New Silhouette Disks with Reflection Nebulae and Outflows in the Orion Nebula and M43

We report the detection of several new circumstellar disks seen in silhouette in the outskirts of the Orion nebula and M43, detected as part of our Halpha survey of Orion with the HST/ACS. Several of the disks show bipolar reflection nebulae, microjets, or temporal variability. Two disks in our sample are large and particularly noteworthy: A nearly edge-on disk, d216-0939, is located several arcminutes northwest of M43 and resembles the famous HH30 disk/jet system in Taurus. It drives the 0.15 pc long bipolar outflow HH667, and exhibits a remarkable asymmetric reflection nebula. With a diameter of 1200 AU, it is as large as the giant edge-on silhouette disk d114-426 in the core of the Orion Nebula. The large disk d253-1536 is located in a binary system embedded within an externally-ionized giant proplyd in M43. The disk exhibits distortions which we attribute to tidal interactions with a companion. The bipolar jet HH668 emerges orthogonal to the disk, and a bow shock lies 54'' south of this binary system along the outflow axis. Proper motions over 1.4 yr confirm that these emission knots are moving away from d253-1536, with speeds as high as 330 km/s in the HH668 microjet, and slower motion farther from the star.Comment: 19 pages, Fig 2 in color, accepted by A

Elections in digital times: a guide for electoral practitioners

Strengthening democracy and electoral processes in the era of social media and Artificial Intelligence Democracy requires free, periodic, transparent, and inclusive elections. Freedom of expression, freedom of the press, and the right to political participation are also critical to societies ruled by the respect of human rights. In today’s rapidly evolving digital environment, opportunities for communication between citizens, politicians and political parties are unprecedented –– with information related to elections flowing faster and easier than ever, coupled with expanded opportunities for its verification and correction by a growing number of stakeholders. However, with billions of human beings connected, and disinformation and misinformation circulating unhinged around the networks, democratic processes and access to reliable information are at risk. With an estimated 56.8% of the world’s population active on social media and an estimate of 4 billion eligible voters, the ubiquity of social networks and the impact of Artificial Intelligence can intentionally or unintentionally undermine electoral processes, thereby delegitimizing democracies worldwide. In this context, all actors involved in electoral processes have an essential role to play. Electoral management bodies, electoral practitioners, the media, voters, political parties, and civil society organizations must understand the scope and impact of social media and Artificial Intelligence in the electoral cycle. They also need to have access to the tools to identify who instigates and spreads disinformation and misinformation, and the tools and strategies to combat it. This handbook aims to be a toolbox that helps better understand the current scenario and share experiences of good practices in different electoral settings and equip electoral practitioners and other key actors from all over the world to ensure the credibility of the democratic system in times of profound transformations

Absence of system xc⁻ on immune cells invading the central nervous system alleviates experimental autoimmune encephalitis

Background: Multiple sclerosis (MS) is an autoimmune demyelinating disease that affects the central nervous system (CNS), leading to neurodegeneration and chronic disability. Accumulating evidence points to a key role for neuroinflammation, oxidative stress, and excitotoxicity in this degenerative process. System x(c)- or the cystine/glutamate antiporter could tie these pathological mechanisms together: its activity is enhanced by reactive oxygen species and inflammatory stimuli, and its enhancement might lead to the release of toxic amounts of glutamate, thereby triggering excitotoxicity and neurodegeneration. Methods: Semi-quantitative Western blotting served to study protein expression of xCT, the specific subunit of system x(c)-, as well as of regulators of xCT transcription, in the normal appearing white matter (NAWM) of MS patients and in the CNS and spleen of mice exposed to experimental autoimmune encephalomyelitis (EAE), an accepted mouse model of MS. We next compared the clinical course of the EAE disease, the extent of demyelination, the infiltration of immune cells and microglial activation in xCT-knockout (xCT(-/-)) mice and irradiated mice reconstituted in xCT(-/-) bone marrow (BM), to their proper wild type (xCT(+/+)) controls. Results: xCT protein expression levels were upregulated in the NAWM of MS patients and in the brain, spinal cord, and spleen of EAE mice. The pathways involved in this upregulation in NAWM of MS patients remain unresolved. Compared to xCT(+/+) mice, xCT(-/-) mice were equally susceptible to EAE, whereas mice transplanted with xCT(-/-) BM, and as such only exhibiting loss of xCT in their immune cells, were less susceptible to EAE. In none of the above-described conditions, demyelination, microglial activation, or infiltration of immune cells were affected. Conclusions: Our findings demonstrate enhancement of xCT protein expression in MS pathology and suggest that system x(c)- on immune cells invading the CNS participates to EAE. Since a total loss of system x(c)- had no net beneficial effects, these results have important implications for targeting system x(c)- for treatment of MS

