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This article from Four Four Two features a lifelong fan of the Barnet football club, Charlie Cassen, reminiscing about various aspects of the team's history. The article includes a list of the best and worst players in the club's history, as well as memorable moments, games, seasons, signings, and managers. It also highlights notable haircuts, chants, opponents, and away days. The article provides a balanced perspective, showcasing both positive and negative experiences associated with the club. [Extracted from the article]

The design, optimization, and evaluation of a series of novel imidazopyridazine-based subtype-selective positive allosteric modulators (PAMs) for the GABAAligand-gated ion channel are described. From a set of initial hits multiple subseries were designed and evaluated based on binding affinity and functional activity. As designing in the desired level of functional selectivity proved difficult, a probability-based assessment was performed to focus the project’s efforts on a single subseries that had the greatest odds of delivering the target profile. These efforts ultimately led to the identification of two precandidates from this subseries, which were advanced to preclinical safety studies and subsequently to the identification of the clinical candidate PF-06372865.

Oil bodies, also called oleosomes have been the object of an increased interest since the last decade. Different processes of extraction and purification involve an aqueous crushing with methods to soften the cell membranes. An integrated process was used on different oilseeds to compare the different oil-body dispersions obtained. Once extracted with an aqueous crushing, oil bodies are dispersed in a creamy phase containing also an important protein content. Their stability depends on membranous proteins but also surrounding, extraneous ones. To eliminate these non-membranous proteins, the emulsion can be washed with different compounds allowing a good protein solubilization. If the fatty acid, phytosterol, tocopherol contents and distribution are compared between seeds and dispersions of oil bodies, there appears to be little significant change. These valuable compounds are hence preserved in the oil bodies. However, aqueous crushing releases phospholipase partly explaining the lower phospholipid content and the higher relative concentration of phosphatidic acid. To preserve these emulsions, it is possible to dry them either through freeze-drying or spray-drying. Spray-drying allows a better recovery of the physical structure of the emulsion after rehydration but cryo-protectants as Tris or Glycerol can limit emulsion degradation provoked by hard mechanical constraints of a freeze-drying process.

Whereas most fields devoted to the study of minorities define the subjects of their inquiries in opposition to the ethnic, racial, religious, or gender hierarchies of society, Jewish studies has, traditionally fashioned itself along the norms of the European, western humanistic tradition. In this essay I suggest that the study of Jews and Jewish life in and out of early modern Europe provides an opportunity to revise this paradigm and offer two directions for the future of the field: the synthesis of the Jews’ histories of persecution and integration in Europe; and the exploration of the Jews’ role in global history.

The discovery of a Neolithic Alpine jade axehead in Aroche, in the southwest of Spain, revives the question of long-distance exchange between the Iberian Peninsula and the rest of Europe. This polished blade belongs to a typological model quite characteristic of Alpine production during the second half of the 5th millennium B.C. Different mineralogical approaches (macroscopic features examination, specific gravity, direct XRD, non-destructive μXRF spectroscopy, optical stereomicroscopy, magnetic susceptibility determination and microprobe analysis) have identified the rock as an omphacitic jadeitite (mixed jade) with some tiny garnets and a weak retromorphosis. This analysis and the comparison of the rock structure with the referential JADE of Alpine natural jade samples, as well as the extraction modalities and shaping of the axe, provide strong arguments to assign the Aroche axe to a production of Mont Viso: the origin of thousands of axes that circulated in Europe between Ireland and Sicily. The Aroche axe, discovered not far from the variscite mines of Encinasola, could be considered as part of a possible exchange system between the Iberian Peninsula and the Gulf of Morbihan, in Brittany.

In the course of making a digital record of a bow engraved on the lower face of a capstone in the Déhus passage grave, on Guernsey, several new motifs were observed, necessitating a reinterpretation of the composition as a whole.While the presence of a bow and two arrows is confirmed by photogrammetry and images obtained under directional lighting, the anthropomorphic figure can now be better defined, and compared to figures recently recognised in the Paris Basin. The presence of ‘hands’, however, cannot be confirmed, and these engravings may instead represent two horned animals in contact with two further motifs, one of which is certainly a throwing stick.

