Deep Reinforcement Learning (DRL) algorithms have been increasingly employed during the last decade to solve various decision-making problems such as autonomous driving, trading decisions, and ...robotics. However, these algorithms have faced great challenges when deployed in safety-critical environments since they often exhibit erroneous behaviors that can lead to potentially critical errors. One of the ways to assess the safety of DRL agents is to test them to detect possible faults leading to critical failures during their execution. This raises the question of how we can efficiently test DRL policies to ensure their correctness and adherence to safety requirements. Most existing works on testing DRL agents use adversarial attacks that perturb states or actions of the agent. However, such attacks often lead to unrealistic states of the environment. Furthermore, their main goal is to test the robustness of DRL agents rather than testing the compliance of the agents' policies with respect to requirements. Due to the huge state space of DRL environments, the high cost of test execution, and the black-box nature of DRL algorithms, exhaustive testing of DRL agents is impossible. In this paper, we propose a Search-based Testing Approach of Reinforcement Learning Agents (STARLA) to test the policy of a DRL agent by effectively searching for failing executions of the agent within a limited testing budget. We rely on machine learning models and a dedicated genetic algorithm to narrow the search toward faulty episodes (i.e., sequences of states and actions produced by the DRL agent). We apply STARLA on Deep-Q-Learning agents trained on two different RL problems widely used as benchmarks and show that STARLA significantly outperforms Random Testing by detecting more faults related to the agent's policy. We also investigate how to extract rules that characterize faulty episodes of the DRL agent using our search results. Such rules can be used to understand the conditions under which the agent fails and thus assess the risks of deploying it.
MicroRNAs are ∼21-nucleotide-long regulators of gene expression that gain access to their target mRNAs by complementary base pairing. Recent studies have revealed that animal microRNAs might take ...diverse routes to repress gene expression, affecting both target mRNA levels and translation. Mechanistic details of microRNA-mediated repression are starting to emerge but a comprehensive picture of the inhibition, and particularly the effects on mRNA translation, is still lacking. Recent data support different microRNA mechanisms and a role for cytoplasmic processing bodies in the degradation and storage of mRNAs targeted by microRNA regulators.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Repetitive-element-derived Piwi-interacting RNAs (piRNAs) act together with Piwi proteins Mili (also known as Piwil2) and Miwi2 (also known as Piwil4) in a genome defence mechanism that initiates ...transposon silencing via DNA methylation in the mouse male embryonic germ line. This silencing depends on the participation of the Piwi proteins in a slicer-dependent piRNA amplification pathway and is essential for male fertility. A third Piwi family member, Miwi (also known as Piwil1), is expressed in specific postnatal germ cells and associates with a unique set of piRNAs of unknown function. Here we show that Miwi is a small RNA-guided RNase (slicer) that requires extensive complementarity for target cleavage in vitro. Disruption of its catalytic activity in mice by a single point mutation causes male infertility, and mutant germ cells show increased accumulation of LINE1 retrotransposon transcripts. We provide evidence for Miwi slicer activity directly cleaving transposon messenger RNAs, offering an explanation for the continued maintenance of repeat-derived piRNAs long after transposon silencing is established in germline stem cells. Furthermore, our study supports a slicer-dependent silencing mechanism that functions without piRNA amplification. Thus, Piwi proteins seem to act in a two-pronged mammalian transposon silencing strategy: one promotes transcriptional repression in the embryo, the other reinforces silencing at the post-transcriptional level after birth.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Compressive strength characteristics analysed using microstructural investigation.•Binders mixed with lower mass ratio of SS/SH tend to react more efficiently.•Evaporation of free water molecule ...causes weight loss in the specimen.•Nano materials in binders with low pozzolanic oxide content is important to form SiOAlO bond.
