Effect of Blade Geometry on γ' Lattice Parameter and Primary Orientation of SX Cored Turbine Blades (II).

The distributions of the lattice parameter of the γ'-phase (aγ') and angular components of the primary crystal orientation along the lines parallel to the main axis of the single-crystalline CMSX 4-cored turbine blades were studied. The studies were carried out on the regions of the blades located far from the selector and its continuer extension (CE), positioned asymmetrically relative to the blade's axis. It was found that, similarly to the regions of the blade located close to the CE (studied in part I), at the level of the blade related to the change of its cross-section, there were correlated local changes in aγ' and the angular components of the primary crystal orientation representing the bending of the dendrites. However, the correlation was less clear due to the presence of low-angle boundaries (LABs) and the intensification of the consequences of the "fanning effect" in the regions far from the CE. It was found that the range of local changes in aγ' and the angular components of the primary crystal orientation of the blade regions were influenced by both the distance from the CE and the separation of these regions from the CE by surfaces of the cooling bores. It was found that the deviation angle in the [001] direction from the blade axis increased with an increase in the distance from the CE. Based on the aγ' changes, differences in the alloying element concentration near the cooling bores were discussed.

Correlation between the Dendritic Structure and Lattice Parameter of γ'-Phase in Single-Crystalline Turbine Blades Made of Superalloys.

The dendritic structure and the distribution of the γ'-phase lattice parameter (aγ') along selected lines of the longitudinal section in a model single-crystalline blade made of CMSX-4® nickel-based superalloy were studied. It was established that there is a correlation between the value of the aγ' and the predomination of initial or ending fragments of the secondary dendrite arms. It is most noticed for the areas where the dendrite growth conditions are similar to steady. They are located in the center and near the root's selector extension (SE) area. The correlation has been related to the dendritic segregation mechanism. It was shown that in the single-crystalline blades obtained by the directional crystallization using a spiral selector, the "walls" of the primary dendrite arms that grow at a low angle to the blade axis are created. It was found for the first time that the value of the lattice parameter aγ' is decreased near such "walls". Additionally, it was found that competitive growth of the dendrites may occur at a distance of even several millimeters from the bottom surface of the root. The first-time applied X-ray diffraction measurements of aγ' made in a single-pass along the line allow the analysis of the dendritic segregation in the whole blade cast.

Effect of Blade Geometry on γ' Lattice Parameter and Primary Orientation of SX Cored Turbine Blades (I).

The γ' lattice parameter aγ' and the α angle defining the primary crystal orientation of the single-crystalline cored turbine blades made of CMSX-4 superalloy were measured in the areas located near the selector situated asymmetrically, considering the top view of the blade. The distributions of the aγ' and the α angle were determined along the lines parallel to the vertical blade axis Z using X-ray diffraction methods. The relations between changes in the aγ'(Z) and α(Z) were analyzed on the Z levels where the shape of the blade's cross-section changes. For the first time, the local increase in aγ'(Z) was found near the root-airfoil connection level and near certain other root levels, which is related to the change in blade section shapes on such levels. The local extremes in α(Z), representing the dendrite bend, were observed at these levels. The increase in the aγ'(Z) with the local bending of dendrites was discussed concerning the local redistribution of alloying elements and local residual stresses of the γ-dendrites. For the first time, a method of analyzing the local bending of the dendrites was proposed by studying the behavior of the α(Z). The presented results concern the first stage of the research covering areas relatively close to the selector, considering the top view of the blades. The second stage will include the analysis of the areas of the blade localized at a longer distance from the selector.

Management of High-Risk Atherosclerotic Patients by Statins May Be Supported by Logistic Model of Intima-Media Thickening.

