Data-Driven Forecasting of High-Dimensional Chaotic Systems with Long Short-Term Memory Networks

We introduce a data-driven forecasting method for high-dimensional chaotic systems using long short-term memory (LSTM) recurrent neural networks. The proposed LSTM neural networks perform inference of high-dimensional dynamical systems in their reduced order space and are shown to be an effective set of nonlinear approximators of their attractor. We demonstrate the forecasting performance of the LSTM and compare it with Gaussian processes (GPs) in time series obtained from the Lorenz 96 system, the Kuramoto-Sivashinsky equation and a prototype climate model. The LSTM networks outperform the GPs in short-term forecasting accuracy in all applications considered. A hybrid architecture, extending the LSTM with a mean stochastic model (MSM-LSTM), is proposed to ensure convergence to the invariant measure. This novel hybrid method is fully data-driven and extends the forecasting capabilities of LSTM networks.Comment: 31 page

Ultrasound as a repulsive cue for neuronal development: real-time morphological observations in-vitro

Session IUS1-PA4: Bioeffects and metrology: abstract no. IUS1-PA4-6The Conference program & abstracts' website is located at http://www.ewh.ieee.org/conf/uffc/2013/BACKGROUND, MOTIVATION AND OBJECTIVE: A core event in neuronal development is the outgrowth of neurite branches from a neuron’s cell body. It is known that, by presenting physical or chemical cues to the extracellular environment, neuronal development can potentially be modulated. In this work, we seek to investigate the use of ultrasound in modifying neuronal development behavior. We hypothesize that ultrasound, when applied at low intensity and pulsed settings, can possibly serve as a physical cue that operates like mechanical stimulation. STATEMENT OF CONTRIBUTION/METHODS: Our study was carried out on a customized platform that allows real-time imaging of neuronal morphology. Pulsed ultrasound (1 MHz frequency, 20 or 100 cycle pulse lengths, 500 or 2500 Hz PRF) was applied through a waveguide at a 45 degree angle with respect to the microscope’s field of view, which is aligned to the center of a 100mm polystyrene cell dish. Three different peak acoustic pressures (measured in-situ) were used: 0.13, 0.40, 0.84 MPa (correspond to SPTA intensities of up to 1.168 W/cm2 for our given pulsing parameters). In this work, N2a mouse neuroblastoma was used as the …postprin

Headspace Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometric Analysis of Volatile Components of Raw and Stir-Fried Fruit of C. Pinnatifida (FCP)

Purpose: To investigate the change of volatile components associated with odor of C. Pinnatifida (FCP) fruit and its stir-fried forms.Methods: FCP fruit was stir-fried and monitored by an online-type and non-contact temperature measurement system (ONTMS). Headspace solid-phase  microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to analyze the volatile composition of raw FCP and its various stir-fried forms.Results: The color of FCP turned darker with the stir-frying process. In all, 47 volatile compounds with contents > 1 % were identified. The major volatile components were methyl acetate (4.40 %), n-hexane (2.90 %), 2-methyl-furan (1.80 %), 3-methyl-butyraldehyde (3.64 %), hexanal (2.08 %), furaldehyde (5.77 %), and D-limonene (7.99 %) in raw FCP. Following stir-frying, the contents of furaldehyde, 5- methyl-furaldehyde, methyl acetate, 2-methyl-butyraldehyde, D-limonene and 2-methyl-furaldehyde were altered significantly, which might have resulted in odor changes.Conclusion: HS-SPME coupled with GC-MS is a rapid and eco-friendly method with the potential to analyze volatile compounds in raw and processed FCP.Keywords: Crataegus pinnatifida, Stir-frying, Online-type and non-contact temperature measurement system, Headspace solid-phase microextraction, Volatile components, Odo

Contrasting sensitivity of weathering proxies to Quaternary climate and sea-level fluctuations on the southern slope of the South China Sea

Tropical marginal seas host important sedimentary archives that may be exploited to reveal past changes in continental erosion, chemical weathering, and ocean dynamics. However, these records can be challenging to interpret due to the complex interactions between climate and particulate transport across ocean margins. For the southern South China Sea over the last 90 Kyr, we observe a contrasting temporal relationship between the deposition of clay minerals and magnetic minerals, which were associated with two different hydrodynamic modes. Fine-grained clay minerals can be carried in suspension by ocean currents, leading to a rapid response to regional climate-driven inputs. In contrast, changes in magnetic mineralogy were linked to glacial-interglacial sea level variability, from which we infer a control by bedload transport and resuspension. Overall, this study indicates that the transfer pathways and mechanisms imparted by varying hydrodynamic conditions exert a substantial influence on the distribution of terrigenous material in continental margin sediments

