The high corrosion rate of magnesium alloys is the main drawback to their widespread use, especially in biomedical applications. There is a need for developing new coatings that provide ...simultaneously corrosion resistance and enhanced biocompatibility. In this work, a composite coating containing polyether imide, with several diethylene triamine and hydroxyapatite contents, was applied on AZ31 magnesium alloys pre-treated with hydrofluoric acid by dip coating. The coated samples were immersed in Hank’s solution and the coating performance was studied by electrochemical impedance spectroscopy and scanning electron microscopy. In addition, the behavior of MG63 osteoblastic cells on coated samples was investigated. The results confirmed that the new coatings not only slow down the corrosion rate of AZ31 magnesium alloys in Hank’s solution, but also enhance the adhesion and proliferation of MG63 osteoblastic cells, especially when hydroxyapatite nanoparticles were introduced in the coating formulation.
NiTi is an increasingly applied material in industrial applications. However, the difficulties faced when welding and joining is required, limits its broader use in the production of complex shaped ...components. The main weldability problems associated with NiTi are: strength reduction, formation of intermetallic compounds, modification of phase transformation and transformation temperatures, as well as, changes in both superelastic and shape memory effects. Additionally, NiTi is envisaged to be joined to other materials, in dissimilar joints with more complex problems depending on the other base material. Thus, intensive research in welding and its effects on the joints performance has been conducted since the early stages of NiTi. This paper presents a detailed review of welding and joining processes applied to NiTi, in similar and dissimilar combinations considering both fusion and solid-state processes. Since laser is the most studied and applied welding process, a special section is devoted to this technique.
The sepsis burden on acute care services in middle-income countries is a cause for concern. We estimated incidence, prevalence, and mortality of sepsis in adult Brazilian intensive care units (ICUs) ...and association of ICU organisational factors with outcome.
We did a 1-day point prevalence study with follow-up of patients in ICU with sepsis in a nationally representative pseudo-random sample. We produced a sampling frame initially stratified by geographical region. Each stratum was then stratified by hospitals' main source of income (serving general public vs privately insured individuals) and ICU size (ten or fewer beds vs more than ten beds), finally generating 40 strata. In each stratum we selected a random sample of ICUs so as to enrol the total required beds in 1690 Brazilian adult ICUs. We followed up patients until hospital discharge censored at 60 days, estimated incidence from prevalence and length of stay, and generated national estimates. We assessed mortality prognostic factors using random-effects logistic regression models.
On Feb 27, 2014, 227 (72%) of 317 ICUs that were randomly selected provided data on 2632 patients, of whom 794 had sepsis (30·2 septic patients per 100 ICU beds, 95% CI 28·4–31·9). The ICU sepsis incidence was 36·3 per 1000 patient-days (95% CI 29·8–44·0) and mortality was observed in 439 (55·7%) of 788 patients (95% CI 52·2–59·2). Low availability of resources (odds ratio OR 1·67, 95% CI 1·02–2·75, p=0·045) and adequacy of treatment (OR 0·56, 0·37–0·84, p=0·006) were independently associated with mortality. The projected incidence rate is 290 per 100 000 population (95% CI 237·9–351·2) of adult cases of ICU-treated sepsis per year, which yields about 420 000 cases annually, of whom 230 000 die in hospital.
The incidence, prevalence, and mortality of ICU-treated sepsis is high in Brazil. Outcome varies considerably, and is associated with access to adequate resources and treatment. Our results show the burden of sepsis in resource-limited settings, highlighting the need to establish programmes aiming for sepsis prevention, early diagnosis, and adequate treatment.
Fundação de Apoio a Pesquisa do Estado de São Paulo (FAPESP).
To identify the emotional and motivational processes that reinstate palatable food intake following removal of high-fat diet (HFD) and associated neuroadaptations tied to neurochemical and ...behavioural changes underlying dopaminergic function.
Adult male C57Bl6 mice were placed on a HFD (58% kcal fat) or ingredient-matched, low-fat diet (LFD; 11% kcal fat) for 6 weeks. At the end of diet-regimen mice were either maintained on their respective diets, or HFD and LFD were replaced with normal chow (withdrawal). Effort-based operant responding for sucrose and high-fat food rewards was measured along with basal and stress-induced corticosterone levels and anxiety (elevated-plus maze). Protein levels for tyrosine hydroxylase (TH), corticosterone releasing factor type 1 receptor (CRF-R1), brain-derived neurotrophic factor (BDNF), phospho-CREB (pCREB) and ΔFosB (truncated splice variant of FosB) were assessed in the amygdala, nucleus accumbens (NAc) and ventral tegmental area (VTA) via western immunoblotting.