ABSTRACTThe high frequency bathymetric surveys in the surf zone are difficult and hazardous because of the breaking waves. It is however in these intense energy zones that the morphological evolutions are typically useful to know. A local measurement technique of the bed level evolution that can be used in the surf zone has been developed. This is a resistivity measurement based method and we have here the preliminary results of a 30 days in situ measurement. The extended fields of application of this method are multiple. We present how they can be extended to water level measurement and under specific conditions, to give information on the variations of ground resistivity under wave action.

We present a series of high-resolution, three-dimensional hydrodynamics simulations of a gravitationally unstable solar nebula model. The influences of both azimuthal grid resolution and the treatment of thermal processes on the origin and evolution of gravitational instabilities are investigated. In the first set of simulations, we vary the azimuthal resolution for a locally isothermal simulation, doubling and quadrupling the resolution used in a previous study; the largest number of grid points is (256, 256, 64) in cylindrical coordinates (r, ph, z). At this resolution, the disk breaks apart into a dozen short-lived condensations. Although our previous calculations underresolved the number and growth rate of clumps in the disk, the overall qualitative, but fundamental, conclusion remains: fragmentation under the locally isothermal condition in numerical simulations does not in itself lead to the survival of clumps to become gaseous giant protoplanets. Since local isothermality represents an extreme assumption about thermal processes in the disk, we also present several extended simulations in which heating from an artificial viscosity scheme and cooling from a simple volumetric cooling function are applied to two different models of the solar nebula. The models are differentiated primarily by disk temperature: a high-Q model generated directly by our self-consistent field equilibrium code and a low-Q model generated by cooling the high-Q model in a two-dimensional version of our hydrodynamics code. Here, "high-Q" and "low-Q" refer to the minimum values of the Toomre stability parameter Q in each disk, Qmin = 1.8 and 0.9, respectively. Previous simulations, by ourselves as well as others, have focused on initial states that are already gravitationally unstable, i.e., models similar to the low-Q model. This paper presents for the first time the numerical evolution of an essentially stable initial equilibrium state (the high-Q model) to a severely unstable one by cooling. The additional heating and cooling are applied to each model over the outer half of the disk or the entire disk. The models are subject to the rapid growth of a four-armed spiral instability; the subsequent evolution of the models depends on the thermal behavior of the disk. The cooling function tends to overwhelm the heating included in our artificial viscosity prescription, and as a result the spiral structure strengthens. The spiral disturbances transport mass at prodigious rates during the early nonlinear stages of development and significantly alter the disk's vertical surface. Although dense condensations of material can appear, their character depends on the extent of the volumetric cooling in the disk. In the simulation of the high-Q model with heating and cooling applied throughout the disk, thin, dense rings form at radii ranging from 1 to 3 AU and steadily increase in mass; later companion formation may occur in these rings as cooling drives them toward instability. When heating and cooling are applied only over the outer radial half of the disk, however, a succession of single condensations appears near 5 AU. Each clump has roughly the mass of Saturn, and some survive a complete orbit. Since the clumps form near the artificial boundary in the treatment of the disk gas physics, the production of a clump in this case is a numerical artifact. Nevertheless, radially abrupt transitions in disk gas characteristics, for example, in opacity, might mimic the artificial boundary effects in our simulations and favor the production of stable companions in actual protostellar and protoplanetary disks. The ultimate survival of condensations as eventual stellar or substellar companions to the central star is still largely an open question.

