Promene krivine vratne kičme i morfologije cervikalnih pršljenova u različitim uzrastima i mogućnost procene skeletne zrelosti

Introduction During growth, proportions of craniofacial and cervical structures are changed. Craniofacial and cervicovertebral structures are morphologically and functionally connected, but their each other's influence is still unknown. Objective The aim of this study was to determine the changes in cervical lordosis and cervicovertebral morphology in different age periods and the possibility of estimating skeletal maturity, based on the percentage of anterior cervical vertebrae body height sum in the total anterior C2-C5 height. Methods The study included lateral radiographs of 120 patients of both sexes, divided into three different age groups: eight, 12-13 and 17-18 years of age. Five craniofacial and 15 cervical parameters were measured and analyzed. Results The results showed significant correlation between cervical lordosis angle and age, gender, anterior and posterior body height of C3, C4, C5, anterior C4-C5 and posterior C2-C3, C3-C4, C4-C5 intervertebral space, anterior body height of C2-C5. Overall values of all cervical body heights were more present in the total height of the spine in females, while all intervertebral spaces were more present in males. The percentage of anterior and posterior C2, C3, C4, C5 body height sum compared to total C2-C5 height increases with age. Conclusion The cervical lordosis becomes more curved and vertebral bodies occupy more space in females, while intervertebral spaces occupy more in males. Skeletal maturity could be estimated following vertebral percentage distribution in the total anterior C2-C5 part.Uvod Tokom rasta proporcije kraniofacijalnih i cervikovertebralnih struktura se menjaju. Ove strukture su morfološki i funkcionalno povezane, ali je njihov međusobni uticaj i dalje nepoznat. Cilj rada Cilj ove studije je bio da se uoče promene krivine vratne kičme i morfologije vratnih pršljenova u različitim uzrasnim grupama, kao i mogućnost procene skeletne zrelosti zasnovane na procentualnoj zastupljenosti zbira prednjih visina vratnih pršljenova C2, C3, C4 i C5 u ukupnoj dužini prednje visine kičme od C2 do C5. Metode rada Studija je obuhvatila 120 ispitanika oba pola koji su svrstani u tri starosne grupe: 8, 12-13 i 17-18 godina. Pet kranijalnih i 15 cervikalnih parametara je mereno i analizirano. Rezultati Rezultati su pokazali statistički značajnu korelaciju između zakrivljenosti vratne kičme i godina, pola, prednje i zadnje visine tela pršljena C2, C3, C4, prednjeg C4-C5 i zadnjeg C2-C3, C3-C4, C4-C5 međupršljenskog prostora. Prosečne vrednosti visine tela vratnih pršljenova procentualno su bile češće kod ispitanica, a svi međupršljenski prostori kod osoba muškog pola. Procenat zbira prednje i zadnje visine pršljena C2, C3, C4 i C5 povećavao se sa godinama. Zaključak Krivina vratne kičme postaje zakrivljenija i tela pršljenova zauzimaju više prostora kod žena, a međupršljenski prostor više kod muškaraca. Procena skeletne zrelosti bi mogla da se prati na osnovu procentualne zastupljenosti visine tela pršljena u ukupnoj dužini prednjeg dela kičme (C2-C5)

The contact and compacting pressures influences on the quality of the friction welded joint

The theoretical and experimental analyses of the friction welding pressure influence on the plastic deformation level and the quality of the friction welded joint are presented in this paper. The joint of the tempering and the High-Speed steel was realized by the friction welding. The objective was to relate the two basic process parameters - the friction and compacting pressures - to plastic deformation parameters during the friction welding of two the steels. The fact that materials are dissimilar additionally complicates the welding procedure and its analysis. The friction welding is a specific and complex process, since in the joint zone material is heated and plasticized with necessary action of the multi-step pressure to realize the joint. The total deformations in the axial and radial directions are directly dependent on the applied welding pressure. Considering that geometry and shape of the friction welded joint directly depend on the friction pressure, some welded joints' basic shapes obtained with various pressures are presented. The experimental investigation was conducted on cylindrical samples made of the two steels and the analysis of results served for establishing the influences of the friction and compacting pressures on changes of the steel samples dimensions and shapes.

