Enhancement of tribological properties of mineral oil by addition of sorbitan monostearate and borate

Thesis (Doctoral)--Izmir Institute of Technology, Chemical Engineering, Izmir, 2010Includes bibliographical references (leaves: 225-235)Text in English; Abstract: Turkish and Englishxxviii, 248 leavesThe development of modern automobile and engine industries requires lubricants that can withstand high temperatures and pressures. Recent advances made in the chemistry provide the use of inorganic particles as lubricant additives. Therefore inorganic boron-based additives have been the focus of much attention, as they posses a good combination of properties, such as wear resistance, friction-reducing ability. In this study, the state of art in the field of inorganic particle, zinc borate synthesis and its employment in tribology were investigated. The synthesis of zinc borate was achieved not just by precipitation, but also production methods such as inverse emulsions. The products were characterized by SEM, FTIR, TGA, DSC, EDX. In lubrication part, the friction reducing and antiwear ability of the particles as an additive in the mineral oil was focused. Sorbitan monostearate was used to cover the surfaces of inorganic particles in order to provide better dispersion of additives in the oil. Friction and wear behavior of the lubricants were measured by four-ball wear test machine. The effects of dispersing agent, zinc borate type as well as surfactant concentration on the tribological properties of the lubricants were investigated. Sorbitan monostearate not only outperformed as a dispersing agent of inorganic particles, but also it proved to be an efficient antiwear agent. The lowest wear scar diameter was obtained by the lubricant containing zinc borate synthesized via coordination precipitation method. The addition of this sample with the surfactant in the oil reduced the wear scar diameter from 1.402 mm to 0.550 mm

Synthesis of zinc borate by inverse emulsion technique for lubrication

Lubricating oil additives based on boron compounds are promising materials for lubrication due to their tribological advantages such as antiwear efficiency, good film strength, and high temperature resistance. This article deals with the preparation of zinc borate particles that are well dispersed and colloidally stabilized in mineral oil. This method starts with preparing two inverse emulsions (water-in-oil) with sorbitan monostearate (Span 60) as a surfactant, light neutral oil as a continuous phase, and the aqueous solutions of borax decahydrate (Na2B4O7·10H 2O) and zinc nitrate (Zn(NO3)2·6H 2O) as the dispersed phases. The produced particles were zinc borate crystals having both rod-like and spherical morphologies, and the diameters of spherical particles were changing between 20 and 30 nm. FTIR spectra of the obtained particles showed the characteristic peaks of trihedral borate (B(3)-O) and tetrahedral borate (B(4)-O) groups as well as the specific peaks of the sorbitan monostearate. TG showed 30.42% and 22.08% mass loss at 600 °C for the samples prepared by inverse emulsion and precipitation techniques, respectively. The endothermic peak at 50 °C is observed due to the melting of sorbitan monostearate and the heat of melting is evaluated as -3.50 J/g. Tribological studies revealed that sorbitan monostearate not only outperformed as a dispersing agent of inorganic particles, but also it proved to be an anti-wear agent. Zinc borate produced by precipitation decreased the wear scar diameter from 1.402 to 0.639 mm and the friction coefficient from 0.099 to 0.064. The inverse emulsion was effective in decreasing wear scar diameter and the friction coefficient by lowering them to 0.596 and 0.089 mm, respectively.Scientific and Technical Research Council of Turkey (105M358

Restoring Aesthetics and Function in a Young Boy with Hypomature Amelogenesis Imperfecta: A Case Report

Amelogenesis imperfecta has been described as a complex group of inherited conditions that disturbs the developing enamel structure and exists independent of any related systemic disorder. It is a rare dental disease but represents a great restorative challenge for dentists. A 12-year-old boy presented with sensitive, discolored, and mutilated teeth and decreased vertical dimension of occlusion. Direct composite resin restorations were applied to all teeth to modify the occlusion, to restore mild crowding, and to improve aesthetics. The 24-month recall examination revealed no pathology associated with the rehabilitation, and the patient's aesthetic and functional expectations were satisfied. The rehabilitation included multiple anterior and posterior composite resins to eliminate tooth sensitivity, improve the aesthetics and occlusion, and restore function

