. Notably, γ-H2A enrichment overlaps with loci prone to replication-fork stalling and is caused by the action of Mec1 and Tel1, indicating that these loci are prone to breakage. Moreover, about half the sites enriched for γ-H2A map to repressed protein-coding genes, and histone deacetylases are necessary for formation of γ-H2A at these loci. Finally, our work indicates that high-resolution mapping of γ-H2AX is a fruitful route to map fragile sites in eukaryotic genomes. [ABSTRACT FROM AUTHOR]

Copyright of International Review of Education / Internationale Zeitschrift für Erziehungswissenschaft is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The terrestrial sediment record indicates that the Earth’s climate varied drastically in the Precambrian era (before 550 million years ago), ranging from surface temperatures similar to or higher than today’s to global glaciation events. The most continuous record of sea surface temperatures of that time has been derived from variations in oxygen isotope ratios of cherts (siliceous sediments), but the long-term cooling of the oceans inferred from those data has been questioned because the oxygen isotope signature could have been reset through the exchange with hydrothermal fluids after deposition of the sediments. Here we show that the silicon isotopic composition of cherts more than 550 million years old shows systematic variations with age that support the earlier conclusion of long-term ocean cooling and exclude post-depositional exchange as the main source of the isotopic variations. In agreement with other lines of evidence, a model of the silicon cycle in the Precambrian era shows that the observed silicon isotope variations imply seawater temperature changes from about 70 °C 3,500 million years ago to about 20 °C 800 million years ago. [ABSTRACT FROM AUTHOR]

The signature of carbonate minerals has long been suspected in the mid-infrared spectra of various astrophysical environments such as protostars. Abiogenic carbonates are considered as indicators of aqueous mineral alteration in the presence of CO2-rich liquid water. The recent claimed detection of calcite associated with amorphous silicates in two planetary nebulae and protostars devoid of planetary bodies questions the relevance of this indicator; but in the absence of an alternative mode of formation under circumstellar conditions, this detection remains controversial. The main dust component observed in circumstellar envelopes is amorphous silicates, which are thought to have formed by non-equilibrium condensation. Here we report experiments demonstrating that carbonates can be formed with amorphous silicates during the non-equilibrium condensation of a silicate gas in a H2O-CO2-rich vapour. We propose that the observed astrophysical carbonates have condensed in H2O(g)-CO2(g)-rich, high-temperature and high-density regions such as evolved stellar winds, or those induced by grain sputtering upon shocks in protostellar outflows. [ABSTRACT FROM AUTHOR]

ObjectiveTo explain a cause of high signal intensity on T1-weighted MR images in calcified intervertebral disks associated with spinal fusion.Design and patientsMagnetic resonance and radiological examinations of 13 patients were reviewed, presenting one or several intervertebral disks showing a high signal intensity on T1-weighted MR images, associated both with the presence of calcifications in the disks and with peripheral fusion of the corresponding spinal segments. Fusion was due to ligament ossifications ( n=8), ankylosing spondylitis ( n=4), or posterior arthrodesis ( n=1). Imaging files included X-rays and T1-weighted MR images in all cases, T2-weighted MR images in 12 cases, MR images with fat signal suppression in 7 cases, and a CT scan in 1 case. Histological study of a calcified disk from an anatomical specimen of an ankylosed lumbar spine resulting from ankylosing spondylitis was examined.ResultsThe signal intensity of the disks was similar to that of the bone marrow or of perivertebral fat both on T1-weighted MR images and on all sequences, including those with fat signal suppression. In one of these disks, a strongly negative absorption coefficient was focally measured by CT scan, suggesting a fatty content. The histological examination of the ankylosed calcified disk revealed the presence of well-differentiated bone tissue and fatty marrow within the disk.ConclusionThe high signal intensity of some calcified intervertebral disks on T1-weighted MR images can result from the presence of fatty marrow, probably related to a disk ossification process in ankylosed spines. [ABSTRACT FROM AUTHOR]

We describe an algorithm for discovering regulatory networks of gene modules, GRAM (Genetic Regulatory Modules), that combines information from genome-wide location and expression data sets. A gene module is defined as a set of coexpressed genes to which the same set of transcription factors binds. Unlike previous approaches that relied primarily on functional information from expression data, the GRAM algorithm explicitly links genes to the factors that regulate them by incorporating DNA binding data, which provide direct physical evidence of regulatory interactions. We use the GRAM algorithm to describe a genome-wide regulatory network in Saccharomyces cerevisiae using binding information for 106 transcription factors profiled in rich medium conditions data* from over 500 expression experiments. We also present a genome-wide location analysis data set for regulators in yeast cells treated with rapamycin, and use the GRAM algorithm to provide biological insights into this regulatory network.*Note: In the version of this article initially published online, the word "and" was omitted from the fourth sentence of the abstract, altering the meaning. The sentence should read: "We use the GRAM algorithm to describe a genome-wide regulatory network in Saccharomyces cerevisiae using binding information for 106 transcription factors profiled in rich medium conditions and data from over 500 expression experiments." This mistake has been corrected for the HTML and print versions of the article. [ABSTRACT FROM AUTHOR]

