Online Meta-learning by Parallel Algorithm Competition

The efficiency of reinforcement learning algorithms depends critically on a few meta-parameters that modulates the learning updates and the trade-off between exploration and exploitation. The adaptation of the meta-parameters is an open question in reinforcement learning, which arguably has become more of an issue recently with the success of deep reinforcement learning in high-dimensional state spaces. The long learning times in domains such as Atari 2600 video games makes it not feasible to perform comprehensive searches of appropriate meta-parameter values. We propose the Online Meta-learning by Parallel Algorithm Competition (OMPAC) method. In the OMPAC method, several instances of a reinforcement learning algorithm are run in parallel with small differences in the initial values of the meta-parameters. After a fixed number of episodes, the instances are selected based on their performance in the task at hand. Before continuing the learning, Gaussian noise is added to the meta-parameters with a predefined probability. We validate the OMPAC method by improving the state-of-the-art results in stochastic SZ-Tetris and in standard Tetris with a smaller, 10$\times$10, board, by 31% and 84%, respectively, and by improving the results for deep Sarsa($\lambda$) agents in three Atari 2600 games by 62% or more. The experiments also show the ability of the OMPAC method to adapt the meta-parameters according to the learning progress in different tasks.Comment: 15 pages, 10 figures. arXiv admin note: text overlap with arXiv:1702.0311

Development of a lightweight camera for high altitude platform systems

We describe the development of a lightweight, high-resolution surveillance camera for deployment on high altitude platform systems. The instrument is designed to operate at an altitude of ∼20 km and has an expected ground resolution of better than 120 mm with an appropriate sensor. While designed specifically for imaging at visible wavelengths, it is shown that the design is capable of diffraction-limited imaging at NIR and SWIR wavelengths up to 2.5 μm. We have combined a range of materials from aluminum and titanium alloys through to carbon fiber reinforced plastic to produce an instrument with structural components that match the thermal expansion of the optical glasses used. The use of these materials has resulted in an instrument that weighs <2 kg, including a sensor package, and is designed to weigh <3 kg once integrated with an enclosure and actuated gimbal. The successful testing of two prototype systems is described, including several design outcomes from the program intended for implementation in advance of flight trials

The high hydraulic conductivity of three wooded tropical peat swamps in northeast Peru : measurements and implications for hydrological function

This research was supported by a NERC PhD studentship to the lead author, as well as by a Dudley Stamp Memorial Award from the Royal Geographical Society.The form and functioning of peatlands depend strongly on their hydrological status, but there are few data available on the hydraulic properties of tropical peatlands. In particular, the saturated hydraulic conductivity (K) has not previously been measured in neotropical peatlands. Piezometer slug tests were used to measure K at two depths (50 and 90 cm) in three contrasting forested peatlands in the Peruvian Amazon: Quistococha, San Jorge and Buena Vista. Measured K at 50 cm depth varies between 0.00032 and 0.11 cm s−1, and at 90 cm, it varies between 0.00027 and 0.057 cm s−1. Measurements of K taken from different areas of Quistococha showed that spatial heterogeneity accounts for ~20% of the within-site variance and that depth is a good predictor of K. However, K did not vary significantly with depth at Buena Vista and San Jorge. Statistical analysis showed that ~18% of the variance in the K data can be explained by between-site differences. Simulations using a simple hydrological model suggest that the relatively high K values could lead to lowering of the water table by >10 cm within ~48 m of the peatland edge for domed peatlands, if subjected to a drought lasting 30 days. However, under current climatic conditions, even with high K, peatlands would be unable to shed the large amount of water entering the system via rainfall through subsurface flow alone. We conclude that most of the water leaves these peatlands via overland flow and/or evapotranspiration.PostprintPeer reviewe

Analyzing Market-based Opportunities in the Mango Supply Chain of Davao City: A Rapid Market Assessment

