The Influence of Wagon Structure Part Shape Optimization on Ultimate Fatigue Strength

This study investigates how shape optimisation affects the ultimate fatigue strength of a mechanical part. The mechanical part chosen for this investigation is an axle guard of running gear elements of the Hccrrs 2x2 axle car-carrying wagon. The static and fatigue strength analysis procedure according to the UIC 517 standard and numerical methods have been applied. Material properties were determined experimentally and the necessary numerical calculations were performed by using the finite element method. The observed axle guard is exposed to low cycle fatigue. ε-N curves and material properties of the S355J2+N steel grade are obtained by combining theoretical formulae and a mathematical function. According to the obtained experimental and numerical results the number of cycles until failure for both shapes of axle guards is obtained

Influence of body mass, tryptophan concentration and certain environmental factors on behavior and production parameters of weaned piglets

Istraživanje je sprovedeno prema postavljenom cilju na eksperimentalnoj farmi Instituta za stočarstvo, Beograd - Zemun. Istraživanje je obuhvatalo 432 zalučene prasadi oba pola, rasa veliki jorkšir i švedski landras, kao i meleze tih rasa. Prasad su uvedena u istraživanje nakon odbijanja (u starosti od 30 dana), kada su izmerene telesne mase. Na osnovu telesne mase i pola su formirane homogene grupe (osim u tretmanu sa neujednačenim telesnim masama). U svakoj grupi je bilo po 7 jedinki (4 muška i 3 ženska praseta), osim u trećem tretmanu, kada je bio ispitivan uticaj gustine naseljenosti. Ispitivanja su trajala do šestog dana po zalučenju, kada je bilo i završno merenje telesne mase. Svi tretmani podrazumevali su formiranje 4 grupe prasadi - kontrolna (KG) i ispitivane grupe (IG1, IG2 i IG3) prema sledećem rasporedu: u prvom tretmanu koristio se L-triptofan kao dodatak potpunoj smeši u 3 različite koncentracije (za IG1, IG2 i IG3, redom: 0,1%, 0,2% i 0,3% u starter-smešama sa početkom od 10 dana pre uvođenja u istraživanje i tokom trajanja istraživanja); u drugom tretmanu se pratio uticaj intenziteta osvetljenja (KG - 60 lx, pojačano osvetljenje za IG1 i IG2 - 100 i 150 lx, redom, i smanjeno osvetljenje za IG3 - 40 lx); u trećem tretmanu je bio ispitivan uticaj gustine naseljenosti (KG -7, povećana gustina naseljenosti za IG3 i IG2 – 11 i 9 prasadi, smanjena za IG1 – 5 prasadi u kavezu); u četvrtom se pratio uticaj telesne mase (KG – 7 prasadi približne telesne mase, za IG1 – 2 teža i 5 lakših prasadi, za IG2 - 3 teža i 4 lakša praseta, i IG3 - 5 težih i 2 lakša praseta); i u petom tretmanu se ispitivao uticaj obogaćenja sredine (crvena lopta prečnika 10 cm sa kracima (IG1), pamučna užad dužine 40 cm okačena za stranice kaveza (IG2) i slama 200g dnevno na punom delu poda (IG3)) na ponašanje i proizvodne rezultate. Tokom istraživanja praćeni su prozvodni parametri (konzumacija hrane, dnevni prirast i konverzija hrane), kompletno ponašanje (pomoću kamera) i parametri krvi (Pig-MAP, laktati i haptoglobin). Dodatak triptofana u standardnu farmsku smešu nije značajno uticao na proizvodne parametre i na parametre krvi, ali je imao pozitivan efekat na izmenu obrazaca ponašanja kod prasadi. Različiti intenziteti osvetljenja nisu značajno uticali na proizvodne parametre i ponašanje kod prasadi, ali su značajno uticali (p<0,05) na koncentraciju laktata u krvi. Povećana gustina naseljenosti je značajno pozitivno uticala na proizvodne parametre (prosečan dnavni prirast i konverziju hrane) (p<0,05) i na koncentraciju Pig-Map-a u krvi (p<0,05; p<0,01), dok je negativno uticala na pojavu agresije i griže kod prasadi (p<0,05). Telesna masa je značajno i veoma značajno uticala na koncentraciju Pig-MAP-a (p<0,05; p<0,01) i laktata (p<0,05) između ispitivanih grupa. Obogađivanje sredine je značajno uticalo (p<0,05) na smanjenje broja konflikata i griže između ispitivanih grupa prasadi. Slama se pokazala kao najbolji material za obogaćivanje sredine u istraživanju. Obogaćivanje sredine je pozitivno uticalo (p<0,05) na poboljšanje aftektivnih stanja kod prasadi tokom prvih 24 časa nakon formiranja grupa.According to the set goal, the research was carried out at the experimental farm of the Institute for Animal Husbandry, Belgrade - Zemun. The research included 432 reared piglets of both sexes, Large White and Swedish Landrace breeds, as well as their crossbreeds. Piglets were introduced into the research after weaning (at the age of 30 days) when their body weights were measured. Homogeneous groups were formed based on body mass and gender (except in the trial with uneven body mass). There were 7 individuals in each group (4 male and 3 female pigs), except in the third treatment when the influence of population density was examined. The examinations lasted until the sixth day after the mixing when the final measurement of body weight took place. All treatments were based on the formation of 4 groups of piglets - control (KG) and test groups (IG1, IG2 and IG3) according to the following schedule: in the first treatment, L-tryptophan was used as an addition to the complete mixture in 3 different concentrations (for IG1, IG2 and IG3 , respectively: 0.1%, 0.2% and 0.3% in starter-mixtures starting 10 days before introduction into the experiment and during the research); in the second treatment, the influence of lighting intensity was monitored (KG - 60 lx, increased lighting for IG1 and IG2 - 100 and 150 lx, and reduced lighting for IG3 - 40 lx); in the third treatment, the influence of population density was examined (KG -7, increased population density for IG3 and IG2 – 11 and 9 piglets, decreased for IG1 – 5 piglets in a cage); in the fourth, the influence of body weight was monitored (KG - 7 piglets of similar body weight, for IG1 - 2 heavier and 5 lighter piglets, for IG2 - 3 heavier and 4 lighter piglets, and IG3 - 5 heavier and 2 lighter piglets); and in the fifth treatment, the influence of environmental enrichment (a red ball with arms with a diameter of 10 cm (IG1), cotton ropes 40 cm long suspended from the sides of the cage (IG2) and straw 200g per day on the full part of the floor (IG3)) on behavior and production results was examined. During the experiment, production parameters (food consumption, daily gain and feed conversion), complete behaviour (using cameras) and blood parameters (Pig-MAP, lactates and haptoglobin) were monitored. The addition of tryptophan to the standard farm mixture did not significantly affect the production parameters and the blood parameters, but it had a positive effect on changing the behaviour patterns of the piglets. Different lighting regimes did not affect the production parameters and behaviour of piglets, but they affected (p<0.05) the concentration of lactate in the blood. Increased population density had a significant positive effect on production parameters (average daily gain and feed conversion) (p<0.05), on Pig-Map concentration in blood (p<0.05; p<0.01), while it had a negative effect on the aggression and biting in piglets (p<0.05). Body mass significantly and very significantly influenced the concentration of Pig-MAP (p<0.05; p<0.01) and lactate (p<0.05) between the studied groups. Environment enrichment had a significant effect (p<0.05) on the reduction of the number of conflicts and biting between the examined groups of piglets. Straw proved was the best manipulative material in the experiment. Enrichment of the environment had a positive effect (p<0.05) on the improvement of affective states in piglets during the first 24 hours after the formation of groups

