Supramolecular Assembly-Induced Yellow Emission of 9,10-Distyrylanthracene Bridged Bis(pillar[5]arene)s

Chem. Commun., 2014, Accepted Manuscript
DOI: 10.1039/C4CC08205B, Communication
Nan Song, Dai-Xiong Chen, Meng-Chan Xia, Xi-Long Qiu, ke ma, Bin Xu, Wenjing Tian, Ying-Wei Yang
9,10-Distyrylanthracene has been introduced to bridge two pillarenes to form a dimeric host, which can assemble into linear supramolecular polymer upon cooperatively binding with a neutral guest linker, exhibiting yellow…
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Titania photocatalysis through two-photon band-gap excitation with built-in rhodium redox mediator

Chem. Commun., 2014, Accepted Manuscript
DOI: 10.1039/C4CC07049F, Communication
Joanna Kuncewicz, Bunsho Ohtani
Titania particles modified with extremely small amount (< 0.01mol%) of rhodium species exhibited photocatalytic activity for oxidative decomposition of acetaldehyde in air under visible-light irradiation through two-photon band-gap excitation mechanism,…
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How the pterosaur got its wings

ABSTRACT

Throughout the evolutionary history of life, only three vertebrate lineages took to the air by acquiring a body plan suitable for powered flight: birds, bats, and pterosaurs. Because pterosaurs were the earliest vertebrate lineage capable of powered flight and included the largest volant animal in the history of the earth, understanding how they evolved their flight apparatus, the wing, is an important issue in evolutionary biology. Herein, I speculate on the potential basis of pterosaur wing evolution using recent advances in the developmental biology of flying and non-flying vertebrates. The most significant morphological features of pterosaur wings are: (i) a disproportionately elongated fourth finger, and (ii) a wing membrane called the brachiopatagium, which stretches from the posterior surface of the arm and elongated fourth finger to the anterior surface of the leg. At limb-forming stages of pterosaur embryos, the zone of polarizing activity (ZPA) cells, from which the fourth finger eventually differentiates, could up-regulate, restrict, and prolong expression of 5′-located Homeobox D (Hoxd) genes (e.g. Hoxd11, Hoxd12, and Hoxd13) around the ZPA through pterosaur-specific exploitation of sonic hedgehog (SHH) signalling. 5′Hoxd genes could then influence downstream bone morphogenetic protein (BMP) signalling to facilitate chondrocyte proliferation in long bones. Potential expression of Fgf10 and Tbx3 in the primordium of the brachiopatagium formed posterior to the forelimb bud might also facilitate elongation of the phalanges of the fourth finger. To establish the flight-adapted musculoskeletal morphology shared by all volant vertebrates, pterosaurs probably underwent regulatory changes in the expression of genes controlling forelimb and pectoral girdle musculoskeletal development (e.g. Tbx5), as well as certain changes in the mode of cell–cell interactions between muscular and connective tissues in the early phase of their evolution. Developmental data now accumulating for extant vertebrate taxa could be helpful in understanding the cellular and molecular mechanisms of body-plan evolution in extinct vertebrates as well as extant vertebrates with unique morphology whose embryonic materials are hard to obtain.

Coupling between atmospheric layers in gaseous giant planets due to lightning-generated electromagnetic pulses

Abstract

Atmospheric electricity has been detected in all gaseous giants of our solar system and is therefore likely present also in extrasolar planets. Building upon measurements from Saturn and Jupiter, we investigate how the electromagnetic pulse emitted by a lightning stroke affects upper layers of a gaseous giant. This effect is probably significantly stronger than that on Earth. We find that electrically active storms may create a localized but long-lasting layer of enhanced ionization of up to 103 cm−3 free electrons below the ionosphere, thus extending the ionosphere downward. We also estimate that the electromagnetic pulse transports 107 J to 1010 J toward the ionosphere. There emissions of light of up to 108 J would create a transient luminous event analogous to a terrestrial “elve.”

Survey analysis of chorus intensity at Saturn

Abstract

In order to conduct theoretical studies or modeling of pitch angle scattering of electrons by whistler mode chorus emission at Saturn, a knowledge of chorus occurrence and magnetic intensity levels, PB, as well as the distribution of PB relative to frequency and spatial parameters is essential. In this paper an extensive survey of whistler mode magnetic intensity levels at Saturn is carried out, and Gaussian fits of PB are performed. We fit the spectrum of wave magnetic intensity between the lower hybrid frequency and fceq/2 and for frequencies in the interval fceq/2 < f < 0.9 fceq, where fceq is the cyclotron frequency mapped to the equator. Saturn chorus is observed over most local times, but is dominant on the nightside in the range of 4.5 < L <7.5, with minimum power at the equator and peak power in the range of 5° < λ < 10°. Saturn wave magnetic intensity averaged in frequency bins peaks in the range of 10−5 < PB < 10−4 nT2 for 0.4 < β < 0.5 (β = f/fceq). Gaussian fits of PB with frequency and latitude are obtained for lower band chorus. Plasma injection regions are occasionally encountered with significant chorus power levels. Upper band chorus is seen almost exclusively within plasma injection regions, and the number of events is very limited, but when present, the average levels of PB can be higher than the lower band chorus. The overall magnetic intensity contribution of the upper band, however, is insignificant relative to the lower band.

