Investors are said to “abhor uncertainty,” but if there were no uncertainty they could earn only the risk‐free rate. A fundamental result in the analytical accounting literature shows that investors ...buying into a CARA‐normal CAPM market pay lower asset prices, gain higher ex‐ante expected returns, and obtain higher expected utility, when the market payoff has higher variance. New investors obtain similar “welfare” gains from risk under a log/power utility CAPM. These results do not imply that investors “abhor information.” To realize investors' ex‐ante expectations, the subjective probability distributions representing market expectations must be accurate. Greater payoff risk can add to investors' expected utility, but higher ex‐post(realized) utility comes from better information and more accurate ex‐ante expectations. An important implication for accounting is that greater disclosure can have the simultaneous effects of (i) exposing more fully or perceptibly firms' payoff uncertainty, thereby increasing new investors' expected utility, and (ii) improving market estimates of firms' payoff parameters (means, variances, covariances), thereby giving investors a better chance of realizing their expectations. Paradoxically, better information can be valuable to new investors by exposing more fully and more accurately the risk in firms' business operations and results–new investors maximizing expected utility want both more risk and better information.
Interpenetrated Cage Structures Frank, Marina; Johnstone, Mark D.; Clever, Guido H.
Chemistry : a European journal,
September 26, 2016, Letnik:
22, Številka:
40
Journal Article
Recenzirano
This Review covers design strategies, synthetic challenges, host–guest chemistry, and functional properties of interlocked supramolecular cages. Some dynamic covalent organic structures are ...discussed, as are selected examples of interpenetration in metal–organic frameworks, but the main focus is on discrete coordination architectures, that is, metal‐mediated dimers. Factors leading to interpenetration, such as geometry, flexibility and chemical makeup of the ligands, coordination environment, solvent effects, and selection of suitable counter anions and guest molecules, are discussed. In particular, banana‐shaped bis‐pyridyl ligands together with square‐planar metal cations have proven to be suitable building blocks for the construction of interpenetrated double‐cages obeying the formula M4L8. The peculiar topology of these double‐cages results in a linear arrangement of three mechanically coupled pockets. This allows for the implementation of interesting guest encapsulation effects such as allosteric binding and template‐controlled selectivity. In stimuli‐responsive systems, anionic triggers can toggle the binding of neutral guests or even induce complete structural conversions. The increasing structural and functional complexity in this class of self‐assembled hosts promises the construction of intelligent receptors, novel catalytic systems, and functional materials.
Entangling alliances: Interlocked supramolecular cages represent a rapidly growing compound class whose preparation has evolved from serendipitous findings to the application of rational design strategies. Owing to their topological peculiarities, such self‐assemblies show interesting properties as receptors (tunable selectivity, allosteric regulation and switching) and structural motifs for adaptive materials.
We present Atacama Large Millimeter Array 850 m continuum observations of the Orion Nebula Cluster that provide the highest angular resolution (∼0 1 40 au) and deepest sensitivity (∼0.1 mJy) of the ...region to date. We mosaicked a field containing ∼225 optical or near-IR-identified young stars, ∼60 of which are also optically identified "proplyds." We detect continuum emission at 850 m toward ∼80% of the proplyd sample, and ∼50% of the larger sample of previously identified cluster members. Detected objects have fluxes of ∼0.5-80 mJy. We remove submillimeter flux due to free-free emission in some objects, leaving a sample of sources detected in dust emission. Under standard assumptions of isothermal, optically thin disks, submillimeter fluxes correspond to dust masses of ∼0.5-80 Earth masses. We measure the distribution of disk sizes, and find that disks in this region are particularly compact. Such compact disks are likely to be significantly optically thick. The distributions of submillimeter flux and inferred disk size indicate smaller, lower-flux disks than in lower-density star-forming regions of similar age. Measured disk flux is correlated weakly with stellar mass, contrary to studies in other star-forming regions that found steeper correlations. We find a correlation between disk flux and distance from the massive star θ1 Ori C, suggesting that disk properties in this region are influenced strongly by the rich cluster environment.
The rapid pace of disease gene discovery has resulted in tremendous advances in the field of epilepsy genetics. Clinical testing with comprehensive gene panels, exomes, and genomes are now available ...and have led to higher diagnostic rates and insights into the underlying disease processes. As such, the contribution to the care of patients by medical geneticists, neurogeneticists and genetic counselors are significant; the dysmorphic examination, the necessary pre‐ and post‐test counseling, the selection of the appropriate next‐generation sequencing‐based test(s), and the interpretation of sequencing results require a care provider to have a comprehensive working knowledge of the strengths and limitations of the available testing technologies. As the underlying mechanisms of the encephalopathies and epilepsies are better understood, there may be opportunities for the development of novel therapies based on an individual's own specific genotype. Drug screening with in vitro and in vivo models of epilepsy can potentially facilitate new treatment strategies. The future of epilepsy genetics will also probably include other—omic approaches such as transcriptomes, metabolomes, and the expanded use of whole genome sequencing to further improve our understanding of epilepsy and provide better care for those with the disease.