Uticaj dodavanja organskog selena na proizvodne karakteristike fazana

The effect of organic selenium as feed additive contained in the feed was investigated, applied in concentrations of 0.3 and 0.4 mg Se/kg mixture on production characteristics pheasant. The study was conducted on a total of 45 common pheasant individuals Phasianus colchicus, six weeks old, divided into three equal groups of 15 individuals for 60 days. The control pheasants group was fed with a standard mixture without addition of selenium during the experiment, while the mixture of group I contained 0.15 g/kg and pheasants group II had 0.20 g/kg additives with organic selenium. The results showed that different amounts of organic selenium presence in pheasants' feed had a positive effect on analyzed productivity indicators of pheasants' growth rate, both their final body weight and weight gain (p (lt) 0.05). Among examined groups of pheasant, gained differences in average feed conversion and total production index were not statistically significant (p> 0.05). The best production results were achieved by individual II group, which also had the highest selenium content in muscle tissue of the pectoral muscles, drumstick and thigh (p (lt) 0.05).Na osnovu sprovedenih istraživanja može se zaključiti da je upotreba organskog selena kao dodatka smešama za ishranu fazana imala povoljan učinak na ispitivane proizvodne rezultate i sadržaj selena u mišićnom tkivu i jetri. Najbolje proizvodne rezultate je postigla II grupa fazana u čijoj hrani je upotrebljen organski selen u koncentraciji od 0,4 mg/kg. Nešto niže vrednosti proizvodnih pokazatelja su ostvarili fazani I grupe, čija je smeša sadržavala 0,3 mg/kg selena, dok su najniže vrednosti ispitivanih parametara ustanovljene u K grupi. Rezultati ovog istraživanja pokazuju da fazani osim statusa lovne divljači mogu imati veliki značaj u proizvodnji kvalitetnog mesa sa značajnim sadržajem antioksidanta selena koji bi doprineo prevenciji raznih oboljenja imunog sistema i poboljšanja zdravlja ljudi. Takođe, sa ekonomske tačke gledišta optimatizacijom smeša za ishranu fazana koje sadrže selen može se racionalizovati konverzija hrane i ujedno smanjiti troškovi ishrane

