Spatial distribution of Mercury’s flux ropes and reconnection fronts: MESSENGER observations

We perform a statistical study of flux ropes and reconnection fronts based on MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) magnetic field and plasma observations to study the implications for the spatial distribution of reconnection sites in Mercury’s near magnetotail. The results show important differences of temporal and spatial distributions as compared to Earth. We have surveyed the plasma sheet crossings between −2 RM and −3 RM downtail from the planet, i.e., the location of Near‐Mercury Neutral Line (NMNL). Plasma sheets were defined to be regions with β ≥ 0.5. Using this definition, 39 flux ropes and 86 reconnection fronts were identified in the plasma sheet. At Mercury, the distributions of flux ropes and reconnection fronts show clear dawn‐dusk asymmetry with much higher occurrence rate on the dawnside plasma sheet than on the duskside. This suggests that magnetic reconnection in Mercury’s magnetotail occurs more frequently in the dawnside than in the duskside plasma sheet, which is different than the observations in Earth’s magnetotail showing more reconnection signatures in the duskside plasma sheet. The distribution of plasma sheet thickness shows that plasma sheet near the midnight is the thinnest part and does not show obvious asymmetry. Thus, the reasons that cause magnetic reconnection to preferentially occur on the dawnside of the magnetotail at Mercury may not be the plasma sheet thickness and require further study. The peak occurrence rates of flux ropes and reconnection fronts in Mercury’s plasma sheet are ~ 60 times higher than that of Earth’s values, which we interpret to be due to the highly variable magnetospheric conditions at Mercury. Such higher occurrence rate of magnetic reconnection would generate more plasma flows in the dawnside plasma sheet than in the duskside. These plasma flows would mostly brake and initiate the substorm dipolarization on the postmidnight sector at Mercury rather than the premidnight susbtorm onset location at Earth.Key PointsOccurrence rate of FRs and RFs at Mercury is ~ 60 times higher than at Earth, due to the variable magnetospheric conditions at MercuryMagnetic reconnection occurs more frequently in the dawnside than in the duskside in Mercury’s plasma sheet, opposite to Earth’s resultsPlasma flows would brake and initiate dipolarizations on the postmidnight sector at Mercury different to the premidnight locations at EarthPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134095/1/jgra52821.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134095/2/jgra52821_am.pd

Viral quasispecies inference from 454 pyrosequencing

10.1186/1471-2105-14-355BMC Bioinformatics141-BBMI

ToyBox Study Malaysia: improving healthy energy balance and obesity-related behaviours among pre-schoolers in Malaysia

The prevalence of childhood overweight and obesity is increasing in Malaysia and currently nearly 10% of children aged between 6 months and 12 years are overweight and almost 12% are obese. Early interventions to prevent excess weight gain are needed. ToyBox Study Malaysia is a feasibility project, funded by the Medical Research Council Newton-Ungku Omar Fund, to assess the practicalities of adapting the existing European ToyBox Study intervention programme to the Malaysian kindergarten setting. The main aims of all ToyBox programmes are related to improving four key energy balance-related behaviours, namely drinking water, eating healthy snacks and meals, reducing sedentary behaviour and increasing physical activity. Using stratified sampling, the ToyBox Study Malaysia intervention will be delivered and compared to usual practice by assessing behaviour, physical activity and health-related outcomes as measured by questionnaires, accelerometry and anthropometry. It is hoped that the evidence-based ToyBox Study Malaysia will help to achieve healthier energy balance-related behaviours in the children and their families and provide lifelong benefits to health. This article provides information on the dietary patterns, physical activity levels and prevalence of overweight and obesity in Malaysian children, and the approach of the ToyBox Study Malaysia

A Statistical Study of the Force Balance and Structure in the Flux Ropes in Mercury’s Magnetotail

This study presents a statistical investigation of the force balance and structures in the flux ropes in Mercury’s magnetotail plasma sheet by using the measurements of MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER). One hundred sixty-eight flux ropes were identified from the 14 hot seasons of MESSENGER from 11 March 2011 to 30 April 2015, and 143 of them show clear magnetic field enhancements with the core field being -20% higher than the background magnetic field. The investigation on the force balance of these 143 flux ropes shows that magnetic pressure gradient force cannot be solely balanced by magnetic tension force, implying that thermal plasma pressure gradient force cannot be neglected in the flux ropes. We employ a non-force-free model considering the contribution of thermal pressure to resolve the physical properties of flux ropes in Mercury’s magnetotail. Twenty-eight flux ropes are obtained through the fitting to the non-force-free model. The flux ropes are found to be consistent with the flattened structures, in which the mean semimajor is -851 km and semiminor is -333 km, both are several times the local proton inertial length. The average core field is estimated to be -57.5 nT, and flux content is -0.019 MWb, much larger than the previous results obtained from force-free flux rope model. The importance of thermal pressure gradient in the force balance of the flux ropes and the flattened structure indicates that the flux ropes in Mercury’s magnetotail plasma sheet are mostly in early stage of the evolution, and still contain enough plasma to affect their magnetic structures.Key PointsThermal pressure gradient is significant for the flux ropes in Mercury’s magnetotailNon-force-free modeling reveals the flatten structure and much higher magnetic flux of the flux ropes different from the previous studiesFlux ropes in this study should be in their early stage of evolution and could be strongly affected by thermal pressurePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151305/1/jgra55044_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151305/2/jgra55044.pd