Conventional arterial imaging focuses on the vessel lumen but lacks specificity because different pathologies produce similar luminal defects. Wall imaging can characterize extracranial arterial ...pathology, but imaging intracranial walls has been limited by resolution and signal constraints. Higher-field scanners may improve visualization of these smaller vessels.
Three-tesla contrast-enhanced MRI was used to study the intracranial arteries from a consecutive series of patients at a tertiary stroke center.
Multiplanar T2-weighted fast spin echo and multiplanar T1 fluid-attenuated inversion recovery precontrast and postcontrast images were acquired in 37 patients with focal neurologic deficits. Clinical diagnoses included atherosclerotic disease (13), CNS inflammatory disease (3), dissections (3), aneurysms (3), moyamoya syndrome (2), cavernous angioma (1), extracranial source of stroke (5), and no definitive clinical diagnosis (7). Twelve of 13 with atherosclerotic disease had focal, eccentric vessel wall enhancement, 10 of whom had enhancement only in the vessel supplying the area of ischemic injury. Two of 3 with inflammatory diseases had diffuse, concentric vessel wall enhancement. Three of 3 with dissection showed bright signal on T1, and 2 had irregular wall enhancement with a flap and dual lumen.
Three-tesla contrast-enhanced MRI can be used to study the wall of intracranial blood vessels. T2 and precontrast and postcontrast T1 fluid-attenuated inversion recovery images at 3 tesla may be able to differentiate enhancement patterns of intracranial atherosclerotic plaques (eccentric), inflammation (concentric), and other wall pathologies. Prospective studies are required to determine the sensitivity and specificity of arterial wall imaging for distinguishing the range of pathologic conditions affecting cerebral vasculature.
Before information ϕ arrives, market observers must be uncertain whether the stock price conditioned on ϕ will be higher or lower than the current price. Otherwise there is an obvious arbitrage ...opportunity. By assuming this minimal condition of efficient markets, it is shown under the mean‐variance CAPM that information that leaves the future value of a firm more certain, in the sense that its perceived covariance with the market is reduced towards zero, can lead to a higher expected return on that asset. A further result is that it is theoretically possible that the required return on the stock will necessarily fall after observing signal ϕ, or (in other circumstances) that it will necessarily rise. In general, information that allows better discrimination between firms leads some firms to have higher costs of capital and other firms to have lower costs of capital. Less obviously, better discrimination between firms can induce a higher average cost of capital across the market.
Highlights • Near infrared light (NIr), directed transcranially, is neuroprotective in rodent models of neurodegeneration. • We assessed the neuroprotective efficacy of remotely-applied NIr in an ...MPTP mouse model of parkinsonism. • As with transcranial NIr, remote NIr protects dopaminergic cells from damage due to mild MPTP doses. • The findings have important implications for the clinical translation of light-based therapies.
We present the SCUBA Legacy Catalogues, two comprehensive sets of continuum maps (and catalogs) using data at 850 and 450 mu m of the various astronomical objects obtained with the Submillimetre ...Common User Bolometer Array (SCUBA). The Fundamental Map Data Set contains data only where superior atmospheric opacity calibration data were available. The Extended Map Data Set contains data regardless of the quality of the opacity calibration. Each data set contains 1.2 degree x 1.2 degree maps at locations where data existed in the JCMT archive, imaged using the matrix inversion method. The Fundamental Data Set is composed of 1423 maps at 850 mu m and 1357 maps at 450 mu m. The Extended Data Set is composed of 1547 maps at 850 mu m. Neither data set includes high sensitivity, single-chop SCUBA maps of "cosmological fields" nor solar system objects. Each data set was used to determine a respective object catalogue, consisting of objects identified within the respective 850 mu m maps using an automated identification algorithm. The Fundamental and Extended Map Object Catalogues contain 5061 and 6118 objects, respectively. Objects are named based on their respective J2000.0 position of peak 850 mu m intensity. The catalogues provide for each object the respective maximum 850 mu m intensity, estimates of total 850 mu m flux and size, and tentative identifications from the SIMBAD Database. Where possible, the catalogues also provide for each object its maximum 450 mu m intensity and total 450 mu m flux and flux ratios.
Context.
Water is a key molecule in the physics and chemistry of star and planet formation, but it is difficult to observe from Earth. The
Herschel
Space Observatory provided unprecedented ...sensitivity as well as spatial and spectral resolution to study water. The Water In Star-forming regions with
Herschel
(WISH) key program was designed to observe water in a wide range of environments and provide a legacy data set to address its physics and chemistry.
Aims.