While the use of statins in treating patients with atherosclerosis is an undisputed success, the questions regarding an optimal starting time for treatment and its strength remain open. We proposed in our earlier paper published in Int. J. Mol. Sci. (2019, 20) that the growth of intima-media thickness of the carotid artery follows an S-shape (i.e., logistic) curve. In our subsequent paper in PLoS ONE (2020, 15), we incorporated this feature into a logistic control-theoretic model of atherosclerosis progression and showed that some combinations of patient age and intima-media thickness are better suited than others to start treatment. In this study, we perform a new and comprehensive calibration of our logistic model using a recent clinical database. This allows us to propose a procedure for inferring an optimal age to start statin treatment for a particular group of patients. We argue that a decrease in the slope of the IMT logistic growth curve, induced by statin treatment, is most efficient where the curve is at its steepest, whereby the efficiency means lowering the future IMT levels. Using the procedure on an aggregate group of severely sick men, 38 years of age is observed to correlate with the steepest point of the logistic curve, and, thus, it is the preferred time to start statin treatment. We believe that detecting the logistic curve's steepest fragment and commencing statin administration on that fragment are courses of action that agree with clinician intuition and may support decision-making processes.

The Influence of the Cooling Bores on Crystal Orientation and Lattice Parameter in Single-Crystalline Cored Turbine Blades.

The areas located near the cooling bores of single-crystalline cored turbine blades made of nickel-based CMSX-4 superalloy were studied. The blades were solidified by the vertical Bridgman technique in the industrial ALD furnace. Longitudinal sections of the blades were studied by Scanning Electron Microscopy, X-ray diffraction topography, X-ray diffraction measurements of the γ'-phase lattice parameter a, and the α angle of the primary crystal orientation. The local changes in α were analyzed in relation to the changes of the dendrite's growth direction near the cooling bores. It was found that in the area approximately 3 ÷ 4 mm wide around the cooling bores, changes of α and a, both in the blade root and in the airfoil occurred. The local temperature distribution near the cooling bores formed a curved macroscopic solidification front, which caused changes in the chemical composition and, consequently, changes in the a value in a range of 0.002 Å to 0.014 Å. The mechanism of alloying elements segregation by tips of the dendrites on the bent solidification front was proposed. The multi-scale analysis that allows determining a relation between processes proceed both on a millimeter-scale and a micrometric and nanometric scale, was applied in the studies.

The Influence of the Cooling Bores on the Dendritic Structure and Crystal Orientation in Single-Crystalline Cored CMSX-4 Turbine Blades.

Single-crystalline cored CMSX-4 blades obtained at a withdrawal rate of 3 mm/min by the vertical Bridgman method were analyzed. The dendritic structure and crystal orientation near the cooling bores of the blades were studied through Scanning Electron Microscopy, the X-ray diffraction measurements of α and ß angular components of the primary crystal orientation, and the γ angular component of the secondary crystal orientation. Additionally, the primary arm spacing (PAS) was studied in areas near and far from the cooling bores. It was found that in the area approximately 3-4 mm wide around the cooling bores, changes occurred in the α, ß, and γ angles, as well as in the PAS. The PAS determined for the transverse section of the root and the linear primary arm spacing (LPAS) determined for the longitudinal sections, as well as their relationship, have been defined for the areas located near the cooling bores and those at a distance from them. The vertical temperature gradient of 29.5 K/cm was estimated in the root areas located near the cooling bores based on the PAS values. The value of this gradient was significantly higher compared to the growth chamber operating gradient of 16 K/cm. The two-scale analysis applied in this study allowed for the determination of the relationship between the process of dendrite array creation proceeding on a millimeter scale, which is associated with the local changes in crystal orientation near the cooling bores, and that which proceeds on a scale of tens of millimeters, associated with the changes in crystal orientation in the whole blade cast.

High-flow nasal oxygen therapy in the treatment of acute respiratory failure in severe COVID-19 pneumonia: a prospective observational study.

