Repair Welding of Titanium Alloy Construction

Problematika zavarivanja titana i njegovih legura bez korištenja specijalnih komora sa vakuum ili inertnom atmosferom izražena je kod popravaka gdje zavarivani dijelovi mogu biti različitih dimenzija i oblika. Preskupo je za svaki pojedinačni slučaj konstruirati zaštitnu komoru. Najčešće su komore neugodne za zavarivača i ograničavaju uvođenje pištolja i dodatnog materijala. Rad se bavi analizom mogućnosti obavljanja kvalitetnog popravka bez korištenja komore. Praktični dio rada jest popravak zavarivanjem kućišta kamere za snimanje unutrašnjosti plašta peći klinkera u tvornici cementa. Zbog ekstremnih radnih uvjeta dolazi do intenzivnog trošenja dijela plašta, te isti otkazuje ovisno o položaju u peći ili hladnjaku nakon 6 - 12 mjeseci eksploatacije. Popravak se obavlja zavarivanjem TIG postupkom uz primjenu dvostruke sekundarne zaštite zavara (lica i korijena) argonom. Ispitana je mikrostruktura uzoraka, te izmjerena tvrdoća po izvodnici koja se proteže od osnovnog materijala, preko zone utjecaja topline, do samog zavara. Ispitivanje je pokazalo da nema značajnih promjena u mikrostrukturi zavara u odnosu na osnovni materijal, te da su tvrdoće mjerene po izvodnici prilično ujednačene. Nakon ispitivanja uzoraka izvršen je popravak zavarivanjem plašta kućišta. Popravljeno kućište ima vijek trajanja koji odgovara novom kućištu što ukazuje da je sanacija obavljeno uspješno.Problems of welding titanium and titanium alloys, without the usage of special vacuum or inert atmosphere chambers, is expressed in welding repairs where parts may be different sizes and shapes. It would be too expensive to construct a protective atmosphere chamber for each individual case. Chambers usually are awkward for welders and also limit the process control. The purpose of this work is to find out the possibilities for performing quality repairs without the use of the special chamber. The practical part of our work deals with repair welding of clincker furnace camera case in a cement factory. The extreme working conditions lead to intensive wear of the camera case. Depending on the location in the clinker furance it needs to be changed or repaired after 6-12 months of exploitation. Repair is done by TIG welding process using dual secondary weld protection (face and root) with argon. The microstructure of the samples was analysed, and also hardness tests were done on the base material, heat affected zone and the weld. The study showed no significant changes in the microstructure of welds in relation to the base material, and the results of hardness tests were fairly uniform. After acceptable testing results the repair of camera case was done. The repaired camera case had the same expaltation life as the new case. This indicates that the repairs were carried out successfully

The influence of low and high annealing on the hardness of steel EN 42CRMO4

Hollomon i Jaffe [1],[2] su dali funkcionalnu ovisnost parametra popuštanja (temperature i trajanja) P=f(T, t). Drugim riječima ako se koriste kombinacije temperature i trajanja popuštanja, koje rezultiraju jednakom vrijednošću parametra, tvrdoća će ostati nepromijenjena. Ova funkcija se odnosi samo na čelike. Za određivanje parametara popuštanja uz postizanje željene mikrostrukture i tvrdoće nakon obrade, potrebno je poznavati dijagram popuštanja promatranog čelika. U ovom radu je istražena mogućnost dobivanja izraza gdje je tvrdoća u funkciji temperature i vremena popuštanja (H=f(T, t)). Plan pokusa i statistička analiza rezultata su obavljeni korištenjem programa „Design expert 6.0“[3]. Izrađeni su cilindrični uzorci duljine 10 mm i promjera 25 mm. Pokus je obavljen u dva dijela. Prvi dio se odnosio na visokotemperaturno popuštanje, a drugi dio na niskotemperaturno. Ovakav pristup ispitivanju je odabran zbog bitno različitih struktura koje se pojavljuju na niskim i visokim temperaturama popuštanja.Hollomon and Jaffe [1], [2] have given the functional dependence of the annealing parameters (temperature and time) P = f (T, t). In other words, if using a combination of temperature and annealing time, resulting in equal parameters value, hardness will remain unchanged. This function refers only on steels. To determine the parameters of annealing for desired hardness after treatment, it is necessary to know the annealing diagram (H=f(T)) of the observed steel. This paper investigates the possibility of obtaining a mathematical model where the hardness is function of annealing temperature and time (H=f(T, t)). Design of experiments and statistical analysis were performed using the program "Design Expert 6.0" [3]. The cylindrical specimens were 10 mm length and 25 mm in diameter. The experiment was conducted in two levels. The first level was related to high temperature annealing, while the second level was related to the low temperature annealing. The reason for this approach was based on significantly different microstructure that appears at low and high annealing temperatures

