The Eccentric Nature of Eccentric Tidal Disruption Events

Upon entering the tidal sphere of a supermassive black hole, a star is ripped apart by tides and transformed into a stream of debris. The ultimate fate of that debris, and the properties of the bright flare that is produced and observed, depends on a number of parameters, including the energy of the center of mass of the original star. Here we present the results of a set of smoothed particle hydrodynamics simulations in which a 1M ⊙, γ = 5/3 polytrope is disrupted by a 106 M ⊙ supermassive black hole. Each simulation has a pericenter distance of r p = r t (i.e., β ≡ r t/r p = 1 with r t the tidal radius), and we vary the eccentricity e of the stellar orbit from e = 0.8 up to e = 1.20 and study the nature of the fallback of debris onto the black hole and the long-term fate of the unbound material. For simulations with eccentricities e ≲ 0.98, the fallback curve has a distinct, three-peak structure that is induced by self-gravity. For simulations with eccentricities e ≳ 1.06, the core of the disrupted star reforms following its initial disruption. Our results have implications for, e.g., tidal disruption events produced by supermassive black hole binaries.

Korozja władzy. Dystopijna zapowiedź przyszłości w komiksie „Sędzia Dredd. Ameryka” (1990) Johna Wagnera i Colina MacNeila

The article draws out the parallels between the story presented in Judge Dredd: America (1990) and the contemporary events taking place on the streets of the United States. The comic book itself takes place in the dystopian setting of Mega City One which deprives its citizens of freedom, self-determination, and takes away their hope for a better tomorrow. The immigrants, presented in the comic book, who are dreaming of realizing their American Dream, instead, fi nd themselves living an American nightmare. The similarities between the comic book and the previously published V for Vendetta are noted, as both novels have had a strong influence on the deheroisation of the protagonist of a superhero comic book, particularly in relation to the European comic book (1985–1990). Here, the morally ambiguous figure of Judge Dredd is relegated to the background, and the plot itself, as well as further research discussion, focuses on the characters of America Jara and her friend, Bennett Beeny. Their friendship significantly affects the story and the ultimate fate of America. Both of them are harmed by the system based on the superiority of the Judges, whose attitude is often reminiscent of the current actions of the American police, which is particularly interesting in the context of contemporary movements like Black Lives Matter. The authors of Judge Dredd: America provoke their readers to ask questions about the meaning of freedom, the place of an individual in a society whose actions are normalized and restricted by law, and even to rebellion against an oppressive authority. The article concludes by considering the meaning of democracy in modern socjety.

The Earth: A Lost Planet from another Universe

There are several competing theories about the ultimate fate of the universe and possibility of anything preceding the Big Bang, while other physicists and philosophers refuse to speculate, doubting that information about prior states will ever be accessible. Some scientist have suggested various multiverse hypotheses, in which our universe might be one among many universes that likewise exist. There has been so many possibilities that are yet to be explored and investigated about our earth. The Earth is strangely different from other member of the universe. This study and observation intended to interpret the likelihood of our Earth been a stranger in a foreign universe.

Turkey’s dealing with the Syrian Kurds (Part II)

This Commentary survey’s Turkey's interaction with Syria's surprisingly influential Kurds and explores the Turkish-US confrontation over the US support of the Syrian Kurds against ISIS. It concludes that the Biden administration will likely continue to implement the limited, but effective role his predecessors Trump and Obama had carried out, but that the ultimate fate of Syria and its embattled Kurds remains unclear.

Microplastics in Terrestrial and Freshwater Environments

In recent years, the focus of microplastic research has begun to observe a shift from the marine towards terrestrial and freshwater environments. This is in response to a greater awareness of the predominance of land-based sources in marine microplastic contamination. In this regard, terrestrial and freshwater environments are often perceived as conduits for microplastic particles to the oceans, but this overlooks substantial and important complexities associated with these systems, as well as the need to protect these ecosystems in their own right. This chapter focuses on several critical sources and pathways deemed to be highly important for the release of microplastics to the environment. These include road-associated microplastic particles (RAMP) and emissions related to agriculture that are, thus far, under-researched. Transfers and accumulations of particles within terrestrial and freshwater systems are also reviewed, including the state of knowledge on the occurrence of microplastics in different environmental compartments (air, water, sediments, biota). Methodological constraints are addressed, with particular focus on the need for greater harmonisation along all stages of sampling, analysis, and data handling. Finally, the chapter discusses the ultimate fate of particles released to terrestrial and freshwater environments and highlights critical research gaps that should be addressed to evolve our understanding of microplastic contamination in complex and dynamic environmental systems.