Six weeks of HFD resulting in significant weight gain elicited sucrose anhedonia, anxiety-like behaviour and hypothalamic-pituitary-adrenocortical axis (HPA) hypersensitivity to stress. Withdrawal from HFD but not LFD-potentiated anxiety and basal corticosterone levels and enhanced motivation for sucrose and high-fat food rewards. Chronic high-fat feeding reduced CRF-R1 and increased BDNF and pCREB protein levels in the amygdala and reduced TH and increased ΔFosB protein in NAc and VTA. Heightened palatable food reward in mice withdrawn from HFD coincided with increased BDNF protein levels in NAc and decreased TH and pCREB expression in the amygdala.
Anhedonia, anxiety and sensitivity to stressors develops during the course of HFD and may have a key role in a vicious cycle that perpetuates high-fat feeding and the development of obesity. Removal of HFD enhances stress responses and heightens vulnerability for palatable foods by increasing food-motivated behaviour. Lasting changes in dopamine and plasticity-related signals in reward circuitry may promote negative emotional states, overeating and palatable food relapse.
Aim
To compare six reciprocating instruments regarding their geometric design, metallurgical characteristics, mechanical behaviour and ability to prepare root canals.
Methodology
A total of 246 new ...25‐mm NiTi instruments (41 per group) from six reciprocating systems (Reciproc, Reciproc Blue, One Files, One Files Blue, Reverso Silver, and WaveOne Gold) were evaluated throughout a multimethod approach regarding their design using stereomicroscopy (number of blades and helix angle) and scanning electron microscopy (blades symmetry, cross section and surface finishing), nickel‐titanium composition, phase transformation temperatures, mechanical performance (cyclic fatigue, torsional and bending resistance) and unprepared canal surface area on anatomically matched mandibular molars assessed by micro‐CT. One‐way ANOVA and post hoc Tukey’s or Mood's median tests were selected depending on sample distribution with significance level set at 5%.
Results
The instruments had similarities regarding their metal composition and unprepared canal area, whilst differences in phase transformation temperatures and geometric design (number of blades, surface finishing and tip geometry) were observed. Overall, no difference was observed regarding the maximum torque values (P > 0.05), whilst One Files (72 s) and One Files Blue (414 s) had the shortest and longest times to fracture, respectively (P < 0.05). Similar angles of rotation were observed in Reciproc (310°), One Files (285°) and Reverso Silver (318°) instruments (P > 0.05), which were significantly lower than Reciproc Blue (492°), One Files Blue (456°) and WaveOne Gold (492°; P < 0.05). Maximum bending load demonstrated that Reciproc Blue (201.3 gf) was significantly more flexible that the other instruments (P < 0.05).
Conclusion
Although there were similarities in metal composition and percentage of unprepared canal surface, the instruments had differences in the overall geometric design, phase transformation temperatures and in the four mechanical resistance parameters (time to fracture, maximum torque, angle of rotation and maximum bending load).
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Transition metal dichalcogenides (TMDs), like other two-dimensional layered materials beyond graphene, have gained enormous interest in recent years owing to their distinct electronic ...and optical properties, and potential applicability in areas such as sensing, nanoelectronics and catalysis. Surfactant-assisted exfoliation is commonly used to prepare aqueous dispersions of TMD nanosheets, but a clear picture of the TMD and surfactant features that influence the dispersion process is still lacking. In this work, we present a systematic study of the dispersibility of MoS2, WS2 and MoSe2 in aqueous medium using a cationic (cetyltrimethylammonium bromide, CTAB) and an anionic (sodium cholate, SC) dispersant, in a wide concentration range (seven orders of magnitude) and resorting to a carefully controlled sonication-centrifugation procedure. We present detailed, high precision dispersibility curves (concentration of dispersed TMD versus concentration of surfactant used), together with zeta potential and pH measurements, allowing insight into the influence of the type of metal and chalcogen, surfactant charge and surfactant concentration, on the effectiveness of the exfoliation and stabilization. The metal (Mo vs. W) influences the dispersibility at low surfactant concentrations, while the chalcogen (S vs. Se) plays a more significant role as the surfactant concentration is increased, alongside the surfactant charge. Structural characterization by scanning electron microscopy (SEM), Raman spectroscopy and atomic force microscopy (AFM) shows that the methodology applied yields well-exfoliated nanosheets with controlled mean lateral dimension (≈ 100 nm) and thickness (≤5 layers). Finally, the type of ionic surfactant (cationic vs. anionic) and its concentration play a pivotal role in the profile of the dispersibility curves, leading us to propose two types of master curves with distinct regions of phase behavior.
