3,310 research outputs found
Exact bond percolation thresholds in two dimensions
Recent work in percolation has led to exact solutions for the site and bond
critical thresholds of many new lattices. Here we show how these results can be
extended to other classes of graphs, significantly increasing the number and
variety of solved problems. Any graph that can be decomposed into a certain
arrangement of triangles, which we call self-dual, gives a class of lattices
whose percolation thresholds can be found exactly by a recently introduced
triangle-triangle transformation. We use this method to generalize Wierman's
solution of the bow-tie lattice to yield several new solutions. We also give
another example of a self-dual arrangement of triangles that leads to a further
class of solvable problems. There are certainly many more such classes.Comment: Accepted for publication in J. Phys
Lunar navigation study, volume 2 Final report, Jan. - Dec. 1966
Performance data utilization in mission phase, lunar exploration phase, and navigational phase of lunar roving vehicle mission
Unconditionally verifiable blind computation
Blind Quantum Computing (BQC) allows a client to have a server carry out a
quantum computation for them such that the client's input, output and
computation remain private. A desirable property for any BQC protocol is
verification, whereby the client can verify with high probability whether the
server has followed the instructions of the protocol, or if there has been some
deviation resulting in a corrupted output state. A verifiable BQC protocol can
be viewed as an interactive proof system leading to consequences for complexity
theory. The authors, together with Broadbent, previously proposed a universal
and unconditionally secure BQC scheme where the client only needs to be able to
prepare single qubits in separable states randomly chosen from a finite set and
send them to the server, who has the balance of the required quantum
computational resources. In this paper we extend that protocol with new
functionality allowing blind computational basis measurements, which we use to
construct a new verifiable BQC protocol based on a new class of resource
states. We rigorously prove that the probability of failing to detect an
incorrect output is exponentially small in a security parameter, while resource
overhead remains polynomial in this parameter. The new resource state allows
entangling gates to be performed between arbitrary pairs of logical qubits with
only constant overhead. This is a significant improvement on the original
scheme, which required that all computations to be performed must first be put
into a nearest neighbour form, incurring linear overhead in the number of
qubits. Such an improvement has important consequences for efficiency and
fault-tolerance thresholds.Comment: 46 pages, 10 figures. Additional protocol added which allows
arbitrary circuits to be verified with polynomial securit
Quantum computing on encrypted data
The ability to perform computations on encrypted data is a powerful tool for
protecting privacy. Recently, protocols to achieve this on classical computing
systems have been found. Here we present an efficient solution to the quantum
analogue of this problem that enables arbitrary quantum computations to be
carried out on encrypted quantum data. We prove that an untrusted server can
implement a universal set of quantum gates on encrypted quantum bits (qubits)
without learning any information about the inputs, while the client, knowing
the decryption key, can easily decrypt the results of the computation. We
experimentally demonstrate, using single photons and linear optics, the
encryption and decryption scheme on a set of gates sufficient for arbitrary
quantum computations. Because our protocol requires few extra resources
compared to other schemes it can be easily incorporated into the design of
future quantum servers. These results will play a key role in enabling the
development of secure distributed quantum systems
Feedback that works: a realist review of feedback interventions for written tasks
Despite feedback being considered important to learning, its potential is rarely fully realised. Promoting learning through feedback in open-ended written tasks (e.g. essays and reports) is a complex endeavour that requires students who are motivated to identify and utilise appropriate information. We set out to understand the mechanisms that enable feedback interventions to work, for whom and in what contexts. Using a realist review research methodology, 19,065 papers mentioning feedback in undergraduate courses were screened, 375 full-text papers were assessed for rigour and relevance, resulting in 58 papers for analysis. Self-determination theory was identified as a good fit for understanding what is required of feedback interventions to mobilise students to engage with the process. Findings indicate that the design of feedback processes in open-ended tasks needs to afford opportunities for students to have a sense of relatedness to their teacher, and perceptions of competence and autonomy. In addition, the role of emotion in mediating perceptions of competence needs to be considered. This review supports the use of feedback designs which include scaffolded tasks, dialogue, action plans and sequenced tasks. These designs promote students’ perceptions of relatedness, competence and autonomy, leading to motivation to engage in feedback, and thus improved performance