Abstract—We describe results of 32 N‐body planetary accretion simulations that investigate the dependence of terrestrial‐planet formation on nebula surface density profile σ and evolution of the eccentricities of Jupiter and Saturn ej,s. Two surface density profiles are examined: a decaying profile with σ ∝ 1/a, where ais orbital semi‐major axis, and a peaked profile in which σ increases for a< 2 AU and decreases for a> 2 AU. The peaked profiles are generated by models of coagulation in an initially hot nebula. Models with initial ej,s= 0.05 (the current value) and 0.1 are considered. Simulations using the decaying profile with ej,s= 0.1 produce systems most like the observed planets in terms of mass‐weighted mean aand the absence of a planet in the asteroid belt. Simulations with doubled σ produce planets roughly twice as massive as the nominal case. Most initial embryos are removed in each simulation viaejection from the solar system or collision with the Sun. The asteroid belt is almost entirely cleared on a timescale of 10–100 Ma that depends sensitively on ej,s. Most initial mass with a< 2 AU survives, with the degree of mass loss increasing with a. Mass loss from the terrestrial region occurs on a timescale that is long compared to the mass loss time for the asteroid belt. Substantial radial mixing of material occurs in all simulations, but is greater in simulations with initital ej,s= 0.05. The degree of mixing is equivalent to a feeding zone of half width 1.5 and 0.9 AU for an Earth mass planet at 1 AU for the cases ej,s= 0.05 and 0.1, respectively. In simulations with ej,s= 0.05, roughly one‐third and 5–10% of the mass contained in final terrestrial planets originated in the region a> 2.5 AU for the decaying and peaked profiles, respectively. In the case ej,s= 0.1, the median mass accreted from a> 2.5 AU is zero for both profiles.

It is remarkable that we possess samples of Solar System solids which have retained a record of galactic and stellar events that occurred well before the birth of the Sun, as well as samples which contain evidence of Solar System processes that occurred during the earliest stages of planet building. The signatures of such processes are most commonly recognized in isotopic anomalies, identifiable against a pervasive background of isotopic homogeneity, and systematic trends in the elemental abundance patterns of primitive meteoritic materials. Although the significance of these anomalies and patterns is unmistakable, their interpretation in terms of specific processes is problematic. Central to such interpretations are questions of spatial scale: do cosmogonically significant isotopic and elemental compositions reflect processes that occurred on the grand scale of the proto–solar cloud, or do they result from many localized events within a nebular or planetary environment? The question is fundamental to our understanding of the formation of solid objects in the Solar System. This question will be examined here, with specific reference to theoretical models of nebular evolution and planet building, and evidence regarding the survival of presolar signatures, the origin of short–lived radionuclides and oxygen isotopic systematics.

Abstract—Models of the solar nebula are constructed to investigate the hypothesis that surviving planetary objects began to form as the nebula cooled from an early, hot epoch. The imprint of such an epoch might be retained in the spatial distribution of planetary material, the systematic deviations of its elemental composition from that of the Sun, chemical indicators of primordial oxidation state, and variations in oxygen and other isotopic compositions. Our method of investigation is to calculate the time‐dependent, two‐dimensional temperature distributions within model nebulas of prescribed dynamical evolution, and to deduce the consequences of the calculated thermal histories for coagulated solid material. The models are defined by parameters which characterize nebular initial states (mass and angular momentum), mass accretion histories, and coagulation rates and efficiencies. It is demonstrated that coagulation during the cooling of the nebula from a hot state is expected to produce systematic heterogeneities which affect the chemical and isotopic compositions of planetary material. The radial thermal gradient at the midplane results in delayed coagulation of the more volatile elements. Vertical thermal gradients isolate the most refractory material and concentrate evaporated heavy elements in the gas phase. It is concluded that these effects could be responsible for the distribution of terrestrial planetary masses, the systematic depletion patterns of the moderately volatile elements in chondritic meteorites and the Earth, the range of oxygen isotopic compositions exhibited by calcium‐aluminum‐rich inclusions (CAIs) and other refractory inclusions, and some geochemical evidence for a moderately enhanced oxidation state. However, nebular fractionations on a global scale are unlikely to account for the more oxidizing conditions inferred for some CAIs and chondritic silicates, which require dust enhancements greater than a few hundred. This conclusion, along with the well‐established evidence from studies of chondrules and CAIs for thermal excursions of short duration, make it likely that local environments, unrelated to nebular thermal evolution, were also important.