Cholesterol is an essential component of cell membranes and the precursor for the synthesis of steroid hormones and bile acids. The synthesis of this molecule occurs partially in a membranous world ...(especially the last steps), where the enzymes, substrates, and products involved tend to be extremely hydrophobic. The importance of cholesterol has increased in the past half-century because of its association with cardiovascular diseases, which are considered one of the leading causes of death worldwide. In light of the current need for new drugs capable of controlling the levels of cholesterol in the bloodstream, it is important to understand how cholesterol is synthesized in the organism and identify the main enzymes involved in this process. Taking this into account, this review presents a detailed description of several enzymes involved in the biosynthesis of cholesterol. In this regard, the structure and catalytic mechanism of the enzymes involved in cholesterol biosynthesis, from the initial two-carbon acetyl-CoA building block, will be reviewed and their current pharmacological importance discussed. We believe that this review may contribute to a deeper level of understanding of cholesterol metabolism and that it will serve as a useful resource for future studies of the cholesterol biosynthesis pathway.
The objective of this study was to identify genomic regions that are associated with meat quality traits in the Nellore breed. Nellore steers were finished in feedlots and slaughtered at a commercial ...slaughterhouse. This analysis included 1,822 phenotypic records of tenderness and 1,873 marbling records. After quality control, 1,630 animals genotyped for tenderness, 1,633 animals genotyped for marbling, and 369,722 SNPs remained. The results are reported as the proportion of variance explained by windows of 150 adjacent SNPs. Only windows with largest effects were considered. The genomic regions were located on chromosomes 5, 15, 16 and 25 for marbling and on chromosomes 5, 7, 10, 14 and 21 for tenderness. These windows explained 3,89% and 3,80% of the additive genetic variance for marbling and tenderness, respectively. The genes associated with the traits are related to growth, muscle development and lipid metabolism. The study of these genes in Nellore cattle is the first step in the identification of causal mutations that will contribute to the genetic evaluation of the breed.
Mg alloys can be used as bioresorsable metallic implants. However, the high corrosion rate of magnesium alloys has limited their biomedical applications. Although Mg ions are essential to the human ...body, an excess may cause undesirable health effects. Therefore, surface treatments are required to enhance the corrosion resistance of magnesium parts, decreasing its rate to biocompatible levels and allowing its safe application as bioresorbable metallic implants. The application of biocompatible silane coatings is envisaged as a suitable strategy for retarding the corrosion process of magnesium alloys. In the current work, a new glycidoxypropyltrimethoxysilane (GPTMS) based coating was tested on AZ31 magnesium substrates subjected to different surface conditioning procedures before coating deposition. The surface conditioning included a short etching with hydrofluoric acid (HF) or a dc polarisation in alkaline electrolyte. The silane coated samples were immersed in Hank's solution and the protective performance of the coating was studied through electrochemical impedance spectroscopy (EIS). The EIS data was treated by new equivalent circuit models and the results revealed that the surface conditioning process plays a key role in the effectiveness of the silane coating. The HF treated samples led to the highest impedance values and delayed the coating degradation, compared to the mechanically polished samples or to those submitted to dc polarisation.
► New ormosil coating for improved corrosion protection of bioresorsable Mg alloys. ► New equivalent circuit model for interpretation of the EIS data. ► Surface conditioning is a key step for improved corrosion resistance of the coating.
High entropy alloys have emerged as novel engineering alloys with remarkable mechanical properties in a wide range of temperatures. Among the several high entropy alloys that were already described, ...the equiatomic CrMnFeCoNi alloy is the most studied one. In this work, gas tungsten arc welding of as-rolled CrMnFeCoNi high entropy alloy sheets was performed. The microstructural characterization encompassed the use of electron microscopy, including electron backscattered diffraction, synchrotron X-ray diffraction analysis, microhardness testing and mechanical evaluation. A comprehensive description of the microstructural evolution, including texture and microstrain determination, of the joint is presented and discussed. Upon mechanical testing, the joints systematically failed in the fusion zone due. The large grain size and low hardness of this region justifies the failure location. The joints' mechanical behaviour is correlated with the material microstructure.
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•Gas tungsten arc welding of as-rolled CrMnFeCoNi high entropy alloys is performed.•Defect-free joints with good mechanical behaviour were obtained.•Synchrotron X-ray diffraction was used to study the texture and microstrain along the joint.•Arc-based welding techniques are suitable for welding these novel advanced engineering alloys.
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