The contact and compacting pressures influences on the quality of the friction welded joint

The theoretical and experimental analyses of the friction welding pressure influence on the plastic deformation level and the quality of the friction welded joint are presented in this paper. The joint of the tempering and the High-Speed steel was realized by the friction welding. The objective was to relate the two basic process parameters - the friction and compacting pressures - to plastic deformation parameters during the friction welding of two the steels. The fact that materials are dissimilar additionally complicates the welding procedure and its analysis. The friction welding is a specific and complex process, since in the joint zone material is heated and plasticized with necessary action of the multi-step pressure to realize the joint. The total deformations in the axial and radial directions are directly dependent on the applied welding pressure. Considering that geometry and shape of the friction welded joint directly depend on the friction pressure, some welded joints' basic shapes obtained with various pressures are presented. The experimental investigation was conducted on cylindrical samples made of the two steels and the analysis of results served for establishing the influences of the friction and compacting pressures on changes of the steel samples dimensions and shapes.

Etching of Uncompensated Convex Corners with Sides along <n10> and <100> in 25 wt% TMAH at 80 °C

This paper presents etching of convex corners with sides along and crystallographic directions in a 25 wt% tetramethylammonium hydroxide (TMAH) water solution at 80 °C. We analyzed parallelograms as the mask patterns for anisotropic wet etching of Si (100). The sides of the parallelograms were designed along and crystallographic directions (1 and crystallographic directions were smaller than 45°. All the crystallographic planes that appeared during etching in the experiment were determined. We found that the obtained types of 3D silicon shape sustain when n > 2. The convex corners were not distorted during etching. Therefore, no convex corner compensation is necessary. We fabricated three matrices of parallelograms with sides along crystallographic directions and as examples for possible applications. Additionally, the etching of matrices was simulated by the level set method. We obtained a good agreement between experiments and simulations

The variable contact pressure influence on the tensile force in the process of strip sliding in the flat die in ironing

Possibilities to influence the deep drawing process during its duration are limited and generally consist of influences at the flange of the thin sheet, mainly by the contact pressure (the blank holding force). The common characteristics of previous investigations were setting of the fixed values of the blank holding force or the holder's pressure within the ironing tool. The objective of this investigation was the continuous setting of the variable pressure during the sliding process, via the preset functions, in order to analyze the variable pressure influence on the ironing process. This is why an experimental computerized device was designed and constructed for analyzing the influence of the variable contact pressure on the sliding process of the model strip during the flat-die test. The multi-parameter experiment was conducted; various materials of the tested pieces were applied (primarily thin sheet made of Al alloys and low-carbon steels sheet, with and without coating); different versions of the tool's contact elements were used, with various friction regimes and influential parameters (variable contact pressure during the sliding process, etc.). This experimental device practically represents a simulator for realization and studying of the physical model of an important segment of the ironing process in the completely realistic conditions (materials, tools, etc.). The aim was to find the optimal combination of the variable contact pressure and the tribological parameters, so that the punch force, as one of the process output parameters, would have the minimal value, as well as to avoid the undesired effects during the forming (difficult sliding of the flange, appearance of thin sheet's wrinkling, structural destruction, etc.). Understanding the mutual dependence of the holder's variable pressure and other influences should enable improvement of the ironing process control and should contribute to better understanding of the phenomena occurring at the thin sheet's flange.

Analysis of the cause of the girth gear tooth fracture occurrence at the bucket wheel excavator

Premature damages and fractures of components and structures of bucket-wheel excavators at open-pit mine often occur in exploitation, caused either by inadequate design or insufficient knowledge of the material properties, welded joints and flaws in component production technology. The bucket-wheel excavator, TAKRAF SRs 2000 x 32/5.0 was employed on the excavation of barren soil for 5.000 h (a few weeks more than a year after the assembly) when the fracture of the tooth of the girth gear, which enables the circular motion of the upper structure of the bucket-wheel excavator, occurred. The gear was, according to the manufacturer's certificate, made of the cast steel GS 40 MnCrSi3 V. The paper presents calculations of the stress variations cycles' number for one tooth, as well as of the fracture mechanics parameters - the critical stress intensity factor and critical crack length. It was established that the fracture of the tooth occurred due to an initial crack existing in its base, which originated during the gear's manufacturing, i.e. due to the so-called "manufacturing-in defect"

