A value chain analysis of interventions to control production diseases in the intensive pig production sector

Value chain analysis (VCA) calculated the financial effects on food chain actors of interventions to improve animal health and welfare in the intensive pig sector. Two interventions to reduce production diseases were studied. A generic chain diagram of linkages between stakeholders and value-added dimensions was designed. Data on structure and financial performance were collected for the sector. The production parameters and financial effects of the interventions were then described to illustrate impact on the supply chain. The effects of the interventions were also assessed at market level using economic welfare analysis. The sectors in Finland and the UK are small in farm numbers and few companies produced much of the output in a largely vertically-integrated structure. The most beneficial intervention in financial terms to farmers was improved hygiene in pig fattening (around +50% in gross margin). It was calculated to reduce the consumer price for pig meat by up to 5% when applied at large, whereas for improved management measures, it would reduce consumer price by less than 0.5%. However, the latter added value also through food quality attributes. We show that good hygiene and animal care can add value. However, evaluation of the financial and social viability of the interventions is needed to decide what interventions are adopted. The structure of supply chains influences which policy measures could be applied. Of the two interventions, improved pig hygiene had the largest potential to improve efficiency and reduce costs. The studied interventions can also provide new business opportunities to farms, slaughterhouses and food sector companies. More evidence is needed to support public policies and business decision-making in the sector. For this, evidence on consumer attitudes to production diseases is needed. Nevertheless, the study makes an important contribution by showing how improvements in health and welfare benefit the whole chain

Quantum identification system

A secure quantum identification system combining a classical identification procedure and quantum key distribution is proposed. Each identification sequence is always used just once and new sequences are ``refuelled'' from a shared provably secret key transferred through the quantum channel. Two identification protocols are devised. The first protocol can be applied when legitimate users have an unjammable public channel at their disposal. The deception probability is derived for the case of a noisy quantum channel. The second protocol employs unconditionally secure authentication of information sent over the public channel, and thus it can be applied even in the case when an adversary is allowed to modify public communications. An experimental realization of a quantum identification system is described.Comment: RevTeX, 4 postscript figures, 9 pages, submitted to Physical Review

Performing joint measurements and transformations on several qubits by operating on a single control qubit

An n-qubit quantum register can in principle be completely controlled by operating on a single qubit that interacts with the register via an appropriate fixed interaction. We consider a hypothetical system consisting of n spin-1/2 nuclei that interact with an electron spin via a magnetic interaction. We describe algorithms that measure non-trivial joint observables on the register by acting on the control spin only. For large n this is not an efficient model for universal quantum computation but it can be modified to an efficient one if one allows n possible positions of the control particle. This toy model of measurements illustrates in which way specific interactions between the register and a probe particle support specific types of joint measurements in the sense that some joint observables can be measured by simple sequences of operations on the probe particle.Comment: 7 pages, revtex, 3 figure

Vulnerability of "A novel protocol-authentication algorithm ruling out a man-in-the-middle attack in Quantum Cryptography"

In this paper we review and comment on "A novel protocol-authentication algorithm ruling out a man-in-the-middle attack in quantum cryptography", [M. Peev et al., Int. J. Quant. Inform., 3, 225, (2005)]. In particular, we point out that the proposed primitive is not secure when used in a generic protocol, and needs additional authenticating properties of the surrounding quantum-cryptographic protocol.Comment: 6 page

Pauli Exchange Errors in Quantum Computation

In many physically realistic models of quantum computation, Pauli exchange interactions cause a subset of two-qubit errors to occur as a first order effect of couplings within the computer, even in the absence of interactions with the computer's environment. We give an explicit 9-qubit code that corrects both Pauli exchange errors and all one-qubit errors.Comment: Final version accepted for publication in Phys. Rev. Let

Complexity of decoupling and time-reversal for n spins with pair-interactions: Arrow of time in quantum control

Well-known Nuclear Magnetic Resonance experiments show that the time evolution according to (truncated) dipole-dipole interactions between n spins can be inverted by simple pulse sequences. Independent of n, the reversed evolution is only two times slower than the original one. Here we consider more general spin-spin couplings with long range. We prove that some are considerably more complex to invert since the number of required time steps and the slow-down of the reversed evolutions are necessarily of the order n. Furthermore, the spins have to be addressed separately. We show for which values of the coupling parameters the phase transition between simple and complex time-reversal schemes occurs.Comment: Completely rewritten, new lower bounds on the number of time steps, applications and references adde

An Efficient Triangle Mesh Slicing Algorithm for All Topologies in Additive Manufacturing

To date, slicing algorithms for additive manufacturing are most effective for favourable triangular mesh topologies; worst case models, where a large percentage of triangles intersect each slice-plane, take significantly longer to slice than a like-for-like file. In larger files, this results in a significant slicing duration, when models are both worst case and contain more than 100,000 triangles. The research presented here introduces a slicing algorithm which can slice worst case large models effectively. A new algorithm is implemented utilising an efficient contour construction method, with further adaptations, which make the algorithm suitable for all model topologies. Edge matching, which is an advanced sorting method, decreases the number of sorts per edge from n total number of intersections to two, alongside additional micro-optimisations that deliver the enhanced efficient contour construction algorithm. The algorithm was able to slice a worst-case model of 2.5 million triangles in 1025s. Maximum improvement was measured as 9,400% over the standard efficient contour construction method. Improvements were also observed in all parts in excess of 1000 triangles. The slicing algorithm presented offers novel methods that address the failings of other algorithms described in literature to slice worst case models effectively

Ascension

https://digitalcommons.georgiasouthern.edu/ascen/1001/thumbnail.jp