Anti-phase variation of long eccentricity and precipitation in inland Asia during the middle Miocene Climatic Optimum (MMCO)

The mechanisms and pace of orbital forcing on precipitation in inland Asia during the Cenozoic remain poorly understood. Many previous studies have shown a consistent signal of long eccentricity (405 kyr) on precipitation records of central China that are younger than ~11 Ma. These studies suggest that variations of rainfall amount were controlled by Northern Hemisphere summer insolation, with peak of precipitation associated with eccentricity maxima. We report here multiple records dating back to the middle Miocene Climatic Optimum (MMCO, ~14-17 Ma ago) that show the exact opposite, including a detailed record from a new section in the Qaidam Basin, dated by a combination of magnetostratigraphy, U-Pb geochronology and apatite low-temperature thermochronology. Our records display dominant 405 kyr wet-dry cycles, but the wetter intervals correspond to eccentricity minima and ice-volume maxima during the MMCO. These results question the origin (monsoonal or westerly-derived?) of the precipitation reaching central China during Greenhouse episodes and the mechanisms enhancing monsoonal penetration inland Asia; they indicate that higher atmospheric pCO2 significantly impacts East Asian monsoonal circulation and its response to orbital forcing

Anti-phase variation of long eccentricity and precipitation in inland Asia during the middle Miocene Climatic Optimum (MMCO)

The mechanisms and pace of orbital forcing on precipitation in inland Asia during the Cenozoic remain poorly understood. Many previous studies have shown a consistent signal of long eccentricity (405 kyr) on precipitation records of central China that are younger than ~11 Ma. These studies suggest that variations of rainfall amount were controlled by Northern Hemisphere summer insolation, with peak of precipitation associated with eccentricity maxima. We report here multiple records dating back to the middle Miocene Climatic Optimum (MMCO, ~14-17 Ma ago) that show the exact opposite, including a detailed record from a new section in the Qaidam Basin, dated by a combination of magnetostratigraphy, U-Pb geochronology and apatite low-temperature thermochronology. Our records display dominant 405 kyr wet-dry cycles, but the wetter intervals correspond to eccentricity minima and ice-volume maxima during the MMCO. These results question the origin (monsoonal or westerly-derived?) of the precipitation reaching central China during Greenhouse episodes and the mechanisms enhancing monsoonal penetration inland Asia; they indicate that higher atmospheric pCO2 significantly impacts East Asian monsoonal circulation and its response to orbital forcing

Anti-phase variation of long eccentricity and precipitation in inland Asia during the middle Miocene Climatic Optimum (MMCO)

The mechanisms and pace of orbital forcing on precipitation in inland Asia during the Cenozoic remain poorly understood. Many previous studies have shown a consistent signal of long eccentricity (405 kyr) on precipitation records of central China that are younger than ~11 Ma. These studies suggest that variations of rainfall amount were controlled by Northern Hemisphere summer insolation, with peak of precipitation associated with eccentricity maxima. We report here multiple records dating back to the middle Miocene Climatic Optimum (MMCO, ~14-17 Ma ago) that show the exact opposite, including a detailed record from a new section in the Qaidam Basin, dated by a combination of magnetostratigraphy, U-Pb geochronology and apatite low-temperature thermochronology. Our records display dominant 405 kyr wet-dry cycles, but the wetter intervals correspond to eccentricity minima and ice-volume maxima during the MMCO. These results question the origin (monsoonal or westerly-derived?) of the precipitation reaching central China during Greenhouse episodes and the mechanisms enhancing monsoonal penetration inland Asia; they indicate that higher atmospheric pCO2 significantly impacts East Asian monsoonal circulation and its response to orbital forcing