An inversion recovery (IR) artifact was used to delineate the blood/wall boundary in left ventricles. The artifact consisted of a hypointensity signal in pixels located at the boundary of two contiguous tissues with different T1relaxation times. The feasibility of measuring the ejection fraction using the artifact was tested in ten healthy volunteers, with two IR snapshot‐FLASH sequences possessing different times of repetition (TR = 11msec and TR = 3.5msec) and appropriate times of inversion. The comparison with a cine‐MRI sequence showed that ejection fraction measurements are feasible when performed with a snapshot‐FLASH sequence that has a sufficiently short TR (3.5msec). J. Magn. Reson. Imaging 2001;13:461–466. © 2001 Wiley‐Liss, Inc.

In this paper, the effects of thermal energetics on the evolution of gravitationally unstable protostellar disks are investigated by means of three-dimensional hydrodynamic calculations. The initial states for the simulations correspond to stars with equilibrium, self-gravitating disks that are formed early in the collapse of a uniformly rotating, singular isothermal sphere. In a previous paper (Pickett et al.), it was shown that the nonlinear development of locally isentropic disturbances can be radically different than that of locally isothermal disturbances, even though growth in the linear regime may be similar. When multiple low-order modes grew rapidly in the star and inner disk region and saturated at moderate nonlinear levels in the isentropic evolution, the same modes in the isothermal evolution led to shredding of the disk into dense arclets and ejection of material. In this paper, we (1) examine the fate of the shredded disk with calculations at higher spatial resolution than the previous simulations had and (2) follow the evolution of the same initial state using an internal energy equation rather than the assumption of locally isentropic or locally isothermal conditions. Despite the complex structure of the nonlinear features that developed in the violently unstable isothermal disk referred to above, our previous calculation produced no gravitationally independent, long-lived stellar or planetary companions. The higher resolution calculations presented here confirm this result. When the disk of this model is cooled further, prompting even more violent instabilities, the end result is qualitatively the same--a shredded disk. At least for the disks studied here, it is difficult to produce condensations of material that do not shear away into fragmented spirals. It is argued that the ultimate fate of such fragments depends on how readily local internal energy is lost. On the other hand, if a dynamically unstable disk is to survive for very long times without shredding, then some mechanism must mitigate and control any violent phenomena that do occur. The prior simulations demonstrated a marked difference in final outcome, depending upon the efficiency of disk cooling under two different, idealized thermal conditions. We have here incorporated an internal energy equation that allows for arbitrary heating and cooling. Simulations are presented for adiabatic models with and without artificial viscosity. The artificial viscosity accounts for dissipation and heating due to shocks in the code physics. The expected nonaxisymmetric instabilities occur and grow as before in these energy equation evolutions. When artificial viscosity is not present, the model protostar displays behavior between the locally isentropic and locally isothermal cases of the last paper; a strong two-armed spiral grows to nonlinear amplitudes and saturates at a level higher than in the locally isentropic case. Since the amplitude of the spiral disturbance is large, it is expected that continued transport of material and angular momentum will occur well after the end of the calculation at nearly four outer rotation periods. The spiral is not strong enough, however, to disrupt the disk as in the locally isothermal case. When artificial viscosity is present, the same disturbances reach moderate nonlinear amplitude, then heat the gas, which in turn greatly reduces their strength and effects on the disk. Additional heating in the low-density regions of the disk also leads to a gentle flow of material vertically off the computational grid. The energy equation and high-resolution isothermal calculations are used to discuss the importance and relevance of the different thermal regimes so far examined, with particular attention to applications to star and planet formation.