INTRODUCTION: A significant proportion of patients with COVID­19 present with a rapidly progressing severe acute respiratory failure. OBJECTIVES: We aimed to assess the efficacy of high­flow nasal oxygen (HFNO) therapy in severe acute respiratory failure in the course of COVID­19 in a noncritical care setting as well as to identify predictors of HFNO failure. PATIENTS AND METHODS: This prospective observational study was conducted between March and December 2020. We enrolled all consecutive patients hospitalized with confirmed SARS­CoV­2 infection in whom HFNO therapy was used. The primary outcome was death or endotracheal intubation within 30 days from admission. RESULTS: Of the 380 patients with COVID­19 hospitalized at our tertiary center, 116 individuals (30.5%) requiring HFNO due to severe pneumonia were analyzed. The primary outcome occurred in 54 patients (46.6%). The overall 30­day mortality rates were 30.2% (35 out of 116 patients) in the entire cohort and 64.7% (34 out of 51 patients) among individuals requiring endotracheal intubation. A multivariable analysis revealed that the ROX index (the ratio of oxygen saturation / fraction of inspired oxygen to respiratory rate) below 3.85 measured within the first 12 hours of therapy was related to increased mortality (hazard ratio, 5.86; 95% CI, 3.03-11.35) compared with the ROX index of 4.88 or higher. CONCLUSIONS: The results of our study suggest that nearly half of patients treated with HFNO due to severe COVID­19 pneumonia will require mechanical ventilation. The ROX index is a useful tool for predicting HFNO failure in this population.

A clinical profile and factors associated with severity of the disease among Polish patients hospitalized due to COVID-19 - an observational study.

INTRODUCTION: The coronavirus disease 2019 (COVID-19) is one of the greatest clinical challenges of the last decades. Clinical factors associated with severity of the disease remain unclear. The aim of the study was to characterize Polish patients hospitalized due to COVID-19 and to evaluate potential prognostic factors of severe course of the disease. MATERIAL AND METHODS: An observational study was conducted from March to July 2020 in the Pulmonology and Allergology Department of the University Hospital in Kraków, Poland. Consecutive patients with confirmed SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) infection were enrolled, and data about past medical history, signs and symptoms, laboratory results, imaging studies results, in-hospital management and outcomes was prospectively gathered. RESULTS: The study sample comprised 100 patients at the mean age of 59.2 (SD 16.1) years among whom 63 (63.0%) were male. Among them 10 (10.0%) died, 47 (47%) presented respiratory failure, 15 (15.0%) were transferred to the intensive care unit, 17 (17.0%) developed acute kidney injury, 7 (7.0%) had sepsis and 10 (10.0%) were diagnosed with pulmonary embolism. Multivariable analysis revealed age (OR 1.1; 95% CI 1.01-1.15), body mass index (BMI; OR 1.24; 95% CI 1.01-1.53), modified early warning score (MEWS; OR 3.95; 95% CI 1.48-12), the highest d-dimer value (OR 1.73; 95% CI 1.03-2.9) and lactate dehydrogenase (LDH; OR 1.16; 95% CI 1.03-1.3) to be associated with severe course of COVID-19. CONCLUSION: This observational study showed that almost half of hospitalized patients with COVID-19 developed respiratory failure in the course of the disease. Increasing age, BMI, MEWS, d-dimer value and LDH concentration were associated with the severity of COVID-19.

Heterogeneity of the Dendrite Array Created in the Root of Cored SX Turbine Blades during Initial Stage of Crystallization.

The roots of cored single-crystalline turbine blades made of a nickel-based CMSX-4 superalloy were studied. The casts were solidified by the vertical Bridgman method in an industrial ALD furnace using the spiral selector and selector continuer situated asymmetrically in the blade root transverse section. Scanning electron microscopy, the Laue diffraction and X-ray diffraction topography were used to visualize the dendrite array and the local crystal misorientation of the roots. It has been stated that heterogeneity of the dendrite array and creation of low-angle boundaries (LABs) are mostly related to the lateral dendrite branching and rapid growth of the secondary and tertiary dendrites near the surface of the continuer-root connection. These processes have an unsteady character. Additionally, the influence of the mould walls on the dendrite array heterogeneity was studied. The processes of the lateral growth of the secondary dendrites and competitive longitudinal growth of the tertiary dendrites are discussed and a method of reducing the heterogeneity of the root dendrite array is proposed.

The Number of Subgrain Boundaries in the Airfoils of Heat-Treated Single-Crystalline Turbine Blades.