Process evaluation of a kindergarten-based intervention for obesity prevention in early childhood: the Toybox study Malaysia

BackgroundToybox is a kindergarten-based intervention program that targets sedentary behavior, snacking and drinking habits, as well as promoting physical activity in an effort to improve healthy energy balance-related behaviors among children attending kindergartens in Malaysia. The pilot of this program was conducted as a randomized controlled trial (RCT) involving 837 children from 22 intervention kindergartens and 26 control kindergartens respectively. This paper outlines the process evaluation of this intervention.MethodsWe assessed five process indicators: recruitment, retention, dosage, fidelity, and satisfaction for the Toybox program. Data collection was conducted via teachers’ monthly logbooks, post-intervention feedback through questionnaires, and focus group discussions (FGD) with teachers, parents, and children. Data were analyzed using quantitative and qualitative data analysis methods.ResultsA total of 1072 children were invited. Out of the 1001 children whose parents consented to join, only 837 completed the program (Retention rate: 88.4%). As high as 91% of the 44 teachers and their assistants engaged positively in one or more of the process evaluation data collection methods. In terms of dosage and fidelity, 76% of parents had received newsletters, tip cards, and posters at the appropriate times. All teachers and their assistants felt satisfied with the intervention program. However, they also mentioned some barriers to its implementation, including the lack of suitable indoor environments to conduct activities and the need to make kangaroo stories more interesting to captivate the children’s attention. As for parents, 88% of them were satisfied with the family-based activities and enjoyed them. They also felt that the materials provided were easy to understand and managed to improve their knowledge. Lastly, the children showed positive behaviors in consuming more water, fruits, and vegetables.ConclusionsThe Toybox program was deemed acceptable and feasible to implement by the parents and teachers. However, several factors need to be improved before it can be expanded and embedded as a routine practice across Malaysia

Multiple Traits for People Identification

Present biometric systems mostly rely on a single physical or behavioral feature for either identification or verification. However, day to day use of single biometries in massive or uncontrolled scenarios still has several shortcomings. These can be due to complex or unstable hardware settings, to changing environmental conditions or even to immature software procedures: some classification problems are intrinsically hard to solve. Possible spoofing of single biometric features is an additional issue. Last but not least, some features may occasionally lack the requisite of universality. As a consequence, biometric systems based on a single feature often have poor reliability, especially in applications where high security is needed. Multimodal systems, i.e., systems that concurrently exploit multiple features, are a possible way to achieve improved effectiveness and reliability. There are several issues that must be addressed when designing such a system, including the choice of the set of biometric features, the normalization method, the integration schema and the fusion process, and the use of a measure of reliability for each subsystem on a single response basis. This chapter describes the state of the art regarding such issues and sketches some suggestions for future work

Discovery of very-high-energy emission from RGB J2243+203 and derivation of its redshift upper limit

Very-high-energy (VHE; $>$ 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 21 and 24 December 2014. The VERITAS energy spectrum from this source can be fit by a power law with a photon index of $4.6 \pm 0.5$, and a flux normalization at 0.15 TeV of $(6.3 \pm 1.1) \times 10^{-10} ~ \textrm{cm}^{-2} \textrm{s}^{-1} \textrm{TeV}^{-1}$. The integrated \textit{Fermi}-LAT flux from 1 GeV to 100 GeV during the VERITAS detection is $(4.1 \pm 0.8) \times 10^{\textrm{-8}} ~\textrm{cm}^{\textrm{-2}}\textrm{s}^{\textrm{-1}}$, which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, ($4.0 \pm 0.1 \times 10^{\textrm{-9}} ~ \textrm{cm}^{\textrm{-2}}\textrm{s}^{\textrm{-1}}$). The detection with VERITAS triggered observations in the X-ray band with the \textit{Swift}-XRT. However, due to scheduling constraints \textit{Swift}-XRT observations were performed 67 hours after the VERITAS detection, not simultaneous with the VERITAS observations. The observed X-ray energy spectrum between 2 keV and 10 keV can be fitted with a power-law with a spectral index of $2.7 \pm 0.2$, and the integrated photon flux in the same energy band is $(3.6 \pm 0.6) \times 10^{-13} ~\textrm{cm}^{-2} \textrm{s}^{-1}$. EBL model-dependent upper limits of the blazar redshift have been derived. Depending on the EBL model used, the upper limit varies in the range from z $<~0.9$ to z $<~1.1$

