The Melbourne Shuffle: Improving Oblivious Storage in the Cloud

We present a simple, efficient, and secure data-oblivious randomized shuffle algorithm. This is the first secure data-oblivious shuffle that is not based on sorting. Our method can be used to improve previous oblivious storage solutions for network-based outsourcing of data

Choosing Colors for Geometric Graphs via Color Space Embeddings

Graph drawing research traditionally focuses on producing geometric embeddings of graphs satisfying various aesthetic constraints. After the geometric embedding is specified, there is an additional step that is often overlooked or ignored: assigning display colors to the graph's vertices. We study the additional aesthetic criterion of assigning distinct colors to vertices of a geometric graph so that the colors assigned to adjacent vertices are as different from one another as possible. We formulate this as a problem involving perceptual metrics in color space and we develop algorithms for solving this problem by embedding the graph in color space. We also present an application of this work to a distributed load-balancing visualization problem.Comment: 12 pages, 4 figures. To appear at 14th Int. Symp. Graph Drawing, 200

Data-Oblivious Graph Algorithms in Outsourced External Memory

Motivated by privacy preservation for outsourced data, data-oblivious external memory is a computational framework where a client performs computations on data stored at a semi-trusted server in a way that does not reveal her data to the server. This approach facilitates collaboration and reliability over traditional frameworks, and it provides privacy protection, even though the server has full access to the data and he can monitor how it is accessed by the client. The challenge is that even if data is encrypted, the server can learn information based on the client data access pattern; hence, access patterns must also be obfuscated. We investigate privacy-preserving algorithms for outsourced external memory that are based on the use of data-oblivious algorithms, that is, algorithms where each possible sequence of data accesses is independent of the data values. We give new efficient data-oblivious algorithms in the outsourced external memory model for a number of fundamental graph problems. Our results include new data-oblivious external-memory methods for constructing minimum spanning trees, performing various traversals on rooted trees, answering least common ancestor queries on trees, computing biconnected components, and forming open ear decompositions. None of our algorithms make use of constant-time random oracles.Comment: 20 page

Mice Infected with Low-virulence Strains of Toxoplasma gondii Lose their Innate Aversion to Cat Urine, Even after Extensive Parasite Clearance

Toxoplasma gondii chronic infection in rodent secondary hosts has been reported to lead to a loss of innate, hard-wired fear toward cats, its primary host. However the generality of this response across T. gondii strains and the underlying mechanism for this pathogen mediated behavioral change remain unknown. To begin exploring these questions, we evaluated the effects of infection with two previously uninvestigated isolates from the three major North American clonal lineages of T. gondii, Type III and an attenuated strain of Type I. Using an hour-long open field activity assay optimized for this purpose, we measured mouse aversion toward predator and non-predator urines. We show that loss of innate aversion of cat urine is a general trait caused by infection with any of the three major clonal lineages of parasite. Surprisingly, we found that infection with the attenuated Type I parasite results in sustained loss of aversion at times post infection when neither parasite nor ongoing brain inflammation were detectable. This suggests that T. gondii-mediated interruption of mouse innate aversion toward cat urine may occur during early acute infection in a permanent manner, not requiring persistence of parasitecysts or continuing brain inflammation.Comment: 14 pages, 3 figure

Heath Lake SSSI, Berkshire: report on sediment analysis 2016

Heath Lake is located in the county of Berkshire (Figure 1) and was designated as a Site of Special Scientific Interest (SSSI) in 1989 for its “specialist communities of native plants and animals...[and] populations of some uncommon and rare aquatic plant species” (Natural England, 2016). Described as a lowland acid lake with nutrient poor waters, it has historically been habitat to both aquatic and marginal plant communities which are more characteristic of upland lakes in Wales, northern England and Scotland

Hedgecourt Lake: SSSI condition summary

Hedgecourt Lake is a shallow lake located in the upper reaches of the Eden Brook a tributary of the River Medway. The lake, which has a surface area of approximately 17 ha, is entirely artificial, created and altered over the centuries to provide a head of water for Hedgecourt Watermill which was located below the dam wall on Eden Brook. The age of the lake is uncertain, but there is evidence of a watermill in this area since 1562 (Felbridge & District History Group 2004), suggesting it to have been in existence for at least 500 years

Heath Lake SSSI, Berkshire: Report on ecological lake monitoring 2016

Heath Lake is located in the county of Berkshire (Figure 1) and was designated as a Site of Special Scientific Interest (SSSI) in 1989 for its “specialist communities of native plants and animals...[and] populations of some uncommon and rare aquatic plant species” (Natural England, 2016). Described as a lowland acid lake with nutrient poor waters, it has historically been habitat to both aquatic and marginal plant communities which are more characteristic of upland lakes in Wales, northern England and Scotland. The SSSI citation lists alternate water-milfoil (Myriophyllum alterniflorum) to be growing abundantly, alongside floating club-rush (Eleogiton fluitans), six-stamened waterwort (Elatine hexandra), blunt-leaved and lesser pondweeds (Potamogeton obtusifolius and Potamogeton pusillus) and shoreweed (Litorella uniflora). In addition to this, Coral Necklace (Illecebrum verticillatum), was reported as present at Heath Lake in Crawley’s 2004 edition of The Flora of Berkshire, and there are records of Pillwort (Pilularia globulifera) (Porley 1994). The distribution of Coral Necklace is currently in decline due to increasingly restricted ranges of heathland habitat and has not been recorded at Heath Lake in recent years. Heath Lake is currently in unfavourable condition due to nutrient enrichment and increased base levels of the lake. This has resulted in a significant and rapid change to the aquatic macrophyte communities both submerged and marginal to the lake

