Key-Value Store Using a Network Packet Filter Situated in the OS Kernel

When thousands of machines coordinate a small piece of information, a network key-value store can struggle to keep up with the query load. An underlying cause of the capacity bottleneck is that the key-value store is usually held in user space, not kernel space. This disclosure leverages the run-in-kernel capabilities of a network packet filter to deliver very fast responses to key-value (hash map) requests. The network packet filter is capable of communicating with hash-map type memory accesses and can rewrite and redirect packets. When assembled this way, a packet with the query key can be returned to the requester with the value, with the entire request-response operation taking place in kernel space

Statistics of trajectories in two-state master equations

We derive a simple expression for the probability of trajectories of a master equation. The expression is particularly useful when the number of states is small and permits the calculation of observables that can be defined as functionals of whole trajectories. We illustrate the method with a two-state master equation, for which we calculate the distribution of the time spent in one state and the distribution of the number of transitions, each in a given time interval. These two expressions are obtained analytically in terms of modified Bessel functions.Comment: 4 pages, 3 figure

Basal rot of narcissus : understanding pathogenicity in fusarium oxysporum f. sp. narcissi

Fusarium oxysporum is a globally distributed soilborne fungal pathogen causing root rots, bulb rots, crown rots and vascular wilts on a range of horticultural plants. Pathogenic F. oxysporum isolates are highly host specific and are classified as formae speciales. Narcissus is an important ornamental crop and both the quality and yield of flowers and bulbs can be severely affected by a basal rot caused by F. oxysporum f. sp. narcissi (FON); 154 Fusarium isolates were obtained from different locations and Narcissus cultivars in the United Kingdom, representing a valuable resource. A subset of 30 F. oxysporum isolates were all found to be pathogenic and were therefore identified as FON. Molecular characterisation of isolates through sequencing of three housekeeping genes, suggested a monophyletic origin with little divergence. PCR detection of 14 Secreted in Xylem (SIX) genes, previously shown to be associated with pathogenicity in other F. oxysporum f. spp., revealed different complements of SIX7, SIX9, SIX10, SIX12 and SIX13 within FON isolates which may suggest a race structure. SIX gene sequences were unique to FON and SIX10 was present in all isolates, allowing for molecular identification of FON for the first time. The genome of a highly pathogenic isolate was sequenced and lineage specific (LS) regions identified which harboured putative effectors including the SIX genes. Real-time RT-PCR, showed that SIX genes and selected putative effectors were expressed in planta with many significantly upregulated during infection. This is the first study to characterise molecular variation in FON and provide an analysis of the FON genome. Identification of expressed genes potentially associated with virulence provides the basis for future functional studies and new targets for molecular diagnostics

Imaging Earth's crustal magnetic field with satellite data: a regularized spherical triangle tessellation approach

We present a method for imaging the global crustal magnetic field at Earth's surface using a local basis representation and a minimum norm model regularization approach. The local basis consists of a spherical triangle tessellation (STT) parametrization of the radial component of the crustal field at Earth's reference spherical surface. The Green's function for Laplace's equation in spherical geometry with Neumann boundary conditions provides the necessary forward modelling scheme. We solve the inverse problem of estimating the crustal field from satellite magnetic observations by minimizing an objective function comprising a mean absolute deviation (L1-norm) measure of misfit plus a norm measuring model complexity. Both quadratic and entropy measures of field complexity are investigated. We report results from synthetic tests performed on a geophysically motivated scenario; these include a successful benchmark of the method and a comparison between quadratic and entropy regularization strategies. Applying our technique to real observations collected by the CHAMP, Ørsted and SAC-C satellites, we obtain stable images of the crustal magnetic field at Earth's surface that include sharp features with high amplitudes. We present details of two prototype crustal field models STT-CRUST-Q and STT-CRUST-E regularized using quadratic and entropy norms respectively; these provide a perspective complementary to that given by conventional spherical harmonic crustal field model

Maximum entropy regularization of time-dependent geomagnetic field models

We incorporate a maximum entropy image reconstruction technique into the process of modelling the time-dependent geomagnetic field at the core-mantle boundary (CMB). In order to deal with unconstrained small lengthscales in the process of inverting the data, some core field models are regularized using a priori quadratic norms in both space and time. This artificial damping leads to the underestimation of power at large wavenumbers, and to a loss of contrast in the reconstructed picture of the field at the CMB. The entropy norm, recently introduced to regularize magnetic field maps, provides models with better contrast, and involves a minimum of a priori information about the field structure. However, this technique was developed to build only snapshots of the magnetic field. Previously described in the spatial domain, we show here how to implement this technique in the spherical harmonic domain, and we extend it to the time-dependent problem where both spatial and temporal regularizations are required. We apply our method to model the field over the interval 1840-1990 from a compilation of historical observations. Applying the maximum entropy method in space—for a fit to the data similar to that obtained with a quadratic regularization—effectively reorganizes the magnetic field lines in order to have a map with better contrast. This is associated with a less rapidly decaying spectrum at large wavenumbers. Applying the maximum entropy method in time permits us to model sharper temporal changes, associated with larger spatial gradients in the secular variation, without producing spurious fluctuations on short timescales. This method avoids the smearing back in time of field features that are not constrained by the data. Perspectives concerning future applications of the method are also discusse

The Roll of the Burgh Courts of Aberdeen, August-October 1317

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