Burulmaya maruz millerde korozyon oyuklarının gerilme dağılımının belirlenmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Anahtar kelimeler: Korozyon oyuğu, Burulma, Gerilme yığılması katsayısı, MilKorozyon oyuğu, korozif ortamın etkisi altındaki başta çelik, yüksek dayanımlı alüminyum alaşımları ve metallerde gözlenmekte ve çatlak oluşumunun başlangıç potansiyeli olarak tanımlanmaktadır. Birçok sanayi kolunda malzemelerin güvenli ve emniyetli kullanımını sınırlamaktadır. Yük taşıyan, hareket ileten yapı elemanları çalıştıkları ortamlardan dolayı yüzeylerinde oluşan korozyon oyukları neticesinde görev yapamaz duruma gelirler. Belirli bir tork kuvveti altında güç iletim elemanı olarak görev alan dairesel kesitli yapı elemanı miller bu duruma maruz kalabilirler. Bu çalışmada korozyon oyuğu oluşmuş millerin burulma gerilmesi altındaki davranışları incelenmiş sonlu elemanlar yöntemiyle gerilme analizleri yapılmıştır. Korozyon oyukları için küresel oyuk, eliptik oyuk ve ikincil oyuk geometrileri Ansys paket programında modelize edilmiştir. Küresel oyuk modelleri sığ oyuk modelinden derin oyuk modeline doğru değişik derinliklerde, eliptik oyuk modelleri ise değişik derinliklerde sığ modelden, derin modele doğru değiştirilmiş, ayrıca mil eksenine göre sistematik bir açı değişimiyle eliptik oyuklar konumlandırılmıştır. Bununla beraber yarı küresel oyuk tabanında ikincil bir küresel oyuğun varlığı düşünülmüş, bu ikincil küresel oyuk geometrisi değişik çap ve derinliklerde büyültülerek modelize edilmiştir. Bu modellemelerden sonra, yüzeyinde korozyon oyuğu bulunmayan burulma gerilmesi etkisi altındaki milin dış yüzeyinde 1 MPa kayma gerilmesi meydana getirecek bir tork kuvveti tespit edilmiştir. Aynı tork değeri yukarıda bahsi geçen farklı boyut ve geometrilere sahip korozyon oyuklu millere Ansys paket programı yardımıyla sonlu elemanlar yöntemi kullanılarak uygulanmıştır. Ve çok daha yüksek kayma gerilmeleri ortaya çıkmıştır. Bu durum gerilme yığılması etkisiyle açıklanabilir. Elde edilen sonuçlar tek tek ? ort a bölünerek boyutsuz olarak ölçülmüş, bu sayede gerilme yığılması katsayısı Kt doğrudan elde edilmiştirKey Words : Corrosion pit, Torsion, Tension agglomeration factor, PinCorrosion pit is observed particularly at steel, high strength aluminum alloys and metals under the influence of corrosive medium and is defined as the beginning of potential crack formation. Safe and secure usage of materials are limited in many industry branches. The structural elements that carry loads and transmit motion become unable to match the task because of corrosion pits that form on the environment they work. The circular cross section that serves as structural element under the force of certain torque force and may be exposed to this situation. In this study the behaviours under torsinoal stress where corrosion pits formed in pins are examined and stress analysis are made with finite element method. For corrosion pits spherical pit, elliptical pit, and secondary pit geometries have been modelized in Ansys package program. Spherical pit models are changed from shallow pit model to deep pit model in different depths, elliptical pit models in different depths are changed from shallow pit model to deep pit model, also a change in shaft angle to the axis of the elliptical pits are positioned systematically. At the same time, a secondary spherical pit presence is thought at the base of semi-spherical pit, this secondary spherical pit geometry is modelized by magnifying in different diameters and depths. After these modelizing under torsional stres effect where there is no corrosion pit on the surface, a torque force is determined on the outer surface of the pins that may cause 1 MPa shear stress. The same torque of the above-mentioned hollow shafts of corrosion in different sizes and geometries using finite element method was applied using the program package Ansys. And much higher shear stresses emerged. This situation can be explained by the effect of stress concentration. The obtained results are measured as dimensionless by dividing them to ? ort one by one, so the stress concentration factor Kt is obtained directly

Bilateral avascular necrosis of the femoral head due to the use of heroin: A case report

