Predicting the trend of indicators related to Covid-19 using the combined MLP-MC model.

Although more than a year has passed since the coronavirus outbreak globally, the Covid-19 pandemic conditions still exist in many countries, including Iran. Predicting the number of future patients and deaths can help governments and policymakers make better decisions to enforce disease control restrictions. In this study, we aim to use a combined multilayer perceptron (MLP) neural network and Markov chain (MC) model to predict two indicators of the number of discharged and death cases according to their relationship with the number of hospitalized cases in Bushehr province, Iran. This hybrid model is called MLP-MC. In this study, 136 data (days) are collected from May 13, 2020, to April 1, 2021, divided into two parts: training and test. The training data are used to train the MLP network, and the trained MLP network is used to predict the test data and the next 40 days. Then the residual errors of actual and predicted values are calculated. In the next step, the MC model is used to classify the errors and predict the values of the indicators according to the probabilities related to the error states and improve the performance of the MLP model in forecasting. Finally, the prediction accuracy of MLP and MLP-MC models are compared using three evaluation metrics: MAD, MSE and RMSE. This comparison showed that the MLP-MC model has slightly higher prediction accuracy than the MLP model.

Titanium dioxide nanoparticles affect the toxicity of silver nanoparticles in common carp (Cyprinus carpio).

The present study assessed the individual and combined toxicity effects of Ag- and TiO2- nanoparticles (NPs) on Ag bioaccumulation, oxidative stress, and gill histopathology in common carp as an aquatic animal model. The 96-h acute toxicity tests showed that TiO2NPs enhanced the toxicity of AgNPs deducted from the decreased LC50 in co-exposure to these NPs. Chronic toxicity tests included a 10-day exposure and a 10-day recovery period. In most cases, histological damages were more severe in co-exposure to Ag- and TiO2- NPs compared with the individual AgNPs however, they were reduced in some cases and also after the recovery period. In co-exposure to Ag- and TiO2- NPs, the Ag bioaccumulation was decreased in the gills but increased in the liver and intestine compared with the singular exposure. After the recovery period, Ag bioaccumulation decreased especially in the liver. Decreased levels of antioxidant enzymes were observed in the AgNPs exposed groups, which were partially alleviated by TiO2NPs. The reduction of condition factor (CF) and hepatosomatic index (HSI) and a severe decrease of weight gain (WG) were observed in co-exposure to Ag- and TiO2- NPs. After the recovery period, the CF and HSI increased but the WG decreased less compared with the exposure period. The present results emphasize the importance of considering the co-existence and interaction of NPs in realizing their bioavailability and toxicity in aquatic environments.

Comparative toxicity of nanoparticulate and ionic copper following dietary exposure to common carp (Cyprinus carpio).

Copper is an essential element for the normal growth and survival of all organisms including fish. However, its excessive presence in the environment can cause bioaccumulation and aquatic toxicology. The aim of the present study was to compare the dietary toxicity effects of two different Cu compounds, copper oxide nanoparticles (CuO-NPs) and ionic copper (CuSO4) in juvenile common carp, Cyprinus carpio. To prepare experimental diets, two nominal concentrations of 100 and 1000 mg Cu kg-1 diet were added to a basal diet. Carp (n = 450, average initial weight of 35.94 ± 5.35 g) were fed on the Cu-supplemented diets and basal diets for two 21-day courses as dietary exposure and recovery periods, respectively. The growth performance, survival rate and blood biochemical indices as well as copper accumulation in target organs of fish were investigated at the end of each exposure period. The results showed that the weight gain (WG) of carp significantly decreased coincident with increasing concentration of the both dietary Cu forms (P = 0.00). Both Cu sources at concentrations of 100 mg kg-1 diet decreased the survival rate of fish (P = 0.003), likely due to more feed intake and thus increased copper toxicity. The both forms of dietary Cu at two different concentrations significantly decreased the plasma glutamate oxaloacetate transaminase (GOT) level compared to the control group (P = 0.008). Fish exposed to diets containing Cu sources except 100 mg Cu kg-1 of CuO-NPs showed the lower glutamate pyruvate transaminase (GPT) activity in comparison to the control (P = 0.00). The plasma sodium level in1000 mg CuO-NPs kg-1 diet was significantly lower than the control (P = 0.001). The plasma potassium level increased in the all Cu-supplemented groups except 100 mg kg-1 of CuO-NPs after the dietary exposure period (P = 0.035). The copper accumulation was dose-dependent in all target organs. In 100 mg Cu kg-1 dietary groups, the liver showed the highest Cu accumulation (P = 0.00), while in 1000 mg Cu kg-1 dietary groups, the highest Cu content was observed in the intestine (P = 0.00). The results demonstrated the enhanced toxicological responses in fish after 21 days of dietary exposure, but the levels of most of biochemical indices and tissues Cu content decreased or returned to the control values after the recovery period.