Inertia Induces Strong Orientation Fluctuations of Nonspherical Atmospheric Particles.

The orientation of nonspherical particles in the atmosphere, such as volcanic ash and ice crystals, influences their residence times and the radiative properties of the atmosphere. Here, we demonstrate experimentally that the orientation of heavy submillimeter spheroids settling in still air exhibits decaying oscillations, whereas it relaxes monotonically in liquids. Theoretical analysis shows that these oscillations are due to particle inertia, caused by the large particle-fluid mass-density ratio. This effect must be accounted for to model solid particles in the atmosphere.

Ethical challenges of nurses related COVID-19 pandemic in inpatient wards: An integrative review.

INTRODUCTION: The COVID-19 pandemic is a social problem. Nurses face ethical challenges in providing care activities related to COVID-19. AIM: Therefore, this study aimed to explore the ethical challenges of nurses in COVID-19 pandemic. METHOD: This is an integrative review study conducted from 2007 to 2020. Databases of PubMed, Google Scholar, Scopus, Web of Science were searched. The results of the eligible studies (12 cases) were analyzed. RESULTS: A total of 228 articles satisfied the inclusion criteria, and 12 articles were selected for analysis. The study units showed that the ethical challenges of nurses in caring for patients with COVID-19 consisted of three areas, including nursing; patient and family; and treatment equipment and facilities. CONCLUSION: Providing care for patients with COVID-19 pandemic has increased nurses' ethical challenges. Therefore, nurses need to pay more attention to not face psychological problems and premature burnout.

In situ cloud particle tracking experiment.

The collision-coalescence process of inertial particles in turbulence is held responsible for the quick growth of cloud droplets from ∼15 to ∼50 µm in diameter, but it is not well understood. Turbulence has two effects on cloud droplets: (1) it brings them closer together, preferentially concentrating them in certain parts of the flow, and (2) it sporadically creates high accelerations, causing droplets to detach from the underlying flow. These turbulence-cloud droplet interactions are difficult to study numerically or in the laboratory due to the large range of scales involved in atmospheric turbulence, so in situ measurements are needed. Here, we present a Lagrangian particle tracking (LPT) experimental setup situated close to the summit of Mt. Zugspitze at an altitude of 2650 m above the sea level on top of the environmental research station Schneefernerhaus. Clouds naturally occur at this location about a quarter of the time. The LPT experiment probes a volume of ∼40 × 20 × 12 mm3, has a spatial resolution of 5 µm and a temporal resolution of 0.1 ms, and measures accelerations to within 0.1 m s-2. Furthermore, the experiment can slide over a set of rails, driven by a linear motor, to compensate for the mean wind. It can slide up to 7.5 m s-1. By doing so, the average residence time of the particles in the measurement volume increases. The mean wind compensation allows us to study various dynamical quantities, such as the velocity autocorrelation, or the dynamics of clustering. Moreover, it is beneficial for particle tracking, in general, since longer particle tracks allow us to apply better filtering to the tracks and thus increase accuracy. We present the radial distribution function, which quantifies clustering, the longitudinal relative velocity distribution, and the Lagrangian velocity autocorrelation, all computed from cloud droplet trajectories.

Cardioprotective effects of insulin on carbon monoxide-induced toxicity in male rats.

Carbon monoxide (CO) poisoning is a significant cause of death especially in developing countries. The current study investigated cardioprotective effects of insulin in CO-poisoned rats. Male rats were exposed to 3000 ppm CO for 1 h. Insulin (100 and 120 U/kg intraperitoneally) was immediately administered after CO exposure and on the next 4 days, on a daily basis (a total of 5 doses). On day 5, animals were euthanized, and the hearts were harvested for Western blotting and histopathological studies. The electrocardiograms (ECG) were recorded postexposure to CO and after the completion of insulin treatment period. Histopathological evaluations showed reduction of myocardial necrosis in insulin-treated animals compared to controls. BAX/BCL2 ratio, as a proapoptotic index, was significantly reduced in treatment groups ( p < 0.01). The ECG findings showed no differences among groups; also, compared to control animals, myocardial Akt levels were not markedly affected by insulin. The current study showed that insulin significantly reduces myocardial necrotic and apoptotic indices in CO-poisoned rats.

Study on the influence of leucine-rich amelogenin peptide (LRAP) on the remineralization of enamel defects via micro-focus x-ray computed tomography and nanoindentation.

Regeneration of severely damaged enamel (e.g. deep demineralized lesions) is currently not possible, because the structural units of enamel crystal construction are removed after its maturation. The aim of this in vitro study was to evaluate the effect of surface impregnation by leucine-rich amelogenin peptide (LRAP) on the remineralization of eroded enamel using micro-focus x-ray computed tomography (µCT). Fifteen bovine enamel blocks were embedded in resin and three zones (sound, demineralization, and remineralization) were defined on each specimen. Lesions were prepared by immersing the samples in demineralization solution for 7 d. The samples were soaked in distilled water or 60 or 120 µg mL(-1) solution of LRAP in water for 30 min. After the surface treatment, specimens were incubated in artificial saliva for either 5 or 10 d at 37 °C. The amount of mineral gain (dΔZ%) and the relative changes in the lesion depth (dLD%), obtained from µCT, were used to evaluate the effect of LRAP on the remineralization of lesions. The effects of LRAP on cross-sectional integrated hardness ΔINH were studied after 10 d using nanoindentation. ANOVA test was used to determine the effect of time and/or LRAP concentration on dΔZ%, dLD% and ΔINH mean values. Tukey's analysis was used for multiple comparison testing (α = 0.05). Analysis of µCT data showed significant effect of time and LRAP concentration on the dΔZ% (p = 0.013, p = 0.003) and the dLD% (p < 0.001, p = 0.002) mean values. The nanoindentation hardness was significantly improved by 120 µg mL(-1) LRAP (p = 0.02). Also, the peptide treatment affected the mineral distribution throughout the lesion by inhibiting of superficial deposition. This study showed that the treatment of eroded lesions in enamel by LRAP can improve and regulate the pattern of remineralization in vitro.

