Learning with Biased Complementary Labels

In this paper, we study the classification problem in which we have access to easily obtainable surrogate for true labels, namely complementary labels, which specify classes that observations do \textbf{not} belong to. Let $Y$ and $\bar{Y}$ be the true and complementary labels, respectively. We first model the annotation of complementary labels via transition probabilities $P(\bar{Y}=i|Y=j), i\neq j\in\{1,\cdots,c\}$, where $c$ is the number of classes. Previous methods implicitly assume that $P(\bar{Y}=i|Y=j), \forall i\neq j$, are identical, which is not true in practice because humans are biased toward their own experience. For example, as shown in Figure 1, if an annotator is more familiar with monkeys than prairie dogs when providing complementary labels for meerkats, she is more likely to employ "monkey" as a complementary label. We therefore reason that the transition probabilities will be different. In this paper, we propose a framework that contributes three main innovations to learning with \textbf{biased} complementary labels: (1) It estimates transition probabilities with no bias. (2) It provides a general method to modify traditional loss functions and extends standard deep neural network classifiers to learn with biased complementary labels. (3) It theoretically ensures that the classifier learned with complementary labels converges to the optimal one learned with true labels. Comprehensive experiments on several benchmark datasets validate the superiority of our method to current state-of-the-art methods.Comment: ECCV 2018 Ora

A realtime observatory for laboratory simulation of planetary flows

Motivated by the large-scale circulation of the atmosphere and ocean, we develop a system that uses observations from a laboratory analog to constrain, in real time, a numerical simulation of the laboratory flow. This system provides a tool to rapidly prototype new methods for state and parameter estimation, and facilitates the study of prediction, predictability, and transport of geophysical fluids where observations or numerical simulations would not independently suffice. A computer vision system is used to extract measurements of the physical simulation. Observations are used to constrain the model-state of the MIT General Circulation Model in a probabilistic, ensemble based assimilation approach. Using a combination of parallelism, domain decomposition and an efficient scheme to select ensembles of model-states, we show that estimates that effectively track the fluid state can be produced. To the best of our knowledge this is the first such observatory for laboratory analogs of planetary circulation that functions in real time.National Science Foundation (U.S.) (CNS-0540259)National Science Foundation (U.S.) (grant CNS-0540248

Polar vortex formation in giant-planet atmospheres due to moist convection

A strong cyclonic vortex has been observed on each of Saturn’s poles, coincident with a local maximum in observed tropospheric temperature. Neptune also exhibits a relatively warm, although much more transient, region on its south pole. Whether similar features exist on Jupiter will be resolved by the 2016 Juno mission. Energetic, small-scale storm-like features that originate from the water-cloud level or lower have been observed on each of the giant planets and attributed to moist convection, suggesting that these storms play a significant role in global heat transfer from the hot interior to space. Nevertheless, the creation and maintenance of Saturn’s polar vortices, and their presence or absence on the other giant planets, are not understood. Here we use simulations with a shallow-water model to show that storm generation, driven by moist convection, can create a strong polar cyclone throughout the depth of a planet’s troposphere. We find that the type of shallow polar flow that occurs on a giant planet can be described by the size ratio of small eddies to the planetary radius and the energy density of its atmosphere due to latent heating from moist convection. We suggest that the observed difference in these parameters between Saturn and Jupiter may preclude a Jovian polar cyclone.National Science Foundation (U.S.). Graduate Research FellowshipNational Science Foundation (U.S.) (ATM-0850639)National Science Foundation (U.S.) (AGS-1032244)National Science Foundation (U.S.) (AGS-1136480)United States. Office of Naval Research (N00014-14-1-0062

Soil pH effects on the interactions between dissolved zinc, non-nano- and nano-ZnO with soil bacterial communities

Zinc oxide nanoparticles (ZnO NPs) are used in an array of products and processes, ranging from personal care products to antifouling paints, textiles, food additives, antibacterial agents and environmental remediation processes. Soils are an environment likely to be exposed to manmade nanoparticles due to the practice of applying sewage sludge as a fertiliser or as an organic soil improver. However, understanding on the interactions between soil properties, nanoparticles and the organisms that live within soil is lacking, especially with regards to soil bacterial communities. We studied the effects of nanoparticulate, non-nanoparticulate and ionic zinc (in the form of zinc chloride) on the composition of bacterial communities in soil with a modified pH range (from pH 4.5 to pH 7.2). We observed strong pH dependent effects on the interaction between bacterial communities and all forms of zinc, with the largest changes in bacterial community composition occurring in soils with low and medium pH levels (pH 4.8 and 5.9). The high pH soil (pH 7.2) was less susceptible to the effects of zinc exposure. At the highest doses of zinc (2500 mg/kg dw soil) both nano and non-nano particulate zinc applications elicited a similar response in the soil bacterial community, and this differed significantly to the ionic zinc salt treatment. The results highlight the importance of considering soil pH in nanotoxicology studies, although further work is needed to determine the exact mechanisms controlling the toxicity and fate and interactions of nanoparticles with soil microbial communities

A rotating annulus driven by localized convective forcing: a new atmosphere-like experiment