AbstractIntroductionFemoral head avascular necrosis is caused by disruption of the blood supply of the femoral head, which finally results in hip dysfunction. Non traumatic osteonecrosis may related with corticosteroid use, alcohol abuse, SLE, hemoglobinopathies or exposure to cytotoxic agents. But avascular necrosis of the femoral head (ANFH) due to heroin use is a rare condition. We report a patient with bilateral ANFH due to heroin use treated by simultaneous bilateral hip arthroplasty.Presentation of case37 year-old male patient presented with bilateral hip pain that had been occurring for four years. The patient had no history of smoking, excessive drinking, using corticosteroid and the other drugs or trauma but used heroin for 10 years. In clinic and radiologic examination indicated advanced degenerative changes on both hip due to femoral head avascular necrosis. The patient was treated with simultaneous bilateral total hip arthroplasty. After 6 months postoperatively the active hip range of motion was painless.DiscussionAvascular femoral head necrosis caused by the using of heroin is rare. Ultimately, osteonecrosis of the femoral head occurs through one final common pathway, which is decreased blood flow to the femoral head that leads bone ischemia and death. But it is still unknown that heroin’s systemic effects. Intravenous drug use more as a serious problem for today. There is a need for comprehensive studies to demonstrate effects of heroin on bone and vascularity metabolism.ConclusionHeroin use will be important problem for population. That’s why is crucial to understand the effect of heroin

Treatment of adolescent idiopathic scoliosis with global (ROD) derotation maneuver using pedicle screws

Introduction: Adolescent idiopathic scoliosis is a three dimensional deformity. For the treatment of deformity, nature of deformity should be well understood and treatment strategy has to be directed to the coronal, sagittal and axial components of deformity. Global Derotation (GD) maneuver is based on simple rod derotation from concave side aiming to correct the deformity on coronal, sagittal and axial profile. In this report we reviewed AIS surgery results treated by global derotation maneuver with all pedicle screw instrumentation.Material& Methods: Between 2003 and 2011, 253 patients had been operated using GD technique.80 of 253 patients was included to our study. The patients routinely evaluated with preoperative-postoperative and last follow up standing ortho-x-rays. Coronal and sagittal profile parameters measured on x-rays with digital software using Cobb method. Rotational component of the deformity was measured according to Nash-Moe method at the apical vertebra.Results: 80 patients (71 female ; 9 male)had been followed up average 19,8 (7-37) months. Patients age average were 15,1(12-21) at operation date. Coronal cobb angle measure in thoracic curves preoperative were 48,9° decreased to mean 3,2° postoperatively. The mean coronal thoracolumbar curve were 45,8° preoperatively and decreased to mean 2°. Apical vertebra rotation measure regressed to mean 0,68 (0-1). Thoracic kyphosis showed downward tendency from mean 37,8° to mean 27,8°.Conclusion: Rod derotation technique enable to correct coronal and axial profile. Coronal Cobb angle improvement seen obviously with correction of axial profile rotation. Sagittal hypokyphotic effect of GD should be kept in mind

Does amikacin treatment cause subclinical hearing loss in patients with cystic fibrosis?

AbstractIntroductionAminoglycosides (AGs) have been widely used for potential life-threatening bacterial infections. Although AGs are well known for their ototoxic side effects, some AGs such as amikacin are considered less harmful to auditory functions; thus, auditory monitoring is mostly neglected during treatment with these drugs.ObjectiveTo reflect the potential auditory hazards of repeated amikacin use on the patients with cystic fibrosis (CF).Method32CF patients with prior exposure to at least 3 courses of amikacin (the CF group) and 35 non-CF patients visiting the outpatient clinic with any complaint other than hearing loss and no history of treatment with any AG(the control, or C group) were compared with pure-tone audiometry(PTA). The diagnosis of CF was made by Nanoduck sweat test.ResultsThe average age of the participants were 8.25±2.76years in the CF group and 8.58±2.00years in the C group (ranging from 5 to 13 years). 29 (43.28%) of the cases were female and 38 (56.71%) were male. Clinical SNHL(sensorineural hearing loss) was detected in 4 of the 32 subjects in the CF group. None of the subjects in the C group exhibited clinical SNHL. There was no statistically significant difference between the groups with regard to presence or absence of clinical SNHL (p>0.05). However, hearing levels of the CF group were around 20dB(decibel) HL(hearing loss), whereas hearing levels of the C group were around 5dB. This difference was statistically significant for the pure tone averages of both all frequencies and speech frequencies (p<0.05).ConclusionRepetitive exposure to AGs can cause permanent, although mild, sensorineural hearing loss. For prevention, hearing status of the patient should be closely monitored and treatment of choice should be precisely tailored according to the audiological evaluation. This is especially important in patients with CF who frequently experience medical conditions necessitating AGs use

