A geological model of the chalk of East Kent

This report describes the geological modelling of the Chalk in the North Downs of East Kent, within the catchment of River Great Stour and eastwards to the coast, including the Isle of Thanet. This work was funded by the Environment Agency to support investigations of the local hydrogeology and thereby to enhance catchment management. The whole area is underlain by the Upper Cretaceous Chalk Group, with the Palaeogene succession of the Thanet Sand Formation, the Lambeth Group and the Thames Group overlying it in the northern and central eastern parts. The project included a desk study revision of the Chalk of the North Downs, using the new Chalk lithostratigraphy. The revisions to the geology are shown on the 1:50 000 scale geological map which accompanies this report. Together with evidence from boreholes and from seismic surveys, the new outcrop patterns have been incorporated into a geological model, using both computer software (EarthVision) and manual methods. The introduction describes the background to the project. The second chapter describes the sources for the data used in the model: published and unpublished geological maps, borehole records (both lithological and geophysical), seismic surveys, biostratigraphic records, digital topographic information, and the published literature. Each Chalk formation present in the area is then briefly described in the third chapter, noting its relationship to the older lithostratigraphic divisions, and to biostratigraphic zones. The local Chalk succession extends from the base of the Chalk Group to the Newhaven Chalk Formation, here represented by the Margate Chalk Member. Evidence for the thickness of each formation is reviewed. The early Palaeogene formations (the Thanet Sand, Upnor, Harwich and London Clay formations) are also briefly described (Chapter 4) and the local superficial deposits mentioned, with references to detailed descriptions (Chapter 5). Apart from minor adjustments to the outcrop of the basal Palaeogene surface, no revision of these formations was done for this study

Midinfrared third-harmonic generation from macroscopically aligned ultralong single-wall carbon nanotubes

We report the observation of strong third-harmonic generation from a macroscopic array of aligned ultralong single-wall carbon nanotubes (SWCNTs)with intensemidinfrared radiation. Through power-dependent experiments, we determined the absolute value of the third-order nonlinear optical susceptibility !(3) of our SWCNT film to be 5.53 × 10−12 esu, three orders of magnitude larger than that of the fused silica reference we used. Taking account of the filling factor of 8.75% for our SWCNT film, we estimate a !(3) of 6.32 × 10−11 esu for a fully dense film. Furthermore, through polarization-dependent experiments, we extracted all the nonzero elements of the !(3) tensor, determining the magnitude of the weaker tensor elements to be #1/6 of that of the dominant !(3) zzzz component

Decay of the key 92-keV resonance in the 25Mg(p,γ) reaction to the ground and isomeric states of the cosmic γ-ray emitter 26Al

The 92-keV resonance in the 25Mg(p,γ)26Al reaction plays a key role in the production of 26Al at astrophysical burning temperatures of ≈100 MK in the Mg-Al cycle. However, the state can decay to feed either the ground, 26gAl, or isomeric state, 26mAl. It is the ground state that is critical as the source of cosmic γ rays. It is therefore important to precisely determine the ground-state branching fraction f0 of this resonance. Here we report on the identification of four γ-ray transitions from the 92-keV resonance, and determine the spin of the state and its ground-state branching fraction f0=0.52(2)stat(6)syst. The f0 value is the most precise reported to date, and at the lower end of the range of previously adopted values, implying a lower production rate of 26gAl and its cosmic 1809-keV γ rays.peerReviewe

Features of spatial distribution of oscillations in faculae regions

We found that oscillations of LOS velocity in H-alpha are different for various parts of faculae regions. Power spectra show that the contribution of low-frequency modes (1.2 - 2 mHz) increase at the network boundaries. Three and five- minute periods dominate inside cells. The spectra of photosphere and chromosphere LOS velocity oscillations differ for most faculae. On the other hand, we detected several cases where propagating oscillations in faculae were manifest with a five-minute period. Their initiation point on spatial-temporal diagrams coincided with the local maximum of the longitudinal magnetic field.Comment: 6 pages, 4 figure

Spectroscopy of P 30 and the abundance of Si 29 in presolar grains

The astrophysical Si29(p,γ) reaction is expected to play a key role in determining the final Si29 yields ejected in nova explosions. Such yields are used to accurately identify the stellar origins of meteoritic stardust and recently, distinctive silicon isotopic ratios have been extracted from a number of presolar grains. Here, the light-ion Si28(He3,p) fusion-evaporation reaction was used to populate low-spin proton-unbound excited states in the nucleus P30 that govern the rate of the astrophysical Si29(p,γ) reaction. In particular, γ decays were observed from resonances up to Er=500keV, and key resonances at 217 and 315 keV have now been identified as 2+ and 2-levels, respectively. The present paper provides the first estimate of the 217-keV resonance strength and indicates that the strength of the 315-keV resonance, which dominates the rate of the Si29(p,γ) reaction over the entire peak temperature range of oxygen-neon novae, is higher than previously expected. As such, the abundance of Si29 ejected during nova explosions is likely to be less than that predicted by the most recent theoretical models

