MELEES - e-support or mayhem?

This paper reports on progress in developing a web-based environment to support non-specialist mathematics students taking University level Mathematics as a compulsory subject in their first and second years. The scale and diversity of the service teaching provision at Nottingham invites the use of a technology-based framework in order to make available the ‘good practice’ features developed both locally and elsewhere. Initially the two year development is focusing on: • establishing a supportive environment; • providing feedback to students, their lecturers and importantly to their home Schools; • identifying and supporting e-learning strategies; • improving student motivation. Current activities have been primarily directed to the first three bullet points

Control of Black Root Rot in Dark Tobacco

Reports of the increasing prevalence of black root rot in the areas where dark tobacco types are grown has triggered an accelerated effort from the tobacco research staff to develop and release additional varieties with high resistance to this disease. The high level of resistance to black root rot found in Nicotiana debneyi (an Australian species) is being used as the source of resistance in the breeding program

Leaf litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests

Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivity of leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical montane wet forests where the warming trend may be amplified compared to tropical wet forests at lower elevations. We quantified leaf litter decomposition rates along a highly constrained 5.2 ◦C mean annual temperature (MAT) gradient in tropical montane wet forests on the Island ofHawaii. Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release. Leaf litter decomposition rates were a positive linear function of MAT, causing the residence time of leaf litter on the forest floor to decline by ∼31 days for each 1 ◦C increase in MAT. Our estimate of the Q10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5–2.5) across a broad range of ecosystems. The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site. The lack of net N immobilization during all three litter collection periods at all MAT plots indicates that N was not limiting to leaf litter decomposition, regardless of temperature. These results suggest that leaf litter decay in tropical montane wet forests may be more sensitive to rising MAT than in tropical lowland wet forests, and that increased rates of N release from decomposing litter could delay or prevent progressive N limitation to net primary productivity with climate warming

Relationships between soil macroinvertebrates and nonnative feral pigs (Sus scrofa) in Hawaiian tropical montane wet forests

Abstract Nonnative feral pigs (Sus scrofa) are recognized throughout the New World as a highly significant introduced species in terms of ecosystem alteration. Similarly, nonnative soil macroinvertebrates (e.g. earthworms, ground beetles) invade and alter the structure and function of native habitats globally. However, the relationship between feral pigs and soil macroinvertebrates remains largely unknown. This study analyzed relationships between these taxa using nine sites located inside and outside of feral pig management units representing a * 25 year chronosequence of removal in tropical montane wet forests in Hawai‘i. Soil macroinvertebrates were sampled from plots categorized as: actively trampled by feral pigs, actively rooted by feral pigs, feral pigs present with no signs of recent activity, or feral pigs removed over time. In total, we found 13 families of primarily nonnative soil macroinvertebrates. Plots with active trampling correlated with lower total macroinvertebrate abundance, biomass, and family richness. Plots with active rooting were correlated with higher abundance of nonnative earthworms (Lumbricidae and Megascolicidae) and ground beetles (Carabidae). The abundance, biomass, and biodiversity of macroinvertebrates did not vary with time since feral pig removal. Collectively, these results indicate: (1) trampling by feral pigs negatively influences soil macroinvertebrates; (2) feral pigs either modify habitats while rooting thereby facilitating earthworm and ground beetle habitat use or selectively seek out target prey species of soil macroinvertebrates; and (3) removal of feral pigs has minimal impacts on soil macroinvertebrates over time. These results are important globally due to the broadly overlapping ranges of S. scrofa and nonnative macroinvertebrates

Neutral-Donor-Bound-Exciton Complexes in ZnO Crystals

Neutral-donor–bound-exciton transitions have been observed in ZnO. The isolated neutral donors are made up of defect pair complexes. The neutral-donor nature of these pair complexes was determined from magneticfield measurements and from two-electron transitions. Excited states of the neutral-donor bound excitons were observed in the form of rotator states analogous to rotational states of the H2 molecule

Biology and Impacts of Pacific Island Invasive Species. 9. Capra hircus, the Feral Goat (Mammalia: Bovidae)

