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Some UK insurers have been using real-world economic scenarios for more than 30 years. Popular approaches have included random walks, time series models, arbitrage-free models with added risk premiums or 1-year Value at Risk distribution fits. Based on interviews with experienced practitioners as well as historical documents and meeting minutes, this paper traces historical model evolution in the United Kingdom and abroad. We examine the possible catalysts for changes in modelling practice with a particular emphasis on regulatory and socio-cultural influences. We apply past lessons to provide some guidance to the direction of capital market modelling in future, which has been key for business and strategy decisions.
Communication deviance (CD) reflects features of the content or manner of a person's speech that may confuse the listener and inhibit the establishment of a shared focus of attention. The construct was developed in the context of the study of familial risks for psychosis based on hypotheses regarding its effects during childhood. It is not known whether parental CD is associated with nonverbal parental behaviors that may be important in early development. This study explored the association between CD in a cohort of mothers (n = 287) at 32 weeks gestation and maternal sensitivity with infants at 29 weeks in a standard play procedure. Maternal CD predicted lower overall maternal sensitivity (B = –.385; p < .001), and the effect was somewhat greater for sensitivity to infant distress (B = –.514; p < .001) than for sensitivity to nondistress (B = –.311; p < .01). After controlling for maternal age, IQ and depression, and for socioeconomic deprivation, the associations with overall sensitivity and sensitivity to distress remained significant. The findings provide new pointers to intergenerational transmission of vulnerability involving processes implicated in both verbal and nonverbal parental behaviors.
Fomesafen is a protoporphyrinogen oxidase–inhibitor herbicide with an alternative mode of action that provides PRE weed control in strawberry [Fragaria×ananassa (Weston) Duchesne ex Rozier (pro sp.) [chiloensis×virginiana]] produced in a plasticulture setting in Florida. Plasticulture mulch could decrease fomesafen dissipation and increase crop injury in rotational crops. Field experiments were conducted in Balm, FL, to investigate fomesafen persistence and movement in soil in Florida strawberry systems for the 2014/2015 and 2015/2016 production cycles. Treatments included fomesafen preplant at 0, 0.42, and 0.84 kg ai ha−1. Soil samples were taken under the plastic from plots treated with fomesafen at 0.42 kg ha−1 throughout the production cycle. Fomesafen did not injure strawberry or decrease yield. Fomesafen concentration data for the 0.0- to 0.1-m soil depth were described using a three-parameter logistic function. The fomesafen 50% dissipation times were 37 and 47 d for the 2014/2015 and 2015/2016 production cycles, respectively. At the end of the study, fomesafen was last detected in the 0.0- to 0.1-m depth soil at 167 and 194 d after treatment in the 2014/2015 and 2015/2016 production cycles, respectively. Fomesafen concentration was less than 25 ppb on any sampling date for 0.1- to 0.2-m and 0.2- to 0.3-m depths. Fomesafen concentration decreased significantly after strawberry was transplanted and likely leached during overhead and drip irrigation used during the crop establishment.
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
Velocity and strain-rate patterns in a small temperate valley glacier display flow effects of channel geometry, ice thickness, surface slope, and ablation. Surface velocities of 20–55 m/year show year-to-year fluctuations of 1.5–3 m/year. Transverse profiles of velocity have the form of a higher-order parabola modified by the effects of flow around a broad bend in the channel, which makes the velocity profile asymmetric, with maximum velocity displaced toward the outside of the bend. Marginal sliding rates are 5–22 m/year against bedrock and nil against debris. Velocity vectors diverge from the glacier center-line near the terminus, in response to surface ice loss, but converge toward it near the firn line because of channel narrowing. Plunge of the vectors gives an emergence flow component that falls short of balancing ice loss by about 1 m/year. Center-line velocities vary systematically with ice thickness and surface slope. In the upper half of the reach studied, effects of changing thickness and slope tend to compensate, and velocities are nearly constant; in the lower half, the effects are cumulative and velocities decrease progressively down-stream. Where the slope increases down-stream from 7° to 9°, reflecting a bedrock step, there is localized longitudinal extension of 0.03 year–1 followed by compression of 0.08 year–1 where the slope decreases. Marginal shear (up to 0.5 year–1) is strongly asymmetric due to flow around the bend: the stress center-line, where one of the principal axes becomes longitudinal, is displaced 150 m toward the inside of the bend. This effect is prominently visible in the crevasse pattern. Ice fluxes calculated independently by “laminar” flow theory and by continuity disagree in a way which shows that internal deformation of the ice is controlled not by local surface slope but by an effective slope that is nearly constant over the reach studied.
Ice unquestionably exists on Mars. Annual polar-region frost blankets are principally solid CO2, and perennial residual ice caps near each pole are probably water ice, except for a part of the north polar cap which may consist of a 1 km thick mass of solid CO2. Minor amounts of carbon-dioxide clathrate (CO2 · ≈ 6H2O) presumably accompany the solid CO2. The annual frost blankets may have a concentric banding with an outermost very thin layer of water frost, an intermediate narrow zone of clathrate, and a major central core of solid CO2.