Products and services become meaningful when available and positioned from the customer’s perspective. Exploring the supply chain of mango in Davao City, Southern Philippines, unveils different nodes having different characteristics and buying requirements. We analyzed market-based opportunities in the mango supply chain to inform mango producers which attractive markets they should prioritize as well as identified opportunities for improvement in production and marketing. We utilized a rapid market assessment (RMA) approach to identify the different market nodes and their characteristics. Snowball sampling was used to determine the respondents for this study. A total of 28 face-to-face interviews were done using a semi-structured questionnaire. From the producers’ point of view, we assess the relative attractiveness of the nodes by employing a simple scoring method on the data on volume of requirement, buying price (at the time of interview), support services provided to farmers, and stage of node life cycle. Results show that the exporters’ node has the highest attractiveness score followed by direct wholesalers, primary wholesalers, and processors. We recommend the following practical suggestions for producer groups to target these attractive markets: (1) improve overall quality of mangoes; (2) perform sorting and grading; (3) adopt cost-effective postharvest technology; and (4) develop cost-effective off-season production farming system

Higher harmonic anisotropic flow measurements of charged particles at 2.76 TeV with the ALICE detector

We report the measurements of elliptic flow $v_{2}$, as well as higher harmonics triangular flow $v_{3}$ and quadrangular flow $v_{4}$, in $\sqrt{s_{_{NN}}} =$ 2.76 TeV Pb--Pb collisions, measured with the ALICE detector. We show that the measured elliptic and triangular flow can be understood from the initial spatial anisotropy and its event--by--event fluctuations. The resulting fluctuations of $v_{2}$ and $v_{3}$ are also discussed.Comment: 6 pages, 4 figures, proceeding of Strangeness in Quark Matter 2011, Cracow, Polan

Assessing a New Clue to How Much Carbon Plants Take Up

Current climate models disagree on how much carbon dioxide land ecosystems take up for photosynthesis. Tracking the stronger carbonyl sulfide signal could help

A Complete Expression Profile of Matrix-Degrading Metalloproteinases in Dupuytren’s Disease

Dupuytren’s disease (DD) is a common fibrotic condition of the palmar fascia, leading to deposition of collagen-rich cords and finger contractions. The metzincin superfamily contains key enzymes in the turnover of collagen and other extracellular matrix macromolecules. A number of broad-spectrum matrix metalloproteinase inhibitors, used in cancer clinical trials, caused side effects of DD-like contractures. We tested the hypothesis that changes in the expression of specific metalloproteinases underlie or contribute to the fibrosis and contracture seen in DD. We collected tissue from patients with DD and used normal palmar fascia as a control. We profiled the expression of the entire matrix metalloproteinase (MMP), tissue inhibitor of metalloproteinases (TIMP), and a disintegrin and metalloproteinase domain with thrombospondin motif (ADAMTS) gene families in these tissues using real-time reverse-transcription polymerase chain reaction. A number of metalloproteinases and inhibitors are regulated in DD. The expression of 3 key collagenases, MMP1, MMP13, and MMP14 is increased significantly in the DD nodule, as is the expression of the collagen biosynthetic enzyme ADAMTS14. The expression of MMP7, an enzyme with broad substrate specificity, is increased in the DD nodule and remains equally expressed in the DD cord. TIMP1 expression is increased significantly in DD nodule compared with normal palmar fascia. This study measured the expression of all MMP, ADAMTS, and TIMP genes in DD. Contraction and fibrosis may result from: (1) increased collagen biosynthesis mediated by increased ADAMTS-14; (2) an increased level of TIMP-1 blocking MMP-1– and MMP-13–mediated collagenolysis; and (3) contraction enabled by MMP-14–mediated pericellular collagenolysis (and potentially MMP-7), which may escape inhibition by TIMP-1. The complete expression profile will provide a knowledge-based approach to novel therapeutics targeting these genes

Increased Oxidative Burden Associated with Traffic Component of Ambient Particulate Matter at Roadside and Urban Background Schools Sites in London