The influence of low and high annealing on the hardness of steel EN 42CRMO4

Hollomon i Jaffe [1],[2] su dali funkcionalnu ovisnost parametra popuštanja (temperature i trajanja) P=f(T, t). Drugim riječima ako se koriste kombinacije temperature i trajanja popuštanja, koje rezultiraju jednakom vrijednošću parametra, tvrdoća će ostati nepromijenjena. Ova funkcija se odnosi samo na čelike. Za određivanje parametara popuštanja uz postizanje željene mikrostrukture i tvrdoće nakon obrade, potrebno je poznavati dijagram popuštanja promatranog čelika. U ovom radu je istražena mogućnost dobivanja izraza gdje je tvrdoća u funkciji temperature i vremena popuštanja (H=f(T, t)). Plan pokusa i statistička analiza rezultata su obavljeni korištenjem programa „Design expert 6.0“[3]. Izrađeni su cilindrični uzorci duljine 10 mm i promjera 25 mm. Pokus je obavljen u dva dijela. Prvi dio se odnosio na visokotemperaturno popuštanje, a drugi dio na niskotemperaturno. Ovakav pristup ispitivanju je odabran zbog bitno različitih struktura koje se pojavljuju na niskim i visokim temperaturama popuštanja.Hollomon and Jaffe [1], [2] have given the functional dependence of the annealing parameters (temperature and time) P = f (T, t). In other words, if using a combination of temperature and annealing time, resulting in equal parameters value, hardness will remain unchanged. This function refers only on steels. To determine the parameters of annealing for desired hardness after treatment, it is necessary to know the annealing diagram (H=f(T)) of the observed steel. This paper investigates the possibility of obtaining a mathematical model where the hardness is function of annealing temperature and time (H=f(T, t)). Design of experiments and statistical analysis were performed using the program "Design Expert 6.0" [3]. The cylindrical specimens were 10 mm length and 25 mm in diameter. The experiment was conducted in two levels. The first level was related to high temperature annealing, while the second level was related to the low temperature annealing. The reason for this approach was based on significantly different microstructure that appears at low and high annealing temperatures

Therapeutic Efficacy of 5% NaCl Hypertonic Solution in Patients with Bullous Keratopathy

A clinical trial was undertaken to evaluate the efficacy of hypertonic solution (5% NaCl) in patients who have bullous keratopathy (BK). The aim of the study was to define the stage of the disease and the thickness of cornea in micrometers, which would be the threshold for therapeutic approach. This was a prospective study on 70 eyes of 55 patients. Patients were divided in two groups at the beginning of the study.The first group (n=33 eyes) included patients with initial stage of BK: only stromal component of corneal oedema was present. The second group (n=37 eyes) included patients with advanced stage of BK: the epithelial component of the disease with bullae on the corneal surface had already developed. Visual acuity, central and peripheral thickness of cornea and morphology of the disease was recorded before therapy, 7 days and 4 weeks after administration of hypertonic solution. Our results shown that the efficacy of hypertonic solution correlates with the severity of clinical picture in patients with BK. When 5% NaCl hypertonic solution was applied in the early stage of the disease, when only stromal component of corneal oedema was presented, visual acuity and pachymetry readings were significantly improved. The threshold pachymerty measurement of corneal thickness justifying the application of hypertonic solution was 613–694 _m(in the central corneal area), and 633–728 _m(at corneal periphery). It seems reasonable to apply hypertonic solution to the patients who have BK and whose pachymetric values are below mentioned range. In terminal stages of BK, when superficial bullae (epithelial component) had already developed, treatment with NaCl was not effective and patients had to be submitted to penetrating keratoplasty

Therapeutic Efficacy of 5% NaCl Hypertonic Solution in Patients with Bullous Keratopathy