Abstract—Motivated by recent observations of T‐Tauri stars and the interpretation of these observations in terms of the properties of circumstellar disks, we derive internal (midplane) temperatures for disks around mature (age ∼1 Ma) T‐Tauri stars. The estimates are obtained by combining published results for disk masses, sizes, accretion rates, and surface temperatures. For 26 stars (for which adequate data are available), we derive midplane temperatures at 1 AU primarily in the range 200–800 K, and 100–400 K at 2.5 AU. It is likely that the solar nebula, at the same stage of evolution, contained planetesimals and objects destined to become meteorite parent bodies. Observations of young stellar objects at earlier stages of evolution (age ∼0.1 Ma) imply that accretion rates were, on the average, at least two orders of magnitude greater than the 10−8M⊙/year rates typical for mature T‐Tauri stars. Such high values would result in midplane temperatures at or near the silicate vaporization temperature in the terrestrial planet region.

Sudden loss of vision occurred in two young healthy patients who had the clinical findings of partial retinal artery and partial retinal vein occlusion. This might represent a severe variant of papillophlebitis.

Abstract: If a molten, or partially molten, lunar core exists at present, constraints would be placed on the viscosity of the solid mantle and the distribution of radioactive heat sources. Models in which the heat sources have been concentrated near the surface would rapidly solidify if the effective viscosity was equal to, or less than, 1022 cm2 s−1. Retention of most of the heat sources throughout the mantle would permit present day solid convection to occur without cooling the core.

Turbulent convection may have played a major role in determining the structure and evolution of the primordial solar nebula, but current, incomplete models of convection and turbulence give very different results and remain largely untested in the absence of detailed astronomical observations. Numerical simulations provide an "experimental" database for comparison with these models, and, to this end, direct numerical simulations of turbulent convection were performed with modifications intended to mimic some of the unique physical features of thin accretion disks, such as the primordial solar nebula: internal heating, a gravitational acceleration that is linearly proportional to the distance from midplane of the nebula, and rapid rotation. Péclét numbers in the simulations are comparable to those in solar nebula models; Rossby numbers in the simulations are an order of magnitude larger than those in solar nebula models because of the unrealistically high Prandtl and low Reynolds numbers required to resolve all scales of the convective flow.We find that, despite the loss of buoyancy at midplane, turbulent motions easily penetrate the midplane region with little loss of intensity, providing efficient transport of heat and turbulent kinetic energy throughout the interior. A simple mixing length model modified to include rotation is found to give convective heat fluxes for the interior flow in rough agreement with the numerical simulations. We discuss these preliminary results with regard to assumptions about heating distributions and convective heat fluxes made in standard solar nebula models. More definitive comparisons with solar nebula modelling will become possible when more realistic effects of shear, density stratification, and compression are included.

J. Japan. Int. Econ., September 1996,10(3), pp. 326–334. Queen Elizabeth House, 21 St. Giles, Oxford OX1 3LA, United Kingdom.

We present a simplified analysis of some effects of disk accretion on the early evolution of fully convective, low-mass pre-main-sequence stars. Our analysis builds on the previous seminal work of Stahler, but it differs in that the accretion of material occurs over a small area of the stellar surface, such as through a disk or magnetospheric accretion column, so that most of the stellar photosphere is free to radiate to space. This boundary condition is similar to the limiting case considered by Palla & Stahler for intermediate-mass stars. We argue that for a wide variety of disk mass accretion rates, material will be added to the star with relatively small amounts of thermal energy. Protostellar evolution calculated assuming this "low-temperature" limit of accretion generally follows the results of Stahler because of the thermostatic nature of deuterium fusion, which prevents protostars from contracting below a "birthline" in the H-R diagram. Our calculated protostellar radii tend to fall below Stahler's at higher masses; the additional energy loss from the stellar photosphere in the case of disk accretion tends to make the protostar contract. The low-temperature disk accretion evolutionary tracks never fall below the deuterium-fusion birthline until the internal deuterium is depleted, but protostellar tracks can lie above the birthline in the H-R diagram if the initial radius of the protostellar core is large enough or if rapid disk accretion (such as might occur during FU Ori outbursts) adds significant amounts of thermal energy to the star. These possibilities cannot be ruled out by either theoretical arguments or observational constraints at present, so that individual protostars might evolve along a multiplicity of birthlines with a modest range of luminosity at a given mass. Our results indicate that there are large uncertainties in assigning ages for the youngest stars from H-R diagram positions, given the uncertainty in birthline positions. Our calculations also suggest that the relatively low disk accretion rates characteristic of T Tauri stars below the birthline cause low-mass stars to contract only slightly faster than normal Hayashi track evolution, so that ages for older pre-main-sequence stars estimated from H-R diagram positions are relatively secure.