Relationships between broiler final weights and microbiota of certain segments of the intestine

Only healthy animals can expect good production results. Gastrointestinal tract (GIT) health is of particular importance in broilers. GIT health has been protected by antibiotics as growth promoters for years. Since their use is forbidden, alternatives are required. One alternative is the use of medium chain fatty acid (MCFA) in broiler nutrition, in order to ensure the health of digestive tract, that is, prevent the activity of pathogenic bacteria, coccidias and viruses. Today, commercial MCFA supplement is used on the market in nutrition of broilers and piglets. Previous experiences of using MCFA in nutrition of broilers suggest that MCFA can be used as a substitute for antibiotics. In the duodenum of experimental broilers (a group of birds fed with added MCFA), the numbers of Enterococcus spp. and E. coli were significantly correlated with bird weight, but this was not the case in other intestinal segments (ileum or caecum)

Evolution of Si Crystallographic Planes-Etching of Square and Circle Patterns in 25 wt % TMAH

Squares and circles are basic patterns for most mask designs of silicon microdevices. Evolution of etched Si crystallographic planes defined by square and circle patterns in the masking layer is presented and analyzed in this paper. The sides of square patterns in the masking layer are designed along predetermined crystallographic directions. Etching of a (100) silicon substrate is performed in 25 wt % tetramethylammonium hydroxide (TMAH) water solution at the temperature of 80 °C. Additionally, this paper presents three-dimensional (3D) simulations of the profile evolution during silicon etching of designed patterns based on the level-set method. We analyzed etching of designed patterns in the shape of square and circle islands. The crystallographic planes that appear during etching of 3D structures in the experiment and simulated etching profiles are determined. A good agreement between dominant crystallographic planes through experiments and simulations is obtained. The etch rates of dominant exposed crystallographic planes are also analytically calculated

Katastar klizišta Beograda

Za prostor Generalnog plana Beograda urađen je Katastar klizišta (2008-2010.) sa bazom podataka i informacionim sistemom (IS). Registrovano je 1155 klizišta i za svako su u bazu uneti podaci o: lokaciji, geol. uslovima, istražnim i radovima na prevenciji i sanaciji. Klizišta su kategorisana po stepenu hazarda i rizika od aktiviranja. IS i baza obezbeđuju neophodne informacije planerima, investitorima i graditelјima u cilјu kontinualnog praćenja i upravlјanja rizikom od klizišta

Antioxidant activity, the content of total phenols and flavonoids in the ethanol extracts of Mentha longifolia (L.) Hudson dried by the use of different techniques

In this study, we have examined the yield of extracted substances obtained by means of extraction using 70 % ethanol (v/v), the content of total phenols and flavonoids, as well as the antioxidant activity of the extracts obtained from the samples of the herbs dried by means of different techniques. Wild mint Mentha longifolia (L.) Hudson was dried naturally in a laboratory oven at a temperature of 45 °C and in an absorptive low temperature condensation oven at 35°C. The highest yield of extracts was obtained from the naturally dried herbs and the lowest from the herbs dried in the low temperature condensation drying oven. The content of total phenols and flavonoids was determined by spectrophotometric methods with an FC reagent and by the complexation reaction with aluminium-chloride, respectively. The extract of the naturally dried herbs had the highest overall content of phenols (113.8±2.0 mg of gallic acid/g of the dry extract) and flavonoids (106.7±0.3 mg of rutin/g of the dry extract). The highest antioxidant activity determined by the FRAP and DPPH assay was determined in the extracts obtained from naturally dried herbs (2.76±0.15 mmol Fe2+/mg of the dry extract and EC50=0.022±0.001 mg/ml), while the lowest was obtained from the extracts of herbs dried in the laboratory oven (1.13±0.11 mmol Fe2+/mg of the dry extract and EC50=0.033±0.001 mg/ml). The HPLC-DAD analysis result show that the greatest content of phenolic compounds show extract obtained from naturally dried plant material. The dominant phenolic component in the all extracts is Kaempferol 3-O-glucoside. The content of all phenolic compound strongly depend on the drying conditions