İÇME SUYU ŞEBEKE HATTININ FARKLI BORU TİPLERİ İÇİN TASARIMI VE MALİYETİ: ERZURUM İLİ HORASAN İLÇESİ ÖRNEĞİ

Günümüzde nüfusun artmasından dolayı yaşam alanları genişlemekte olup, mevcut kullanılmakta olan içme suyu şebeke sistemleri yetersiz kalabilmektedir. Yapılacak olan içme suyu projelerinin en uygun şekilde hidrolik hesaplarının yapılması ve boyutlandırılması, maliyetin optimum seviyelere düşmesine imkan sağlayacaktır. Buna bağlı olarak ülke ekonomisine katkı sağlanabilecektir. Bu çalışmada İller Bankası Teknik Şartnamesinde belirtilen kriterler göz önüne alınarak içme suyu şebekesi için netcad yazılımının içerisinde bulunan ölü noktalar yöntemi ile hidrolik hesaplamalar yapılmıştır. Boru tipinin maliyete etkisi araştırılmıştır. Poli etilen, polivinil klorür, çelik ve düktil borular kullanılarak hidrolik hesaplamalar gerçekleştirilmiştir. En yüksek maliyetli borunun çelik, en düşük maliyetli borunun ise poli etilen boru olduğu belirlenmiştir

Petrolgy of the volcanic/subvolcanic members of the volcanosedimentary Maden Complex in Eastern Turkey

Maden Complex exposed in Eastern Turkey, is a succession of volcano-sedimentary rocks and tectonically overlain by Bitlis Metamorphics and Cretaceous ophiolitic rocks. The succession includes shallow-water deposits and deep marine pelagic sediments intercalated with pillow lavas ranging from a few centimeters to ten meters in diameter. The planktonic foraminiferal assemblages from micritic limestones and zircon U-Pb ages from selected sedimentary rocks indicate the age of Late Ypresian - Early Lutetian. Plagioclase and clinopyroxenes are the main mineral phases, olivine rarely found as altered phenocrysts. Clinopyroxenes are augite and diopside, and their compositions are ranging between Wo44-51, En27-43, Fe10-21. The anorthite contents of plagioclases are between 32- 67 % in unaltered grains. The crystallization temperatures and pressures obtained from clinopyroxene chemistry are ranging from 1126 to 1250oC and 3 to 8 Kbar, respectively. The majority of the volcanic/subvolcanic rocks are subalkaline-tholeiitic basalts however; a few andesitic and rhyolitic derivatives are also present. The whole – rock and Sr-Nd-Pb isotope compositions reveal that the basaltic rocks are originated from E-MORB like asthenospheric mantle source without a subduction component

Adnexal Torsion in the Third Trimester of Pregnancy: A Challenging Diagnosis

The incidence of adnexal torsion (AT) is reported 1 in 10000 births. AT is emergency condition in pregnancy, while the risk of late diagnosis is increased, in third trimester. Since it has been described as a severe complication after controlled ovarian hyper-stimulation for in vitro fertilization (IVF), it is more common in IVF pregnancies. This condition mainly occurs in the first trimester; it is rare during the late third trimester. Herein, we report a case of a 26-year-old woman, gravida 1, singleton pregnancy in the 30th week of gestation was presented to emergency department with 24-hour history of a stabbing pain because of AT. Removal of adnexa performed by laparotomy. The patient had labour pain and cervical dilatation at the 36th week of gestation and a healthy girl weighing 2,200 g was born by emergency caesarean section due to breech presentation

The effect of new Turkish foreign policy on international trade

Turkish foreign policy has changed substantially within the last decade. Even though its relationship with the West still has significance, relations with neighboring countries and other countries in Africa, the Middle East, and Asia have improved. This new foreign policy incorporates Turkey's political and economic aspirations. Its aim is to utilize the country's economic strength in order to reach political goals while simultaneously using political tools to obtain economic benefits. This study analyzes the effects of the recent change in foreign policy on Turkey's international trade. Specifically, we investigate the influence of Turkish Prime Minister Erdoǧan's foreign visits on international trade by using a standard trade gravity model. Statistical analyses imply that Erdoǧan's visits help increase Turkish international trade

Assessment of renal volume by 3D VOCAL Ultrasonography method in late-onset growth-restricted fetuses with normal amniotic fluid index

Objectives: The aim of this study was to study renal volumetric alterations and renal artery doppler changes in late-onsetfetal growth restricted (FGR) fetuses with normal amniotic fluid compared to healthy pregnancies.Material and methods: This prospective study was composed of pregnant women with late-onset FGR and a control groupof uncomplicated pregnancies within 32–37 weeks of gestation. Following the assessment of umbilical, bilateral uterine,middle cerebral using Doppler Ultrasonography (US), three dimensional (3D) US Virtual Organ Computer-aided Analysis(VOCAL) was executed to calculate bilateral renal volumes.Results: A total of 76 fetuses with FGR and 51 healthy fetuses (control group) were evaluated. Umbilical artery Dopplersystole/diastole and Pulsatility index values were found to be significantly different between the two groups (p = 0.001 andp = 0.001, respectively). Middle cerebral, bilateral uterine, and bilateral renal arteries’ Doppler indices revealed no differencebetween the two groups. Right, left, and mean renal volume of the fetuses with FGR were smaller than the controlgroup, and the differences were statistically significant (p = 0.025, p = 0.004, p = 0.004, respectively). Left renal volume wassignificantly greater than the right renal volume in the control group (p = 0.009).Conclusion: Although not accompanied by oligohydramnios, and having similar renal vascular resistance as the controlgroup, renal volumes of fetuses with late-onset FGR were still observed lower than the control group. This difference wasexplained by not decreased blood flow via redistribution but other mechanisms like glomeruli reduction and glomerularapoptosis