Layered deposits and underlying homogeneous materials mantle large areas within both polar regions. These blankets are probably composed of dust, volcanic ash, or both, and possibly contain frozen volatiles. They may comprise the largest reservoir of water substance on the Martian surface.
Ground ice formed by the freezing of ascending de-gassed water substance may underlie the surface of Mars. Localized collapse of small areas may be due to ground-ice deterioration, and recession of steep slopes may have been caused by ground-ice sapping.
If liquid water ever existed in significant quantities on the Martian surface, intense frost shattering, widespread creep, and prolific development of patterned structures should have occurred because the thermal regimen of the surface is highly favorable to the freeze–thaw process. It is ineffective at present owing to the lack of liquid water.
No evidence suggests that the residual ice caps have ever acted like terrestrial glaciers in terms of erosion and deposition. Currently, they are too thin, too cold, and presumably frozen to their substrates. Their most important function is to buffer the atmosphere in terms of its H2O and CO2 content, thereby exerting a modifying influence on the surface environment of the entire planet.
Temperatures were measured within the firn and ice of the upper reaches of the Seward Glacier (referred to in this paper as the “upper Seward Glacier”) to a depth of 204 ft. (62.2 m.) by means of thermohms and a Wheatstone bridge. Thermal boring proved a feasible means of penetrating this glacier. The winter’s chilled layer here develops a thickness of 40–50 ft. (12.2–15.2 m.) and attains temperatures of at least −13° C. Deterioration of the chilled Iayer is rapid and irregular in the final phase and is attributed largely to freezing of percolating melt water. Melt water exerts such a powerful influence on thermal regimen that bodies of firn in environments with mean annual temperatures below freezing may, nonetheless, be geophyaically temperate because of extensive warming by melt water in summer. In both 1948 and 1949, the annual chilled layer on the upper Seward Glacier disappeared within the first 10 days of July. The slow development and rapid deterioration of diurnal crusts on firn and the lag effects at depth reproduce in miniature the behavior of the annual chilled layer. On the basis of its thermal regimen the upper Seward Glacier is geophysically temperate.
Ice streams composing a compound valley glacier may be juxtaposed, inset or superimposed, and Demorest’s concepts of ice flowage provide a plausible explanation for these relations. If valley floors are accordant, juxtaposition results because the waxing force of gravity and obstructed gravity flow in the tributary glacier overcomes the waning force of obstructed extrusion flow from the trunk glacier enabling the tributary to force its way into a juxtaposed position with the trunk glacier in the main valley. If discordance in valley floors is less than the thickness of the trunk glacier, an insert position develops by the same mechanism. If the discordance is greater than the thickness of the trunk glacier, superimposition results. Locally, superimposed or inset relations may be established by exceptionally rapid advances, even with accordant valley floors, but any superimposed ice stream shortly becomes inset by sinking into the underlying ice, at least in temperate glaciers.
Chronic fatigue syndrome is likely to be a heterogeneous condition. Previous studies have empirically defined subgroups using combinations of clinical and biological variables. We aimed to explore the heterogeneity of chronic fatigue syndrome.
We used baseline data from the PACE trial, which included 640 participants with chronic fatigue syndrome. Variable reduction, using a combination of clinical knowledge and principal component analyses, produced a final dataset of 26 variables for 541 patients. Latent class analysis was then used to empirically define subgroups.
The most statistically significant and clinically recognizable model comprised five subgroups. The largest, ‘core’ subgroup (33% of participants), had relatively low scores across all domains and good self-efficacy. A further three subgroups were defined by: the presence of mood disorders (21%); the presence of features of other functional somatic syndromes (such as fibromyalgia or irritable bowel syndrome) (21%); or by many symptoms – a group which combined features of both of the above (14%). The smallest ‘avoidant–inactive’ subgroup was characterized by physical inactivity, belief that symptoms were entirely physical in nature, and fear that they indicated harm (11%). Differences in the severity of fatigue and disability provided some discriminative validation of the subgroups.
In addition to providing further evidence for the heterogeneity of chronic fatigue syndrome, the subgroups identified may aid future research into the important aetiological factors of specific subtypes of chronic fatigue syndrome and the development of more personalized treatment approaches.
