Optimization of the final settings for the Space-borne Hard X-ray Compton Polarimeter POLAR

POLAR is a compact wide field space-borne detector dedicated for precise measurements of the linear polarization of hard X-rays emitted by transient sources in the energy range from 50 keV to 500 keV. It consists of 1600 plastic scintillator bars grouped in 25 detector modules that are used as gamma-ray detection material. Its energy range sensitivity is optimized for detection of the prompt emission photons from the gamma-ray bursts. Measurements of the GRB polarization provide unique information on emission mechanisms as well as on composition and structure of the GRB jets. The POLAR instrument was developed by international collaboration of Switzerland, China and Poland. It was launched in space on-board the China Space Laboratory TG-2 on September 15th, 2016. Based on the ground calibration data, several high voltage and threshold settings were calculated and verified in order to obtain various energy ranges and optimized signal to background conditions for different measurement purposes. In this paper we present optimization procedure details and current test results.Comment: For 2017 ICRC conferenc

A Novel Algorithm for Solving Structural Optimization Problems

In the past few decades, metaheuristic optimization methods have emerged as an effective approach for addressing structural design problems. Structural optimization methods are based on mathematical algorithms that are population-based techniques. Optimization methods use technology development to employ algorithms to search through complex solution space to find the minimum. In this paper, a simple algorithm inspired by hurricane chaos is proposed for solving structural optimization problems. In general, optimization algorithms use equations that employ the global best solution that might cause the algorithm to get trapped in a local minimum. Hence, this methodology is avoided in this work. The algorithm was tested on several common truss examples from the literature and proved efficient in finding lower weights for the test problems

Unconstrained Dynamic Simulation on Offshore Dual Derrick

With the increase in demand for oil and oil products, the petroleum industry is faced with the requirement for more complex tools to increase production at lower prices. The complexity of drilling tools is manifested in the complex geometry, fabrication, assembly, deformations, stresses and loads acting on them. This study introduces a dual derrick simulation procedure in a marine environment which provides a step towards a better understanding by giving a simulation close to the real state. The derrick was considered in equilibrium, and then the derrick vibration was simulated using field data in order to obtain stress distribution. This implies that the derrick can move freely and cause deformations in all directions without constraints. In this paper, the finite element method was employed to simulate the derrick in a static state and in motion, and then the obtained stress distribution was compared for both cases. A literature review on the analysis of environment working conditions is provided. The results showed that the vibration of the platform increased the stress considerably. The maximum combined stress increased by 27 %, while the maximum bending stress increased by 40 % and reached considerably higher values in the beams connected to the top of the derrick

The Lyman-α\alpha Emission in a C1.4 Solar Flare Observed by the Extreme Ultraviolet Imager aboard Solar Orbiter

The hydrogen Lyman-$\alpha$ (H {\sc i} Ly$\alpha$) emission during solar flares has rarely been studied in spatially resolved images and its physical origin has not been fully understood. In this paper, we present novel Ly$\alpha$ images for a C1.4 solar flare (SOL2021-08-20T22:00) from the Extreme Ultraviolet Imager aboard Solar Orbiter, together with multi-waveband and multi-perspective observations from the Solar Terrestrial Relations Observatory Ahead and the Solar Dynamics Observatory spacecraft. It is found that the Ly$\alpha$ emission has a good temporal correlation with the thermal emissions at 1--8 \AA\ and 5--7 keV, indicating that the flaring Ly$\alpha$ is mainly produced by a thermal process in this small event. However, nonthermal electrons play a minor role in generating Ly$\alpha$ at flare ribbons during the rise phase of the flare, as revealed by the hard X-ray imaging and spectral fitting. Besides originating from flare ribbons, the Ly$\alpha$ emission can come from flare loops, likely caused by plasma heating and also cooling that happen in different flare phases. It is also found that the Ly$\alpha$ emission shows fairly similar features with the He {\sc ii} 304 \AA\ emission in light curve and spatio-temporal variation along with small differences. These observational results improve our understanding of the Ly$\alpha$ emission in solar flares and also provide some insights for investigating the Ly$\alpha$ emission in stellar flares.Comment: 19 pages, 7 figures, and 2 tables. ApJ accepted. Comments are welcom

Lack of Protection following Passive Transfer of Polyclonal Highly Functional Low-Dose Non-Neutralizing Antibodies

Recent immune correlates analysis from the RV144 vaccine trial has renewed interest in the role of non-neutralizing antibodies in mediating protection from infection. While neutralizing antibodies have proven difficult to induce through vaccination, extra-neutralizing antibodies, such as those that mediate antibody-dependent cellular cytotoxicity (ADCC), are associated with long-term control of infection. However, while several non-neutralizing monoclonal antibodies have been tested for their protective efficacy in vivo, no studies to date have tested the protective activity of naturally produced polyclonal antibodies from individuals harboring potent ADCC activity. Because ADCC-inducing antibodies are highly enriched in elite controllers (EC), we passively transferred highly functional non-neutralizing polyclonal antibodies, purified from an EC, to assess the potential impact of polyclonal non-neutralizing antibodies on a stringent SHIV-SF162P3 challenge in rhesus monkeys. Passive transfer of a low-dose of ADCC inducing antibodies did not protect from infection following SHIV-SF162P3 challenge. Passively administered antibody titers and gp120-specific, but not gp41-specific, ADCC and antibody induced phagocytosis (ADCP) were detected in the majority of the monkeys, but did not correlate with post infection viral control. Thus these data raise the possibility that gp120-specific ADCC activity alone may not be sufficient to control viremia post infection but that other specificities or Fc-effector profiles, alone or in combination, may have an impact on viral control and should be tested in future passive transfer experiments