Vortex cluster arising from an axisymmetric inertial wave attractor

We present an experimental and numerical study of the nonlinear dynamics of an inertial wave attractor in an axisymmetric geometrical setting. The rotating ring-shaped fluid domain is delimited by two vertical coaxial cylinders, a conical bottom and a horizontal wave generator at the top: the vertical cross-section is a trapezium, while the horizontal cross-section is a ring. Forcing is introduced via axisymmetric low-amplitude volume-conserving oscillatory motion of the upper lid. The experiment shows an important result: at sufficiently strong forcing and long time scale, a saturated fully nonlinear regime develops as a consequence of an energy transfer draining energy towards a slow two-dimensional manifold represented by a regular polygonal system of axially oriented cyclonic vortices undergoing a slow prograde motion around the inner cylinder. We explore the long-term nonlinear behaviour of the system by performing a series of numerical simulations for a set of fixed forcing amplitudes. This study shows a rich variety of dynamical regimes, including a linear behaviour, a triadic resonance instability, a progressive frequency enrichment reminiscent of weak inertial wave turbulence and the generation of a slow manifold in the form of a polygonal vortex cluster confirming the experimental observation. This vortex cluster is discussed in detail, and we show that it stems from the summation and merging of wave-like components of the vorticity field. The nature of these wave components, the possibility of their detection under general conditions and the ultimate fate of the vortex clusters at even longer time scale remain to be explored.

Marine Gel Interactions with Hydrophilic and Hydrophobic Pollutants

Microgels play critical roles in a variety of processes in the ocean, including element cycling, particle interactions, microbial ecology, food web dynamics, air–sea exchange, and pollutant distribution and transport. Exopolymeric substances (EPS) from various marine microbes are one of the major sources for marine microgels. Due to their amphiphilic nature, many types of pollutants, especially hydrophobic ones, have been found to preferentially associate with marine microgels. The interactions between pollutants and microgels can significantly impact the transport, sedimentation, distribution, and the ultimate fate of these pollutants in the ocean. This review on marine gels focuses on the discussion of the interactions between gel-forming EPS and pollutants, such as oil and other hydrophobic pollutants, nanoparticles, and metal ions.

Ghettos in the Holocaust

The surprising aspect of Nazi ghettoization is that there was no centralized German policy and no clear agreement on what comprised a ghetto. Most decisions about ghettoization were taken at the regional or local level. The most workable definition of a ghetto is that it was a place where Jews were concentrated, consisting generally of entire family units, as opposed to forced labor camps for Jews that contained Jews selected for labor. In fact, not all ghettos were fenced, as some towns had open ghettos marked only by signs or just an occasional police patrol. Others had quite porous barbed-wire fences, whereas the larger ghettos, such as those in Łódź and Warsaw, were defined by their high walls that were very difficult to cross. A great wealth of information on ghettos can be found in the respective memorial (Yizkor) books, only a small sample of which can be mentioned here. Other key information can be found in memoirs, chronicles, and diaries. By contrast, relatively few monographs have been devoted specifically to ghettos, and even fewer to the general topic of ghettos. However, much useful information, including additional references, can be found in the more detailed encyclopedias devoted to the topic. Several regional overviews of the Holocaust also provide an excellent analysis of the role played by ghettos in the Nazi plans for the destruction of the Jews. In terms of geographical organization, three main subdivisions have been used below. The General Government and territories incorporated into the Reich form one large region that covers most of modern-day Poland as well as the western fringes of what is now Ukraine and Belarus. Here the majority of the Jews were deported by rail from ghettos to extermination centers. In Nazi-occupied territory of the Soviet Union (as of 1940, including the Baltic States), Jews were mostly marched out of the ghettos to be shot in nearby forests and ravines. Finally, the ghettos under Hungarian and Romanian administration are treated as a third regional group, as here the chronology of ghettoization and the ultimate fate of the Jews varied somewhat from the other two areas.

Identification of ubiquitin variants that inhibit the E2 ubiquitin conjugating enzyme, Ube2k

Transfer of ubiquitin to substrate proteins regulates most processes in eukaryotic cells. E2 enzymes are a central component of the ubiquitin machinery, and generally determine the type of ubiquitin signal generated and thus the ultimate fate of substrate proteins. The E2, Ube2k, specifically builds degradative ubiquitin chains on diverse substrates. Here we have identified protein-based reagents, called ubiquitin variants (UbVs), that bind tightly and specifically to Ube2k. Crystal structures reveal that the UbVs bind to the E2 enzyme at a hydrophobic cleft that is distinct from the active site and previously identified ubiquitin binding sites. We demonstrate that the UbVs are potent inhibitors of Ube2k and block both ubiquitin charging of the E2 enzyme, and E3-catalysed ubiquitin transfer. The binding site of the UbVs suggests they directly clash with the ubiquitin activating enzyme, while potentially disrupting interactions with E3 ligases via allosteric effects. Our data reveal the first protein-based inhibitors of Ube2k and unveil a hydrophobic groove that could be an effective target for inhibiting Ube2k and other E2 enzymes.