In the present study, the dendrites deflection mechanism from the mold walls were subjected to verification regarding its heat-treated turbine rotor blades. The number of macroscopic low-angle boundaries created on the cross-section of the blades' airfoil near the tip was experimentally determined and compared to the number of low-angle boundaries calculated from a model based on the dendrites deflection mechanism. Based on the Laue patterns and geometrical parameters of airfoils, the number of low-angle boundaries occurring at the upper part of the blades airfoil after heat treatment was calculated. This number for the analyzed group of blades ranged from 5 to 9.

Controlling the thickness of the atherosclerotic plaque by statin medication.

Atherosclerosis, a chronic inflammatory disorder of the arterial wall, is a complex process whose dynamics are affected by multiple factors. The disease control consists of restraining it by administering statins. Slowing down or halting the plaque growth depends on the patient age at which the statin treatment begins and on the thickness of the intima-media (IMT) at that time. In this paper, we propose a mathematical model to estimate the sets of atherosclerosis states, from which the use of statins can restrain the disease. Our model is control-theoretic, and the estimated sets are the viability kernels, in the parlance of viability theory. To our best knowledge, this way of modelling the atherosclerosis progression is original. We compute two viability kernels, each for a different statin-treatment dose. Each kernel is composed of the vector [age, IMT] from which the disease can be restrained. By extension, the disease can't be restrained from the kernel complements, this being mainly because of the disease and patient-age advancement. The kernels visualise tradeoffs between early and late treatments, which helps the clinician to decide when to start the statin treatment and which statin dose may be sufficient.

Variation of Crystal Orientation and Dendrite Array Generated in the Root of SX Turbine Blades.

The variation of the crystal orientation and the dendrite array generated in the root of the single-crystalline (SX) turbine blades made of CMSX-4 superalloy were studied. The blades with an axial orientation of the [001] type were solidified by the industrial Bridgman technique using a spiral selector at a withdrawal rate of 3 mm/min. The analysis of the crystal orientation and dendrite arrangement was carried out using scanning electron microscopy, X-ray diffraction topography, and Laue diffraction. It was found that the lateral growth of such secondary dendrite arms, which are defined as "leading" and grow in the root at first, is related to the rotation of their crystal lattice, which is the reason for creation of the low-angle boundary (LAB) type defects. The primary crystal orientation of the selector extension (SE) area determines the areas and directions of the lateral growth of the leading arms. Additionally, it was found that in the SE areas of the root, near the connection with the selector, the spatial distribution of the [001]γ' crystallographic direction has a complex wave-like character and may be related to the shape of the crystallization front.

Primary Crystal Orientation of the Thin-Walled Area of Single-Crystalline Turbine Blade Airfoils.

The thin-walled airfoil areas of as-cast single-crystalline turbine blades made of CMSX-4 superalloy were studied. The blades were produced by the industrial Bridgman technique at withdrawal rates of 2, 3 and 4 mm/min. The angle between the [001] crystallographic direction and blade axis, related to the primary orientation, was defined by the Ω-scan X-ray diffraction method at points on the camber line located near the tip of an airfoil and at points of a line located in parallel and near the trailing edge. Additionally, primary crystal orientation was determined by Laue diffraction at the selected points of an airfoil. The influence of mould wall inclination on the primary crystal orientation of the thin-walled areas is discussed. The effect of change in the [001] crystallographic direction, named as "force directing", was considered with regard to the arrangement of primary dendrite arms in relation to the trailing edge and the camber line. It was stated that when the distance between the mould walls is less than the critical value of about 1.5 mm the "force directing" increases as the distance between the walls of the mould decreases. The effect may be controlled by selecting an appropriate secondary orientation using a seed crystal in the blade production process. The model of dendrite interaction with the mould walls, including bending and "deflection", was proposed.

Defect Creation in the Root of Single-Crystalline Turbine Blades Made of Ni-Based Superalloy.

An analysis of the defects in the vicinity of the selector⁻root connection plane occurring during the creation of single-crystalline turbine blades made of CMSX-6 Ni-based superalloy was performed. X-ray diffraction topography, scanning electron microscopy, and positron annihilation lifetime spectroscopy were used. Comparing the area of undisturbed axial growth of dendrites to the area of lateral growth concluded that the low-angle boundaries-like (LAB-like) defects were created in the root as a result of unsteady-state lateral growth of some secondary dendrite arms in layers of the root located directly at the selector⁻root connection plane. Additional macroscopic low-angle boundaries (LABs) with higher misorientation angles were created as a result of concave curvatures of liquidus isotherm in platform-like regions near selector⁻root connections. Two kinds of vacancy-type defects, mono-vacancies and vacancy clusters, were determined in relation to the LABs and LAB-like defects. Only mono-vacancies appeared in the areas of undisturbed axial growth. Reasons for the creation of macroscopic LABs and LAB-like defects, and their relationships with vacancy-type defects were discussed.

A Control-Theoretic Model of Atherosclerosis.

We propose a control-theoretic aggregate model of the progression of atherosclerosis plaque, a chronic inflammatory disease of the arterial wall, to study the basic features of this disease. In the model, we exploit the role of inflammation in the disease progression, and use statins-drugs commonly recommended in atherosclerosis-to control this progression. We use a logistic function to allow for constrained growth of plaque. In the model, both the patient's age and overall health impact the plaque growth and its sensitivity to statins. The model parameters are estimated using original data, or calibrated using published research as well as our own clinical and laboratory studies. We contend that our model helps to gauge the statins' impact on a patient's plaque thickness, hence the disease's progression and cardiovascular risk, without requiring artery scans.

Percutaneous extrapedicular vertebroplasty with expandable intravertebral implant in compression vertebral body fracture in pediatric patient-technical note.

PURPOSE: The aim of the article is to present the new extrapedicular percutaneous technique for posttraumatic vertebral column fracture. METHODS: A 15-year-old boy needed a surgical Th8 posttraumatic vertebral body (VB) compressive fracture reduction due to insufficient conservative treatment and consistent severe clinical symptoms. After 6 months of external Jevett long-roll brace stabilization, progressive sagittal balance disturbance of thoracic kyphosis was measured and persistent clinical symptoms were observed. It was decided to present a surgical technique method allowing to attempt to reduce VB fracture, rebalance the vertebral column (VC) without any motion limitation, and decrease clinical symptoms. The procedure was performed percutaneously from extrapedicular approach with intravertebral implant (Spine Jack®-Vexim™) and cement (Interface®-Vexim™) under fluoroscopic imaging (Ziehm™ 8000®). RESULTS: The whole procedure was uneventful. Now, the child is free from clinical symptoms and the partial reduction of VB fracture was achieved. The patient has been followed for 3 months. In the control CT scans, the VB fracture reduction is stable and no progression of thoracic kyphosis angle is observed. Furthermore since the surgical procedure, the patient is clinical symptom free. CONCLUSION: The extrapedicular percutaneus technique of VB fracture reduction with intravertebral fixation allowed to partially reduce the VB compressive fracture, rebalance the VC without any motion limitation, avoid external long-roll brace, and eliminate clinical symptoms. The procedure is minimally invasive, fast, and clinically effective. However, the technique should be restricted only to carefully selected clinical cases.

A hybrid technique for ventriculoatrial shunt implantation--technical note.

PURPOSE: The aim of the article is to present the new hybrid technique for ventriculoatrial shunt implantation. METHODS: Two-and-a-half-year-old boy needed ventriculoatrial shunt implantation due to communicating hydrocephalus and impaired absorptive ability of the peritoneum. Because of a complete occlusion of the right internal jugular vein and critical stenosis of a distal part of the left internal jugular vein, the procedure was performed under fluoroscopy guidance in the catheterisation laboratory equipped with a 3-dimensional single plane angiography machine (Philips Allura--The Netherlands). At the level of critical stenosis of the left jugular vein, it was decided to perform a percutaneous venous balloon angioplasty. This procedure allowed inserting the ventriculoatrial shunt into the right atrium. RESULTS: The whole postoperative period was uneventful. Now, the child is free from symptoms of increased intracranial pressure. The boy has been followed for 9 months. In the control MRI examination, the ventricular system did not change as compared with the previous study. CONCLUSION: The disadvantage of the hemodynamic technique is a higher dose of X-ray irradiation in comparison to other techniques. The hybrid technique should be reserved only to very complicated cases.

Towards prediction of HCV therapy efficiency.

We investigate a correlation between genetic diversity of hepatitis C virus population and the level of viral RNA accumulation in patient blood. Genetic diversity is defined as the mean Hamming distance between all pairs of virus RNA sequences representing the population. We have found that a low Hamming distance (i.e. low genetic diversity) correlates with a high RNA level; symmetrically, high diversity corresponds to a low RNA level. We contend that the obtained correlation strength justifies the use of the viral RNA level as a measure enabling prediction of efficiency of an established therapy. We also propose that patient qualification for therapy, based on viral RNA level, improves its efficiency.

Neuroendoscopic techniques in the treatment of arachnoid cysts in children and comparison with other operative methods.

OBJECTIVE: The authors intended to evaluate the application of neuroendoscopic techniques for the treatment of arachnoid cysts in children and compare it with other operative methods. METHODS: The analysis covered the results of treatment of 44 children with arachnoid cysts who were subjected to neuroendoscopic procedures and 62 patients who underwent other operations. RESULTS: The neuroendoscopic treatment of arachnoid cysts was very effective because of low rate of reoperative treatment (six out of 44 patients), no need to change the operative method (40 effective out of total 44 operative procedures), and low rate of persistent worsening (none of 44 patients worsened). CONCLUSIONS: Summing up all the mentioned aspects of neuroendoscopic techniques, the neuroendoscopic techniques were the most suitable operative procedures in the treatment of arachnoid cysts in the presented group of patients, providing that the connection between the lumen of the arachnoid cyst and the cerebrospinal fluid cisterns was of good quality.

Influence of neuroendoscopic third ventriculostomy on the size of ventricles in chronic hydrocephalus.

Our intention was to compare the clinical outcome after surgical treatment of chronic hydrocephalus between patients who were subjected to neuroendoscopic third ventriculostomy and patients who underwent shunt implantation. At the Department of Neurosurgery of the Research Institute of Polish Mothers' Memorial Hospital from 1999 to 2001, 29 children, of an average age of 7 years (+/-7.1 years SD), underwent successful neuroendoscopic procedures, and from 1992 to 1994, 59 children, of an average age of 2 months (+/-1.9 months SD), underwent shunt implantation. The size of the ventricular system was described by the Frontal Horn Index and its change after operative procedures by the ratio of the final to the primary Frontal Horn Index. Head circumference was measured in percentiles according to the Kurniewicz-Witczakowa chart for Polish children. The reduction in head circumference after a neuroendoscopic procedure was, on average, significantly less than after a shunt implantation (0.39 percentiles +/-29.6 SD vs 17.93 percentiles +/-19.93 SD). Concerning the change in ventricular size after a neuroendoscopic procedure, it was noticed that the average ratio of the final to the primary Frontal Horn Index was 0.9. Meanwhile, the same parameter after a shunt implantation was 0.55. Based on the values of the Frontal Horn Indexes, it was observed that the ventricular system in infants after neuroendoscopic procedures was significantly larger than in other age groups (0.7 vs 0.5). After successful neuroendoscopic operations in a group of children suffering from Chiari II malformation, ventricular systems were slightly enlarged. The ratio of the final Frontal Index to the primary Frontal Horn Index was 1.31. In children suffering from chronic hydrocephalus, the average reduction in the size of the ventricular system and the rate of head circumference growth are lower after neuroendoscopic operations than after shunt implantations. Successful neuroendoscopic procedures are characterized by, on average, a higher rate of head circumference growth in infants than in neonates. In addition, the rate of head circumference growth after successful neuroendoscopic procedures could be higher than before the operation, which is clearly visible in children suffering from Chiari II malformation, but it does not mean a constant increase of that parameter during the postoperative period.