Relaksacija aorte pacova indukovana novosintetisanim orto-hlornim derivatom propafenona

The information on the inhibitory effect of propafenone in vascular smooth muscle is sparse. Propafenone acts through blockage of voltage-dependent cardiac Na+ channels, L-type Ca2+ channels, voltage-sensitive K+ (Kv) channels, as well as β-adrenergic receptors in the heart. The introduction of different chemical groups in the benzyl moiety of propafenone influences pharmacological properties of newly developed derivate of propafenone. Here we investigated the effect of new ortho-chloro derivate of propafenone (5OCl) on the vascular tone of precontracted rat aorta. 5OCl produced endothelium-independent relaxation of rat aorta. In order to test the involvement of different ion channels in 5OCl mechanism of action, antagonist of Na+, lidocaine, KV channels, 4-aminopyiridine (4-AP) and L-type Ca2+ channels, nifedipine were used. All tested antagonists of ion channels did not influence the relaxation of rat aorta induced by high a concentration of 5OCl (≥10 μM), but antagonized the relaxation induced by low concentrations of this propafenone derivate. Thus, 5OCl derivate has comparable potency and efficacy as propafenone. According to its interaction with lidocaine, 4-AP and nifedipine it seems that 5OCl partly shares the mechanism of action with propafenone. The mechanism of vasodilatation induced by high micromolar concentration of 5OCl is not defined and further investigations are necessary.Informacije o efektima propafenona na vaskularne glatke mišiće su oskudne. Propafenon blokira voltažno-zavisne Na+ kanale, Ca2+ kanale L-tipa, voltažno-senzitivne K+ (Kv) kanale i β-adrenergičke receptore u srcu. Uvođenje različitih hemijskih grupa u benzilni deo molekula propafenona utiče na promenu njegovih farmakoloških osobina. U ovoj studiji je ispitivan uticaj novog orto-hloro derivata (5OCl) propafenona na vaskularni tonus prekontrahovane aorte pacova. Orto hlorni derivat (5OCl) je izazvao endotel-nezavisnu relaksaciju aortnih prstenova. Da bi se ispitala uloga različitih jonskih kanala u ovoj relaksaciji, korišćeni su lidokain, (antagonist Na+ kanala), 4-aminopiridin (antagonist Kv kanala) i nifedipin (antagonist Ca2+ kanala L-tipa). Testirani antagonisti jonskih kanala nisu uticali na relaksaciju aorte pacova izazvanu visokom koncentracijom 5OCl (≥10 μM), ali su zato antagonizovali relaksaciju aorte koncentracijama 5OCl koje su bile manje od 10 μM. Prema tome, 5OCl derivat ima sličnu jačinu i efikasnost kao propafenon. Prema njegovoj interakciji sa lidokainom, 4-AP i nifedipinom može se reći da je mehanizam dejstva 5OCl sličan propafenonu. Mehanizam vazodilatacije 5OCl derivata u koncentracijama većim od 10 μM nije definisan i za to su potrebna dalja istraživanja

Upravljanje vjetroagregatom otporno na oštećenja kaveza asinkronog generatora

Wind turbines are usually installed on remote locations and in order to increase their economic competence malfunctions should be reduced and prevented. Faults of wind turbine generator electromechanical parts are common and very expensive. This paper proposes a fault-tolerant control strategy for variable-speed variable-pitch wind turbines in case of identified and characterised squirrel-cage generator rotor bar defect. An upgrade of the torque control loop with flux-angle-based torque modulation is proposed. In order to avoid or to postpone generator cage defects, usage of pitch controller in the low wind speed region is introduced. Presented fault-tolerant control strategy is developed taking into account its modular implementation and installation in available control systems of existing wind turbines to extend their life cycle and energy production. Practical implementation aspects such as estimation of variables used in control and estimate errors are considered and respected in operation, as well as fault-induced asymmetries. Simulation results for the case of a megawatt class wind turbine and the identified rotor bar fault are presented.Vjetroagregati se obično postavljaju na udaljene, nepristupačne lokacije te je potrebno spriječiti nastanak kvarova da bi se povećala njihova ekonomska konkurentnost. Kvarovi elektromehaničkih dijelova generatora vjetroagregata česti su i vrlo skupi. U ovom radu predstavljen je koncept upravljanja vjetroagregatima s promjenjivom brzinom vrtnje i zakretom lopatica za slučaj identificiranog i okarakteriziranog oštećenja kaveza asinkronog generatora. Predložena je nadogradnja na postojeći algoritam upravljanja momentom zasnovana na njegovoj modulaciji s obzirom na položaj magnetskog toka generatora. Da bi se izbjeglo ili usporilo širenje napuknuća kaveza generatora, predložena je primjena regulacijskog kruga za zakret lopatica i u režimu rada vjetroagregata ispod nazivne brzine vrtnje. Predstavljena strategija upravljanja razvijena je uvažavajući mogućnost modularnog nadovezivanja na postojeće metode upravljanja već postavljenih vjetroagregata s ciljem produženja njihova životnog vijeka i povećanja proizvodnje energije. Razmatrani su i uvaženi aspekti vezani uz praktičnu izvedbu, kao što je estimacija varijabli korištenih u upravljačkom algoritmu i pripadajuće pogreške estimata, kao i nesimetrije uzrokovane nastankom kvara. U radu su dani simulacijski rezultati za slučaj vjetroagregata iz megavatne klase s dijagnosticiranim napuknućem kaveza rotora

