The influence of the toxin producing Dinoflagellate, Alexandrium catenella (1119/27), on the feeding and survival of the marine Copepod, Acartia tonsa

Blooms of harmful algae are increasing globally, yet their impacts on copepods, an important link between primary producers and higher trophic levels, remain largely unknown. Algal toxins may have direct, negative effects on the survival of copepods. They may also indirectly affect copepod survival by deterring feeding and thus decreasing the availability of energy and nutritional resources. Here we present a series of short-term (24 h) experiments in which the cosmopolitan marine copepod, Acartia tonsa, was exposed to a range of concentrations of the toxic dinoflagellate, Alexandrium catenella (strain 1119/27, formerly Alexandrium tamarense), with and without the presence of alternative, non-toxic prey (Rhodomonas sp.). We also present the toxin profile concentrations for A. catenella. The survival and feeding of A. tonsa were not affected across the range of concentrations recorded for A. catenella in the field; increased mortality of A. tonsa was only discernible when A. catenella was present at concentrations that exceed their reported environmental concentrations by two orders of magnitude. The observed lethal median concentration (LC50) for A. tonsa exposed to A. catenella was 12.45 ng STX eq L−1. We demonstrate that A. tonsa is capable of simultaneously ingesting both toxic and non-toxic algae, but increases clearance rates towards non-toxic prey as the proportional abundance of toxic A. catenella increases. The ability to actively select non-toxic algae whilst also ingesting toxic algae suggests that consumption of the latter does not cause physical incapacitation and thus does not affect ingestion in A. tonsa. This work shows that short-term exposure to toxic A. catenella is unlikely to elicit major effects on the grazing or survival of A. tonsa. However, more work is needed to understand the longer-term and sub-lethal effects of toxic algae on marine copepods

Preparation of Mortar with Fe2O3 Nanoparticles for Radiation Shielding Application

The current study aims to investigate the radiation shielding properties of mortar samples with Fe2O3 nanoparticles for radiation protection applications. For the reference mortar (free Fe2O3 nanoparticles) and the mortar with different concentrations of Fe2O3 nanoparticles, we experimentally measured the transmission factor (I/I0) for four different thicknesses of the prepared mortar. The I/I0 results indicated that the transmission of the photons through the mortars decreases with increases in the mortar’s thickness. The lowest TF was found for the mortar coded as MI-25 (contains 25 wt.% of Fe2O3 nanoparticles), which gives an indication about the development in the attenuation ability of the prepared mortar samples due to the addition of Fe2O3. Similarly, the linear attenuation coefficient (LAC) results showed an increasing trend with the addition of Fe2O3 nanoparticles for the four tested energies. These results confirm that increasing the ratio of Fe2O3 nanoparticles can lead to a remarkable improvement in the gamma ray shielding. We reported the half value layer (HVL) and we found that the HVL for the reference mortar at 0.06 MeV is 1.223 cm, while it changed from 1.19 to 1.074 cm for the mortar with 5 and 25 wt.% of Fe2O3 nanoparticles. The HVL results demonstrated that increasing the ratio of Fe2O3 nanoparticles can lead to a notable reduction in the HVL. The tenth value layer results proved that we can develop new mortars for radiation shielding applications by introducing more concentrations of Fe2O3 nanoparticles

Shielding Properties of Epoxy Matrix Composites Reinforced with MgO Micro- and Nanoparticles

The aim of the current study is to investigate the impact of introducing micro- and nanoparticle MgO as a filler into epoxy resin on the radiation shielding abilities of the prepared samples. To this end, we performed a gamma-radiation spectroscopy experiment with the help of an HPGe detector and Am-241, Cs-137, and Co-60 sources. We evaluated the particle size effect (PSE) and detected the maximum PSE value with the addition of 50 wt% MgO particles, indicating that nanoparticle MgO was more successful in shielding against incoming radiation than microparticle MgO. We compared the half-value layer (HVL) for the samples with 10 wt%, 20 wt%, and 30 wt % micro-MgO and nano-MgO and found that the HVL values were lower for the nanoparticle samples than for the microparticles samples, confirming that smaller particle sizes enhanced the shielding ability of the samples against radiation. The MFP results showed that epoxy matrices containing micro-MgO, for all investigated energies, resulted in higher MFP values that those containing nano-MgO

