MESSENGER Magnetic Field Observations of Upstream Ultra-Low Frequency Waves at Mercury

The region upstream from a planetary bow shock is a natural plasma laboratory containing a variety of wave particle phenomena. The study of foreshocks other than the Earth's is important for extending our understanding of collisionless shocks and foreshock physics since the bow shock strength varies with heliocentric distance from the Sun, and the sizes of the bow shocks are different at different planets. The Mercury's bow shock is unique in our solar system as it is produced by low Mach number solar wind blowing over a small magnetized body with a predominately radial interplanetary magnetic field. Previous observations of Mercury upstream ultra-low frequency (ULF) waves came exclusively from two Mercury flybys of Mariner 10. The MESSENGER orbiter data enable us to study of upstream waves in the Mercury's foreshock in depth. This paper reports an overview of upstream ULF waves in the Mercury's foreshock using high-time resolution magnetic field data, 20 samples per second, from the MESSENGER spacecraft. The most common foreshock waves have frequencies near 2 Hz, with properties similar to the I-Hz waves in the Earth's foreshock. They are present in both the flyby data and in every orbit of the orbital data we have surveyed. The most common wave phenomenon in the Earth's foreshock is the large-amplitude 30-s waves, but similar waves at Mercury have frequencies at near 0.1 Hz and occur only sporadically with short durations (a few wave cycles). Superposed on the "30-s" waves, there are spectral peaks at near 0.6 Hz, not reported previously in Mariner 10 data. We will discuss wave properties and their occurrence characteristics in this paper

A Time to Mourn: Cultural Considerations and Community Preferences for Verbal Autopsy in Vietnam

Reliable mortality data becomes necessary to realise the full functioning of national health systems. Verbal autopsy (VA) is a viable tool to identify cause-of-death in Vietnam and has already utilised in a number of studies. This qualitative study (in-depth interviews and focus group discussions) had been done with the aim to examine the views of six ethnic groups in Vietnam on the suitable timing for implementing VA after a death. Recommendations on what were the suitable timing varied significantly between minorities ethnic groups, reflecting their particular cultural beliefs and burial practices. For the dominant Kinh people, the suitable timing for VA was around 49-100 days after the funeral. By providing better understanding of the best timing for VA interview, our study enables researchers to optimally use VA methods, producing more reliable data for mortality rates and cause of death in the lack of a complete vital registration in Vietnam

Take a Step Back: Evoking Reasoning via Abstraction in Large Language Models

We present Step-Back Prompting, a simple prompting technique that enables LLMs to do abstractions to derive high-level concepts and first principles from instances containing specific details. Using the concepts and principles to guide the reasoning steps, LLMs significantly improve their abilities in following a correct reasoning path towards the solution. We conduct experiments of Step-Back Prompting with PaLM-2L models and observe substantial performance gains on a wide range of challenging reasoning-intensive tasks including STEM, Knowledge QA, and Multi-Hop Reasoning. For instance, Step-Back Prompting improves PaLM-2L performance on MMLU Physics and Chemistry by 7% and 11%, TimeQA by 27%, and MuSiQue by 7%

Microwave sintering of porous Ti-Nb-HA composite with high strength and enhanced bioactivity for implant applications

In the present study, high order porous Ti-Nb(50-x)-HA(x) (x=0,10,20 wt. %) composites have been fabricated for orthopedic application by using powder metallurgical route consisting temporary space alloying and rapid microwave sintering process. Structural porosity, elastic modulus, compressive strength, corrosion resistance, and in-vitro bioactivity of as-sintered TiNb-HA composites were studied. Results showed that the reinforcement of the HA assists in the formation of structural porosity, which reduced the elastic modulus. Porous Ti-Nb (with HA 10- 20% content) composite possessed 40-60% structural porosity with a pore size of 150-260 μm and exhibited elastic modulus in the range of 12.5 – 29 GPa (near to human bone 8-20 GPa), which overcome the problem of stress shielding. The as-sintered composite not only possessed low elastic modulus but also exhibit high compressive strength (205-395 MPa). The alloying of HA improved the corrosion resistance and the protective efficiency of Ti-40Nb-10HA and Ti- 30Nb-20HA composites was measured 40% and 72%, respectively higher than the Ti-Nb composite. In-vitro biological evaluation tests confirmed that the developed composites are noncytotoxic and porous structure provides a vehicle for cell adhesion and growth. Moreover, various biocompatible phases such as Ca3(PO4)2 (known as TCP), Ti5P3 and CaO were developed, which helped in cell proliferation and differentiation. High biological activities were found on the Ti-30Nb-20HA composite have when compared with the Ti-Nb and Ti-40Nb-10HA composite and could be used as a potential biomaterial for the various possible orthopedic applications