A theoretical model of aerodynamic heating of a meteoric particle upon entry into a parent body atmosphere is presented. The model includes the effects of melting, vaporization, and heat conduction into the particle interior. Properties of chondrule rims are interpreted in the context of the model. We conclude that the formation of true melt rims by atmospheric entry requires that a low-melting-temperature component be fractionated in the outer part of the chondrule prior to rim formation, and that the range of thermal alteration effects observed in UOC chondrites reflects the variety of encounter conditions and chondrite types. Further tests of the model are suggested.

Models of the primitive solar nebula based on a combination of theory, observations of T Tauri stars, and global conservation laws are presented. The models describe the motions of nebular gas, mixing of interstellar material during the formation of the nebula, and evolution of thermal structure in terms of several characteristic parameters. The parameters describe key aspects of the protosolar cloud (its rotation rate and collapse rate) and the nebula (its mass relative to the Sun, decay time, and density distribution). For most applications, the models are heuristic rather than predictive. Their purpose is to provide a realistic context for the interpretation of solar system data, and to distinguish those nebula characteristics that can be specified with confidence, independently of the assumptions of particular models, from those that are poorly constrained. It is demonstrated that nebular gas typically experienced large radial excursions during the evolution of the nebula and that both inward and outward mean radial velocities on the order of meters per second occurred in the terrestrial planet region, with inward velocities predominant for most of the evolution. However, the time history of disk size, surface density, and radial velocities are sensitive to the total angular momentum of the protosolar cloud, which cannot be constrained by purely theoretical considerations. It is shown that a certain amount of "formational" mixing of interstellar material was an inevitable consequence of nebular mass and angular momentum transport during protostellar collapse, regardless of the specific transport mechanisms involved. Even if the protosolar cloud was initially homogeneous, this mixing was important because it had the effect of mingling presolar material that had experienced different degrees of thermal processing during collapse and passage through the accretion shock. Nebular thermal structure is less sensitive to poorly constrained parameters than is dynamical history. A simple criterion is derived for the condition that silicate grains are evaporated at midplane, and it is argued that this condition was probably fulfilled early in nebular history. Cooling of a hot nebula due to coagulation of dust and consequent local reduction of optical depth is examined, and it is shown how such a process leads naturally to an enrichment of rock-forming elements in the gas phase. Copyright 1994, 1999 Academic Press