Effect of WO₃ Nanoparticles on the Radiative Attenuation Properties of SrTiO₃ Perovskite Ceramic

In the present work, an experimental study is performed to study the radiation shielding characteristics of SrTiO3 (STO) perovskite ceramic added with different amounts (x = 0, 2, 5, and 10%) of tungsten trioxide nanoparticles (WO3 NPs). The four ceramic samples were prepared using the solid-state reaction method. The structural properties were examined using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The analysis showed the successful formation of WO3- doped STO samples. The crystallite size, estimated using the Scherrer equation, was found in the range of 50.86–41.17 nm. The effect of WO3 NPs on the radiation shielding performance of these ceramics was studied. Different parameters, such as linear attenuation coefficient (LAC) and other related factors, were experimentally determined. The linear attenuation coefficient results demonstrated that the additional amount of WO3 in the ceramics correlates with an improvement in their shielding abilities. The half-value layer (HVL) values for the ceramics with 2% WO3 nanoparticles are equal to 0.071, 1.760, 2.407, and 2.564 cm at 0.060, 0.662, 1.173, and 1.333 MeV, respectively. As the energy increases, more radiation can pass through the material; therefore, a larger thickness is required to absorb half of the total photons, leading to a greater HVL. The tenth value results reaffirmed that increasing the WO3 content in the STO ceramics improves their shielding efficiency. The radiation protection efficiency (RPE) of the four prepared STO ceramics was reported. From the RPE, we found that more photons can be attenuated at lower energies

Effect of WO3 Nanoparticles on the Radiative Attenuation Properties of SrTiO3 Perovskite Ceramic

In the present work, an experimental study is performed to study the radiation shielding characteristics of SrTiO3 (STO) perovskite ceramic added with different amounts (x = 0, 2, 5, and 10%) of tungsten trioxide nanoparticles (WO3 NPs). The four ceramic samples were prepared using the solid-state reaction method. The structural properties were examined using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The analysis showed the successful formation of WO3- doped STO samples. The crystallite size, estimated using the Scherrer equation, was found in the range of 50.86–41.17 nm. The effect of WO3 NPs on the radiation shielding performance of these ceramics was studied. Different parameters, such as linear attenuation coefficient (LAC) and other related factors, were experimentally determined. The linear attenuation coefficient results demonstrated that the additional amount of WO3 in the ceramics correlates with an improvement in their shielding abilities. The half-value layer (HVL) values for the ceramics with 2% WO3 nanoparticles are equal to 0.071, 1.760, 2.407, and 2.564 cm at 0.060, 0.662, 1.173, and 1.333 MeV, respectively. As the energy increases, more radiation can pass through the material; therefore, a larger thickness is required to absorb half of the total photons, leading to a greater HVL. The tenth value results reaffirmed that increasing the WO3 content in the STO ceramics improves their shielding efficiency. The radiation protection efficiency (RPE) of the four prepared STO ceramics was reported. From the RPE, we found that more photons can be attenuated at lower energies

The affinity of bentonite and WO3 nanoparticles toward epoxy resin polymer for radiation shielding

A thorough comparative analysis was conducted between pure epoxy and a novel epoxy composite that included bentonite and WO3 nanoparticles in varying ratios. This study examined five distinct novel epoxy samples (E00, EB0, EBW1, EBW2, and EBW3) to assess their radiation shielding efficiency (RSE), taking into account the addition of bentonite and WO3 nanoparticles. Furthermore, the study compared the RSE of pure epoxy with that of the novel epoxy composite. To evaluate the radiation shielding ability of the studied epoxy samples, a few radiation shielding parameters such as linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), mean free path (MFP), RSE, and transition factor (I/I 0) were calculated. The RSE values of the epoxy samples were E00 (63.41%), EB0 (87.17%), EBW1 (98.26%), EBW2 (99.82%), and EBW3 (99.99%) at an energy of 0.06 MeV with 4 cm thickness. With the increase in the incident energy, the half-value layer and MFP values were increased, whereas the LAC and MAC values decreased. In conclusion, it can be stated that the sample EBW3 is more suitable among the five epoxy samples studied for attenuating the incident photon energy from 0.06 to 1.33 MeV. Noteworthily, the obtained results demonstrate that the addition of WO3 nanoparticles enhances the shielding ability of epoxy when compared to the addition of the same amount of bentonite

Impact of WO3 and BaO nanoparticles on the radiation shielding characteristics of polydimethylsiloxane composites