The utmost priority in reducing the usage of ordinary Portland cement (OPC) while replicating the cementitious properties by utilizing industrial by-products in construction materials is seriously undertaken by many researchers. The technology of geopolymerization that utilizes materials and activator solution to form geopolymer matrix could lead to alleviate some of the issues related to OPC based concrete. Numerous experiments have established that geopolymer concrete has higher compressive strength, higher acid resistivity and lower shrinkage than ordinary concrete. This review article focusses on the microstructure analyses of the geopolymer specimens and comparison of geopolymers with various binders. The review analysis of various binders used and their microstructural investigations reveal that different molarity of sodium hydroxide or phosphoric acid solution, liquid-to-binder ratio, curing temperature and duration yield geopolymers of diverse properties. Most of the geopolymer products revealed a wide hump in the XRD analysis due to the amorphous structure of aluminosilicate. Investigation of MIP and Micro CT reveals that aged geopolymer has a denser matrix arrangement and produce high compressive strength. Geopolymerization prevents interconnectivity of micropores due to the formation of denser matrix of geopolymer gel. Generally, the use of 12M of sodium hydroxide solution, low liquid-to-binder ratio of about 0.4 and curing temperature at approximately 70 °C for at least 24 h produced high strength geopolymers. The binders mixed with lower sodium silicate to sodium hydroxide mass ratio of 2.0–2.5 tend to react more efficiently.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Understanding adaptive immunity to SARS-CoV-2 is important for vaccine development, interpreting coronavirus disease 2019 (COVID-19) pathogenesis, and calibration of pandemic control measures. Using ...HLA class I and II predicted peptide “megapools,” circulating SARS-CoV-2-specific CD8+ and CD4+ T cells were identified in ∼70% and 100% of COVID-19 convalescent patients, respectively. CD4+ T cell responses to spike, the main target of most vaccine efforts, were robust and correlated with the magnitude of the anti-SARS-CoV-2 IgG and IgA titers. The M, spike, and N proteins each accounted for 11%–27% of the total CD4+ response, with additional responses commonly targeting nsp3, nsp4, ORF3a, and ORF8, among others. For CD8+ T cells, spike and M were recognized, with at least eight SARS-CoV-2 ORFs targeted. Importantly, we detected SARS-CoV-2-reactive CD4+ T cells in ∼40%–60% of unexposed individuals, suggesting cross-reactive T cell recognition between circulating “common cold” coronaviruses and SARS-CoV-2.
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•Measuring immunity to SARS-CoV-2 is key for understanding COVID-19 and vaccine development•Epitope pools detect CD4+ and CD8+ T cells in 100% and 70% of convalescent COVID patients•T cell responses are focused not only on spike but also on M, N, and other ORFs•T cell reactivity to SARS-CoV-2 epitopes is also detected in non-exposed individuals
An analysis of immune cell responses to SARS-CoV-2 from recovered patients identifies the regions of the virus that is targeted and also reveals cross-reactivity with other common circulating coronaviruses
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Struvite precipitation is a simple technology for phosphorus recovery from source-separated urine. However, production costs can be high if expensive magnesium salts are used as precipitants. ...Therefore, waste products can be interesting alternatives to industrially-produced magnesium salts. We investigated the technical and financial feasibility of wood ash as a magnesium source in India. In batch experiments with source-separated urine, we could precipitate 99% of the phosphate with a magnesium dosage of 2.7molMgmolP−1. The availability of the magnesium from the wood ash used in our experiment was only about 50% but this could be increased by burning the wood at temperatures well above 600°C. Depending on the wood ash used, the precipitate can contain high concentrations of heavy metals. This could be problematic if the precipitate were used as fertilizer depending on the applicable fertilizer regulations. The financial study revealed that wood ash is considerably cheaper than industrially-produced magnesium sources and even cheaper than bittern. However, the solid precipitated with wood ash is not pure struvite. Due to the high calcite and the low phosphorus content (3%), the precipitate would be better used as a phosphorus-enhanced conditioner for acidic soils. The estimated fertilizer value of the precipitate was actually slightly lower than wood ash, because 60% of the potassium dissolved into solution during precipitation and was not present in the final product. From a financial point of view and due to the high heavy metal content, wood ash is not a very suitable precipitant for struvite production. Phosphate precipitation from urine with wood ash can be useful if (1) a strong need for a soil conditioner that also contains phosphate exists, (2) potassium is abundant in the soil and (3) no other cheap precipitant, such as bittern or magnesium oxide, is available.
