SURGE PROTECTION OF BUILDINGS CONNECTED TO AN OVERHEAD LOW-VOLTAGE NETWORK

U prenaponskoj zaštiti na niskom naponu postoje tri klase uređaja prenaponske zaštite. Predstavljena metoda izbora uređaja prenaponske zaštite može se koristiti pri donošenju odluke koje klase treba biti uređaj prenaponske zaštite koji se postavlja u priključni mjerni ormarić objekta. Metoda je testirana na jednoj tipičnoj nazemnoj niskonaponskoj mreži u Hrvatskoj. S obzirom na dobro iskustvo s uređajima prenaponske zaštite klase II u transformatorskim stanicama u toj mreži, može se zaključiti da je uređaj prenaponske zaštite klae II sasvim primjeren i za objekte spojene na niskonaponsku mrežu.There are three clases of surge protective devices for low-voltage system. The method for the selection of surge protective devices presented can be used to determine which class of surge protectice device should be inastalled in the service entrance of a building. The method has been tested on a typical ovehead low-voltage network in Croatia. Based upon good experience with Class II surge protective devices in the transformer stations of this network, it can be concluded that Class II surge protective devices are quite suitable for buildings connected to a low-voltage network

EVALUATION OF ENERGY STRESS ON LINE ARRESTERS

Line Surge Arresters (LSAs) are efficient means for the improvement of the lightning performance of transmission lines. Determination of optimal LSA number, location and rating is important for the improvement of the reliability and availability of a transmission system. In selection of the LSA special attention should be paid to their energy stress which depends on complex interactions between the arrester locations, grounding, shielding and the local lightning environment. LSAs experience higher energy stress compared to station arresters, because the incoming surge to a station is limited by insulator flashover on the transmission line and impulse corona. In this paper calculations of energy stresses were carried out for a double-circuit 220 kV line with a single shielding wire. Parametric studies were conducted in which arrester discharge energy was a function of: time to half value of stroke current, number of towers with arresters, footing resistance, span length and angle of power frequency voltage. Arrester energy stress is analyzed in case of stroke to tower and shielding failure. From conducted analysis it can be concluded that energy stress on LSAs is lower for shorter span lengths. Tower footing resistance has only minor effect on the discharge energy. Arrester discharge energy strongly depends on time to half of the stroke current, number of towers with installed arresters and angle of power frequency voltage

Relationship Between Osteonecrosis of the Jaw and Bisphosphonate Treatment

Terapija bisfosfonatima i njezina etiopatogenetska povezanost s aseptičkom osteonekrozom čeljusti važan je javnozdravstveni problem današnjice. Svrha je rada pregledom suvremene znanstvene literature utvrditi posljedice višestrukog djelovanja bisfosfonata (antiosteoklastična aktivnost, citotoksičnost na meka i koštana tkiva, antiangiogeneza, genski čimbenici, poremećena ravnoteža između osteoklasta i osteoblasta). Terapija bisfosfonatima jedan je od najčešćih uzroka razvoja osteonekroze čeljusti. Epidemiološki podaci pokazuju da se javlja u bolesnika koji su uzimali jedan ili kombinanciju nitrogenih bisfosfonata. Najvažniji čimbenici rizika za ovu nuspojavu su vrsta bisfosfonata (napose visokopotentni pamidronat i zoledronat koji se daju intravenski), njihova doza i duljina medikacije te vrsta bolesti zbog koje se propisuje terapija. Pojava osteonekroze čeljusti zabilježena je uglavnom u onkoloških bolesnika i u samo 5 % bolesnika s osteoporozom koji su liječeni bisfosfonatima. U patogenezi osteonekroze povezane s bisfosfonatima važno je, sa stajališta dentalnomedicinske prakse, dobro opće oralno zdravlje jer se osteonekroza javlja napose nakon prethodnoga parodontološkog i oralnokirurškog zahvata.Bisphosphonate treatment and its aetiopathogenic association with aseptic osteonecrosis of the jaw is one of the more prominent public health issues today. The aim of this review is to see into the mechanisms of bisphosphonate effects on bones described in literature (anti-osteoclastic activity, cytotoxicity, antiangiogenesis, genetic factors, and imbalance between osteoclasts and osteoblasts). Bisphosphonate treatment is the dominant cause of jaw necrosis. Epidemiological data show an exclusive incidence of osteonecrosis of the jaw in patients who took one or a combination of nitrogen-containing bisphosphonates. Risk factors vary by the bisphosphonate potency (particularly risky are the highly potent pamidronate and zoledronate, which are given intravenously), dosage, duration of treatment, and the illness. Jaw necrosis is most common in oncology patients, and only 5 % in patients with osteoporosis. From a dental-medical point of view, a good oral health is important because osteonecrosis often appears after a periodontal or oral surgical procedure

