IK-FA, a new heuristic inverse kinematics solver using firefly algorithm

In this paper, a heuristic method based on Firefly Algorithm is proposed for inverse kinematics problems in articulated robotics. The proposal is called, IK-FA. Solving inverse kinematics, IK, consists in finding a set of joint-positions allowing a specific point of the system to achieve a target position. In IK-FA, the Fireflies positions are assumed to be a possible solution for joints elementary motions. For a robotic system with a known forward kinematic model, IK-Fireflies, is used to generate iteratively a set of joint motions, then the forward kinematic model of the system is used to compute the relative Cartesian positions of a specific end-segment, and to compare it to the needed target position. This is a heuristic approach for solving inverse kinematics without computing the inverse model. IK-FA tends to minimize the distance to a target position, the fitness function could be established as the distance between the obtained forward positions and the desired one, it is subject to minimization. In this paper IK-FA is tested over a 3 links articulated planar system, the evaluation is based on statistical analysis of the convergence and the solution quality for 100 tests. The impact of key FA parameters is also investigated with a focus on the impact of the number of fireflies, the impact of the maximum iteration number and also the impact of (a, ß, ¿, d) parameters. For a given set of valuable parameters, the heuristic converges to a static fitness value within a fix maximum number of iterations. IK-FA has a fair convergence time, for the tested configuration, the average was about 2.3394 × 10-3 seconds with a position error fitness around 3.116 × 10-8 for 100 tests. The algorithm showed also evidence of robustness over the target position, since for all conducted tests with a random target position IK-FA achieved a solution with a position error lower or equal to 5.4722 × 10-9.Peer ReviewedPostprint (author's final draft

Automated Essay Scoring in Australian Schools: Collective Policymaking - Policy Brief

This policy brief outlines critical issues associated with policy and the use of Automated Essay Scoring (AES) technology in the Australian education system. The brief outlines recommends multi-scalar policy development informed by educators, policymakers, and representatives from educational technology companies engaging in cooperative learning and action

Automated Essay Scoring in Australian Schools: Key Issues and Recommendations White Paper

This white paper outlines critical issues associated with the use of Automated Essay Scoring (AES) technology in the Australian education system. The key insights presented in this paper emerged from a collaborative, multi-stakeholder workshop held in July 2022 that explored an automated essay-scoring trial and generated future possibilities aligned with participant interests and expertise. Drawing on the workshop and our expert understanding of the wider landscape, we propose recommendations that can be adopted by various stakeholders, schools, and educational systems

Correction to: Clinical Trials in High-Risk Medulloblastoma: Evolution of the SIOP-Europe HR-MB Trial (Cancers, (2022), 14, 2, (374), 10.3390/cancers14020374)

\ua9 2024 by the authors.In the original publication [1], the funder Cancer Research UK, A2524 was not included. Keith Wheatley, Simon Gates, and Victoria Homer were not included as authors in the original publication. The reason we would like to add the authors is that the statistical element of the trial and the trial design were in a large part done by the statistical authors and the team were necessary for the running of the trial. The corrected Author Contributions Statement appears here. Author Contributions: Conceptualization, S.B., N.A., L.G., M.M., K.W., S.R. and S.C.C.; methodology, K.W., S.G. and V.H.; project administration, S.G. and V.H.; resources, S.B., N.A., L.G., M.M., S.R. and S.C.C.; writing—original draft preparation, S.B., N.A., L.G., M.M., S.R. and S.C.C.; writing—review and editing, S.B., N.A., L.G., M.M., S.R. and S.C.C. All authors have read and agreed to the published version of the manuscript. Author Contributions: Conceptualization, S.B., N.A., L.G., M.M., K.W., S.R. and S.C.C.; methodology, K.W., S.G. and V.H.; project administration, S.G. and V.H.; resources, S.B., N.A., L.G., M.M., S.R. and S.C.C.; writing—original draft preparation, S.B., N.A., L.G., M.M., S.R. and S.C.C.; writing—review and editing, S.B., N.A., L.G., M.M., S.R. and S.C.C. All authors have read and agreed to the published version of the manuscript. Cancer Research UK Clinical Trials Unit, University of Birimingham, Birmingham B15 2TT, UK; [email protected](K.W.); [email protected] (S.G.); [email protected] (V.H.) The authors apologize for any inconvenience caused and state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated

Mercury in deep ice-rich permafrost deposits of Siberia. Russian Conference

The late Pleistocene ice-rich Yedoma permafrost is extremely sensitive to Arctic warming. Warming air temperatures, decreasing sea ice extent lead to an increasing degradation of the Yedoma permafrost and thus to a greater sediment input from coastal shorelines and river floodplains to the Laptev Sea. Thus, so far freeze-locked sediments and any potentially hazardous contaminants contained in them are entering Arctic waters and the biological food chain. Shallow (down to <2m) Arctic permafrost soil layers were found to include high levels of mercury (Hg) due to natural enrichment processes of environmentally available Hg (Schuster et al. 2018). However, opposed to seasonal thaw processes of the active layer and long-term gradual thaw through active layer deepening, abrupt thaw processes such as thermokarst, thermo-erosion, and coastal erosion are capable of mobilising permafrost-soils and stored contaminants from tens of meters depth within years to decades. In this study, we determined Hg concentrations from various deposits in Siberia’s deep permafrost sediments. We studied links between sediment properties and Hg enrichment in order to assess a first deep Hg inventory in late Pleistocene permafrost down to 36 m below surface. To do this, we used sediment profiles from seven sites representing different permafrost degradation states on Bykovsky Peninsula (northern Yakutian coast) and in the Yukechi Alas region (Central Yakutia). We analysed 41 samples for Hg content, total carbon, total nitrogen and organic carbon as well as grain size distribution, bulk density and mass specific magnetic susceptibility. Figure 1: (a) geographical overview and detailed location of the study site at Bykovsky Peninsula (b) and Yukechi Alas in Yakutia (c); (d) stratigraphical transect of the study sites and different states of degrading permafrost in Siberia. The numbers indicate the areas of interest in this study. 1) Talik in Yedoma (unfrozen), 2) late Pleistocene Yedoma (frozen), 3) talik in thermokarst (unfrozen), 4) refrozen drained lake basin = Alas (frozen), 5) talik in thermokarst close to sea (unfrozen), 6) talik below seawater flooded thermokarst basins (= lagoons) (unfrozen). We show that the deep sediments (to 30 meter below surface) are characterized by an Hg concentration of 9.72 ± 9.28 μg kg-1 and an correlation of Hg to organic carbon, total nitrogen, grain-size distribution and mass specific magnetic susceptibility. Hg concentrations are higher in the generally sandier sediment of the Bykovsky Peninsula than in the siltier sediment of the Yukechi Alas. In conclusion, we found that the deep permafrost sediments, frozen since tens of millennia, contain sizeable amounts of Hg. Even though the average amount of Hg is with 9.72 μg/kg below levels immediately critical for life and our median is 85 % less (Schuster et al. 2018) than found in Arctic topsoil outside Siberia. Even if the Hg concentrations are not particularly high compared to other sites, the permafrost’s huge spatial coverage results in a significant amount of Hg that can be introduce into nearby aquatic environments and food webs. As the next step, the consequences of old Hg re-entering the active biogeochemical cycles and food webs with ongoing Arctic warming remain unclear and need to be studied in more detail. References 1. Schuster, P. et al. Geophysical Research Letters, 2018, 45, 1463– 1471, https://doi.org/10.1002/2017GL07557

NADPH and glutathione redox link TCA cycle activity to endoplasmic reticulum homeostasis

Many metabolic diseases disrupt endoplasmic reticulum (ER) homeostasis, but little is known about how metabolic activity is communicated to the ER. Here, we show in hepatocytes and other metabolically active cells that decreasing the availability of substrate for the tricarboxylic acid (TCA) cycle diminished NADPH production, elevated glutathione oxidation, led to altered oxidative maturation of ER client proteins, and attenuated ER stress. This attenuation was prevented when glutathione oxidation was disfavored. ER stress was also alleviated by inhibiting either TCA-dependent NADPH production or Glutathione Reductase. Conversely, stimulating TCA activity increased NADPH production, glutathione reduction, and ER stress. Validating these findings, deletion of the Mitochondrial Pyruvate Carrier-which is known to decrease TCA cycle activity and protect the liver from steatohepatitis-also diminished NADPH, elevated glutathione oxidation, and alleviated ER stress. Together, our results demonstrate a novel pathway by which mitochondrial metabolic activity is communicated to the ER through the relay of redox metabolites

Constraining stellar assembly and AGN feedback at the peak epoch of star formation

We study stellar assembly and feedback from active galactic nuclei (AGN) around the epoch of peak star formation (1<z<2), by comparing hydrodynamic simulations to rest-frame UV-optical galaxy colours from the Wide Field Camera 3 (WFC3) Early-Release Science (ERS) Programme. Our Adaptive Mesh Refinement simulations include metal-dependent radiative cooling, star formation, kinetic outflows due to supernova explosions, and feedback from supermassive black holes. Our model assumes that when gas accretes onto black holes, a fraction of the energy is used to form either thermal winds or sub-relativistic momentum-imparting collimated jets, depending on the accretion rate. We find that the predicted rest-frame UV-optical colours of galaxies in the model that includes AGN feedback is in broad agreement with the observed colours of the WFC3 ERS sample at 1<z<2. The predicted number of massive galaxies also matches well with observations in this redshift range. However, the massive galaxies are predicted to show higher levels of residual star formation activity than the observational estimates, suggesting the need for further suppression of star formation without significantly altering the stellar mass function. We discuss possible improvements, involving faster stellar assembly through enhanced star formation during galaxy mergers while star formation at the peak epoch is still modulated by the AGN feedback.Comment: 6 pages, 4 figures, accepted for publication in MNRAS Letter