A clinical trial was undertaken to evaluate the efficacy of hypertonic solution (5% NaCl) in patients who have bullous keratopathy (BK). The aim of the study was to define the stage of the disease and the thickness of cornea in micrometers, which would be the threshold for therapeutic approach. This was a prospective study on 70 eyes of 55 patients. Patients were divided in two groups at the beginning of the study.The first group (n=33 eyes) included patients with initial stage of BK: only stromal component of corneal oedema was present. The second group (n=37 eyes) included patients with advanced stage of BK: the epithelial component of the disease with bullae on the corneal surface had already developed. Visual acuity, central and peripheral thickness of cornea and morphology of the disease was recorded before therapy, 7 days and 4 weeks after administration of hypertonic solution. Our results shown that the efficacy of hypertonic solution correlates with the severity of clinical picture in patients with BK. When 5% NaCl hypertonic solution was applied in the early stage of the disease, when only stromal component of corneal oedema was presented, visual acuity and pachymetry readings were significantly improved. The threshold pachymerty measurement of corneal thickness justifying the application of hypertonic solution was 613–694 _m(in the central corneal area), and 633–728 _m(at corneal periphery). It seems reasonable to apply hypertonic solution to the patients who have BK and whose pachymetric values are below mentioned range. In terminal stages of BK, when superficial bullae (epithelial component) had already developed, treatment with NaCl was not effective and patients had to be submitted to penetrating keratoplasty

Povezanost proteina nm23 i ketapsina D sa kliničkim i patološkim značajkama oralnog karcinoma pločastih stanica

The most important prognostic factor in oral squamous cell carcinoma (OSCC) is the presence of metastases in regional lymph nodes. Study group comprised of 107 patients with OSCC and control group comprised of 77 specimens of unchanged oral mucosa. The purpose of this study was to determine the immunohistochemical expression of cathepsin D and nm23 protein in OSCC and to compare it to the other clinical and histological features and to the occurrence of regional metastases, in order to assess their prognostic value. In contrast to normal epithelium a diff use expression of cathepsin D and nm23 protein in OSCC has been found. By comparing the expression of cathepsin D and nm23 protein in tumor cells and in tumor stroma and the type of reaction to the pT, the degree of diff erentiation, mode of invasion and tumor stroma the following has been found: a signifi cant connection between nm23 protein in tumor cells with the degree of diff erentiation, nm23 protein with the characteristics of the tumor stroma and mode of invasion and cathepsin D with the degree of tumor diff erentiation. The results of this research highlight the important role of tumor stroma in metastatic potential of OSCC.Svrha ovog istraživanja bila je imunohistokemijski utvrditi izraženost proteina nm23 i katepsina D u oralnim pločastim karcinomima, usporediti ju s patohistološkim nalazima, pojavom područnih presadnica i procijeniti njihovu vrijednost u prognozi bolesti. Ispitivano je 107 tkivnih uzoraka bolesne i 77 zdrave ustne sluznice. Uočena je pojačana difuzna izraženost proteina nm23 i katepsina D u bolesnom tkivu. Usporedbom proteina nm23 i katepsina D u tumorskim stanicama i tumorskoj stromi, te tipa reakcije s pT, stupnjem diferencijacije, načinom invazije i izraženošću tumorske strome, nađena je znakovita povezanost izraženosti proteina nm23 u tumorskim stanicama sa stupnjem diferencijacije, proteina nm23s izraženošću tumorske strome i načinom invazije, te katepsina D sa stupnjem diferencijacije tumora. Najvažniji prognostički pokazatelj u oralnim pločastim karcinomima su metastaze u područnim limfnim čvorovima. Rezultati istraživanja pokazuju važnost tumorske strome za metastatski potencijal ostnog ustnog pločastog karcinoma

Povezanost proteina nm23 i ketapsina D sa kliničkim i patološkim značajkama oralnog karcinoma pločastih stanica