Partial Regularity for Minimizers of Discontinuous Quasiconvex Integrals with general growth

We prove the partial Hölder continuity for minimizers of quasiconvex functionals F(u):=∫Ωf(x,u,Du)dx, where f satisfies a uniform VMO condition with respect to the x-variable and is continuous with respect to u. The growth condition with respect to the gradient variable is assumed a general one

Gaudet Luce Golf & Leisure Complex, Worcestershire: Report on aquatic habitats 2017

Gaudet Luce Golf & Leisure Complex is located in the county of Worcestershire (Figure 1), southeast of Droitwich Spa town. Founded in 1995, the golf course has undergone an extensive transformation which has included a new Par Three course, reconfiguration of the 18 hole Phoenix Course and the planting of over 50,000 trees across the golf complex, which were supplied to Gaudet Luce via a Forestry Commission grant. Drainage systems have also been improved over time, alongside the installation of new bunkers and tee renovation (Midlands Business News, 2013; Fernihough, 2017)

A palaeolimnological study of Loch Shin, Scotland. Final report to SEPA and the Forestry Commission

This project reports on analysis of a sediment core collected from the lower basin of Loch Shin in Sutherland, Scotland on 24 August 2015, spanning a total sediment depth of 31.5 cm. Palaeoecological techniques, principally diatom analysis of a dated core, were employed to assess environmental change at the loch since 1850 AD. The project aims to determine the reference conditions of the loch and to establish the onset, rate and magnitude of any changes in the diatom flora. The Scottish Environment Protection Agency are particularly interested in any changes in the loch that may have occurred in association with fish farming and forestry practices and whether the hydropower scheme has had any impact. Radiometric methods were applied to the core in order to date the recent sediments, revealing that the 31.5 cm core dates back to ~1850 AD. There is an increase in sedimentation rates before the 1920s, followed by small changes around a mean value of 0.026 g cm-2 yr-1 until the 2000s, after which the sedimentation rates increase slightly again in recent years to 0.038 g cm-2 yr-1. Diatom analysis was carried out on 21 samples distributed throughout the core and a diatom-total phosphorus (TP) transfer function was applied to the diatom data to reconstruct trophic status. There were marked changes in the diatom assemblages during the 160 year period represented by the core and cluster analysis revealed four major zones with the most significant split, reflecting floristic change, at 7.75 cm which corresponds to 1994. In the period from 1860 to 1930 (Zone 1), the sedimentary diatom assemblages of Loch Shin were very stable with a diatom flora typical of nutrient-poor, deep lakes and the diatom-inferred TP concentrations were low and stable at 5 μg L−1 indicating oligotrophic conditions. The diatom reference conditions of Loch Shin can thus be described as a community of oligotrophic, acidophilous-circumneutral taxa, particularly Cyclotella kuetzingiana, Achnanthidium minutissimum and Brachysira vitrea. The diatom assemblages began to change from ~1930 with the arrival of taxa more typically associated with mesotrophic waters, namely Aulacoseira subarctica and Asterionella formosa, marking an initial enrichment phase (Zone 2). The progressive and gradual nature of the shifts suggests a response to the cumulative effect of increasing pressures in the catchment during the mid to late twentieth century including dam construction and the consequent water level rise in the 1950s, as well as forestry plantation and fertilisation which took place from the 1960s. A more pronounced enrichment phase was evident from the mid-1990s with the expansion of Aulacoseira subarctica, the arrival of Fragilaria crotonensis and the decline, and in some cases the loss, of numerous taxa seen in the early part of the record (Zone 3). The diatom-inferred TP concentrations increased to 16 μg L−1. While the exact causes of these shifts cannot be established, the most marked changes in the diatoms are coincident with the arrival of the fish farms on the loch in 1994-1995 suggesting that aquaculture may have played a role. Since 2009 Fragilaria crotonensis has disappeared although the reasons for this are not clear (Zone 4). A. subarctica remains the dominant species and the planktonic component of the assemblages remains high at 50-60%. The diatom-inferred TP concentrations decreased to 11 μg L-1 at the core surface, indicating that there may be a recent phase of reduction in trophic status. However, given that there are no reported changes in land use or management since 2009 and that diatoms respond to a host of factors in addition to nutrient concentrations, it would be unwise to suggest that the disappearance of F. crotonensis from the recent sediment record is reflective of improving water quality. Clearly a more detailed study of recent management practices in the catchment and fish farms is required to establish whether there have been any real reductions in nutrient loads to the loch