Effect of the spin-orbit interaction and the electron phonon coupling on the electronic state in a silicon vacancy

The electronic state around a single vacancy in silicon crystal is investigated by using the Green's function approach. The triply degenerate charge states are found to be widely extended and account for extremely large elastic softening at low temperature as observed in recent ultrasonic experiments. When we include the LS coupling $\lambda_{\rm Si}$ on each Si atom, the 6-fold spin-orbital degeneracy for the $V^{+}$ state with the valence +1 and spin 1/2 splits into $\Gamma_{7}$ doublet groundstates and $\Gamma_{8}$ quartet excited states with a reduced excited energy of $O(\lambda_{\rm Si}/10)$. We also consider the effect of couplings between electrons and Jahn-Teller phonons in the dangling bonds within the second order perturbation and find that the groundstate becomes $\Gamma_{8}$ quartet which is responsible for the magnetic-field suppression of the softening in B-doped silicon.Comment: 4 pages, 2 figure

Storage Capacity of Two-dimensional Neural Networks

We investigate the maximum number of embedded patterns in the two-dimensional Hopfield model. The grand state energies of two specific network states, namely, the energies of the pure-ferromagnetic state and the state of specific one stored pattern are calculated exactly in terms of the correlation function of the ferromagnetic Ising model. We also investigate the energy landscape around them by computer simulations. Taking into account the qualitative features of the phase diagrams obtained by Nishimori, Whyte and Sherrington [Phys. Rev. E {\bf 51}, 3628 (1995)], we conclude that the network cannot retrieve more than three patterns.Comment: 13pages, 7figures, revtex

Ökologischer Anbau von Zierpflanzen und Baumschulerzeugnissen - Struktur, Entwicklung, Probleme, politischer Handlungsbedarf

In the Federal Organic Farming Scheme Project "Organic production of ornamental plants and nursery trees - structure of the industry, development, problems and required policy initiatives“a quantitative and qualitative survey of certified organic and conventional / integrated nurseries was carried out. The aim was to assess the current status of production and marketing of organic ornamentals in Germany and to provide an overview of the general framework of this industry. • Currently approximately 1 % of the nurseries producing ornamentals in Germany are organic. Considering the small scale of many of the organic units, the share of total sales (2.4 billion Euro or 7.6 % of agricultural production in 2001) is likely to be lower. • Field and greenhouse production of organic annuals and perennials constitutes an estimated 56 ha and 12 ha, respectively. Organic field and container production of trees and shrubs constitutes an estimated 370 ha and 7 ha, respectively. • 90% of the organic nurseries surveyed would choose organic production again, if faced with the question of conversion a second time. • Fewer problems than anticipated were encountered in production - even in pest and disease management. However, problems persist in weed control and continuity of nutrient supply from the growing media. Other challenges were the sourcing of organically acceptable inputs (such as seedlings or growing media) in the production of annuals and perennials. In tree nurseries especially the decline in plant vigour caused by the common practice of successive planting of rosaceae raised difficulties. • Marketing was quoted to be the biggest problem for nurseries which engage in direct marketing. Wholesalers anticipated the biggest problems with the continuity and consistency of the supply of quality product. • The majority of organic operations surveyed encountered financial difficulties during the conversion period and afterwards. • 32 % of growers from integrated operations have already considered organic production, but have - for economic reasons - not pursued this idea further. • The operations surveyed noted that organic standards need expansion and revisions to cover their industry; and that organic inspectors were lacking sufficient technical knowledge. State subsidies for organic ornamental nurseries were found to be inconsistent between the member states of the Federal Republic of Germany. • A high need for an organic advisory service for these types of operations was indicated, but has not been sufficiently met to date. Further, there was almost no research about the organic production of ornamentals. Conclusion Organic production of ornamentals, trees and shrubs is technically feasible - but for further development this sector requires improvement of the basic conditions such as market structure, advisory services, subsidies and research activities

Resonances of the systems \pi-\eta and \pi-\eta' in the reactions \pi-p --> \pi-\eta p and \pi-p --> \pi-\eta' p at COMPASS

We describe partial-wave analyses of the systems \pi-\eta and \pi-\eta' produced in interactions of a \pi- beam (190 GeV/c) with a liquid hydrogen target. The data were recorded during the 2008 COMPASS run, where a slow recoiling proton (|t|>0.1 GeV^2) was required by the trigger. We compare analyses of the \pi-\eta and \pi-\eta' data. Significant contributions can be attributed to the resonances a_2(1320), observed in the D_+-wave, and a_4(2040), observed in the G_+-wave. Between the two systems, we find similar compositions of the even partial waves D_+ and G_+ after taking phase-space factors into account, but a much enhanced P_+-wave in \pi-\eta'. Relative phase-differences indicate a large incoherent contribution of in the P_+-wave of the \eta'\pi- system, but other interpretations are not excluded. The known resonances a_2(1320), a_4(2040) and their parameters could be extracted from the data; their branchings are found to roughly agree with predictions from \eta\eta' mixing.Comment: Proceedings of the Sixth International Conference on Quarks and Nuclear Physics (QNP2012), 7 pages. PoS(QNP2012)074, deviates from version in proceedings by including arXiv hyperlinks in bibliograph