Reward Shaping for User Satisfaction in a REINFORCE Recommender

How might we design Reinforcement Learning (RL)-based recommenders that encourage aligning user trajectories with the underlying user satisfaction? Three research questions are key: (1) measuring user satisfaction, (2) combatting sparsity of satisfaction signals, and (3) adapting the training of the recommender agent to maximize satisfaction. For measurement, it has been found that surveys explicitly asking users to rate their experience with consumed items can provide valuable orthogonal information to the engagement/interaction data, acting as a proxy to the underlying user satisfaction. For sparsity, i.e, only being able to observe how satisfied users are with a tiny fraction of user-item interactions, imputation models can be useful in predicting satisfaction level for all items users have consumed. For learning satisfying recommender policies, we postulate that reward shaping in RL recommender agents is powerful for driving satisfying user experiences. Putting everything together, we propose to jointly learn a policy network and a satisfaction imputation network: The role of the imputation network is to learn which actions are satisfying to the user; while the policy network, built on top of REINFORCE, decides which items to recommend, with the reward utilizing the imputed satisfaction. We use both offline analysis and live experiments in an industrial large-scale recommendation platform to demonstrate the promise of our approach for satisfying user experiences.Comment: Accepted in Reinforcement Learning for Real Life (RL4RealLife) Workshop in the 38th International Conference on Machine Learning, 202

Global observations of magnetospheric high‐m poloidal waves during the 22 June 2015 magnetic storm

We report global observations of high‐m poloidal waves during the recovery phase of the 22 June 2015 magnetic storm from a constellation of widely spaced satellites of five missions including Magnetospheric Multiscale (MMS), Van Allen Probes, Time History of Events and Macroscale Interactions during Substorm (THEMIS), Cluster, and Geostationary Operational Environmental Satellites (GOES). The combined observations demonstrate the global spatial extent of storm time poloidal waves. MMS observations confirm high azimuthal wave numbers (m ~ 100). Mode identification indicates the waves are associated with the second harmonic of field line resonances. The wave frequencies exhibit a decreasing trend as L increases, distinguishing them from the single‐frequency global poloidal modes normally observed during quiet times. Detailed examination of the instantaneous frequency reveals discrete spatial structures with step‐like frequency changes along L. Each discrete L shell has a steady wave frequency and spans about 1 RE, suggesting that there exist a discrete number of drift‐bounce resonance regions across L shells during storm times.Key PointsObserved long‐lasting high‐m poloidal waves associated with second harmonics of field line resonances during a major magnetic stormDemonstrated global spatial extent of storm time poloidal FLR region using observations from a constellation of widely spaced satellitesRevealed discrete spatial structures of resonant L shells with step‐like frequency changesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137558/1/grl55775_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137558/2/grl55775.pd

Sprouty2 mediated tuning of signalling is essential for somite myogenesis

Background: Negative regulators of signal transduction cascades play critical roles in controlling different aspects of normal embryonic development. Sprouty2 (Spry2) negatively regulates receptor tyrosine kinases (RTK) and FGF signalling and is important in differentiation, cell migration and proliferation. In vertebrate embryos, Spry2 is expressed in paraxial mesoderm and in forming somites. Expression is maintained in the myotome until late stages of somite differentiation. However, its role and mode of action during somite myogenesis is still unclear. Results: Here, we analysed chick Spry2 expression and showed that it overlaps with that of myogenic regulatory factors MyoD and Mgn. Targeted mis-expression of Spry2 led to inhibition of myogenesis, whilst its C-terminal domain led to an increased number of myogenic cells by stimulating cell proliferation. Conclusions: Spry2 is expressed in somite myotomes and its expression overlaps with myogenic regulatory factors. Overexpression and dominant-negative interference showed that Spry2 plays a crucial role in regulating chick myogenesis by fine tuning of FGF signaling through a negative feedback loop. We also propose that mir-23, mir-27 and mir-128 could be part of the negative feedback loop mechanism. Our analysis is the first to shed some light on in vivo Spry2 function during chick somite myogenesis

Prime Focus Spectrograph - Subaru's future -

The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project has been endorsed by Japanese community as one of the main future instruments of the Subaru 8.2-meter telescope at Mauna Kea, Hawaii. This optical/near-infrared multi-fiber spectrograph targets cosmology with galaxy surveys, Galactic archaeology, and studies of galaxy/AGN evolution. Taking advantage of Subaru's wide field of view, which is further extended with the recently completed Wide Field Corrector, PFS will enable us to carry out multi-fiber spectroscopy of 2400 targets within 1.3 degree diameter. A microlens is attached at each fiber entrance for F-ratio transformation into a larger one so that difficulties of spectrograph design are eased. Fibers are accurately placed onto target positions by positioners, each of which consists of two stages of piezo-electric rotary motors, through iterations by using back-illuminated fiber position measurements with a wide-field metrology camera. Fibers then carry light to a set of four identical fast-Schmidt spectrographs with three color arms each: the wavelength ranges from 0.38 {\mu}m to 1.3 {\mu}m will be simultaneously observed with an average resolving power of 3000. Before and during the era of extremely large telescopes, PFS will provide the unique capability of obtaining spectra of 2400 cosmological/astrophysical targets simultaneously with an 8-10 meter class telescope. The PFS collaboration, led by IPMU, consists of USP/LNA in Brazil, Caltech/JPL, Princeton, & JHU in USA, LAM in France, ASIAA in Taiwan, and NAOJ/Subaru.Comment: 13 pages, 11 figures, submitted to "Ground-based and Airborne Instrumentation for Astronomy IV, Ian S. McLean, Suzanne K. Ramsay, Hideki Takami, Editors, Proc. SPIE 8446 (2012)