In vitro characterization of hydroxyapatite layers deposited by APS and HVOF thermal spraying methods

Titanium alloys are successfully used in medicine as implants due to their high mechanical properties and good biocompatibility. To improve implant osseointegration of titanium alloys, they are covered with hydroxyapatite because of its bioactive properties. Coating the implants with hydroxyapatite by thermal spraying, due to the temperatures developed during the deposition process, the structure can be degraded, leading to formation of secondary phases, such as TCP, TT CP, CaO. The paper presents the experimental results of hydroxyapatite layers deposition by two thermal spraying methods: Atmospheric Plasma Spraying (APS) and High Velocity Oxy-Fuel (HVOF). The microstructure of the deposited layers is characterized by X-ray diffraction analysis and electronic microscopy. The bioactivity of the hydroxyapatite layers was investigated in Simulated Body Fluid (SBF) by immersing the covered samples deposited by the two thermal spraying methods. In both cases the coatings did not present defects as cracks or microcracks. X-ray diffraction performed on hydroxyapatite deposited layers shows that the structure was strongly influenced by plasma jet temperature, the structure consisting mainly of TCP (Ca3PO4)2. The samples deposited by HVO F after immersing in SBF lead to formation of biological hydroxyapatite, certifying the good bioactivity of the coatings

Identification of the Magnetic Model of Permanent-Magnet Synchronous Machines Using DC-Biased Low-Frequency AC Signal Injection

This paper proposes a simple procedure for accurate identification of the magnetic model of permanent-magnet synchronousmachinesthroughinvertersupply.Theproposedmethod accounts for the magnetic saturation and the cross-saturation effects. The identification methods reported in the literature may require a servomotor to drive the motor under test at controlled constant speed or the motor itself must accelerate and decelerate. The technique proposed here can be applied at standstill with or without rotor locking and uses a dc+ac injection strategy to identify the machine inductances to construct its magnetic model. The direct current sets the operating point, whereas the superimposed ac component estimates the inductance at that particular point. Small ac signal is injected to ensure local linearity of the magnetic characteristic. Saturation effects are automatically accounted for by the dc bias level, and cross-saturation effects are quantified through maintaining a constant current along the cross-axis. The magnetic model thus obtained can be used for optimal control of the machine and for accurate torque estimation in vectorcontrolled drives

Performance analysis of slope and frequency modulated carrier PWM methods for grid connected converters

A detailed analysis of two Pulse-Width Modulation (PWM) methods is performed in this paper for grid connected converters. The considered methods are: sinusoidal carrier regulated by the slope of a trapezoidal waveform PWM (SLPWM) and frequency modulated triangular carrier PWM (HIPWM-FMTC). The analysis of the two PWM methods is realized with four performance indicators: standard and weighted total harmonic distortion (THD and WTHD), fulfillment of the grid connection requirements and minimum pulse width. The results are compared with those obtained for the Space Vector Modulation (SVPWM) and Selective Harmonic Elimination PWM (SHE-PWM). Experimental results are presented for a 1 kVA inverter prototype to validate the paper conclusions

Secondary prevention- an essential component of the comprehensive rehabilitation of patients with heart failure

Heart failure is currently a real public health problem due to the extremely high morbidity and mortality of this disease. In this context, cardiovascular prevention measures should be implemented as early as possible. In addition to classic prevention measures, a number of extremely important specific recommendations should be considered: informing patients about their underlying disease, identifying the cardiovascular and non-cardiovascular factors that have led to cardiac decompensation, reducing daily salt consumption, monitoring body weight, forbidding smoking and recreational substances, conducting a regular exercise program under supervision, and increasing adherence to treatment

Characteristics and Trends of COVID-19 Infection in a Tertiary Hospital in Romania: A Retrospective Study

(1) Background: The outbreak of the COVID-19 pandemic represented a real challenge for all of humanity. Characterized by a complex spectrum of signs and symptoms, by various severity degrees, the disease spread rapidly around the world. After more than two and half years since the beginning of COVID-19 pandemic, in the context of a paradoxical, enigmatic, and relentless COVID-19, the objective of the current study was to evaluate the characteristics and evolution of patients with SARS-CoV-2 infection, hospitalized in “St. Parascheva” Clinical Hospital of Infectious Diseases (Iasi, Romania). (2) Methods: This is a retrospective study that used the medical database recorded between July and November 2021 in order to highlight the characteristics of SARS-CoV-2 infection in patients from the northeastern region of Romania. (3) Results: We enrolled in the study a total of 1732 SARS-CoV-2 infected patients, mean age 67 ± 3.4 years, the female gender predominating (987 cases; 56.98%) as well as patients from the urban environment (982 patients; 56.69%). Moderate form of the disease predominated (814 cases; 47%), pulmonary imaging changes were found in 1042 (60.16%) cases, and 1242 (71.71%) patients had at least one underlying disease. After a median length of hospitalization of 9.5 days, 1359 (78.46%) patients were discharged cured, 48 (2.77%) were transferred to other services by decompensating the associated pathologies, 302 (17.43%) patients needed extensive support in the intensive care unit and there were 325 (18.76%) deaths. (4) Conclusions: The epidemiological characteristics of SARS-CoV-2 infection recorded in our study were mostly the same as characteristics of COVID-19 from all over the world

The effect of cardiac pacemaker implantation on cardiac performance – the experience of a Cardiology – Rehabilitation Department

Background. Although cardiac pacemakers can prevent the occurrence of heart failure secondary to low cardiac output in patients suffering from extreme bradycardia, they can also induce, in some circumstances, heart failure by decreasing the left ventricular stroke volume. In our study, we aim to describe the effect of permanent cardiac pacing on the evolution of patients with heart failure, objectively determined by the N-terminal pro b-type natriuretic peptide (NT-proBNP) dynamics. Material and methods. Complete clinical examination and determination of NT-proBNP were performed before and 5 days after pacemaker implantation. Results. We enrolled in our study 32 patients with an indication for permanent cardiac pacing in which we implanted 21 single-chamber ventricular pacemakers (VVI, 65.6%), 4 single-chamber atrial pacemakers (AAI, 12.5%) and 7 dual-chamber atrio-ventricular pacemakers (DDD, 21.9%). Patients with heart failure had an average NT-proBNP value of 2542.2±2311.12 pg/mL and patients without heart failure (control group), had an average NT-proBNP value of 190.58±98.16pg/mL. Patients in sinus rhythm that received a VVI pacemaker experienced an increase in NT-proBNP values of 103.73%, while patients in atrial fibrillation and VVI of only 0.27%. NT-proBNP values decreased in patients in sinus rhythm that received a DDD or AAI pacemaker by 20.94%. Conclusion. Permanent cardiac pacemakers are able to influence the clinical status of patients with heart failure, especially if they cause the loss of atrio-ventricular synchronis