Dental caries in primary and permanent teeth in children's worldwide, 1995 to 2019: a systematic review and meta-analysis

Background: Early childhood caries (ECC) is a type of dental caries in the teeth of infants and children that is represented as one of the most prevalent dental problems in this period. Various studies have reported different types of prevalence of dental caries in primary and permanent teeth in children worldwide. However, there has been no comprehensive study to summarize the results of these studies in general, so this study aimed to determine the prevalence of dental caries in primary and permanent teeth in children in different continents of the world during a systematic review and meta-analysis. Methods: In this review study, articles were extracted by searching in the national and international databases of SID, MagIran, IranMedex, IranDoc, Cochrane, Embase, ScienceDirect, Scopus, PubMed, and Web of Science (ISI) between 1995 and December 2019. Random effects model was used for analysis and heterogeneity of studies was evaluated by using the I2 index. Data were analyzed by using the Comprehensive Meta-Analysis (Version 2) software. Findings: In this study, a total of 164 articles (81 articles on the prevalence of dental caries in primary teeth and 83 articles on the prevalence of dental caries in permanent teeth) were entered the meta-analysis. The prevalence of dental caries in primary teeth in children in the world with a sample size of 80,405 was 46.2% (95% CI: 41.6–50.8%), and the prevalence of dental caries in permanent teeth in children in the world with a sample size of 1,454,871 was 53.8% (95% CI: 50–57.5%). Regarding the heterogeneity on the basis of meta-regression analysis, there was a significant difference in the prevalence of dental caries in primary and permanent teeth in children in different continents of the world. With increasing the sample size and the year of study, dental caries in primary teeth increased and in permanent teeth decreased. Conclusion: The results of this study showed that the prevalence of primary and permanent dental caries in children in the world was found to be high. Therefore, appropriate strategies should be implemented to improve the aforementioned situation and to troubleshoot and monitor at all levels by providing feedback to hospitals

Epidemiological characteristics of hip fractures in Belgrade from 1990 to 2000

The objective of this study was to estimate the incidence of hip fractures in Belgrade for the period 1990-2000, and to determine distribution of fractures according to sex, age, and causes of injuries. Data based on medical records of the National Health Service in Belgrade were collected from all orthopedic hospitals and departments in Belgrade. A total number of 8904 hip fractures were included in the analysis, out of which 64.7% occurred in women. During the survey period, the estimated average annual incidence rate of hip fractures was 51.7/100 000 (95% Cl= 48.1-55.4); 66.2/100 000 (95% Cl= 60.8-72.1) in women and 35.3/100 000 (95% Cl= 31.4-40.1) in men, respectively. In the age group s50 years, the incidence rates standardized by the 1985 US population were 228 and 96 per 100 000 female and male population, respectively. An exponential increase in the incidence of hip fractures with age was observed in both sexes, especially in women. The number of trochanteric fractures was 4718 (53.0%), compared with 4186 (47.0%) cervical fractures. Observation at three time points, in 1990,1995,2000, indicated the pronounced increase of trochanteric fractures in women and less distinctive in men. Fall on the flat ground resulted in 70.3% of hip fractures among persons aged 50 years or older, and traffic accidents were recorded as the major cause in 59.7% of patients under 50 years of age

“Close–open–close free-flap technique” for the cover of severely injured limbs

The treatment of severely injured extremities still presents a very difficult task for trauma orthopaedic surgeons. Despite improvements in technology and surgical/microsurgical techniques, sometimes a limb must be amputated, otherwise severe and potentially fatal complications may develop. There is a well-established belief that severe open fractures should be left open. However, Godina proved wound coverage in the first 72 h (after an injury) to be safe and to bring good final results. So early wound cover (no later than one week after an injury) with well vascularized free flaps became the gold standard. Yet for many patients (some of whom have serious health problems), operative treatment needs to be postponed when they arrive to specialized microsurgical departments for microsurgical reconstruction much later than one week after incurring an injury. As the definite wound cover period from one week to 3 months seems to be hazardous, especially due to the potential of infection, we developed a safe, original flap technique that prevents infection and covers important structures such as exposed bones, tendons, nerves and vessels. We named this technique the “close–open–close free flap technique”. It enables difficult wound cover in any biological phase of the wound, by combining complete flap cover first, with the removal of stitches from one side of the flap after 6–12 h. This technique works very well for borderline cases as well; where even after a complete debridement, dead tissue still remains in the wound - making wound cover very dangerous. Closing completely severe open fractures with free (or pedicled) flaps and removing the stitches on one side after 6–12 h, enables orthopaedic surgeons to safely cover any kind of wound in any biological phase of the wound. Additional debridements, lavages and reconstructions can easily be performed under the flap and after the danger of a serious infection has disappeared, definitive wound closure can be carried out. © 201