Domestic goats, Capra hircus, were intentionally introduced to numerous oceanic islands beginning in the sixteenth century. The remarkable ability of C. hircus to survive in a variety of conditions has enabled this animal to become feral and impact native ecosystems on islands throughout the world. Direct ecological impacts include consumption and trampling of native plants, leading to plant community modification and transformation of ecosystem structure. Although the negative impacts of feral goats are well known and effective management strategies have been developed to control this invasive species, large populations persist on many islands. This review summarizes impacts of feral goats on Pacific island ecosystems and management strategies available to control this invasive species

Progress in Payload Separation Risk Mitigation for a Deployable Venus Heat Shield

A deployable decelerator known as the Adaptive Deployable Entry and Placement Technology (ADEPT) offers substantial science and mass savings for the Venus In Situ Explorer (VISE) mission. The lander and science payload must be separated from ADEPT during atmospheric entry. This paper presents a trade study of the separation system concept of operations and provides a conceptual design of the baseline: aft-separation with a subsonic parachute. Viability of the separation system depends on the vehicle's dynamic stability characteristics during deceleration from supersonic to subsonic speeds. A trajectory sensitivity study presented shows that pitch damping and Venusian winds drive stability prior to parachute deployment, while entry spin rate is not a driver of stability below Mach 5. Additionally, progress in free-flight CFD techniques capable of computing aerodynamic damping parameters is presented. Exploratory simulations of ADEPT at a constant speed of Mach number of 0.8 suggest the vehicle may have an oscillation limit cycle near 5 angle-of-attack. The proposed separation system conceptual design is thought to be viable

TxProbe: Discovering Bitcoin’s Network Topology Using Orphan Transactions

Bitcoin relies on a peer-to-peer overlay network to broadcast transactions and blocks. From the viewpoint of network measurement, we would like to observe this topology so we can characterize its performance, fairness and robustness. However, this is difficult because Bitcoin is deliberately designed to hide its topology from onlookers. Knowledge of the topology is not in itself a vulnerability, although it could conceivably help an attacker performing targeted eclipse attacks or to deanonymize transaction senders. In this paper we present TxProbe, a novel technique for reconstructing the Bitcoin network topology. TxProbe makes use of peculiarities in how Bitcoin processes out of order, or “orphaned” transactions. We conducted experiments on Bitcoin testnet that suggest our technique reconstructs topology with precision and recall surpassing 90%. We also used TxProbe to take a snapshot of the Bitcoin testnet in just a few hours. TxProbe may be useful for future measurement campaigns of Bitcoin or other cryptocurrency networks

Excitonic photoluminescence linewidths in AlGaAs grown by molecular beam epitaxy

The linewidths of excitonic transitions were measured in AlxGa1−xAs, grown by molecular beam epitaxy as a function of alloy composition x for values of x≲0.43 using high resolution photoluminescence spectroscopy at liquid helium temperature. The values of the linewidths thus measured are compared with the results of several theoretical calculations in which the dominant broadening mechanism is assumed to be the statistical potential fluctuations caused by the components of the alloy. An increase in the linewidth as a function of x is observed which is in essential agreement with the prediction of the various theoretical calculations. The linewidths of the excitonic transitions in AlxGa1−xAs observed in the present work are the narrowest ever reported in the literature, for example σ=2.1 meV for x=0.36, thus indicating very high quality material.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70175/2/APPLAB-48-11-727-1.pd

Performance comparison of property map and bitmap indexing

A data warehouse is a collection of data from different sources that supports analytical querying. A Bitmap Index (BI) allows fast access to individual attribute values that are needed to answer a query by representing the values of an attribute for all tuples separately, as bit strings. A Property Map (PMap) is a multidimensional indexing technique that pre-computes attribute expressions, called properties, for each tuple and stores the results as bit strings [DD97, LD02]. This paper compares the performance of the PMap and the Range-Encoded Bit-Sliced Index (REBSI) [CI98] using cost models to simulate their storage and query processing costs for different kinds of queries over a benchmark schema. We identify parameters that affect performance of these indexes and determine situations in which either technique gives significant improvement over the other. We also explore ways to improve PMap design to enhance performance