Morfometrijska i imunohistohemijska analiza udruženosti strukturnih promena sa distribucijom psamoma telašaca u horoidnim pleksusima moždanih komora tokom starenja čoveka

During the ageing process, numerous structural and functional changes occur in the cerebral ventricles’ choroid plexus. The formation of psamomma bodies starts at an early age, and is considered a physiological consequence of the ageing process. Using histochemical and immunohistochemical methods, autopsy samples of choroid plexus of all four cerebral ventricles were analyzed morphologically and morphometrically. The structure of the choroid plexus, its epithelium morphology, as well as the distribution and characteristics of the psamommma bodies, were investigated in this study. Besides, the expression of CD44, CD68, osteopontin and osteocalcin, was analyzed. The results of this study showed significant structural changes in choroid plexus during ageing. Choroid plexus arborification and its blood vessels density is reduced. The epitelium changed with presence of high domed, flattened spindle, or large cells expanded by its content. Psamomma bodies in the elderly formed large groups, often inside cysts, and showed an increse in their number and size. Increased osteopontin expression is characteristic younger population choroid plexus, unlike osteocalcin whose expression progressively increases withe age. Psamomma bodies formation and their characteristics are in correlation with changes in the structure of the choroid plexus and its epithelium, during the ageing process in humans. After taking into consideration the role of choroid plexus in the central nervous system homeostasis regulation, the stated changes in ageing choroid plexus and psamomma bodies characteristics, may contribute to the reveiling of the mechanism of fuctional impairement of the brain in the elderly

Application of the 3r concept in the production of European antiviperinum on horses - multisite, low volumes immunization protocol and Elisa

During time, both professionals and general public became aware of the importance of animal welfare. This term not only covers endangered wild animal species, animals used in food industry, pets and experimental animals, but also animals used in production of biologics. The implementation of the 3R concept (Replacement, Reduction and Refinement) is especially important in this type of production. In this article, we describe for the first time the low dose, low volume and multi-site immunization protocol, as well as appropriate ELISA we developed for production of European anti-viper (V. ammodytes, long horned) antivenom in horses, which can help to significantly improve the welfare of the used animals

Polymerization quality testing of composite resins cured by led light source

The quality of interface between composite resin materials and hard dental tissues is highly dependent on the polymerization light source. Newly developed blue light- emitting diode units for light polymerization of dental restorative materials are the most innovative light source technology in dentistry nowadays. The aim of this work was to estimate the depth of cure of five different light-activating composite resins exposed to different irradiation times (5s, 10s, 20s and 40s) when the experimental LED light source was used. The tested materials were: Tetric Ceram (Vivadent), Point 4 (Kerr), Admira (VOCO), Filtek Z250 (3M) and Diamond Lite (DRM Lab., Inc). The depth of cure testing was determined using a penetrometer. Results after 40s curing time were as following: the deepest depth of cure was achieved after application of Filtek Z 250, Diamond Lite Point 4 and Tetric Ceram. For the restorative material Admira was found the lowest depth of cure for the light exposure of 40s. An experimental LED light source achieved a sufficient depth of cure (over 2 mm) for all tested materials after curing time of 10s. The polymerization light source spectral distribution should be considered in addition to irradiance as a depth of cure indicator

Experimental and FE Modeling Investigation of Spot Welded Thin Steel Sheets

The spot welded thin steel sheets specimens are experimentally and numerically examined in this paper. The two specimens are joined using Resistance Spot Welding (RSW) method. The spot-welded joints consist of three zones with different material properties. Change of material properties during the welding process is caused by mechanical and thermal loading. The mechanical properties of thin steel sheets are determined by several tension tests. The specimens are cut in three different directions regarding a rolling direction of the basic material plate. Shear resistance of the spot welded joints is experimentally examined on the universal testing machine by displacement-controlled tensile loading tests. The numerical analysis is performed by large-strain plasticity theory implemented into a Finite Element Method based software. Comparison of the Finite Element (FE) modeling and experimental results verifies the proposed stress integration algorithm and modeling technique as powerful tools for prediction of the spot-welded joint behavior