As the incidence of respiratory and allergic symptoms has been reported to be increased in children attending schools in close proximity to busy roads, it was hypothesised that PM from roadside schools would display enhanced oxidative potential (OP). Two consecutive one-week air quality monitoring campaigns were conducted at seven school sampling sites, reflecting roadside and urban background in London. Chemical characteristics of size fractionated particulate matter (PM) samples were related to the capacity to drive biological oxidation reactions in a synthetic respiratory tract lining fluid. Contrary to hypothesised contrasts in particulate OP between school site types, no robust size-fractionated differences in OP were identified due high temporal variability in concentrations of PM components over the one-week sampling campaigns. For OP assessed both by ascorbate (OPAA m−3) and glutathione (OPGSH m−3) depletion, the highest OP per cubic metre of air was in the largest size fraction, PM1.9–10.2. However, when expressed per unit mass of particles OPAA µg−1 showed no significant dependence upon particle size, while OPGSH µg−1 had a tendency to increase with increasing particle size, paralleling increased concentrations of Fe, Ba and Cu. The two OP metrics were not significantly correlated with one another, suggesting that the glutathione and ascorbate depletion assays respond to different components of the particles. Ascorbate depletion per unit mass did not show the same dependence as for GSH and it is possible that other trace metals (Zn, Ni, V) or organic components which are enriched in the finer particle fractions, or the greater surface area of smaller particles, counter-balance the redox activity of Fe, Ba and Cu in the coarse particles. Further work with longer-term sampling and a larger suite of analytes is advised in order to better elucidate the determinants of oxidative potential, and to fuller explore the contrasts between site types.\ud \u

Characterizing the diurnal patterns of errors in the prediction of evapotranspiration by several land‐surface models: An NACP analysis

Land‐surface models use different formulations of stomatal conductance and plant hydraulics, and it is unclear which type of model best matches the observed surface‐atmosphere water flux. We use the North American Carbon Program data set of latent heat flux (LE) measurements from 25 sites and predictions from 9 models to evaluate models' ability to resolve subdaily dynamics of transpiration. Despite overall good forecast at the seasonal scale, the models have difficulty resolving the dynamics of intradaily hysteresis. The majority of models tend to underestimate LE in the prenoon hours and overestimate in the evening. We hypothesize that this is a result of unresolved afternoon stomatal closure due to hydrodynamic stresses. Although no model or stomata parameterization was consistently best or worst in terms of ability to predict LE, errors in model‐simulated LE were consistently largest and most variable when soil moisture was moderate and vapor pressure deficit was moderate to limiting. Nearly all models demonstrate a tendency to underestimate the degree of maximum hysteresis which, across all sites studied, is most pronounced during moisture‐limited conditions. These diurnal error patterns are consistent with models' diminished ability to accurately simulate the natural hysteresis of transpiration. We propose that the lack of representation of plant hydrodynamics is, in part, responsible for these error patterns. Key Points Land‐surface models produce subdaily patterns of latent heat flux error Error patterns are characterized by the stomatal conductance formulation used Current models lack a mechanism to simulate hysteretic transpirationPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108341/1/jgrg20246.pd

Maturity-Associated Polygenic Profiles of under 12–16-Compared to under 17–23-Year-Old Male English Academy Football Players

The purpose of this study was to examine polygenic profiles previously associated with maturity timing in male academy football players across different age phases. Thus, 159 male football players from four English academies (U12–16, n = 86, aged 13.58 ± 1.58 years; U17–23, n = 73, aged 18.07 ± 1.69 years) and 240 male European controls were examined. Polygenic profiles comprised 39 single nucleotide polymorphisms and were analysed using unweighted and weighted total genotype scores (TGSs; TWGSs). There were significant differences in polygenic profiles between groups, whereby U17–23 players had more genetic variants associated with later maturity compared to U12–16 players (TGS, p = 0.010; TWGS, p = 0.024) and controls (TGS, p = 0.038; TWGS, p = 0.020). More specifically, U17–23 players had over two-times the odds of possessing >36 later-maturing alleles than <30 compared to U12–16 players (odds ratio (OR) = 2.84) and controls (OR = 2.08). These results suggest there was a greater proportion of relatively later-maturing players as maturation plateaus towards adulthood, which may be explained by the ‘underdog hypothesis’. This study provides the first known molecular evidence that supports the notion that a maturity selection bias exists within male academy football