Polariton Nanophotonics using Phase Change Materials

Polaritons formed by the coupling of light and material excitations such as plasmons, phonons, or excitons enable light-matter interactions at the nanoscale beyond what is currently possible with conventional optics. Recently, significant interest has been attracted by polaritons in van der Waals materials, which could lead to applications in sensing, integrated photonic circuits and detectors. However, novel techniques are required to control the propagation of polaritons at the nanoscale and to implement the first practical devices. Here we report the experimental realization of polariton refractive and meta-optics in the mid-infrared by exploiting the properties of low-loss phonon polaritons in isotopically pure hexagonal boron nitride (hBN), which allow it to interact with the surrounding dielectric environment comprising the low-loss phase change material, Ge$_3$Sb$_2$Te$_6$ (GST). We demonstrate waveguides which confine polaritons in a 1D geometry, and refractive optical elements such as lenses and prisms for phonon polaritons in hBN, which we characterize using scanning near field optical microscopy. Furthermore, we demonstrate metalenses, which allow for polariton wavefront engineering and sub-wavelength focusing. Our method, due to its sub-diffraction and planar nature, will enable the realization of programmable miniaturized integrated optoelectronic devices, and will lay the foundation for on-demand biosensors.Comment: 15 pages, 4 figures, typos corrected in v

Conservation and divergence of C-terminal domain structure in the retinoblastoma protein family.

The retinoblastoma protein (Rb) and the homologous pocket proteins p107 and p130 negatively regulate cell proliferation by binding and inhibiting members of the E2F transcription factor family. The structural features that distinguish Rb from other pocket proteins have been unclear but are critical for understanding their functional diversity and determining why Rb has unique tumor suppressor activities. We describe here important differences in how the Rb and p107 C-terminal domains (CTDs) associate with the coiled-coil and marked-box domains (CMs) of E2Fs. We find that although CTD-CM binding is conserved across protein families, Rb and p107 CTDs show clear preferences for different E2Fs. A crystal structure of the p107 CTD bound to E2F5 and its dimer partner DP1 reveals the molecular basis for pocket protein-E2F binding specificity and how cyclin-dependent kinases differentially regulate pocket proteins through CTD phosphorylation. Our structural and biochemical data together with phylogenetic analyses of Rb and E2F proteins support the conclusion that Rb evolved specific structural motifs that confer its unique capacity to bind with high affinity those E2Fs that are the most potent activators of the cell cycle

A Symposium to Mark the Publication, by New York University Press, of Ian O’Donnell’s Prison Life: Pain, Resistance, and Purpose

Recognizing the major scholarly contributions to criminology by the noted Irish criminologist, Ian O’Donnell, The Prison Journal invited seven contemporary corrections and punishment scholars to offer insights into O’Donnell’s new book, Prison Life: Pain, Resistance, and Purpose. Offering contextually rich descriptions of prisoner life, the text features four case study prisons—H Blocks, Northern Ireland; Eastham Unit, Texas; Isir Bet, Ethiopia; and ADX Florence, Colorado, in pivotal time periods and through an individual\u27s custodial career in each institution. The symposium discussants focus on O’Donnell\u27s conceptual framework—the degree of prison integration, system and staff regulation, and legitimacy—and how these reflect the key interactions between punishment and society across time and culture

Stratigraphic Architecture of Bedrock Reference Section, Victoria Crater, Meridiani Planum, Mars

The Mars Exploration Rover Opportunity has investigated bedrock outcrops exposed in several craters at Meridiani Planum, Mars, in an effort to better understand the role of surface processes in its geologic history. Opportunity has recently completed its observations of Victoria crater, which is 750 m in diameter and exposes cliffs up to ∼15 m high. The plains surrounding Victoria crater are ∼10 m higher in elevation than those surrounding the previously explored Endurance crater, indicating that the Victoria crater exposes a stratigraphically higher section than does the Endurance crater; however, Victoria strata overlap in elevation with the rocks exposed at the Erebus crater. Victoria crater has a well-developed geomorphic pattern of promontories and embayments that define the crater wall and that reveal thick bedsets (3–7 m) of large-scale cross-bedding, interpreted as fossil eolian dunes. Opportunity was able to drive into the crater at Duck Bay, located on the western margin of Victoria crater. Data from the Microscopic Imager and Panoramic Camera reveal details about the structures, textures, and depositional and diagenetic events that influenced the Victoria bedrock. A lithostratigraphic subdivision of bedrock units was enabled by the presence of a light-toned band that lines much of the upper rim of the crater. In ascending order, three stratigraphic units are named Lyell, Smith, and Steno; Smith is the light-toned band. In the Reference Section exposed along the ingress path at Duck Bay, Smith is interpreted to represent a zone of diagenetic recrystallization; however, its upper contact also coincides with a primary erosional surface. Elsewhere in the crater the diagenetic band crosscuts the physical stratigraphy. Correlation with strata present at nearby promontory Cape Verde indicates that there is an erosional surface at the base of the cliff face that corresponds to the erosional contact below Steno. The erosional contact at the base of Cape Verde lies at a lower elevation, but within the same plane as the contact below Steno, which indicates that the material above the erosional contact was built on significant depositional paleotopography. The eolian dune forms exposed in Duck Bay and Cape Verde, combined with the geometry of the erosional surface, indicate that these outcrops may be part of a larger-scale draa architecture. This insight is possible only as a result of the larger-scale exposures at Victoria crater, which significantly exceed the more limited exposures at the Erebus, Endurance, and Eagle craters

Identification of multiple binding sites for the THAP domain of the Galileo transposase in the long terminal inverted-repeats