The most important prognostic factor in oral squamous cell carcinoma (OSCC) is the presence of metastases in regional lymph nodes. Study group comprised of 107 patients with OSCC and control group comprised of 77 specimens of unchanged oral mucosa. The purpose of this study was to determine the immunohistochemical expression of cathepsin D and nm23 protein in OSCC and to compare it to the other clinical and histological features and to the occurrence of regional metastases, in order to assess their prognostic value. In contrast to normal epithelium a diff use expression of cathepsin D and nm23 protein in OSCC has been found. By comparing the expression of cathepsin D and nm23 protein in tumor cells and in tumor stroma and the type of reaction to the pT, the degree of diff erentiation, mode of invasion and tumor stroma the following has been found: a signifi cant connection between nm23 protein in tumor cells with the degree of diff erentiation, nm23 protein with the characteristics of the tumor stroma and mode of invasion and cathepsin D with the degree of tumor diff erentiation. The results of this research highlight the important role of tumor stroma in metastatic potential of OSCC.Svrha ovog istraživanja bila je imunohistokemijski utvrditi izraženost proteina nm23 i katepsina D u oralnim pločastim karcinomima, usporediti ju s patohistološkim nalazima, pojavom područnih presadnica i procijeniti njihovu vrijednost u prognozi bolesti. Ispitivano je 107 tkivnih uzoraka bolesne i 77 zdrave ustne sluznice. Uočena je pojačana difuzna izraženost proteina nm23 i katepsina D u bolesnom tkivu. Usporedbom proteina nm23 i katepsina D u tumorskim stanicama i tumorskoj stromi, te tipa reakcije s pT, stupnjem diferencijacije, načinom invazije i izraženošću tumorske strome, nađena je znakovita povezanost izraženosti proteina nm23 u tumorskim stanicama sa stupnjem diferencijacije, proteina nm23s izraženošću tumorske strome i načinom invazije, te katepsina D sa stupnjem diferencijacije tumora. Najvažniji prognostički pokazatelj u oralnim pločastim karcinomima su metastaze u područnim limfnim čvorovima. Rezultati istraživanja pokazuju važnost tumorske strome za metastatski potencijal ostnog ustnog pločastog karcinoma

The role of Candida species in peri-implant diseases

BackgroundPeri-implantitis is a chronic, marginal and progressive infection of soft and hard tissue that surrounds dental implants, which results in the loss of the supporting bone, caused by similar microbes as adult periodontitis. Staphylococcus aureus and Candida albicans are microorganisms that are not primarily associated with periodontitis, but certain studies identified them in peri-implant pockets.AimsThe current review aimed to assess the role of Candida species in peri-implant diseases.MethodsThis review has been carried out in accordance with the question: ";;;What is the role of Candida albicans in peri-implant diseases?";;;. To answer this, a bibliographic search was carried out using PubMed, Scopus and Medline and it was limited to works published during 2009-2019.Results Candida albicans appears to play an important role in the formation and stabilization of biofilm on the titanium surfaces and in the implant itself, which subsequently allows the growth of periodontal pathogenic bacteria involved in the development of inflammatory response resulting in the loss of bone supporting the dental implant.ConclusionFurther research is needed to shed more light on the pathophysiology of peri-implant inflammation and to find more effective ways to treat it

Application of Photodynamic Therapy in the Treatment of Osteonecrosis of the Jaw

Osteonecrosis as term represents the death of bone tissue in the body and causes of necrosis can be different. Medication-related osteonecrosis of the jaws (MRONJ) is nowadays known as an inability of the alveolar bone to respond to a local trauma and it can result in severe local and systemic complications. In the etiology of medication-related osteonecrosis there are antiangiogenic and antiresorptive agents which have great effect on alveolar bone, producing an imbalance between resorption (osteoclastic activity) and deposition (osteoblastic activity). The exact mechanisms of development are not todays completely resolved. It is thought that it is a result from combination of medication interactions, microbiological contamination of the area and local tissue trauma. Typical signs and symptoms are painful mucosal lesions, swelling, exposed necrotic bone in the jaws, discomfort and dysesthesias. There is currently no gold standard or clearly defined treatment protocol for the disease itself. Process of treatment is demanding and main goal is to eliminate pain, control infection of soft and hard tissue and minimize progression of osteonecrosis. Besides the conventional surgical treatment, photodynamic therapy can be a viable supportive tool of initial and advanced stages of osteonecrosis and may contribute to improvements of patient′s quality of life

The Correlation of Changes of the Optic Nerve Diameter in the Acute Retrobulbar Neuritis with the Brain Changes in Multiple Sclerosis

The aim of this paper is to compare diameter of healthy and affected optic nerve determined by ultrasound with brain lesions in acute retrobulbar neuritis in patients with multiple sclerosis. In this prospective study 20 patients with multiple sclerosis and acute retrobulbar neuritis were examined. Optic nerve diameter was measured by ultrasound. Brain lesions were detected by magnetic resonance. Correlation between demyelinating lesions of the brain in multiple sclerosis and optic nerve diameter was tested by Kruskal-Wallis test. Significant difference in diameter between healthy and affected optic nerve in acute retrobulbar neuritis was found. Demyelinating brain changes examined by magnetic resonance revealed periventricular lesions, subcortical lesions and lesions in corpus callosum. There is statistically significant correlation between optic nerve diameter and number of brain lesions in multiple sclerosis, p<0.05. Diameter of optic nerve in retrobulbar neuritis measured by ultrasound correlates with brain lesions detected by magnetic resonance in multiple sclerosis