UV-dropout Galaxies in the GOODS-South Field from WFC3 Early Release Science Observations

We combine new high sensitivity ultraviolet (UV) imaging from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) with existing deep HST/Advanced Camera for Surveys (ACS) optical images from the Great Observatories Origins Deep Survey (GOODS) program to identify UV-dropouts, which are Lyman break galaxy (LBG) candidates at z~1-3. These new HST/WFC3 observations were taken over 50 sq.arcmin in the GOODS-South field as a part of the Early Release Science program. The uniqueness of these new UV data is that they are observed in 3 UV/optical (WFC3 UVIS) channel filters (F225W, F275W and F336W), which allows us to identify three different sets of UV-dropout samples. We apply Lyman break dropout selection criteria to identify F225W-, F275W- and F336W-dropouts, which are z~1.7, 2.1 and 2.7 LBG candidates, respectively. Our results are as follows: (1) these WFC3 UVIS filters are very reliable in selecting LBGs with z~2.0, which helps to reduce the gap between the well studied z~>3 and z~0 regimes, (2) the combined number counts agrees very well with the observed change in the surface densities as a function of redshift when compared with the higher redshift LBG samples; and (3) the best-fit Schechter function parameters from the rest-frame UV luminosity functions at three different redshifts fit very well with the evolutionary trend of the characteristic absolute magnitude, and the faint-end slope, as a function of redshift. This is the first study to illustrate the usefulness of the WFC3 UVIS channel observations to select z<3 LBGs. The addition of the new WFC3 on the HST has made it possible to uniformly select LBGs from z~1 to z~9, and significantly enhance our understanding of these galaxies using HST sensitivity and resolution.Comment: Accepted for publication in ApJ (24 pages, 7 figures

Stellar Populations of Lyman Break Galaxies at z=1-3 in the HST/WFC3 Early Release Science Observations

We analyze the spectral energy distributions (SEDs) of Lyman break galaxies (LBGs) at z=1-3 selected using the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) UVIS channel filters. These HST/WFC3 observations cover about 50 sq. arcmin in the GOODS-South field as a part of the WFC3 Early Release Science program. These LBGs at z=1-3 are selected using dropout selection criteria similar to high redshift LBGs. The deep multi-band photometry in this field is used to identify best-fit SED models, from which we infer the following results: (1) the photometric redshift estimate of these dropout selected LBGs is accurate to within few percent; (2) the UV spectral slope (beta) is redder than at high redshift (z>3), where LBGs are less dusty; (3) on average, LBGs at z=1-3 are massive, dustier and more highly star-forming, compared to LBGs at higher redshifts with similar luminosities (0.1L*<~L<~2.5L*), though their median values are similar within 1-sigma uncertainties. This could imply that identical dropout selection technique, at all redshifts, find physically similar galaxies; and (4) stellar masses of these LBGs are directly proportional to their UV luminosities with a logarithmic slope of ~0.46, and star-formation rates are proportional to their stellar masses with a logarithmic slope of ~0.90. These relations hold true --- within luminosities probed in this study --- for LBGs from z~1.5 to 5. The star-forming galaxies selected using other color-based techniques show similar correlations at z~2, but to avoid any selection biases, and for direct comparison with LBGs at z>3, a true Lyman break selection at z~2 is essential. The future HST UV surveys, both wider and deeper, covering a large luminosity range are important to better understand LBG properties, and their evolution.Comment: Accepted for publication in ApJ (29 pages, 9 figures

A link between the ice nucleation activity and the biogeochemistry of seawater

Emissions of ice-nucleating particles (INPs) from sea spray can impact climate and precipitation by changing cloud formation, precipitation, and albedo. However, the relationship between seawater biogeochemistry and the ice nucleation activity of sea spray aerosols remains unclarified. Here, we demonstrate a link between the biological productivity in seawater and the ice nucleation activity of sea spray aerosol under conditions relevant to cirrus and mixed-phase cloud formation. We show for the first time that aerosol particles generated from both subsurface and microlayer seawater from the highly productive eastern tropical North Pacific Ocean are effective INPs in the deposition and immersion freezing modes. Seawater particles of composition similar to subsurface waters of highly productive regions may therefore be an unrealized source of effective INPs. In contrast, the subsurface water from the less productive Florida Straits produced less effective immersion mode INPs and ineffective depositional mode INPs. These results indicate that the regional biogeochemistry of seawater can strongly affect the ice nucleation activity of sea spray aerosol