The aim of WISH is to determine which physical components are traced by the gas-phase water lines observed with
Herschel
and to quantify the excitation conditions and water abundances in each of these components. This then provides insight into how and where the bulk of the water is formed in space and how it is transported from clouds to disks, and ultimately comets and planets.
Methods.
Data and results from WISH are summarized together with those from related open time programs. WISH targeted ~80 sources along the two axes of luminosity and evolutionary stage: from low- to high-mass protostars (luminosities from <1 to > 10
5
L
⊙
) and from pre-stellar cores to protoplanetary disks. Lines of H
2
O and its isotopologs, HDO, OH, CO, and O I, were observed with the HIFI and PACS instruments, complemented by other chemically-related molecules that are probes of ultraviolet, X-ray, or grain chemistry. The analysis consists of coupling the physical structure of the sources with simple chemical networks and using non-LTE radiative transfer calculations to directly compare models and observations.
Results.
Most of the far-infrared water emission observed with
Herschel
in star-forming regions originates from warm outflowing and shocked gas at a high density and temperature (> 10
5
cm
−3
, 300–1000 K,
v
~ 25 km s
−1
), heated by kinetic energy dissipation. This gas is not probed by single-dish low-
J
CO lines, but only by CO lines with
J
up
> 14. The emission is compact, with at least two different types of velocity components seen. Water is a significant, but not dominant, coolant of warm gas in the earliest protostellar stages. The warm gas water abundance is universally low: orders of magnitude below the H
2
O/H
2
abundance of 4 × 10
−4
expected if all volatile oxygen is locked in water. In cold pre-stellar cores and outer protostellar envelopes, the water abundance structure is uniquely probed on scales much smaller than the beam through velocity-resolved line profiles. The inferred gaseous water abundance decreases with depth into the cloud with an enhanced layer at the edge due to photodesorption of water ice. All of these conclusions hold irrespective of protostellar luminosity. For low-mass protostars, a constant gaseous HDO/H
2
O ratio of ~0.025 with position into the cold envelope is found. This value is representative of the outermost photodesorbed ice layers and cold gas-phase chemistry, and much higher than that of bulk ice. In contrast, the gas-phase NH
3
abundance stays constant as a function of position in low-mass pre- and protostellar cores. Water abundances in the inner hot cores are high, but with variations from 5 × 10
−6
to a few × 10
−4
for low- and high-mass sources. Water vapor emission from both young and mature disks is weak.
Conclusions.
The main chemical pathways of water at each of the star-formation stages have been identified and quantified. Low warm water abundances can be explained with shock models that include UV radiation to dissociate water and modify the shock structure. UV fields up to 10
2
−10
3
times the general interstellar radiation field are inferred in the outflow cavity walls on scales of the
Herschel
beam from various hydrides. Both high temperature chemistry and ice sputtering contribute to the gaseous water abundance at low velocities, with only gas-phase (re-)formation producing water at high velocities. Combined analyses of water gas and ice show that up to 50% of the oxygen budget may be missing. In cold clouds, an elegant solution is that this apparently missing oxygen is locked up in larger
μ
m-sized grains that do not contribute to infrared ice absorption. The fact that even warm outflows and hot cores do not show H
2
O at full oxygen abundance points to an unidentified refractory component, which is also found in diffuse clouds. The weak water vapor emission from disks indicates that water ice is locked up in larger pebbles early on in the embedded Class I stage and that these pebbles have settled and drifted inward by the Class II stage. Water is transported from clouds to disks mostly as ice, with no evidence for strong accretion shocks. Even at abundances that are somewhat lower than expected, many oceans of water are likely present in planet-forming regions. Based on the lessons for galactic protostars, the low-
J
H
2
O line emission (
E
up
< 300 K) observed in extragalactic sources is inferred to be predominantly collisionally excited and to originate mostly from compact regions of current star formation activity. Recommendations for future mid- to far-infrared missions are made.
We analytically investigate the modes of gravity-induced star formation possible in idealized finite molecular clouds where global collapse competes against both local Jeans instabilities and ...discontinuous edge instabilities. We examine these timescales for collapse in spheres, disks, and cylinders, with emphasis on the structure, size, and degree of internal perturbations required in order for local collapse to occur before global collapse. We find that internal, local collapse is more effective for the lower dimensional objects. Spheres and disks, if unsupported against global collapse, must either contain strong perturbations or must be unrealistically large in order for small density perturbations to collapse significantly faster than the entire cloud. We find, on the other hand, that filamentary geometry is the most favorable situation for the smallest perturbations to grow before global collapse overwhelms them and that filaments containing only a few Jeans masses and weak density perturbations can readily fragment. These idealized solutions are compared with simulations of star-forming regions in an attempt to delineate the role of global, local, and edge instabilities in determining the fragmentation properties of molecular clouds. The combined results are also discussed in the context of recent observations of Galactic molecular clouds.
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