EVALUATION OF ENERGY STRESS ON LINE ARRESTERS

Line Surge Arresters (LSAs) are efficient means for the improvement of the lightning performance of transmission lines. Determination of optimal LSA number, location and rating is important for the improvement of the reliability and availability of a transmission system. In selection of the LSA special attention should be paid to their energy stress which depends on complex interactions between the arrester locations, grounding, shielding and the local lightning environment. LSAs experience higher energy stress compared to station arresters, because the incoming surge to a station is limited by insulator flashover on the transmission line and impulse corona. In this paper calculations of energy stresses were carried out for a double-circuit 220 kV line with a single shielding wire. Parametric studies were conducted in which arrester discharge energy was a function of: time to half value of stroke current, number of towers with arresters, footing resistance, span length and angle of power frequency voltage. Arrester energy stress is analyzed in case of stroke to tower and shielding failure. From conducted analysis it can be concluded that energy stress on LSAs is lower for shorter span lengths. Tower footing resistance has only minor effect on the discharge energy. Arrester discharge energy strongly depends on time to half of the stroke current, number of towers with installed arresters and angle of power frequency voltage

Evaluation of sensitivity of teeth after mandibular fractures

The sensitivity of teeth anterior to a fracture between the mental and mandibular foramina has been tested and followed up until reinnervation or 3 years has passed. This study assessed the reinnervation period, the number of denervated teeth, and their clinical importance. Fifty patients and 459 teeth were examined. Two hundred and seventy-three teeth were affected and had potentially impaired innervation. Tests after injury showed non-responsive teeth in 81% of affected teeth. Six weeks after injury, 19% of teeth were reinnervated; by 1 year after injury, 92% of initially non-responsive teeth were reinnervated. Most teeth (34%) were reinnervated from 6 weeks to 3 months. All 23/186 initially non-responsive, unaffected, contralateral corresponding teeth were reinnervated within 6 weeks. A year after injury, 95% of incisors, 91% of canines, 94% of premolars, and 82% of molars were reinnervated. Three years after injury, 8% of teeth remain denervated. During the second and third years, no reinnervation occurred, but clinical signs of pulp devitalisation of denervated teeth occurred in 18% or 1% of the initially non-responsive affected teeth. The results revealed the stability of pulp 1 year after injury. Denervated teeth should not be treated if no clinical or radiological signs of devitalisation exist

European Maxillofacial Trauma (EURMAT) project: A multicentre and prospective study

The purpose of this study was to analyse the demographics, causes and characteristics of maxillofacial fractures managed at several European departments of oral and maxillofacial surgery over one year. The following data were recorded: gender, age, aetiology, site of facial fractures, facial injury severity score, timing of intervention, length of hospital stay. Data for a total of 3396 patients (2655 males and 741 females) with 4155 fractures were recorded. The mean age differed from country to country, ranging between 29.9 and 43.9 years. Overall, the most frequent cause of injury was assault, which accounted for the injuries of 1309 patients; assaults and falls alternated as the most important aetiological factor in the various centres.The most frequently observed fracture involved the mandible with 1743 fractures, followed by orbital-zygomatic-maxillary (OZM) fractures. Condylar fractures were the most commonly observed mandibular fracture.The results of the EURMAT collaboration confirm the changing trend in maxillofacial trauma epidemiology in Europe, with trauma cases caused by assaults and falls now outnumbering those due to road traffic accidents.The progressive ageing of the European population, in addition to strict road and work legislation may have been responsible for this change. Men are still the most frequent victims of maxillofacial injuries. (C) 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved

Assault-related maxillofacial injuries: the results from the European Maxillofacial Trauma (EURMAT) multicenter and prospective collaboration

Objective The aim of this study is to present and discuss the demographic characteristics and patterns of assault-related maxillofacial fractures as reported by a European multicenter prospective study. Study Design Demographic and injury data were recorded for each patient who was a victim of an assault. Results Assaults represented the most frequent etiology of maxillofacial trauma with an overall rate of 39% and the values ranging between 60.8% (Kiev, Ukraine) and 15.4% (Bergen, Norway). The most frequent mechanisms of assault-related maxillofacial fractures were fists in 730 cases, followed by kicks and fists. The most frequently observed fracture involved the mandible (814 fractures), followed by orbito-zygomatic-maxillary complex fractures and orbital fractures. Conclusions Our data confirmed the strong possibility that patients with maxillofacial fractures may be victims of physical aggression. The crucial role of alcohol in assault-related fractures was also confirmed by our study