The Magnetic Field Structure of Mercury’s Magnetotail

In this study, we use the magnetic field data measured by MErcury Surface, Space ENvironment, GEochemistry, and Ranging from 2011 to 2015 to investigate the average magnetic field morphology of Mercury’s magnetotail in the down tail 0–3 RM (RM = 2,440 km, Mercury’s radius). It is found that Mercury has a terrestrial‐like magnetotail; the magnetic field structure beyond 1.5 RM down tail is stretched significantly with typical lobe field 50 nT. A cross‐tail current sheet separating the antiparallel field lines of lobes is present in the equatorial plane. The magnetotail width in north‐south direction is about 5 RM, while the transverse width is about 4 RM. Thus, the magnetotail shows elongation along the north‐south direction. At the cross‐tail current sheet center, the normal component of magnetic field (10–20 nT) is much larger than the cross‐tail component. The lobe‐field‐aligned component of magnetic field over current sheet can be well fitted by Harris sheet model. The curvature radius of field lines at sheet center usually reaches a minimum around midnight (100–200 km) with stronger current density (40–50 nA/m2), while the curvature radius increases toward both flanks (400–600 km) with the decreased current density (about 20 nA/m2). The half‐thickness of current sheet around midnight is about 0.25 RM or 600 km, and the inner edge of current sheet is located at the down tail about 1.5 RM. Our results about the field structure in the near Mercury’s tail show an evident dawn‐dusk asymmetry as that found in the Earth’s magnetotail, but reasons should be different. Possible reasons are discussed.Key PointsThe magnetic field distribution, configuration, and current density in Mercury’s magnetotail are quantitatively addressedMercury’s magnetotail is elongated along the south‐north direction, which is probably due to the effect of the dipole offset or the induction effect of coreThe magnetic structure of tail current sheet shows a clear dawn‐dusk asymmetry with smaller Bz and less flaring field on the dusksidePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142544/1/jgra54041.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142544/2/jgra54041_am.pd

Rephasing Invariants of CP and T Violation in the Four-Neutrino Mixing Models

We calculate the rephasing invariants of CP and T violation in a favorable parametrization of the 4x4 lepton flavor mixing matrix. Their relations with the CP- and T-violating asymmetries in neutrino oscillations are derived, and the matter effects are briefly discussed.Comment: RevTex 9 pages. Slight changes. Phys. Rev. D (in press

Mercury's three‐dimensional asymmetric magnetopause

Mercury's magnetopause is unique in the solar system due to its relatively small size and its close proximity to the Sun. Based on 3 years of MErcury Surface, Space ENvironment, GEochemistry, and Ranging orbital Magnetometer and the Fast Imaging Plasma Spectrometer data, the mean magnetopause location was determined for a total of 5694 passes. We fit these magnetopause locations to a three‐dimensional nonaxially symmetric magnetopause which includes an indentation for the cusp region that has been successfully applied to the Earth. Our model predicts that Mercury's magnetopause is highly indented surrounding the cusp with central depth ~0.64 RM and large dayside extension. The dayside polar magnetopause dimension is, thus, smaller than the equatorial magnetopause dimension. Cross sections of the dayside magnetopause in planes perpendicular to the Mercury‐Sun line are prolate and elongated along the dawn‐dusk direction. In contrast, the magnetopause downstream of the terminator plane is larger in the north‐south than the east‐west directions by a ratio of 2.6 RM to 2.2 RM at a distance of 1.5 RM downstream of Mercury. Due to the northward offset of the internal dipole, the model predicts that solar wind has direct access to the surface of Mercury at middle magnetic latitudes in the southern hemisphere. During extremely high solar wind pressure conditions, the northern hemisphere middle magnetic latitudes may also be subject to direct solar wind impact.Key PointsMercury's magnetopause near‐cusp indentationMagnetotail cross sections elongated in north‐south directionExtreme solar wind pressure events were analyzedPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115924/1/jgra52083_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115924/2/jgra52083.pd

PM_{2.5} reductions in Chinese cities from 2013 to 2019 remain significant despite the inflating effects of meteorological conditions

Air pollution is a major environmental issue in China and imposes severe health burdens on Chinese citizens. Consequently, China has deployed a series of control measures to mitigate fine particulate matter (PM_{2.5}). However, the extent to which these measures have been effective is obscured by the existence of confounding meteorological effects. Here, we use a newly developed reduced-form model that can address emission-driven PM_{2.5} trends and control for meteorological effects to examine the level of PM_{2.5} reduction across 367 cities since the introduction of the Air Pollution Prevention and Control Action Plan (the Plan) in 2013. Our findings show that, on average, the national annual mean level of PM_{2.5} decreased by 34% from 2013 to 2019 after the removal of meteorological effects, about 10% less than the reduction level officially observed. Despite this difference, assuming that current control efforts continue through 2035, the long-term air-quality target of 35 μg/m^{3} as determined by the recently updated Plan will be met

SARS-related Virus Predating SARS Outbreak, Hong Kong

Using immunofluorescence and neutralization assays, we detected antibodies to human severe acute respiratory syndrome–associated coronavirus (SARS-CoV) and/or animal SARS-CoV–like virus in 17 (1.8%) of 938 adults recruited in 2001. This finding suggests that a small proportion of healthy persons in Hong Kong had been exposed to SARS-related viruses at least 2 years before the recent SARS outbreak