Percolative shunting on electrified surface
The surface discharge of electrified dielectrics at high humidity is
considered. The percolative nature of charge transport in electrets is
established. Particular attention is given to the phenomena of adsorption and
nucleation of electrically conducting phase in the cause of percolation cluster
growth on electrified surface. The critical index of the correlation lenght for
percolation cluster is found, and its value is in good agreement with the known
theoretical estimations.Comment: 4 pages with 1 figure, revtex, published in Tech. Phys. Lett. 25
(1999) 877-879 with one additional figur
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British research in accounting and finance (2001–2007): the 2008 research assessment exercise
No abstract available
Survival of microencapsulated probiotic Lactobacillus paracasei LBC-1e during manufacture of Mozzarellacheese and simulated gastric digestion
An erythromycin-resistant strain of probiotic Lactobacillus paracasei ssp. paracasei LBC-1 (LBC-1e) was added to part-skim Mozzarella cheese in alginate-microencapsulated or free form at a level of 108 and 107 cfu/g, respectively. Survival of LBC-1e and total lactic acid bacteria (LAB) was investigated through the pasta filata process of cheese making (in which the cheese curd was heated to 55°C and stretched in 70°C-hot brine), followed by storage at 4°C for 6 wk and simulated gastric and intestinal digestion. This included incubation in 0.1 M and 0.01 M HCl, 0.9 M H3PO4, and a simulated intestinal juice consisting of pancreatin and bile salts in a pH 7.4 phosphate buffer. Some reductions were observed in both free and encapsulated LBC-1e during heating and stretching, with encapsulated LBC-1e surviving slightly better. Changes in total LAB losses during heating and stretching did not reach statistical significance. During storage, a decrease was observed in total LAB, but no statistically significant decrease was observed in LBC-1e. Survival during gastric digestion in HCl was dependent on the extent of neutralization of HCl by the cheese, with more survival in the weaker acid, in which pH increased to 4.4 after cheese addition. The alginate microcapsules did not provide any protection against the HCl. It is interesting that survival of the encapsulated LBC-1e was greater during incubation in H3PO4 than in the HCl gastric juices. Proper selection of simulated gastric digestion media is important for predicting the delivery of probiotic bacteria into the human intestinal tract. Neither free nor encapsulated LBC-1e was affected by incubation in the pancreatin-bile solution. Based on the level of probiotic bacteria in cheese needed to provide a health benefit and its survival during simulated gastric digestion, as determined in this study, it should theoretically be possible to lower the amount that needs to be ingested in cheese by up to a factor of 103 compared with other fermented dairy foods or when consumed as supplements
Directed Percolation and Generalized Friendly Walkers
We show that the problem of directed percolation on an arbitrary lattice is
equivalent to the problem of m directed random walkers with rather general
attractive interactions, when suitably continued to m=0. In 1+1 dimensions,
this is dual to a model of interacting steps on a vicinal surface. A similar
correspondence with interacting self-avoiding walks is constructed for
isotropic percolation.Comment: 4 pages, 3 figures, to be published in Phys. Rev. Let
Non-adaptive Measurement-based Quantum Computation and Multi-party Bell Inequalities
Quantum correlations exhibit behaviour that cannot be resolved with a local
hidden variable picture of the world. In quantum information, they are also
used as resources for information processing tasks, such as Measurement-based
Quantum Computation (MQC). In MQC, universal quantum computation can be
achieved via adaptive measurements on a suitable entangled resource state. In
this paper, we look at a version of MQC in which we remove the adaptivity of
measurements and aim to understand what computational abilities still remain in
the resource. We show that there are explicit connections between this model of
computation and the question of non-classicality in quantum correlations. We
demonstrate this by focussing on deterministic computation of Boolean
functions, in which natural generalisations of the Greenberger-Horne-Zeilinger
(GHZ) paradox emerge; we then explore probabilistic computation, via which
multipartite Bell Inequalities can be defined. We use this correspondence to
define families of multi-party Bell inequalities, which we show to have a
number of interesting contrasting properties.Comment: 13 pages, 4 figures, final version accepted for publicatio
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