Postoperative mechanical alignment analysis of total knee replacement patients operated with 3d printed patient specific instruments: A prospective cohort study

Objective: Total knee replacement (TKR) is a surgical treatment for final stage gonarthrosis. The lifespan of the prosthetic implants used in TKR surgery is a major interest for the orthopaedic research community.Previously, proper implant alignment of the implants has been advocated for longevity of the TKR surgery. Recently, patient-specific (PSI) instruments have been proposed to improve the mechanical alignment of the TKR by permitting better implant positioning over conventional TKR surgery. The aim of this study is to compare the mechanical alignment results of patients operated with PSIs and conventional instruments. Methods: Two groups of 20 patients chosen in a quasi-random manner have been compared in this study. In the first group femoral distal and tibial osteotomies were made by a PSI which was produced by the patients’ computed tomography scans. All osteotomies in the control group were made with the TKR set's routine instruments by conventional means. Patients’ preoperative and postoperative mechanical femorotibal angles (mFTA), femoral coronal angles (FCA), tibial coronal angles (TCA) were measured and the number of outliers which showed more than 3° of malalignment were counted in both groups for comparison. Results: The average postoperative mFTA was found to be 2.09° for the PSI group and in was found to be 284° for the control which was not statistically significant. The comparison of postoperative FCA and TCA also did not show significant difference between the groups. The number of outliers showing more than 3° of malalignment per group were found to be 1 out of 20 (5%) for the PSI group and 7 out of 20 (35%) for the control which was statistically significant. Conclusion: In this study patient-specific instrumentation provided significantly better mechanical alignment compared to conventional TKR for the frequency of outlier cases with malalignment beyond 3°. PSI proved no significant difference when the groups were compared for mFTA, FCA and TCA. Our findings support that PSI may improve TKR alignment by improving the ratio of the outlier patients with marked malalignment. Level of Evidence: Level III, Therapeutic Study

Retrospective evaluation of newborns with femur-humerus fractures reflected in forensic medical process: Descriptive study

Amaç: Doğum travmaları, doğum eylemi esnasında mekanik etkiler ile ortaya çıkan fiziksel yaralanmalardır. Doğum sırasında karşılaşılan bu durum medikolegal sorunlara neden olmaktadır. Çalışmamızda, yenidoğan döneminde uzun kemik kırığı saptanarak medikolegal sürece konu olmuş olguların özelliklerinin tartışılması amaçlanmıştır. Gereç ve Yöntemler: Adli Tıp Kurumu 7. İhtisas Kurulunda 2018-2020 yılları arasında medikolegal değerlendirme yapılan uzun kemik (femur/humerus) kırığı geliştiği iddiası bulunan olgular (n=23) dâhil edildi. Olguların sosyodemografik ve klinik özellikleri ile kurul kararları retrospektif olarak incelendi. Çalışma izni 01 Aralık 2020 tarih ve 1114 sayılı Adli Tıp Kurumu Bilimsel Araştırma Komisyonundan alındı. Bulgular: Olguların kız/erkek oranı 8/15 idi. On sekiz (%78,2) raporda hekim şikâyeti vardı. Olgularda femur (n=14) ve humerus (n=9) kırıkları saptandı. Olguların gestasyon haftası ortalaması 33 idi. Olguların ortalama doğum tartıları 2.921 (750-5.140 g) g saptandı. Olguların, term/preterm oranı 18/5 saptandı. Humerus ve femur kırığı saptanan 23 olguda da konservatif tedavi uygulanmıştı. Yirmi iki olguda tıbbi uygulama hatası saptanmadı ve kırıklar komplikasyon olarak değerlendirildi. Sonuç: Medikolegal sürece yansıyan uzun kemik kırıklarının tanı ve takip sürecinin uygun şekilde yönetildiği görülmektedir. Süreçte hasta-hekim arasında yaşanan iletişim sorunlarının güven ilişkisini sarstığı görülmektedir. Tıbbi bakım ve tedavi sırasında meydana gelen ve direkt olarak hekimin hatalı bir eylemi sonucu oluşmayan bu durum doğum süreci açısından komplikasyon olarak tanımlanmaktadır.Objective: Birth injuries, are the phisical injuries that can occur with mechanical effects during delivery. This situation encountered during labor causes medicolegal problems. In this study, we aimed to discuss the characteristics of the cases that were subject to the medicolegal process by detecting due to long bone fractures in the neonatal period. Material and Methods: The long bone fracture cases, evaluated for malpractice (n=23) in 7th Specialization Board of the Council of Forensic Medicine (between 2018-2020), were included in the cohort. The sociodemographic and clinical characteristics of the cases and the decisions of the board were reviewed retrospectively. The study permit was obtained from the Scientific Research Commission of the Council of Forensic Medicine, dated December 01, 2020 and numbered 1114. Results: The female/male ratio of the cases was 8/15. In eighteen reports (78.2%), physicians were the subject of complaints. Femoral (n=14) and humeral fractures (n=9) were detected. The mean gestational age was 33 weeks. The mean birth weight was 2,921 (750-5,140 gr) gr. The term/preterm ratio of the cases was 18/5. Conservative treatment was observed all cases with humerus fractures. Medical malpractice was not detected in 22 cases and fractures were evaluated as complications. Conclusion: The diagnosis and follow-up process was appropriately managed in long bone fractures that were reflected in the medicolegal process. Communication problems between the patient and the doctor undermine the trust relationship. This situation, which occurs during medical care and treatment and does not occur directly as a result of the physician's faulty action, is defined as a complication in terms of the birth process