►Wood ash has been identified as the cheapest magnesium source in India. ► No other chemicals are required to recover all of the phosphate from urine. ► The heavy metal content of the product can be critical. ► Besides struvite, the product contains high amounts of calcite.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
MicroRNAs are sequence-specific regulators of post-transcriptional gene expression in many eukaryotes. They are believed to control the expression of thousands of target mRNAs, with each mRNA ...believed to be targeted by multiple microRNAs. Recent studies have uncovered various mechanisms by which microRNAs down-regulate their target mRNAs and have linked a well-known subcellular structure, the cytoplasmic processing bodies (PBs) to the microRNA pathway. The finding that microRNAs are misexpressed in cancers has reinforced the idea that their regulatory roles are very important.
This article presents a concise review of different types of inhibitors for corrosion protection on metal surfaces. Corrosion inhibitors can be of different types, which include organic, inorganic ...and hybrid (organic/inorganic) materials. They are also classified as cathodic, anodic and/or mixed-type inhibitors, which are based on the active inhibitor molecules that retard the corrosion process. Silicate, nitrites, molybdates, phosphates, zinc salt and cerium salt are widely used as inorganic inhibitors. Many organic compounds have been widely utilized as inhibitors. Corrosion protection will be obtained by various mechanisms such as physisorption, chemisorption, barrier protection, thin-film formation and electrochemical processes. The type of inhibitors, inhibition mechanism and the evaluation methods have been explained in detail.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Hybrid SiO2 nanocomposite coatings were fabricated on mild steel.•Highest coating resistance were exhibited by coatings with 3wt.% SiO2 nanoparticles.•Long-term stability measurement, together with ...hydrophobic surface measurements, were obtained.
The influence of SiO2 nanoparticles on hydrophobicity and the corrosion protection capabilities of hybrid acrylic-silicone polymeric matrix have been investigated. Contact angle measurements (CA), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDX) were used to study the hydrophobicity, morphology, and topography of the coatings. In addition, electrochemical impedance spectroscopy (EIS) and salt spray techniques were employed to evaluate the corrosion protection performance. A coating with 3wt.% SiO2, AS 3, demonstrates significant improvement in corrosion resistance with the highest measured CA of 97.3°. Morphology and topography studies clarify the influence of nano-sized SiO2 fillers on the surface topography and demonstrated the uniform and good distribution of the embedded SiO2 nanoparticles within the polymeric matrix.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Treatment of stabilized landfill leachate is a great challenge due to its poor biodegradability. Present study made an attempt to treat this wastewater by combining electro-Fenton (E-Fenton) and ...biological process. E-Fenton treatment was applied prior to biological process to enhance the biodegradability of leachate, which will be beneficial for the subsequent biological process. This study also investigates the efficiency of iron molybdophosphate (FeMoPO) nanoparticles as a heterogeneous catalyst in E-Fenton process. The effects of initial pH, catalyst dosage, applied voltage and electrode spacing on Chemical Oxygen Demand (COD) removal efficiency were analyzed to determine the optimum conditions. Heterogeneous E-Fenton process gave 82% COD removal at pH 2, catalyst dosage of 50 mg/L, voltage 5 V, electrode spacing 3 cm and electrode area 25 cm2. Combined E-Fenton and biological treatment resulted an overall COD removal of 97%, bringing down the final COD to 192 mg/L.
•Combined electro-Fenton and biological process for stabilized landfill leachate.•Iron molybdophosphate was used a heterogeneous catalyst.•Biodegradability of the leachate enhanced after electro-Fenton treatment.•Final COD of leachate was reduced to 192 mg/L from 7184 mg/L.•Synthesized catalyst is stable and reusable.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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