We use numerical three-dimensional hydrodynamics to investigate how assumptions about local thermal conditions affect the strength and outcome of nonaxisymmetric instabilities in massive protostellar disks. Building on work presented in earlier papers, we generate two protostellar core models that represent equilibrium states that could form from the axisymmetric collapse of uniformly rotating, singular isothermal spheres. Both models are continuous star/disk systems, in which the star, the disk, the star/disk boundary, and the free disk outer boundary are resolved in three dimensions. The models are distinguished primarily by the temperature distribution in the disk, and both can be considered to represent the same early evolutionary stage of disk development, when the disk is massive but small in radial extent. In the "hot" model, the disk is assumed to have the same entropy per gram as the central isentropic star, giving a Toomre Q-parameter ~2.5 over the disk region. In the "cool" model, the entropy per gram decreases radially outward in the disk, resulting in more realistic, cooler disk temperatures and Q [?] 1.5. Each of these protostellar star/disk systems is evolved in our three-dimensional hydrodynamics code under two different assumptions about thermal equilibrium in the disk, namely that either the entropy per gram or the temperature remains constant with position in the disk. We refer to these two cases as locally isentropic evolution and locally isothermal evolution, respectively. All four calculations have been run for at least two outer rotation periods of the disk. With either assumption about the thermal equilibrium, one- and two-armed spiral disturbances, which grow in the hot models, saturate at low amplitude (~1%) and do not alter the protostellar core significantly. On the other hand, the cool model is highly unstable to multiple low-order spirals, which induce significant mass and angular momentum transport in a few dynamical times. Under locally isentropic evolution, the star and star/disk boundary in the cool model are unstable to three- and four-armed disturbances and the disk is unstable to a two-armed spiral, but all these modes saturate at moderate nonlinear (a few tens percent) amplitudes after about 1.5 outer rotation periods. The same instabilities occur under locally isothermal evolution; however, the two-armed spiral in the disk grows more vigorously and does not saturate, ultimately disrupting the disk and concentrating material into thin, dense arcs and arclets that approach stellar densities. In both cool model calculations, there is substantial inward transport of mass and outward transport of angular momentum during the growth phase of the two-armed spiral, but the transport rate drops by over an order of magnitude for locally isentropic evolution when the two-armed spiral saturates. It is clear from these calculations that thermal energetics play a critical role in the development of self-gravitating instabilities and that, under conditions of strong cooling, such instabilities can disrupt a disk very early in its development. We compare these calculations with previous work on gravitational instabilities in disks and discuss implications for star and planet formation.

If a molten, or partially molten, lunar core exists at present, constraints would be placed on the viscosity of the solid mantle and the distribution of radioactive heat sources. Models in which the heat sources have been concentrated near the surface would rapidly solidify if the effective viscosity was equal to, or less than, 1022cm2s-1. Retention of most of the heat sources throughout the mantle would permit present day solid convection to occur without cooling the core.

We use numerical three-dimensional hydrodynamics to investigate how assumptions about local thermal conditions affect the strength and outcome of nonaxisymmetric instabilities in massive protostellar disks. Building on work presented in earlier papers, we generate two protostellar core models that represent equilibrium states that could form from the axisymmetric collapse of uniformly rotating, singular isothermal spheres. Both models are continuous star/disk systems, in which the star, the disk, the star/disk boundary, and the free disk outer boundary are resolved in three dimensions. The models are distinguished primarily by the temperature distribution in the disk, and both can be considered to represent the same early evolutionary stage of disk development, when the disk is massive but small in radial extent. In the "hot" model, the disk is assumed to have the same entropy per gram as the central isentropic star, giving a Toomre Q-parameter ~2.5 over the disk region. In the "cool" model, the entropy per gram decreases radially outward in the disk, resulting in more realistic, cooler disk temperatures and Q? 1.5. Each of these protostellar star/disk systems is evolved in our three-dimensional hydrodynamics code under two different assumptions about thermal equilibrium in the disk, namely that either the entropy per gram or the temperature remains constant with position in the disk. We refer to these two cases as locally isentropic evolution and locally isothermal evolution, respectively. All four calculations have been run for at least two outer rotation periods of the disk. With either assumption about the thermal equilibrium, one- and two-armed spiral disturbances, which grow in the hot models, saturate at low amplitude (~1%) and do not alter the protostellar core significantly. On the other hand, the cool model is highly unstable to multiple low-order spirals, which induce significant mass and angular momentum transport in a few dynamical times. Under locally isentropic evolution, the star and star/disk boundary in the cool model are unstable to three- and four-armed disturbances and the disk is unstable to a two-armed spiral, but all these modes saturate at moderate nonlinear (a few tens percent) amplitudes after about 1.5 outer rotation periods. The same instabilities occur under locally isothermal evolution; however, the two-armed spiral in the disk grows more vigorously and does not saturate, ultimately disrupting the disk and concentrating material into thin, dense arcs and arclets that approach stellar densities. In both cool model calculations, there is substantial inward transport of mass and outward transport of angular momentum during the growth phase of the two-armed spiral, but the transport rate drops by over an order of magnitude for locally isentropic evolution when the two-armed spiral saturates. It is clear from these calculations that thermal energetics play a critical role in the development of self-gravitating instabilities and that, under conditions of strong cooling, such instabilities can disrupt a disk very early in its development. We compare these calculations with previous work on gravitational instabilities in disks and discuss implications for star and planet formation.