Decay of the key 92-keV resonance in the 25Mg(p,γ) reaction to the ground and isomeric states of the cosmic γ-ray emitter 26Al

The 92-keV resonance in the 25Mg(p,γ)26Al reaction plays a key role in the production of 26Al at astrophysical burning temperatures of ≈100 MK in the Mg-Al cycle. However, the state can decay to feed either the ground, 26gAl, or isomeric state, 26mAl. It is the ground state that is critical as the source of cosmic γ rays. It is therefore important to precisely determine the ground-state branching fraction f0 of this resonance. Here we report on the identification of four γ-ray transitions from the 92-keV resonance, and determine the spin of the state and its ground-state branching fraction f0=0.52(2)stat(6)syst. The f0 value is the most precise reported to date, and at the lower end of the range of previously adopted values, implying a lower production rate of 26gAl and its cosmic 1809-keV γ rays

Key resonances in the P30(p,γ)S31 gateway reaction for the production of heavy elements in ONe novae

Material emitted as ejecta from ONe novae outbursts is observed to be rich in elements as heavy as Ca. The bottleneck for the synthesis of elements beyond sulphur is the P30(p,γ)S31 reaction. Its reaction rate is, however, not well determined due to uncertainties in the properties of key resonances in the burning regime. In the present study, gamma-ray transitions are reported for the first time from all key states in S31 relevant for the P30(p,γ)S31 reaction. The spins and parity of these resonances have been deduced, and energies have been measured with the highest precision to date. The uncertainty in the estimated P30(p,γ)S31 reaction rate has been drastically reduced. The rate using this new information is typically higher than previous estimates based on earlier experimental data, implying a higher flux of material processed to high-Z elements in novae, but it is in good agreement with predictions using the Hauser-Feshbach approach at higher burning temperatures

Level structure of S 31: From low excitation energies to the region of interest for hydrogen burning in novae through the P 30 (p, γ) S 31 reaction

Comprehensive measurements of the excitation energy and spin-parity assignments for states in S31 are presented, from the first excited state, up to energies relevant for the P30(p,γ)S31 reaction in ONe novae. This reaction rate strongly influences heavy element abundances in novae ejecta. States in S31 are paired with their P31 analogues using γ rays detected with the Gammasphere detector array following the Si28(He4, n) fusion-evaporation reaction. The evolution of mirror energy differences is explored and the results are compared with new shell-model calculations. The excellent agreement observed in this work between experimental data and shell-model calculations provides confidence in using computed estimates in situations where experimental data are unavailable

Level structure of 30S: Implications for the astrophysical 29P(p,γ)30S reaction rate in ONe novae and x-ray bursts

A γ-ray spectroscopy study of 30S is presented. Excitation energies have been determined with improved precision over previous studies and firm spin-parity assignments have been made for key 29P+p resonant states. An evaluation of the 29P(p,γ)30S reaction for T=0.08-2.5 GK shows that the 3+ and 2+ resonant states located at Er=289(3) and 410(3) keV, respectively, dominate the 29P(p,γ)30S reaction rate in ONe novae, while the 410-keV resonance is expected to govern the rate in x-ray burster environments. These new, precise resonance energy measurements and firm spin-parity assignments have significantly reduced uncertainties in the 29P(p,γ)30S reaction in ONe novae and x-ray bursts. In particular, the reaction rate is now specified precisely enough for calculations of isotopic abundances in ONe novae ejecta

Structure of resonances in the Gamow burning window for the Al 25 (p,γ) Si 26 reaction in novae

A γ-ray spectroscopy study of excited states in Si26 has been performed by using the Mg24(3He,n) reaction at a beam energy of 10 MeV. In particular, states have been studied above the proton threshold relevant for burning in the Al25(p,γ)Si26 reaction in novae. This reaction influences the amount of Al26 injected into the interstellar medium by novae, which contributes to the overall flux of cosmic γ-ray emission from Al26 observed in satellite missions. The present results point strongly to the existence of a 0+ state at an excitation energy of 5890 keV lying within the Gamow burning window, which raises questions about the existence and properties of another, higher-lying state reported in previous experimental work. The existence of two such states within this excitation energy region cannot be understood within the framework of sd-shell-model calculations. © 2015 American Physical Society