Kardiorespiratorni fitnes i njegov značaj u reakcijama kortizola i laktata prilikom zimskih i letnjih marševa

Background: The influence of homeostatically regulated physiological processes, including cardiorespiratory fitness (VO2max), on the response to physical stressors such as acclimatisation and marching, remains understudied. We aimed to investigate the effects of summer and winter acclimatisation and marching on cortisol levels and blood lactate, to gain insight into the role of these physiological processes in the stress response. Methods: Two groups of young Europeans, classified as poor (PCF; n=9) and good physical condition (GCF; n=21), based on a VO2max threshold of 40 mL O2/ kg/min, underwent 2-h march (6–7 km/h) in winter (5 ∘C) and summer (32 ∘C). Commercial tests, UniCel DxI Access Cortisol assay and EKF Biosen Clinic/GP assay were used for cortisol and lactate blood measurements (morning samples and those taken immediately after marches), respectively. Results: Basal cortisol levels were significantly higher at 5 °C than at 32 °C (PCF group: P=0.0079; cortisol dropped after the march at 5 °C in both groups, but increased at 32 °C only in PCF. Basal lactate levels were higher at 32 °C only in the GCF group (compared to PCF, P=0.0014) and post-marching (compared to basal values, P=0.0002). Conclusion: Cold exposure elicits a more significant stress response, based on higher basal cortisol levels, in individuals with worse physical fitness. Anaerobe metabolism prevails in participants with better physical fitness exposed to high ambient temperature based on increased basal and post-marching lactate levels. The study is significant for individual training/performance optimisation as it indicates the association between physiological stress responses and individual physical fitness levels.Uvod: Uticaj homeostatski regulisanih fiziolo{kih procesa, uklju~uju}i kardiorespiratornu kondiciju (VO2max), na odgovor na fizi~ke stresore poput aklimatizacije i mar{i- ranja, ostaje nedovoljno prou~en. Cilj istra`ivanja je bio i da se ispita uticaj aklimatizacije i mar{iranja tokom leta i zime na nivoe kortizola i laktoze u krvi, pru`aju}i uvid u ulogu ovih fiziolo{kih procesa u odgovoru na stres. Metode: Dve grupe mladih Evropljana, klasifikovane kao osobe sa slabom (PCF; n=9) i dobrom fizi~kom kondicijom (GCF; n=21), na osnovu praga VO2max od 40 mL O 2/kg/min, su bile izlo`ene dvosatnom mar{u (6–7 km/h) u dva navrata, zimi na 5 °C i leti, na 32 °C. U uzorcima krvi (jutarnji i neposredno nakon mar{a) su odre|ivani nivoi kortizola i laktata komercijalnim testovima, UniCel DxI Access Cortisol i EKF Biosen Clinic/GP. Rezultati: Bazalni nivoi kortizola su bili zna~ajno vi{i na 5 °C nego na 32 °C (u PCF grupi: P=0,0079); nakon mar{i- ranja na 5 °C kortizol opada u obe grupe a pove}an je na 32 °C samo u PCF grupi. Bazalni nivoi laktoze bili su vi{i na 32 °C samo u GCF grupi (porede}i sa PCF grupom, P=0,0014) i nakon mar{iranja (porede}i sa bazalnim vred- nostima, P=0,0002)

Antiarrhythmic Drugs in Atrial Fibrillation

Atrial fibrillation (AF) represents the most common sustained heart rhythm abnormality. It presents in paroxysmal and persistent forms. The pathogenesis of AF is still debatable with several proposed mechanisms. The main pathway for diagnosis of AF is through electrocardiographic record. Treatment strategies can be divided into two strategies: rate and rhythm control. For rhythm control, antiarrhythmic drugs, direct current cardioversion, and electrophysiological ablation are used, while for rate control, chronotropic drugs are being used, while AV node ablation is required in order to reduce rapid ventricular rate, which is often observed in patients with AF. The rhythm control strategy implies the use of cardioversion to convert AF to normal, sinus rhythm. Cardioversion can be either pharmacological or electrical. Rate control strategy can be implied to patients with permanent AF but should also imply for the patients with paroxysmal AF when relapse occurs. Rapid ventricular rates can cause palpitations or even a syncope and other rate-related symptoms; however, these high ventricular rates lead to degradation of left ventricle performance, mitral regurgitation, and further dilatation of the left atrium. The main antiarrhythmic drugs used in treatment of AF are propafenone, flecainide, beta-blockers, amiodarone, dronedarone, dofetilide, vernakalant, and ranolazine