Topological analysis of polymeric melts: Chain length effects and fast-converging estimators for entanglement length

Primitive path analyses of entanglements are performed over a wide range of chain lengths for both bead spring and atomistic polyethylene polymer melts. Estimators for the entanglement length N_e which operate on results for a single chain length N are shown to produce systematic O(1/N) errors. The mathematical roots of these errors are identified as (a) treating chain ends as entanglements and (b) neglecting non-Gaussian corrections to chain and primitive path dimensions. The prefactors for the O(1/N) errors may be large; in general their magnitude depends both on the polymer model and the method used to obtain primitive paths. We propose, derive and test new estimators which eliminate these systematic errors using information obtainable from the variation of entanglement characteristics with chain length. The new estimators produce accurate results for N_e from marginally entangled systems. Formulas based on direct enumeration of entanglements appear to converge faster and are simpler to apply.Comment: Major revisions. Developed near-ideal estimators which operate on multiple chain lengths. Now test these on two very different model polymers

Angular Correlations in Internal Pair Conversion of Aligned Heavy Nuclei

We calculate the spatial correlation of electrons and positrons emitted by internal pair conversion of Coulomb excited nuclei in heavy ion collisions. The alignment or polarization of the nucleus results in an anisotropic emission of the electron-positron pairs which is closely related to the anisotropic emission of $\gamma$-rays. However, the angular correlation in the case of internal pair conversion exhibits diverse patterns. This might be relevant when investigating atomic processes in heavy-ion collisions performed at the Coulomb barrier.Comment: 27 pages + 6 eps figures, uses revtex.sty and epsf.sty, tar-compressed and uuencoded with uufile

Identifying children with Cystic Fibrosis in population-scale routinely collected data in Wales

IntroductionThe challenges in identifying a cohort of people with a rare condition can be addressed by routinely collected, population-scale electronic health record (EHR) data, which provide large volumes of data at a national level. This paper describes the challenges of accurately identifying a cohort of children with Cystic Fibrosis (CF) using EHR and their validation against the UK CF Registry.ObjectivesTo establish a proof of principle and provide insight into the merits of linked data in CF research; to identify the benefits of access to multiple data sources, in particular the UK CF Registry data, and to demonstrate the opportunity it represents as a resource for future CF research.MethodsThree EHR data sources were used to identify children with CF born in Wales between 1st January 1998 and 31st August 2015 within the Secure Anonymised Information Linkage (SAIL) Databank. The UK CF Registry was later acquired by SAIL and linked to the EHR cohort to validate the cases and explore the reasons for misclassifications.ResultsWe identified 352 children with CF in the three EHR data sources. This was greater than expected based on historical incidence rates in Wales. Subsequent validation using the UK CF Registry found that 257 (73%) of these were true cases. Approximately 98.7% (156/158) of individuals identified as CF cases in all three EHR data sources were confirmed as true cases; but this was only the case for 19.8% (20/101) of all those identified in just a single data source.ConclusionIdentifying health conditions in EHR data can be challenging, so data quality assurance and validation is important or the merit of the research is undermined. This retrospective review identifies some of the challenges in identifying CF cases and demonstrates the benefits of linking cases across multiple data sources to improve quality

On the Geometry of Supersymmetric Quantum Mechanical Systems

We consider some simple examples of supersymmetric quantum mechanical systems and explore their possible geometric interpretation with the help of geometric aspects of real Clifford algebras. This leads to natural extensions of the considered systems to higher dimensions and more complicated potentials.Comment: 18 page

Coupling to haloform molecules in intercalated C60?

For field-effect-doped fullerenes it was reported that the superconducting transition temperature Tc is markedly larger for C60.2CHX_3 (X=Cl, Br) crystals, than for pure C60. Initially this was explained by the expansion of the volume per C60-molecule and the corresponding increase in the density of states at the Fermi level in the intercalated crystals. On closer examination it has, however, turned out to be unlikely that this is the mechanism behind the increase in Tc. An alternative explanation of the enhanced transition temperatures assumes that the conduction electrons not only couple to the vibrational modes of the C60-molecule, but also to the modes of the intercalated molecules. We investigate the possibility of such a coupling. We find that, assuming the ideal bulk structure of the intercalated crystal, both a coupling due to hybridization of the molecular levels, and a coupling via dipole moments should be very small. This suggests that the presence of the gate-oxide in the field-effect-devices strongly affects the structure of the fullerene crystal at the interface.Comment: 4 pages, 1 figure, to be published in PRB (rapid communication