THE EFFECT OF COVID-19 OUTBREAK ON THE MENTAL STATUS OF HEALTH CARE PROFESSIONALS IN THE PEDIATRIC INTENSIVE CARE UNIT

Background: Coronavirus disease 2019 (COVID-19) may affect the mental status of health care professionals. The purpose of our study is to evaluate the mental health effects of the COVID-19 epidemic on health care professionals in the pediatric intensive care units (PICUs). Subjects and methods: Our study was conducted prospectively between 01.04.20 and 10.04.20. The created questionnaire was applied to health care professionals through online platforms. Thus it was involved in 5 different institutions that participated from different regions of Turkey. With the questionnaire, we applied; the participants\u27 age, gender, the general status of contamination and the level of COVID-19 knowledge were questioned. Besides; Beck Anxiety Scale, Acute Stress Scale (PCL-5), STAI-1 and STAI-2 (State and Trait Anxiety Inventory 1-2) scales were used to determine the anxiety levels. Results: A survey of 210 participants, 86 (41%) doctors, 124 (59%) nurses, were included in our study. When we evaluate the Beck anxiety levels, the majority of the participants (44%) were normal, while about one third had mild anxiety. When we evaluated the acute stress scale, all participants had a certain amount of stress levels. The majority (80 people each (38%)) experienced mild and moderate acute stress. Being female and having chronic disease poses a high risk for anxiety (OR, 0.330; 95% CI, 0.087-1.250, p <0.05 and OR, 0.246; 95% CI, 0.068-1.116, p<0.05), preoccupation (OR, 0.603; 95% CI 0.261-1.395, p<0.05 and OR, 0.433; 95% CI, 0.122-1.538, p<0.05) and acute stress (OR, 0.294; 95% CI, 0.033-2.649, p<0.05 and OR, 0.317; 95 % CI 0.060-1.679, p<0.05). Professional definition, marital status and having a child do not pose any risk factors. Conclusion: Our study has shown that the COVID-19 outbreak affects the mental status of health care professionals working at PICU at various levels

THE EFFECT OF COVID-19 OUTBREAK ON THE MENTAL STATUS OF HEALTH CARE PROFESSIONALS IN THE PEDIATRIC INTENSIVE CARE UNIT

Background: Coronavirus disease 2019 (COVID-19) may affect the mental status of health care professionals. The purpose of our study is to evaluate the mental health effects of the COVID-19 epidemic on health care professionals in the pediatric intensive care units (PICUs). Subjects and methods: Our study was conducted prospectively between 01.04.20 and 10.04.20. The created questionnaire was applied to health care professionals through online platforms. Thus it was involved in 5 different institutions that participated from different regions of Turkey. With the questionnaire, we applied; the participants\u27 age, gender, the general status of contamination and the level of COVID-19 knowledge were questioned. Besides; Beck Anxiety Scale, Acute Stress Scale (PCL-5), STAI-1 and STAI-2 (State and Trait Anxiety Inventory 1-2) scales were used to determine the anxiety levels. Results: A survey of 210 participants, 86 (41%) doctors, 124 (59%) nurses, were included in our study. When we evaluate the Beck anxiety levels, the majority of the participants (44%) were normal, while about one third had mild anxiety. When we evaluated the acute stress scale, all participants had a certain amount of stress levels. The majority (80 people each (38%)) experienced mild and moderate acute stress. Being female and having chronic disease poses a high risk for anxiety (OR, 0.330; 95% CI, 0.087-1.250, p <0.05 and OR, 0.246; 95% CI, 0.068-1.116, p<0.05), preoccupation (OR, 0.603; 95% CI 0.261-1.395, p<0.05 and OR, 0.433; 95% CI, 0.122-1.538, p<0.05) and acute stress (OR, 0.294; 95% CI, 0.033-2.649, p<0.05 and OR, 0.317; 95 % CI 0.060-1.679, p<0.05). Professional definition, marital status and having a child do not pose any risk factors. Conclusion: Our study has shown that the COVID-19 outbreak affects the mental status of health care professionals working at PICU at various levels