Leucine-rich amelogenin peptide (LRAP) as a surface primer for biomimetic remineralization of superficial enamel defects: An in vitro study.

This study was carried out to obtain more information about the assembly of hydroxyapatite bundles formed in the presence of Leucine-Rich Amelogenin Peptide (LRAP) and to evaluate its effect on the remineralization of enamel defects through a biomimetic approach. One or 2 mg/mL LRAP solutions containing 2.5 mM of Ca(+2) and 1.5 mM phosphate were prepared (pH = 7.2) and stored at 37 °C for 24 h. The products of the reaction were studied using atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Vickers surface microhardness recovery (SMR%) of acid-etched bovine enamel, with or without LRAP surface treatment, were calculated to evaluate the influence of peptide on the lesion remineralization. Distilled water and 1 or 2 mg/mL LRAP solution (pH = 7.2) were applied on the lesions and the specimens were incubated in mineralization solution (2.5mM Ca(+2) , 1.5mM PO4 (-3) , pH = 7.2) for 24 h. One-way ANOVA and Tukey's multi-comparison tests were used for statistical analysis. The pattern of enamel surface repair was studied using FE-SEM. AFM showed the formation of highly organized hierarchical structures, composed of hydroxyapatite (HA) crystals, similar to the dental enamel microstructure. ANOVA procedure showed significant effect of peptide treatment on the calculated SMR% (p < 0.001). Tukey's test revealed that peptide treated groups had significantly higher values of SMR%. In conclusion, LRAP is able to regulate the formation of HA and enhances the remineralization of acid-etched enamel as a surface treatment agent.

Application of artificial neural networks for optimization of preparation of insulin nanoparticles composed of quaternized aromatic derivatives of chitosan.

The aim of this research was to develop an artificial neural network (ANN) in order to design a nanoparticulate oral drug delivery system for insulin. The pH of polymer solution (X1), concentration ratio of polymer/insulin (X2) and polymer type (X3) in 3 level including methylated N-(4-N,N- dimethyl aminobenzyl) chitosan, methylated N-(4-pyridinyl) chitosan, and methylated N-(benzyl) chitosan are considered as the input values and the particle size, zeta potential, PdI, and entrapment efficiency (EE %) as output data. ANNs are employed to generate the best model to determining the relationships between input and response values. In this research, a multi-layer percepteron with different topologies has been tested in order to define the one with the best accuracy and performance. The optimization was used by minimizing the error between the predicted and observed values. Three training algorithms (Levenberg-Marquardt (LM), Bayesian-Regularization (BR), and Gradient Descent (GD)) were employed to train ANNs with various numbers of nodes, hidden layers and transfer functions by random selection. The accuracy of prediction data were assayed by the mean squared error (MSE).The ability of all algorithms was in the order: BR>LM>GD. Thus, BR was selected as the best algorithm.

Dedicated vertical wind tunnel for the study of sedimentation of non-spherical particles.

A dedicated 4-m-high vertical wind tunnel has been designed and constructed at the University of Geneva in collaboration with the Groupe de compétence en mécanique des fluides et procédés énergétiques. With its diverging test section, the tunnel is designed to study the aero-dynamical behavior of non-spherical particles with terminal velocities between 5 and 27 ms(-1). A particle tracking velocimetry (PTV) code is developed to calculate drag coefficient of particles in standard conditions based on the real projected area of the particles. Results of our wind tunnel and PTV code are validated by comparing drag coefficient of smooth spherical particles and cylindrical particles to existing literature. Experiments are repeatable with average relative standard deviation of 1.7%. Our preliminary experiments on the effect of particle to fluid density ratio on drag coefficient of cylindrical particles show that the drag coefficient of freely suspended particles in air is lower than those measured in water or in horizontal wind tunnels. It is found that increasing aspect ratio of cylindrical particles reduces their secondary motions and they tend to be suspended with their maximum area normal to the airflow. The use of the vertical wind tunnel in combination with the PTV code provides a reliable and precise instrument for measuring drag coefficient of freely moving particles of various shapes. Our ultimate goal is the study of sedimentation and aggregation of volcanic particles (density between 500 and 2700 kgm(-3)) but the wind tunnel can be used in a wide range of applications.

Synthesis, characterization and analytical application of a new inorganic cation exchanger-Titanium(IV) molybdophosphate.

A novel polyoxometalate-cation exchanger, titanium(IV) molybdophosphate (TMP) has been synthesized under varying conditions. The material was characterized by X-ray diffraction, infrared spectroscopy, inductively coupled plasma and thermogravimetry techniques. Its stability was investigated in water, dilute acids, alkaline solutions, and high temperature up to 750 degrees C. Ion-exchange capacity and distribution coefficients (K(d)) for twenty-nine radionuclides and metal ions have been determined. It was found that the TMP has high affinity for Cs(+), Sr(2+), UO(2)(2+), Ba(2+), Pb(2+), Tl(+), Zn(2+), Rb(2+) and Zr(4+) ions. The results of binary separation of metal ions showed that TMP can be potentially useful for analytical applications.