Organic farming and biodiversity - the impact of organic farming on nature

Organic farming is generally acknowledged for its positive effects on biodiversity and other landscape services. However, the intensity of farming has changed significantly through the last decade as ranks of traditional holistic organic farmers have been joined by much more economically-driven new organic farmers. At the same time there have also been steady improvements in farming methodology and crop types resulting in efficiency in organic farming which can often rival its conventional counterparts. Therefore, large variations occur between organic farms

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Økologisk jordbrug som refugier for biodiversitet (Refugia)

• Økologiske marker har mere ukrudtsbiomasse end konventionelle. • Der er flere blomstrende arter i økologiske hegn end konventionelle forudsat, at der er kontinuitet i den økologiske drift. • Der er flere små pattedyr i små økologiske biotoper end konventionelle. • Fjernmålinger fra fly eller satellit, kaldet remote sensing, kan skelne hvilken afgrødetype der dyrkes, samt forekomsten af småbiotoper. • Uanset driftformen er det vigtigt at inddrage naturhensyn i driften, dvs., at der findes ekstensivt drevne arealer (græsmarker, overdrev, enge) til natur og direkte afsatte arealer til natur

`What is a Thing?': Topos Theory in the Foundations of Physics

The goal of this paper is to summarise the first steps in developing a fundamentally new way of constructing theories of physics. The motivation comes from a desire to address certain deep issues that arise when contemplating quantum theories of space and time. In doing so we provide a new answer to Heidegger's timeless question ``What is a thing?''. Our basic contention is that constructing a theory of physics is equivalent to finding a representation in a topos of a certain formal language that is attached to the system. Classical physics uses the topos of sets. Other theories involve a different topos. For the types of theory discussed in this paper, a key goal is to represent any physical quantity $A$ with an arrow \breve{A}_\phi:\Si_\phi\map\R_\phi where \Si_\phi and $\R_\phi$ are two special objects (the `state-object' and `quantity-value object') in the appropriate topos, $\tau_\phi$. We discuss two different types of language that can be attached to a system, $S$. The first, \PL{S}, is a propositional language; the second, \L{S}, is a higher-order, typed language. Both languages provide deductive systems with an intuitionistic logic. With the aid of \PL{S} we expand and develop some of the earlier work (By CJI and collaborators.) on topos theory and quantum physics. A key step is a process we term `daseinisation' by which a projection operator is mapped to a sub-object of the spectral presheaf \Sig--the topos quantum analogue of a classical state space. The topos concerned is \SetH{}: the category of contravariant set-valued functors on the category (partially ordered set) \V{} of commutative sub-algebras of the algebra of bounded operators on the quantum Hilbert space \Hi.Comment: To appear in ``New Structures in Physics'' ed R. Coeck

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

Properties of excited states in Ge77

The nucleus Ge77 was studied through the Ge76(C13,C12)Ge77 reaction at a sub-Coulomb energy. The angular distributions of γ rays depopulating excited states in Ge77 were measured in order to constrain spin and parity assignments. Some of these assignments are of use in connection with neutrinoless double beta decay, where the population of states near the Fermi surface of Ge76 was recently explored using transfer reactions

Shape coexistence from lifetime and branching-ratio measurements in 68,70Ni

© 2016 The Author(s) Shape coexistence near closed-shell nuclei, whereby states associated with deformed shapes appear at relatively low excitation energy alongside spherical ones, is indicative of the rapid change in structure that can occur with the addition or removal of a few protons or neutrons. Near 68Ni (Z=28, N=40), the identification of shape coexistence hinges on hitherto undetermined transition rates to and from low-energy 0+ states. In 68,70Ni, new lifetimes and branching ratios have been measured. These data enable quantitative descriptions of the 0+ states through the deduced transition rates and serve as sensitive probes for characterizing their nuclear wave functions. The results are compared to, and consistent with, large-scale shell-model calculations which predict shape coexistence. With the firm identification of this phenomenon near 68Ni, shape coexistence is now observed in all currently accessible regions of the nuclear chart with closed proton shells and mid-shell neutrons

Two-quasiparticle structures and isomers in Er168, Er170, and Er172

The stable and neutron-rich isotopes Er168, Er170, and Er172 have been studied with Gammasphere using inelastic excitation with energetic Xe136 beams. The previously assigned structures based on the proposed Kπ=4- isomeric intrinsic states in both Er168 and Er170 have been re-evaluated and an equivalent band identified in Er172. In Er170, the identification of a Kπ=6- band with transitions close in energy to those of the 4 - band leads to a modified interpretation, since the overlap would have compromised previous analyses. The gK-gR values for the 4- bands deduced from the in-band γ-ray intensities for the sequence of isotopes suggest a predominantly two-neutron configuration in Er168, an equally mixed two-neutron, two-proton configuration in Er170, and a two-proton configuration in Er172. A comprehensive decay scheme for the previously proposed 6+ isomer in Er172 has also been established, as well as band structures built on this isomer that closely resemble the 6+ and 7- two-neutron structures known in the isotone Yb174. The implied K hindrances are discussed. The main decay path of the 6+ isomer occurs through the newly identified 4- isomer. The measured lifetimes of the 4 - and 6+ isomers in Er172 are 57(3) and 822(90) ns, respectively. Multiquasiparticle calculations support the suggested configuration changes across the isotopic chain

Precise electromagnetic tests of ab initio calculations of light nuclei: States in Be10

In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in Be10 using the Doppler shift attenuation method (DSAM) following the Li7(Li7,α)Be10 reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The Jπ=21+ state at 3.37 MeV has τ=205±(5)stat±(7)sysfs corresponding to a B(E2) of 9.2(3)e2fm4 in broad agreement with many calculations. The Jπ=22+ state at 5.96 MeV was found to have a B(E2) of 0.11(2)e2fm4 and provides a more discriminating test of nuclear models. New Green's function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment

Lifetime of the Kπ=8- isomer in the neutron-rich nucleus Er174, and N=106 E1 systematics

Chopped-beam techniques and γ-ray spectroscopy with Gammasphere have been used to measure the lifetime of the 1112-keV 8- isomeric state in Er174. The value obtained of τ=5.8(4) s corresponds to a reduced hindrance of fν=98 for the 163-keV E1 transition to the 8+ state of the ground-state band, in good agreement with the systematics of the corresponding E1 strengths in the N=106 isotones. The K-mixing in the 8- states is calculated in the context of the particle-rotor model and used to extract the underlying reduced hindrances