In this study, we developed flexible composites using silicone rubber (SR) or polydimethylsiloxane as the matrix and WO3 and BaO nanoparticles as filler to analyze their radiation-shielding performance. The linear attenuation coefficient (LAC) values for the prepared composites were reported to range from 0.059 to 1.333 MeV by using the experimental method. At 0.059 MeV, the SR with 40% of BaO NPs possesses the highest LAC, followed by SR with 20% of BaO and WO3 NPs. The SRs S-2 and S-4 that contain WO3 and/or BaO exhibit continuously greater LAC values than the sample S-1. Numerically, the LAC for S-2 (with 40% of BaO NPs) is 1.6 times greater than that for S-1 (free BaO and WO3) at 0.662 MeV, while the LAC for S-2 is 1.47 times more than that for S-1 at 1.275 MeV. We examined the impact of the thickness of the prepared composites on the attenuation performance by studying the transmission factor (TF) at two different thicknesses (1 and 2 cm). For S-1 and S-2, the TF decreases due to the increase of the thickness from 1 to 2 cm. The TF for S-1 with a thickness of 1 cm is 75% at 0.059 MeV, while it is 56% (for 2 cm). We evaluated the percentage decrease in the TF at 0.059 MeV for every SR as the thickness changes from 1 to 2 cm. For S-3, S-4, S-5, and S-6, the percentage decrease in the TF is extremely significant varying from 98% to 99%. This suggests that increasing the thickness of these SR samples from 1 to 2 cm has a major effect on the shielding capabilities they possess, particularly at low energies

Morphological and Gamma-Ray Attenuation Properties of High-Density Polyethylene Containing Bismuth Oxide

For extensive radiation exposure, inventing a novel radiation shielding material is a burning issue at present for the purpose of life saving. Considering this thought, in this study, by adding sundry amounts of Bi2O3 into pure high-density polyethylene (HDPE), six HDPE systems were prepared to evaluate the radiation shielding efficiency. These HDPE systems were HDPEBi-0 (pure HDPE), HDPEBi-10 (10 wt% Bi2O3), HDPEBi-20 (20 wt% Bi2O3−), HDPEBi-30 (30 wt% Bi2O3), HDPEBi-40 (40 wt% Bi2O3), and HDPEBi-50 (50 wt% Bi2O3). The values of the linear attenuation coefficients of the experimental results (calculated in the lab using HPGe) were compared with the theoretical results (obtained using Phy-X software) at 0.060, 0.662, 1.173, and 1.333 MeV energies. To ensure the accurateness of the experimental results, this comparison was made. It was crystal clear that for energy values from 0.06 MeV to 1.333 MeV, all the experimental values were in line with Phy-X software data, which demonstrated the research setup’s reliability. Here, the linear attenuation coefficient (LAC), and mean free path (MFP) shielding parameters were assessed. At the energy of 1.333 MeV, sample HDPEBi-0 showed an HVL value 1.7 times greater than that of HDPEBi-50, yet it was 23 times greater at 0.0595 MeV. That means that for proper radiation protection, very-low-energy HDPE systems containing 10–50% Bi2O3 could be used; however, the thickness of the HDPE system must be increased according to the energy of incident radiation

Experimental Study of Polypropylene with Additives of Bi2O3 Nanoparticles as Radiation-Shielding Materials

This work aimed to intensively study polypropylene samples (PP) embedded with micro- and nanoparticles of Bi2O3 for their application in radiation shielding. Samples were prepared by adding 10%, 20%, 30%, 40%, and 50% of Bi2O3 microparticles (mBi2O3) by weight, and adding 10% and 50% of Bi2O3 nanoparticles (nBi2O3), in addition to the control sample (pure polypropylene). The morphology of the prepared samples was tested, and also, the shielding efficiency of gamma rays was tested for different sources with different energies. The experimental LAC were determined using a NaI scintillation detector, the experimental results were compared with NIST-XCOM results, and a good agreement was noticed. The LAC values have been used to calculate some specific parameters, such as half value layer (HVL), mean free path (MFP), tenth value layer (TVL), and radiation protection efficiency (RPE), which are useful for discussing the shielding capabilities of gamma rays. The results of the shielding parameters show that the PP embedded with nBi2O3 gives better attenuation than its counterpart, PP embedded with mBi2O3, at all studied energies