The rocks from space initiative and the space safari

This paper reports the successes of a new initiative in the UK using electronic resources, such as virtual learning environments and e-classrooms, for planetary and space science public engagement activities

Organic-inorganic spatial relationships in carbonaceous chondrites

The use of a novel technique to determine the spatial relationships of organic and aqueously produced inorganic phases in carbonaceous chondrites, in order to support proposals of a genetic link between the two

Evidence of Vortex Jamming in Abrikosov Vortex Flux Flow Regime

We report on dynamics of non-local Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the non-local voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipulation, including superconducting wires with engineered pinning centers.Comment: 5 pages, 3 figure

Interpretation of Source Counts and Redshift Data in Evolutionary Universes

Conventional interpretation of the N(S) relation requires cosmic evolution of the radio source population. Investigators agree on the general features of this evolution: it must be confined to the most luminous sources, and must be strong, the numbers of such sources at redshifts of 1 to 4 exceeding the present numbers by a factor ≳103. There is no consensus as to whether density or luminosity evolution prevails (or both), whether a cutoff in redshift is necessary, or whether the source populations found in high-frequency surveys follow even the general evolutionary picture deduced for the low-frequency survey population. It is therefore hardly surprising that the physical basis of the evolution, the ultimate goal of N(S) interpretation, remains largely “in the realm of imaginative speculation” (P. A. G. Scheuer)

Lithium and carbon isotopic fractionations between the alteration assemblages of Nakhla and Lafayette

Nakhla and Lafayette delta 7Li values for samples and extracts (4.1-14.2�) are consistent with brine evaporation. Relatively 13C-poor siderite in Lafayette suggests more than one carbon source was sampled

Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. III: Role of particle-number projection

Starting from HFB-6, we have constructed a new mass table, referred to as HFB-8, including all the 9200 nuclei lying between the two drip lines over the range of Z and N > 6 and Z < 122. It differs from HFB-6 in that the wave function is projected on the exact particle number. Like HFB-6, the isoscalar effective mass is constrained to the value 0.80 M and the pairing is density independent. The rms errors of the mass-data fit is 0.635 MeV, i.e. better than almost all our previous HFB mass formulas. The extrapolations of this new mass formula out to the drip lines do not differ significantly from the previous HFB-6 mass formula.Comment: 9 pages, 7 figures, accepted for publication in Phys. Rev.

Models of radio source evolution - II. The 2700-MHz source count

Our technique for deriving cosmological evolution from source counts and identifications is applied to data at 2700 MHz. The analysis is carried out on the assumption that two populations with different evolutionary behaviours appear in surveys at this frequency: ‘steep-spectrum’ sources with extended radio structures, and ‘non-steep-spectrum’ sources with compact structures, the majority of which are identified with QSOs. The 2700-MHz data add constraints to the evolution deduced for the ‘steep-spectrum’ sources from low-frequency data; in particular, of the two types of model obtained in our analysis of the 408-MHz data, only one now appears tenable. The present results for ‘non-steep-spectrum’ sources agree with the results from luminosity – volume tests on samples of ‘flat-spectrum’ QSOs – the change in space density with epoch appears less dramatic than for the powerful radio sources with steep spectra and extended radio structures

Models of the cosmological evolution of extragalactic radio sources – I. The 408-MHz source count

A simple numerical procedure for analysing the counts of extra-galactic radio sources is described. The scheme makes efficient use of the extensive data base which is now available for studying the spatial distribution of radio sources. The method is first applied to data at 408 MHz. We show that, if proper statistical testing is incorporated, the technique provides strong support for the qualitative conclusions of previous analyses: the comoving density of the more powerful radio sources with extended structure is now less than at earlier epochs by a factor of ≳ 10³. However, several evolution models proposed earlier are quantitatively unsatisfactory, and new models are derived which adequately describe the current data. These new models make contrasting predictions about redshift distributions amongst the faint radio sources (S₄₀₈ ≽ 10 mJy), and identification data at such levels can therefore provide powerful constraints upon the models. Our results are compared with results from recent investigations of the spatial distribution of steep-spectrum radio sources