Investigation of the influence of high-pressure torsion and solution treatment on corrosion and tribocorrosion behavior of CoCrMo alloys for biomedical applications

In this study, the influence of the high-pressure torsion (HPT) processing parameters and solution treatment (ST) on the corrosion and tribocorrosion behavior of CoCrMo (CCM) alloys was investigated for possible usage in biomedical applications. The corrosion behavior of the CCM alloys was investigated by using potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) tests. Tribocorrosion tests were carried out in a reciprocating ball-on-plate tribometer at 1 Hz, 1 N load, and 3 mm stroke length for 2 h. All electrochemical measurements were performed using a potentiostat in standard phosphate-buffered saline (PBS) solution at body temperature (37 ± 2 ◦C). The samples were characterized by using a scanning electron microscope (SEM), transmission electron microscope (TEM), optical microscope (OM), and X-ray diffraction (XRD). The deepness and width of wear tracks were examined by using a profilometer. The results showed that HPT and ST processes did not affect significantly the corrosion resistance of samples. However, the ST-treated samples had a higher material loss during sliding in standard phosphate-buffered saline (PBS) at body temperature as compared to HPT-treated samples.This work was supported by Yildiz Technical University Scientific Research Projects Coordination Unit under project number of 2016-07-02-KAP01, and partially by Portuguese Foundation for Science and Technology (FCT), Portugal, under UIDB/04436/2020 project

Age- and region-specific hepatitis B prevalence in Turkey estimated using generalized linear mixed models: a systematic review

Toy M, Önder FO, Wörmann T, et al. Age- and region-specific hepatitis B prevalence in Turkey estimated using generalized linear mixed models: a systematic review. BMC infectious diseases. 2011;11(1): 337.BACKGROUND: To provide a clear picture of the current hepatitis B situation, the authors performed a systematic review to estimate the age- and region-specific prevalence of chronic hepatitis B (CHB) in Turkey. METHODS: A total of 339 studies with original data on the prevalence of hepatitis B surface antigen (HBsAg) in Turkey and published between 1999 and 2009 were identified through a search of electronic databases, by reviewing citations, and by writing to authors. After a critical assessment, the authors included 129 studies, divided into categories: 'age-specific'; 'region-specific'; and 'specific population group'. To account for the differences among the studies, a generalized linear mixed model was used to estimate the overall prevalence across all age groups and regions. For specific population groups, the authors calculated the weighted mean prevalence. RESULTS: The estimated overall population prevalence was 4.57, 95% confidence interval (CI): 3.58, 5.76, and the estimated total number of CHB cases was about 3.3 million. The outcomes of the age-specific groups varied from 2.84, (95% CI: 2.60, 3.10) for the 0-14-year olds to 6.36 (95% CI: 5.83, 6.90) in the 25-34-year-old group. CONCLUSION: There are large age-group and regional differences in CHB prevalence in Turkey, where CHB remains a serious health problem

Erişkin spinal deformite cerrahisi geçiren hastalarda post-operatif başarı için prognostik kriterler

Erişkin spinal deformite cerrahisi sonrası bildirilen revizyon oranları %8-22 arasındadır. Bu çalışmanın amacı, erişkin spinal cerrahi geçiren ve sonrasında başarısızlıkla sonuçlanıp revize edilen hastaların analiz edilerek, başarısızlık ve revizyon nedenlerini ve olası prognostik kriterleri ortaya koymaktır