World food marketing systems, Butterworth & Co, London, 1986.Faces of hunger. An essay on poverty, justice and development, Studies in applied philosophy, Allen & Unwin, London, 1986. xiii + 178, distributed in South Africa by MacMillan South Africa, Braamfontein.Decentralization and development - Policy implementation in developing countries, Sage Publications, London, 1983, 319 ppSoviet interests in the Third World, Sage Publications, London, 1985, xi + 329 ppNo shortcuts to progress - African development management in perspective, Heinemann Educational Books Ltd, London, 1983, xv + 223 pp.Strategies for African Development, University of California Press, London, 1986, xii + 603 pp.Labour and poverty In Kenya 1900-1980, Clarendon Press, Oxford, 1986, xii + 296, £20,00

The heating and vaporization of dust grains in the protosolar environment is modeled in order to assess the survivability of interstellar solids during the formation of the solar system. A multidimensional, discrete ordinate radiative transfer code is used to compute thermal transport in the collapsing protosolar cloud. The results are combined with estimates of heating at the shock where infalling material arrives at the surface of the solar nebula/accretion disk, and in the interior of the disk, to determine the distances at which various solid phases are vaporized. The thermal coupling between the envelope and the accretion disk (backheating) is treated self-consistently, so its effect on the disk's radial temperature profile is included. This treatment also permits evaluation of the effect of backheating on the observational inference of disk properties.

Leukocytes of hematologically normal human blood have been studied by separating them in bovine serum albumin gradients. The blood cells of the density fractions have been characterized by electronic volume sizing and microscope differential counts. The electronic volumes of different leukocyte populations have been determined from density gradient experiments. Lymphocytes of various sizes can be separated by differences in density. The small lymphocyte population is the most dense while the large population is the least dense. The density of blood cell populations in BSA in order of increasing density were: monocytes, lymphocytes, granulocytes and erythrocytes.

The influence of various polymeric matrices on the phosphorescence of organic molecules is illustrated for the case of 1, 2, 5, 6-dibenzanthracene. The phosphorescence spectra and decay times are compared with low-temperature glasses. Interaction of the aromatic hydrocarbon with the plastic matrices is shown to be greater than with the low-temperature glasses. This interaction is manifested by a higher quantum yield of phosphorescence (relative to fluorescence), but shorter decay times. The effect of the polymer on the triplet state is interpreted in terms of the vibrational structure of the phosphorescence spectra. The degree of polarization and decay time of the phosphorescence emission was studied in the range 77°-365°K and the results are related to the temperature dependence of rotation of the molecule in the matrix. The quenching action of oxygen on phosphorescence is demonstrated with film samples of 20-µ thickness.The relevant physical properties of the plastics employed are discussed and details of sample preparation are presented.

The influence of various polymeric matrices on the phosphorescence of organic molecules is illustrated for the case of 1,2,5,6-dibenzanthracene. The phosphorescence spectra and decay times are compared with low-temperature glasses. Interaction of the aromatic hydrocarbon with the plastic matrices is shown to be greater than with the low-temperature glasses. This interaction is manifested by a higher quantum yield of phosphorescence (relative to fluorescence), but shorter decay times. The effect of the polymer on the triplet state is interpreted in terms of the vibrational structure of the phosphorescence spectra. The degree of polarization and decay time of the phosphorescence emission was studied in the range 77°–365°K and the results are related to the temperature dependence of rotation of the molecule in the matrix. The quenching action of oxygen on phosphorescence is demonstrated with film samples of 20-μ thickness.The relevant physical properties of the plastics employed are discussed and details of sample preparation are presented.