The statistical distribution of all available published D/H ratios of carbonaceous chondrites is presented. The possible interpretations of this distribution are reviewed at the global scale of the solar system planetary objects and at the scale defined by the carbonaceous meteorites. New issues concerning tile chemical Origin of tile deuterium enrichment in solar system water and organic molecules are put into light by this exercise. This distribution is a robust constraint on the origin of water on Earth. [ABSTRACT FROM AUTHOR]

The measured D/H ratios in interstellar environments and in the solar system are reviewed. The two extreme D/H ratios in solar system water - (720±120)×10−6 in clay minerals and (88±11)×10−6 in chondrules, both from LL3 chondritic meteorites - are interpreted as the result of a progressive isotopic exchange in the solar nebula between deuterium-rich interstellar water and protosolar H2. According to a turbulent model describing the evolution of the nebula (Drouart et al., 1999), water in the solar system cannot be a product of thermal (neutral) reactions occurring in the solar nebula. Taking 720×10−6 as a face value for the isotopic composition of the interstellar water that predates the formation of the solar nebula, numerical simulations show that the water D/H ratio decreases via an isotopic exchange with H2. During the course of this process, a D/H gradient was established in the nebula. This gradient was smoothed with time and the isotopic homogenization of the solar nebula was completed in 106 years, reaching a D/H ratio of 88×10−6. In this model, cometary water should have also suffered a partial isotopic re-equilibration with H2. The isotopic heterogeneity observed in chondrites result from the turbulent mixing of grains, condensed at different epochs and locations in the solar nebula. Recent isotopic determinations of water ice in cold interstellar clouds are in agreement with these chondritic data and their interpretation (Texeira et al., 1999). [ABSTRACT FROM AUTHOR]

The aim of this note is to present a synthesis of recent applications or extensions of the Stein-Rosenberg theorem on nonnegative matrices: convergence of non linear iterative process; truncated, or chaotic, or boolean Stein-Rosenberg theorems. The conclusion is the following: As it works through various mathematical contexts, the Stein-Rosenberg theorem expersses a rather deap idea of an essentially algorithmic nature. [ABSTRACT FROM AUTHOR]

This corrects the article DOI: 10.1038/ncomms11977 [ABSTRACT FROM AUTHOR]

Robert & Chaussidon The possibility of a change in δ18O values of the oceans has been discussed for the past 30 years and the comment by Shields and Kasting does not really bring any new insight into this issue. The carbonate δ18O curve is indistinguishable from that of cherts and shows a huge scatter caused by local geological processes. This scatter in δ18O (up to 20‰ at a given age) far exceeds the sensitivity of the isotope thermometer (about 2‰ per 10 °C). It therefore prevents any precise additional test of the model and no consensus was ever reached in the literature on this debate from oxygen-isotope data alone. Our approach, by contrast, was to try to find another isotopic proxy (δ30Si) that could bring new and independent constraints to test the hypothesis of hot oceans in the early Precambrian. Our interpretation of the δ30Si values in terms of temperature is fully coherent not only with the δ18O of cherts but also with that of marine carbonates, and certainly does not overlook these data. In addition, we indicated that our sample set has not the time resolution that would be necessary to look for an effect on silicon isotopes of Precambrian global glaciations. No chert samples from such periods were analysed. [ABSTRACT FROM AUTHOR]

Primitive carbonaceous chondrites contain a large array of organic compounds dominated by insoluble organic matter (IOM). A striking feature of this IOM is the systematic enrichment in deuterium compared with the solar hydrogen reservoir. This enrichment has been taken as a sign of low-temperature ion-molecule or gas-grain reactions. However, the extent to which Solar System processes, especially ionizing radiation, can affect D/H ratios is largely unknown. Here, we report the effects of electron irradiation on the hydrogen isotopic composition of organic precursors containing different functional groups. From an initial terrestrial composition, overall D-enrichments and differential intramolecular fractionations comparable with those measured in the Orgueil meteorite were induced. Therefore, ionizing radiation can quantitatively explain the deuteration of organics in some carbonaceous chondrites. For these meteorites, the precursors of the IOM may have had the same isotopic composition as the main water reservoirs of the inner Solar System. [ABSTRACT FROM AUTHOR]