Galileo is a DNA transposon responsible for the generation of several chromosomal inversions in Drosophila. In contrast to other members of the P-element superfamily, it has unusually long terminal inverted-repeats (TIRs) that resemble those of Foldback elements. To investigate the function of the long TIRs we derived consensus and ancestral sequences for the Galileo transposase in three species of Drosophilids. Following gene synthesis, we expressed and purified their constituent THAP domains and tested their binding activity towards the respective Galileo TIRs. DNase I footprinting located the most proximal DNA binding site about 70 bp from the transposon end. Using this sequence we identified further binding sites in the tandem repeats that are found within the long TIRs. This suggests that the synaptic complex between Galileo ends may be a complicated structure containing higher-order multimers of the transposase. We also attempted to reconstitute Galileo transposition in Drosophila embryos but no events were detected. Thus, although the limited numbers of Galileo copies in each genome were sufficient to provide functional consensus sequences for the THAP domains, they do not specify a fully active transposase. Since the THAP recognition sequence is short, and will occur many times in a large genome, it seems likely that the multiple binding sites within the long, internally repetitive, TIRs of Galileo and other Foldback-like elements may provide the transposase with its binding specificity

Comparing orbiter and rover image-based mapping of an ancient sedimentary environment, Aeolis Palus, Gale crater, Mars

This study provides the first systematic comparison of orbital facies maps with detailed ground-based geology observations from the Mars Science Laboratory (MSL) Curiosity rover to examine the validity of geologic interpretations derived from orbital image data. Orbital facies maps were constructed for the Darwin, Cooperstown, and Kimberley waypoints visited by the Curiosity rover using High Resolution Imaging Science Experiment (HiRISE) images. These maps, which represent the most detailed orbital analysis of these areas to date, were compared with rover image-based geologic maps and stratigraphic columns derived from Curiosity's Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI). Results show that bedrock outcrops can generally be distinguished from unconsolidated surficial deposits in high-resolution orbital images and that orbital facies mapping can be used to recognize geologic contacts between well-exposed bedrock units. However, process-based interpretations derived from orbital image mapping are difficult to infer without known regional context or observable paleogeomorphic indicators, and layer-cake models of stratigraphy derived from orbital maps oversimplify depositional relationships as revealed from a rover perspective. This study also shows that fine-scale orbital image-based mapping of current and future Mars landing sites is essential for optimizing the efficiency and science return of rover surface operations

A Lacustrine Paleoenvironment Recorded at Vera RubinRidge, Gale Crater: Overview of the Sedimentology and Stratigraphy Observed by the Mars ScienceLaboratory Curiosity Rover

For ~500 Martian solar days (sols), the Mars Science Laboratory team explored Vera Rubin ridge (VRR), a topographic feature on the northwest slope of Aeolis Mons. Here we review the sedimentary facies and stratigraphy observed during sols 1,800–2,300, covering more than 100 m of stratigraphic thickness. Curiosity's traverse includes two transects across the ridge, which enables investigation of lateral variability over a distance of ~300 m. Three informally named stratigraphic members of the Murray formation are described: Blunts Point, Pettegrove Point, and Jura, with the latter two exposed on VRR. The Blunts Point member, exposed just below the ridge, is characterized by a recessive, fine‐grained facies that exhibits extensive planar lamination and is crosscut by abundant curvi‐planar veins. The Pettegrove Point member is more resistant, fine‐grained, thinly planar laminated, and contains a higher abundance of diagenetic concretions. Conformable above the Pettegrove Point member is the Jura member, which is also fine‐grained and parallel stratified, but is marked by a distinct step in topography, which coincides with localized meter‐scale inclined strata, a thinly and thickly laminated facies, and occasional crystal molds. All members record low‐energy lacustrine deposition, consistent with prior observations of the Murray formation. Uncommon outcrops of low‐angle stratification suggest possible subaqueous currents, and steeply inclined beds may be the result of slumping. Collectively, the rocks exposed at VRR provide additional evidence for a long‐lived lacustrine environment (in excess of 106 years via comparison to terrestrial records of sedimentation), which extends our understanding of the duration of habitable conditions in Gale crater

Is Violent Radicalisation Associated with Poverty, Migration, Poor Self-Reported Health and Common Mental Disorders?

BACKGROUND: Doctors, lawyers and criminal justice agencies need methods to assess vulnerability to violent radicalization. In synergy, public health interventions aim to prevent the emergence of risk behaviours as well as prevent and treat new illness events. This paper describes a new method of assessing vulnerability to violent radicalization, and then investigates the role of previously reported causes, including poor self-reported health, anxiety and depression, adverse life events, poverty, and migration and socio-political factors. The aim is to identify foci for preventive intervention. METHODS: A cross-sectional survey of a representative population sample of men and women aged 18-45, of Muslim heritage and recruited by quota sampling by age, gender, working status, in two English cities. The main outcomes include self-reported health, symptoms of anxiety and depression (common mental disorders), and vulnerability to violent radicalization assessed by sympathies for violent protest and terrorist acts. RESULTS: 2.4% of people showed some sympathy for violent protest and terrorist acts. Sympathy was more likely to be articulated by the under 20s, those in full time education rather than employment, those born in the UK, those speaking English at home, and high earners (>£75,000 a year). People with poor self-reported health were less likely to show sympathies for violent protest and terrorism. Anxiety and depressive symptoms, adverse life events and socio-political attitudes showed no associations. CONCLUSIONS: Sympathies for violent protest and terrorism were uncommon among men and women, aged 18-45, of Muslim heritage living in two English cities. Youth, wealth, and being in education rather than employment were risk factors