MMS Study of the Structure of Ionâ Scale Flux Ropes in the Earth’s Crossâ Tail Current Sheet

This study analyzes 25 ionâ scale flux ropes in the Magnetospheric Multiscale (MMS) observations to determine their structures. The high temporal and spatial resolution MMS measurements enable the application of multispacecraft techniques to ionâ scale flux ropes. Flux ropes are identified as quasiâ oneâ dimensional (quasiâ 1â D) when they retain the features of reconnecting current sheets; that is, the magnetic field gradient is predominantly northward or southward, and quasiâ 2â D when they exhibit circular cross sections; that is, the magnetic field gradients in the plane transverse to the flux rope axis are comparable. The analysis shows that the quasiâ 2â D events have larger core fields and smaller pressure variations than the quasiâ 1â D events. These two types of flux ropes could be the result of different processes, including magnetic reconnection with different dawnâ dusk magnetic field components, temporal transformation of flattened structure to circular, or interactions with external environments.Plain Language SummaryMagnetic flux ropes are fundamental magnetic structures in space plasma physics and are commonly seen in the universe, such as, astrophysical jets, coronal mass ejections, and planetary magnetospheres. Flux ropes are important in mass and energy transport across plasma and magnetic boundaries, and they are found in a wide range of spatial sizes, from several tens of kilometers, that is, ionâ scale flux ropes, to tens of millions of kilometers, that is, coronal mass ejections, in the solar system. The ionâ scale flux ropes can be formed during magnetic reconnection and are hypothesized to energize electrons and influence the reconnection rate. Previous examinations of the structure of ionâ scale flux ropes were greatly limited by measurement resolution. The unprecedented Magnetospheric Multiscale (MMS) mission high temporal and spatial resolution measurements provide a unique opportunity to investigate flux rope structures. By employing multispacecraft techniques, this study has provided new insights into the magnetic field variations and dimensionality of ionâ scale flux ropes in the Earth’s magnetotail. The results are consistent with the evolution of ionâ scale flux ropes from initially flattened current sheetâ like flux ropes near the time of formation into lower energy state with circular cross section predicted by theory and termed as the â Taylorâ state.Key PointsIonâ scale flux ropes are observed to have either flattened or circular cross sections using MDD and GS reconstructionAnalysis of 25 flux ropes show that circular crossâ section flux ropes have stronger core field and smaller thermal pressures than flattened flux ropesThe two types of flux ropes may be the results of reconnection, temporal evolution, or interactions with external environmentPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150544/1/grl59049.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150544/2/grl59049_am.pd

Planar Graph Coloring with Forbidden Subgraphs: Why Trees and Paths Are Dangerous

We consider the problem of coloring a planar graph with the minimum number of colors such that each color class avoids one or more forbidden graphs as subgraphs. We perform a detailed study of the computational complexity of this problem. We present a complete picture for the case with a single forbidden connected (induced or non-induced) subgraph. The 2-coloring problem is NP-hard if the forbidden subgraph is a tree with at least two edges, and it is polynomially solvable in all other cases. The 3-coloring problem is NP-hard if the forbidden subgraph is a path, and it is polynomially solvable in all other cases. We also derive results for several forbidden sets of cycles

3D Magnetic Reconnection with a spatially confined X-line extent -- Implications for Dipolarizing Flux Bundles and the Dawn-Dusk Asymmetry

Using 3D particle-in-cell (PIC) simulations, we study magnetic reconnection with the x-line being spatially confined in the current direction. We include thick current layers to prevent reconnection at two ends of a thin current sheet that has a thickness on an ion inertial (di) scale. The reconnection rate and outflow speed drop significantly when the extent of the thin current sheet in the current direction is < O(10 di). When the thin current sheet extent is long enough, we find it consists of two distinct regions; an inactive region (on the ion-drifting side) exists adjacent to the active region where reconnection proceeds normally as in a 2D case. The extent of this inactive region is ~ O(10 di), and it suppresses reconnection when the thin current sheet extent is comparable or shorter. The time-scale of current sheet thinning toward fast reconnection can be translated into the spatial-scale of this inactive region; because electron drifts inside the ion diffusion region transport the reconnected magnetic flux, that drives outflows and furthers the current sheet thinning, away from this region. This is a consequence of the Hall effect in 3D. While this inactive region may explain the shortest possible azimuthal extent of dipolarizing flux bundles at Earth, it may also explain the dawn-dusk asymmetry observed at the magnetotail of Mercury, that has a global dawn-dusk extent much shorter than that of Earth.Comment: 9 pages, 9 figures, submitted to JGR on 01/23/201