Late-summer subglacial water pressures have been measured in a dense array of boreholes in the ablation area of Haut Glacier d’Arolla, Switzerland. Interpolated surfaces of minimum diurnal water pressure and diurnal water-pressure variation suggest the presence of a subglacial channel within a more widespread, distributed drainage system. The channel flows along the centre of a variable pressure axis (VPA), some tens of metres wide, that is characterized by low minimum diurnal water pressures (frequently atmospheric) and high diurnal water-pressure variations. These characteristics are transitional over a lateral distance of c. 70 m to higher and more stable subglacial water pressures in the adjacent distributed system. Water-pressure variations recorded in boreholes located close to the centre of the VPA reflect the delivery of surface-derived meltwater to the glacier bed and result in a diurnally reversing, transverse hydraulic gradient that drives water out from the channel into the distributed system during the afternoon and back to the channel overnight. Subglacial observations suggest that such flow occurs through a vertically confined sediment layer. Borehole turbidity records indicate that the resulting diurnal water flows are responsible for the mobilization and transport of fine debris in suspension. Analysis of the propagation velocity and amplitude attenuation cf the diurnal pressure waves suggests that the hydraulic conductivity of the sediment layer decreases exponentially with distance from the channel, falling from c. 10−4 m s−1 at the channel boundary to c. 10−7 m s−1 70 m away. These apparent hydraulic conductivities are consistent with Darcian flow through clean sand and typical glacial till, respectively.
We suggest that fine material is systematically flushed from basal sediments located adjacent to large, melt-season drainage channels beneath warm-based glaciers. This process may have important implications for patterns of glacier erosion, hydro-chemistry and dynamics.
A model has been formulated to determine the stability regimes for water flow in a Subglacial conduit draining from a reservoir. The physics of the water flow is described with a set of differential equations expressing conservation of mass, momentum and energy. Non-steady flow of water in the conduit is considered, the conduit being simultaneously enlarged by frictional heating and compressed by plastic deformation in response to the pressure difference across the tunnel wall. With the aid of simplifying assumptions, a mathematical model has been constructed from two time-dependent, non-linear, ordinary differential equations, which describe the time evolution of the conduit cross-sectional area and the water depth in the reservoir. The model has been used to study the influence of conduit area and reservoir levels on the stability of the water flow for various glacier and ice-sheet configurations. The region of the parameter space where the system can achieve equilibrium has been identified. However, in the majority of cases the equilibrium is unstable, and an initial perturbation from equilibrium may lead to a catastrophic outburst of water which empties the reservoir.
When children have marked problems with motor coordination, they often have problems with attention and impulse control. Here, we map the neuroanatomic substrate of motor coordination in childhood and ask whether this substrate differs in the presence of concurrent symptoms of attention-deficit/hyperactivity disorder (ADHD).
Participants were 226 children. All completed Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5)-based assessment of ADHD symptoms and standardized tests of motor coordination skills assessing aiming/catching, manual dexterity and balance. Symptoms of developmental coordination disorder (DCD) were determined using parental questionnaires. Using 3 Tesla magnetic resonance data, four latent neuroanatomic variables (for the cerebral cortex, cerebellum, basal ganglia and thalamus) were extracted and mapped onto each motor coordination skill using partial least squares pathway modeling.
The motor coordination skill of aiming/catching was significantly linked to latent variables for both the cerebral cortex (t = 4.31, p < 0.0001) and the cerebellum (t = 2.31, p = 0.02). This effect was driven by the premotor/motor cortical regions and the superior cerebellar lobules. These links were not moderated by the severity of symptoms of inattention, hyperactivity and impulsivity. In categorical analyses, the DCD group showed atypical reduction in the volumes of these regions. However, the group with DCD alone did not differ significantly from those with DCD and co-morbid ADHD.
The superior cerebellar lobules and the premotor/motor cortex emerged as pivotal neural substrates of motor coordination in children. The dimensions of these motor coordination regions did not differ significantly between those who had DCD, with or without co-morbid ADHD.
This paper is concerned with a finitely generated module M over a (commutative Noetherian) local ring R. In the case when R is a homomorphic image of a Gorenstein local ring, one can use the well-known associativity formula for multiplicities, together with local duality and Matlis duality, to produce analogous associativity formulae for the local cohomology modules of M with respect to the maximal ideal. The main purpose of this paper is to show that these formulae also hold in the case when R is universally catenary and such that all its formal fibres are Cohen–Macaulay.
These formulae involve certain subsets of the spectrum of R called the pseudosupports of M; these pseudo-supports are closed in the Zariski topology when R is universally catenary and has the property that all its formal fibres are Cohen–Macaulay. However, examples are provided to show that, in general, these pseudo-supports need not be closed. We are able to conclude that the above-mentioned associativity formulae for local cohomology modules do not hold over all local rings.
Model calculations for the interpretations of the CO bands in the IR are discussed. Spherical symmetry is assumed. Profiles of the physical quantities (i.e. temperature, mass, electron density, abundances, etc.) are given by NLTE models which allow for the representation of observed spectra of supernova 1987A in the optical and near infrared. C and O have to be chosen overabundant by a factor of 25 in the helium-rich layers, or a clumpy density distribution structure of a corresponding factor relative to the mean local value is needed. However, the comparison between the observed forbidden OI line at about 6300 A favours the first interpretation. A factor of about 3 has to be taken into account as uncertainty for the overabundance because of the assumptions of the background model. This implies evidence for strong mixing of the helium rich region with more central layers during the stellar evolution and/or the explosion.