We present an experimental study of flows in a cylindrical rotating annulus convectively forced by local heating in an annular ring at the bottom near the external wall and via a cooled circular disk near the axis at the top surface of the annulus. This new configuration is distinct from the classical thermally-driven annulus analogue of the atmosphere circulation, in which thermal forcing is applied uniformly on the sidewalls, but with a similar aim to investigate the baroclinic instability of a rotating, stratified flow subject to zonally symmetric forcing. Two vertically and horizontally displaced heat sources/sinks are arranged so that, in the absence of background rotation, statically unstable Rayleigh-Bénard convection would be induced above the source and beneath the sink, thereby relaxing strong constraints placed on background temperature gradients in previous experimental configurations based on the conventional rotating annulus. This better emulates local vigorous convection in the tropics and polar regions of the atmosphere whilst also allowing stably-stratified baroclinic motion in the central zone of the annulus, as in midlatitude regions in the Earth’s atmosphere. Regimes of flow are identified, depending mainly upon control parameters that in turn depend on rotation rate and the strength of differential heating. Several regimes exhibit baroclinically unstable flows which are qualitatively similar to those previously observed in the classical thermally-driven annulus, However, in contrast to the classical configuration, they typically exhibit more spatiotemporal complexity. Thus, several regimes of flow demonstrate the equilibrated co-existence of, and interaction between, free convection and baroclinic wave modes. These new features were not previously observed in the classical annulus and validate the new setup as a tool for exploring fundamental atmosphere-like dynamics in a more realistic framework. Thermal structure in the fluid is investigated and found to be qualitatively consistent with previous numerical results, with nearly isothermal conditions respectively above and below the heat source and sink, and stably-stratified, sloping isotherms in the near-adiabatic interior

Using a New Odour-Baited Device to Explore Options for Luring and Killing Outdoor-Biting Malaria Vectors: A Report on Design and Field Evaluation of the Mosquito Landing Box.

Mosquitoes that bite people outdoors can sustain malaria transmission even where effective indoor interventions such as bednets or indoor residual spraying are already widely used. Outdoor tools may therefore complement current indoor measures and improve control. We developed and evaluated a prototype mosquito control device, the 'Mosquito Landing Box' (MLB), which is baited with human odours and treated with mosquitocidal agents. The findings are used to explore technical options and challenges relevant to luring and killing outdoor-biting malaria vectors in endemic settings. Field experiments were conducted in Tanzania to assess if wild host-seeking mosquitoes 1) visited the MLBs, 2) stayed long or left shortly after arrival at the device, 3) visited the devices at times when humans were also outdoors, and 4) could be killed by contaminants applied on the devices. Odours suctioned from volunteer-occupied tents were also evaluated as a potential low-cost bait, by comparing baited and unbaited MLBs. There were significantly more Anopheles arabiensis, An. funestus, Culex and Mansonia mosquitoes visiting baited MLB than unbaited controls (P<=0.028). Increasing sampling frequency from every 120 min to 60 and 30 min led to an increase in vector catches of up to 3.6 fold (P<=0.002), indicating that many mosquitoes visited the device but left shortly afterwards. Outdoor host-seeking activity of malaria vectors peaked between 7:30 and 10:30pm, and between 4:30 and 6:00am, matching durations when locals were also outdoors. Maximum mortality of mosquitoes visiting MLBs sprayed or painted with formulations of candidate mosquitocidal agent (pirimiphos-methyl) was 51%. Odours from volunteer occupied tents attracted significantly more mosquitoes to MLBs than controls (P<0.001). While odour-baited devices such as the MLBs clearly have potential against outdoor-biting mosquitoes in communities where LLINs are used, candidate contaminants must be those that are effective at ultra-low doses even after short contact periods, since important vector species such as An. arabiensis make only brief visits to such devices. Natural human odours suctioned from occupied dwellings could constitute affordable sources of attractants to supplement odour baits for the devices. The killing agents used should be environmentally safe, long lasting, and have different modes of action (other than pyrethroids as used on LLINs), to curb the risk of physiological insecticide resistance

Production of phi mesons at mid-rapidity in sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC

We present the first results of meson production in the K^+K^- decay channel from Au+Au collisions at sqrt(s_NN) = 200 GeV as measured at mid-rapidity by the PHENIX detector at RHIC. Precision resonance centroid and width values are extracted as a function of collision centrality. No significant variation from the PDG accepted values is observed. The transverse mass spectra are fitted with a linear exponential function for which the derived inverse slope parameter is seen to be constant as a function of centrality. These data are also fitted by a hydrodynamic model with the result that the freeze-out temperature and the expansion velocity values are consistent with the values previously derived from fitting single hadron inclusive data. As a function of transverse momentum the collisions scaled peripheral.to.central yield ratio RCP for the is comparable to that of pions rather than that of protons. This result lends support to theoretical models which distinguish between baryons and mesons instead of particle mass for explaining the anomalous proton yield.Comment: 326 authors, 24 pages text, 23 figures, 6 tables, RevTeX 4. To be submitted to Physical Review C as a regular article. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm