The Oxidation of the HiSiMo Cast Irons Alloyed with Cr/Al at 800 °C

To improve the oxidation resistance of cast iron containing Si and Mo (HiSiMo), 1wt.% Cr and 3wt.% Al were added into the base alloy to improve high temperature oxidation resistance for exhaust manifold applications. Oxidation tests were performed in both dry and wet air (air + 10% H2O) at 800 °C for 1, 10, 24, and 50 h. The mass change and oxide thickness were measured to evaluate the oxidation resistance. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS) and transmission electron microscopy (TEM) were employed to characterize the oxidized samples. The results showed that the additions of Al or Cr selectively oxidized to form a more oxidation resistant surface oxide layer, which reduced the mass gain during these experiments

Nonmonotonic Effect Of Chemical Heterogeneity On Interfacial Crack Growth At High-angle Grain Boundaries In Fe-Ni-Cr Alloys

An intermittent pattern is observed in the modeling of interfacial cyclic-loading crack growth at high-angle grain boundaries in ternary Fe-Ni-Cr alloys. Different from conventional wisdom of stress-intensity factor, the abrupt crack advances are found driven by extreme value statistics - namely, the aggregation of atoms with most compressive residual stresses. In addition, inherently non-affine atomic stress fluctuations are discovered, and the fluctuations peak at intermediate level of chemical heterogeneity, causing the fastest crack growth. Implications of such nonmonotonic mechanism in regard to the origin of intermediate-temperature embrittlement phenomena are also discussed

Atom Skimmers and Atom Lasers Utilizing Them

Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam

Royan Institute First Attempts: Autotransplantation of Vitrified Human Ovarian Tissue in Cancer Patients

Today, timely diagnosis and therapeutic progress open a road of hope for survival in cancerous patients. Increasedknowledge about the various cytotoxic treatment's impacts on ovarian function and fertility has resulted in a surgein the number of patients seeking to preserve their fertility before starting the anti-cancer treatment process. In thisregard, embryo cryopreservation can be recommended for fertility preservation when the woman is married and hasadequate time for ovarian stimulation. If patients are prepubertal girls or not married women, oocytes or ovarian tissuecan be frozen instead to be used in the future. In this regard, the first attempts for ovarian tissue transplantations wereconducted in 2016 and in 2019 for two cancerous patients whose ovarian tissue was cryopreserved in the RoyanHuman Ovarian Tissue Bank (Tehran, Iran). Unfortunately, the transplantations did not result in a live birth

A pulsed positron beam to measure the DOUBLET-2S(1) to TRIPLET-2P(J) energy intervals in positronium: Discovery of chaotic transport.

A pulsed positron beam has been developed at the University of Michigan to conduct precision measurements of the fine structure intervals (\nu\sb{J}) between the \rm2\sp3S\sb1 and \rm2\sp3P\sb{J} $(J=0,$ 1, 2) states of positronium (Ps) to a precision of }300. This method relies on efficient photoionization of the \rm2\sp3S\sb1 state by a pulsed laser, and subsequent detection of photopositrons. The technique, therefore, necessitates the use of a pulsed positron beam to form Ps. A cylindrical Penning trap was built and optimized to provide such a pulsed positron beam. The Michigan accumulator was originally designed to rely on raising the positron source potential to energetically exclude positrons from returning to the source region. This system, however, exhibited several unexpected behaviors that were ultimately discovered to be due to a stochastic transport between the axial and transverse motions, arising from the end-cap electric fields. Detailed simulations of positron trajectories were conducted. Poincare sections of these simulations display the role of this transport mechanism in transforming the trapped positron phase space and fully explain the accumulation data. This transport was utilized, in conjunction with increasing the positron source potential, to achieve surprisingly high trapping efficiencies (10-45% at 100-1000 Hz), providing the desired pulsed beam. Initial tests of the photoionization detection scheme, however, proved the necessity of improving the pulsed beam characteristics. The trapped positrons were consequently remoderated and focused to obtain a beam that is precisely suited to measure \nu\sb{J} to $\sim$100 kHz, constituting the most sensitive test of Ps energy levels. Moreover, a detailed consideration of this transport may be important to optimization of other Penning traps and also presents the latest opportunity to rigorously study the onset of chaos.Ph.D.Atomic physicsPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/130242/2/9721984.pd

The Relation between Left Coronary Dominancy and Atherosclerotic Involvement of Left Anterior Descending Artery Origin

Introduction: Limited information is available regarding the relationship between coronary vessel dominance and atherosclerotic involvement. Rheological factors have been implicated in the pathogenesis of coronary lesions. More than 90% of the coronary blood flow enters the left coronary if it is the dominant artery. The main purpose of this study was to determine the relation between left coronary dominance and atherosclerotic involvement of left anterior descending artery (LAD) origin. In addition, the prevalence and degree of associated ischemic mitral regurgitation (MR) in these patients were assessed. Methods: The study included 678 consecutive patients with an indication for coronary angiography. One hundred and twenty two patients with right dominant and 61 patients with left dominant arteries were randomly selected for analysis. All demographics, risk factors, coronary dominancy and involvement, left ventricular ejection fraction (LVEF), and MR were recorded. Results: One hundred and eighty three patients (mean age of 57.7 years) were studied. The types of coronary circulation included right, left, and balanced in 78.6%, 8.9%, and 12.5%, of the patients respectively. In 64 patient with significant LAD lesions, 22 (34.9%) had ostial while the remainder had non-ostial involvement. Ischemic MR was present in 5 (2.7%) patients. There was no difference in demographics, risk factors, LVEF, MR, extent of coronary artery disease, and LAD ostial involvement between left and right dominant circulations. Conclusion: In this study, left coronary dominance was not associated with atherosclerotic involvement of LAD ostium and ischemic MR

Predicting the Energetics and Kinetics of Cr Atoms in Fe-Ni-Cr Alloys Via Physics-Based Machine Learning

The energy and activation barrier distributions of Cr atoms in austenitic alloys are investigated over a multiplicity of modeling samples across a wide range of chemical (e.g. solid solutions vs. segregated states) and microstructural (e.g. bulk vs. grain boundaries) environments. Assisted with a physics-based machine learning algorithm, it is found that the thermodynamic and kinetic behaviors of Cr atoms can be reliably predicted according to the local electronegativity (χ) and free volume of local atomic packing (Vv). The corresponding predictive maps in the χ-Vv parameter space are established, which are in line with existing experiments and validated by a parallel modeling with a different interatomic force field. The implications of the present study regarding its potential to guide the design of austenitic alloys with desired properties are also discussed

Area under the Curve-Based Dosing of Vancomycin in Critically Ill Patients Using 6-Hour Urine Creatinine Clearance Measurement

Background. The area under the curve- (AUC-) guided vancomycin dosing is the best strategy for individualized therapy in critical illnesses. Since AUC can be calculated directly using drug clearance (CLvan), any parameter estimating CLvan will be able to achieve the goal of 24-hour AUC (AUC24 h). The present study was aimed to determine CLvan based on 6-hour urine creatinine clearance measurement in critically ill patients with normal renal function. Method. 23 adult critically ill patients with an estimated glomerular filtration rate (eGFR) ≥60 mL/min who received vancomycin infusion were enrolled in this pilot study. Vancomycin pharmacokinetic parameters were determined for each patient using serum concentration data and a one-compartment model provided by MONOLIX software using stochastic approximation expectation-maximization (SAEM) algorithm. Correlation of CLvan with the measured creatinine clearance in 6-hour urine collection (CL6 h) and estimated creatinine clearance by the Cockcroft–Gault formula (CLCG) was investigated. Results. Data analysis revealed that CL6 h had a stronger correlation with CLvan rather than CLCG (r = 0.823 vs. 0.594; p<0.001 vs. 0.003). The relationship between CLvan and CL6 h was utilized to develop the following equation for estimating CLvan: CLvan (mL/min) = ─137.4 + CL6 h (mL/min) + 2.5 IBW (kg) (R2 = 0.826, p<0.001). Regarding the described model, the following equation can be used to calculate the empirical dose of vancomycin for achieving the therapeutic goals in critically ill patients without renal impairment: total daily dose of vancomycin (mg) = (─137.4CL6-h (mL/min) + 2.5 IBW (kg)) × 0.06 AUC24 h (mg.hr/L). Conclusion. For AUC estimation, CLvan can be obtained by collecting urine in a 6-hour period with good approximation in critically ill patients with normal renal function