An altitude and distance correction to the source fluence distribution of TGFs

Abstract

The source fluence distribution of terrestrial gamma ray flashes (TGFs) has been extensively discussed in recent years, but few have considered how the TGF fluence distribution at the source, as estimated from satellite measurements, depends on the distance from satellite foot point and assumed production altitude. As the absorption of the TGF photons increases significantly with lower source altitude and larger distance between the source and the observing satellite, these might be important factors. We have addressed the issue by using the tropopause pressure distribution as an approximation of the TGF production altitude distribution and World Wide Lightning Location Network spheric measurements to determine the distance. The study is made possible by the increased number of Ramaty High Energy Solar Spectroscopic Imager (RHESSI) TGFs found in the second catalog of the RHESSI data. One find is that the TGF/lightning ratio for the tropics probably has an annual variability due to an annual variability in the Dobson-Brewer circulation. The main result is an indication that the altitude distribution and distance should be considered when investigating the source fluence distribution of TGFs, as this leads to a softening of the inferred distribution of source brightness.

The steepness of the magnetic shear angle “saddle”: A parameter for constraining the location of dayside magnetic reconnection?

Abstract

Observations of cutoff velocities in plasma distribution functions within the cusps have been used to remotely map reconnection sites on the dayside magnetopause. From these observations, a model of the location of magnetic reconnection along the dayside magnetopause has been developed during conditions of southward interplanetary magnetic field. The reconnection merging region runs along a crest of maximum magnetic shear across the magnetopause, either along two separate antiparallel lines or along a single continuous line. The single, continuous line also follows along a crest of a “saddle” topology in the magnetic shear angle, crossing local noon at low to middle latitudes. In this study the steepness of the saddle at local noon as a function of the solar wind condition and the dipole tilt angle of the Earth is examined. In addition, the locations of dayside low to middle latitude magnetopause crossings by spacecraft for which plasma velocity signatures suggest that the reconnection X line passed over the spacecraft are compared to the expected location of the model X line and as a function of the steepness of the saddle. The comparisons between model and observations are used to help determine to what extent the steepness of the saddle constrains the location of the X line.

Magnetic field topology for northward IMF reconnection: Ion observations

Abstract

Ion observations from the Cluster spacecraft are used to investigate magnetopause reconnection for northward Interplanetary Magnetic Field (IMF) conditions. When the spacecraft cross the magnetopause and enter the magnetosphere at low latitudes, equatorward of the magnetospheric cusps, multiple ion populations of magnetosheath origin are almost always observed. The bulk flow velocities of these separate populations are consistent with their entry at high northern and southern latitudes. Furthermore, characteristics of the pitch angle distributions provide a means to estimate the entry point of the magnetosheath ions and the relative timing of the reconnections in opposite hemispheres. In the example presented, these entry points are poleward of both magnetospheric cusps and the reconnections are separated by minutes. In a survey of magnetopause crossing events, most ion observations and associated electron observations are consistent with this dual-lobe reconnection process as long as the reconnections are separated in time by several minutes. A small percentage of events are not consistent with this reconnection model and may indicate reconnection at other locations, such as equatorward of the cusp.

Ionospheric flow structures associated with auroral beading at substorm auroral onset

Abstract

Auroral observations have shown that brightening at substorm auroral onset often consists of azimuthally propagating beads forming along a pre-existing arc. However, the ionospheric flow structure related to this wavy auroral structure has been poorly understood. We investigated ionospheric flow patterns associated with auroral onset beads using line-of-sight flow observations from the Super Dual Auroral Radar Network (SuperDARN) and auroral images from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) ground-based all-sky-imager (ASI) array. We selected events when SuperDARN radars operated in a high temporal resolution THEMIS mode (6 seconds) along northward looking beams, a time resolution comparable to that of the imagers, providing a unique tool to detect properties of flows associated with the substorm onset instability. We have found very fast oscillating flows (~1000 m/s) that are correlated with the onset beads propagating across the THEMIS-mode beam meridian. 2-d radar measurements also show a wavy pattern in the azimuthal direction with a wavelength of ~78 km, which is close to the azimuthal separation of individual beads. We also used an imager and SuperDARN in Iceland and identified weak but significant azimuthal flow modulations associated with beads. These strong correlations (in time and space) between auroral beading and the fast ionospheric flows suggest that substorm onset occurs via an instability in the inner plasma sheet and is associated with intense flow shears. The flow shear is clockwise around auroral beads, consistent with converging electric fields associated with upward field-aligned currents in the shear center.

Robust Resilience and Substantial Interest: A Survey of Pharmacological Cognitive Enhancement among University Students in the UK and Ireland

by Ilina Singh, Imre Bard, Jonathan Jackson

Use of ‘smart drugs’ among UK students is described in frequent media reports as a rapidly increasing phenomenon. This article reports findings from the first large-scale survey of pharmacological cognitive enhancement (PCE) among students in the UK and Ireland. Conducted from February to September 2012, a survey of a convenience sample of 877 students measured PCE prevalence, attitudes, sources, purposes and ethics. Descriptive and logistic regression statistical methods were used to analyse the data. Lifetime prevalence of PCE using modafinil, methylphenidate or Adderall was under 10%, while past regular and current PCE users of these substances made up between 0.3%–4% of the survey population. A substantial majority of students was unaware of and/or uninterested in PCE; however about one third of students were interested in PCE. PCE users were more likely to be male, British and older students; predictors of PCE use included awareness of other students using PCEs, ADHD symptomatology, ethical concerns, and alcohol and cannabis use. The survey addresses the need for better evidence about PCE prevalence and practices among university students in the UK. We recommend PCE-related strategies for universities based on the survey findings.