Nanoindentation induced deformation anisotropy in WC, β-Si3N4 and ZrB2 crystals

The influence of crystal orientation on elastic and plastic response of WC, β-Si3N4 and ZrB2 ceramic grains is important to understand, model and enhance its composite mechanical properties. In order to investigate this, nanoindentation testing was carried out using Berkovich tip on selected surface areas which were mapped by electron backscatter diffraction (EBSD) prior to the tests. To study the surface morphology after nanoindentation and to characterize the resulted deformation fields around the imprints additional EBSD, atomic force microscopy (AFM) and scanning electron microscopy (SEM) investigations were performed. Considerable elastic and plastic anisotropy was found is WC and β-Si3N4 (Fig. 1a,b) crystals while the orientation dependence of ZrB2 grains exhibited slight influence on hardness and indentation modulus. The measured indentation modulus, as the elastic response, was compared with the model proposed by Vlassak and Nix and our finite element model (FEM) calculations using single crystal elastic constants, as it is shown for β-Si3N4 in Fig. 1c. To explain the obtained hardness anisotropy, as the plastic response, a theoretical model is proposed in which the critical force for slip activation is determined as a function of crystal orientation, based on the possible slip systems of materials. The predictions of the applied models describing both elastic and plastic behaviors are in good agreement with the experimental results, (for β-Si3N4 see in Fig. 1d

Oxidative status in plasma, urine and saliva of girls with anorexia nervosa and healthy controls: a cross-sectional study

Background Anorexia nervosa (AN) is a serious psychosomatic disorder with unclear pathomechanisms. Metabolic dysregulation is associated with disruption of redox homeostasis that might play a pivotal role in the development of AN. The aim of our study was to assess oxidative status and carbonyl stress in plasma, urine and saliva of patients with AN and healthy controls. Methods Plasma, spot urine, and saliva were collected from 111 girls with AN (aged from 10 to 18 years) and from 29 age-matched controls. Markers of oxidative stress and antioxidant status were measured using spectrophotometric and fluorometric methods. Results Plasma advanced oxidation protein products (AOPP) and advanced glycation end products (AGEs) were significantly higher in patients with AN than in healthy controls (by 96, and 82%, respectively). Accordingly, urinary concentrations of AOPP and fructosamines and salivary concentrations of AGEs were higher in girls with AN compared with controls (by 250, and 41% in urine; by 92% in saliva, respectively). Concentrations of thiobarbituric acid reactive substances (TBARS) in saliva were 3-times higher in the patients with AN than in the controls. Overall antioxidants were lower in plasma of girls with AN compared to the controls, as shown by total antioxidant capacity and ratio of reduced and oxidized glutathione (by 43, and 31%, respectively). Conclusions This is the first study assessing wide range of markers of oxidative status in plasma, urine and saliva of the patients with AN. We showed that both, higher levels of markers of oxidative stress and lower antioxidants play a role in redox disruption. Restoration of redox homeostasis might be of the clinical relevanceThis study was supported by the Grant of Ministry of Health of the Slovak republic 2018/36-LFUK-10 and by the Grant Agency of Ministry of Education, Science, Research and Sport of the Slovak Republic VEGA 1/0613/17. We are grateful to the Dr. Tana Novakova from the practice of general paediatrician (National Institute of Children's diseases), who recruited healthy girls. We would like to thank the children and parents who participated in the study.Ministry of Health of the Slovak republic [2018/36-LFUK-10]; Grant Agency of Ministry of Education, Science, Research and Sport of the Slovak Republic [VEGA 1/0613/17

Oxidative Stress in Animal Models of Acute and Chronic Renal Failure

Introduction. Kidney disease is a worldwide health and economic burden, with rising prevalence. The search for biomarkers for earlier and more effective disease screening and monitoring is needed. Oxidative stress has been linked to both, acute kidney injury (AKI) and chronic kidney disease (CKD). The aim of our study was to investigate whether the concentrations of systemic markers of oxidative stress and antioxidant status are affected by AKI and CKD, and to identify potential biomarkers. Methods. In adult male Wistar rats, AKI was induced by bilateral nephrectomy, and CKD was induced by 5/6 nephrectomy. Blood was collected 48 hours after surgery in AKI and 6 months after surgery in CKD. Advanced oxidation protein products (AOPP), thiobarbituric acid reactive substances (TBARS), advanced glycation end products (AGEs), fructosamine, total antioxidant capacity (TAC), and ferric reducing antioxidant power (FRAP) were measured. Results. Impaired renal function was confirmed by high concentrations of plasma creatinine and urea in AKI and CKD animals. AOPP and fructosamine were higher by 100% and 54% in AKI, respectively, and by 100% and 199% in CKD, respectively, when compared to corresponding control groups. Similarly, there was approximately a twofold increase in AGEs (by 92%) and TAC (by 102%) during AKI. In CKD, concentrations of FRAP, as an antioxidative status marker, were doubled (by 107%) when compared to the control group, but concentration of TAC, another marker of antioxidative status, did not differ between the groups. Conclusions. AKI and CKD led to increased systemic oxidative stress. AOPP and fructosamine could be considered potential biomarkers for both, acute and chronic kidney damage. On the other hand, AGEs, TAC, and FRAP seem to be disease specific, which could help to differentiate between acute and chronic kidney injuries. However, this needs further validation in clinical studies

Transformation of Amorphous Terbium Metal–Organic Framework on Terbium Oxide TbO_x(111) Thin Film on Pt(111) Substrate: Structure of Tb_xO_y Film

The present study is focused on the synthesis and structural properties of amorphous terbium metal–organic framework thin film (TbMOF-TF) and its transformation to terbium oxide by pyrolysis at 450 °C in the air. The crystalline (cTbMOF) and amorphous (aTbMOF) films were prepared by solvothermal synthesis using different amounts (0.4 and 0.7 mmol) of the modulator (sodium acetate), respectively. The powders were characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM). The varied chemical composition of the surface of TbMOFs and TbxOy was investigated by X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that aTbMOF had been fully transformed to a Tb4O7 phase with a cubic crystal structure at 450 °C. The amorphous aTbMOF-TF film was prepared by dropping a colloidal solution of amorphous precursor nanocrystals on the SiO2/Si substrates covered with Pt as an interlayer. XPS confirmed the presence of Tb in two states, Tb3+ and Tb4+. The amorphous film has a rough, porous microstructure and is composed of large clusters of worm-like particles, while terbium oxide film consists of fine crystallites of cubic fluorite cF-TbOx, c-Tb4O7, and c-Tb2O3 phases. The surface topography was investigated by a combination of confocal (CM) and atomic force microscopy (AFM). The amorphous film is porous and rough, which is contrast to the crystalline terbium oxide film