Kesiklerin bazalt / karbon hibrit kompozitlerin serbest titreşim tepkisine etkileri

The current work deals with an experimental investigation about the influence of cut-outs on dynamic characteristics of basalt/carbon hybrid fiber reinforced composite laminates. The composite samples have been fabricated via vacuum assisted resin transfer molding technique and cut-outs in the form of triangular, square and circular shapes with equal areas have been processed on them to systematically analyze the influences of cut-outs. The dynamic characteristics of the samples have been examined by conducting free vibration-damping tests and expressed in terms of natural frequency and damping ratio using the frequency response and time-acceleration response. The results show that the damping characteristics of the composite samples can be remarkably improved with the help of cut-outs which provide improvements approximately between 2.41% and 16.65% in damping ratio values. The maximum and minimum variations in damping ratio have observed for non-hybrid carbon fiber reinforced composite samples with triangular cut-out (T-C6) and hybrid basalt/carbon fiber reinforced composite samples with circular cut-out (C-B6), respectively. On the other hand, the presence of cut-outs have led to decreases in natural frequency values as a result of reduction in stiffness caused by the cut-outs. This point out that employment of cut-outs can be a promising application to meet the natural frequency requirements of engineering systems constructed with hybrid fiber reinforced composite laminates.Mevcut çalışma, kesiklerin bazalt / karbon melez fiber takviyeli lamine kompozitlerin dinamik özellikleri üzerindeki etkisi hakkında deneysel bir araştırma ile ilgilidir. Kompozit numuneler, vakum destekli reçine transfer kalıplama tekniği ile imal edilmiş ve kesiklerin etkilerini sistematik olarak analiz etmek için üzerlerinde eşit alanlara sahip üçgen, kare ve dairesel şekiller şeklinde delikler açılmıştır. Numunelerin dinamik özellikleri, serbest titreşim sönümleme testleri yapılarak incelenmiş ve frekans tepkisi ve zaman-ivme tepkisi kullanılarak doğal frekans ve sönümleme oranı cinsinden ifade edilmiştir. Sonuçlar, kompozit numunelerin sönümleme özelliklerinin, sönümleme oranı değerlerinde yaklaşık %2,41 ile %16,65 arasında artışlar sağlayan kesikler yardımıyla önemli ölçüde iyileştirilebileceğini göstermektedir. Sönümleme oranındaki maksimum ve minimum varyasyonlar, sırasıyla üçgen kesikli hibrit olmayan karbon fiber takviyeli kompozit numuneler (T-C6) ve dairesel kesikli hibrit olmayan bazalt fiber takviyeli kompozit numuneler (C-B6) için gözlemlenmiştir. Öte yandan, kesiklerin varlığı, deliklerin neden olduğu sertlikte azalmanın bir sonucu olarak doğal frekans değerlerinde düşüşlere yol açmıştır. Bu, kesiklerin kullanılmasının, hibrit fiber takviyeli kompozit laminatlarla inşa edilen mühendislik sistemlerinin doğal frekans gereksinimlerini karşılamak için umut verici bir uygulama olabileceğini göstermektedir

The finite element analysis and geometry improvements of some structural parts of a diesel forklift truck

In this work, static analyses of structural parts of a diesel forklift were performed using Finite Element Method and possible modifications based on the original geometry of parts were utilized with respect to stress distributions at critical region to improve reliability of the forklift design. The analyses were carried out according to standard regulations related with the examined parts. The structural parts of forklift such as chassis and head guard were analysed under compulsion loading conditions. The improvements in relevant parts were demonstrated by the comparison of stress values of original and modified geometries. The finite element analyses were carried out using MSC SimXpert Nastran Finite Element software package

The effects of nanosilica on charpy impact behavior of glass/epoxy fiber reinforced composite laminates

Desire to improve the efficiency of composite materials for engineering applications has led to the use of nano-sized additives or fillers such as nanoclay, nanosilica, nano-graphene, carbon nanotubes. The effect of nanoparticle inclusion on mechanical properties of fiber reinforced composite materials has been investigated by many researchers and crucial effects have been reported in several papers. In this work, the effects of nanosilica content on the low velocity impact behaviors of glass/epoxy fiber reinforced composite laminates are determined using Charpy impact tests. The composite laminates are fabricated via hand lay-up followed by hot press molding. The nanosilica particles with different weight percentages are dispersed in epoxy resins using mechanical stirring. The absorbed impact energy values of flatwise-unnotched and edgewise-notched beam specimens, and impact damages are analyzed as a measure of impact behavior. The results show that the incorporation of nanosilica particles have significant effects on the Charpy impact behavior

Effects of etanercept, a tumor necrosis factor receptor fusion protein, on primary cell cultures prepared from intact human intervertebral disc tissue

The aim of the present study was to investigate the effects of etanercept (ETA), a tumor necrosis factor (TNF) inhibitor, on human cell cultures prepared from intact intervertebral disc tissue. ETA is used as a treatment for cases of rheumatoid arthritis, psoriatic arthritis, axial spondyloarthritis and ankylosing spondylitis accompanied by moderate or severe joint pain. ETA was applied to primary cell cultures [annulus fibrosus and nucleus pulposus (NP) from intact intervertebral disc tissue]. Cell cultures without ETA treatment served as the control group. Morphological and quantitative molecular analyses of the two groups were performed. The number of viable cells and cell proliferation decreased in the ETA-treated cultures as compared with those in the control group. Furthermore, in the treatment group, the chondroadherin gene, an NP-specific marker, was not expressed after 24 h. By contrast, the cartilage oligo matrix protein was expressed 24, 48 and 72 h post-ETA treatment, while its expression was significantly lower than that in the control group. In addition, the expression of interleukin-1 beta, as well as matrix metallopeptidase-7 and -19, was markedly decreased. Overall, the cell proliferation and gene expression in the ETA-treated cells were significantly different from those in the control group (P<0.05). These results suggest that the treatment duration and dosage of TNF inhibitors, which are used to suppress active inflammation, should be considered in the clinical setting. These biological agents may delay the healing of intervertebral disc tissue damage by slowing cell proliferation and altering gene expression via anabolic and catabolic pathways

Evaluation of the effect of apixaban on the primary intact intervertebral disc cell cultures

Aim: Apixaban is a frequently preferred pharmacological agent in clinics to prevent deep vein thrombosis and pulmonary embolism.Such new oral anticoagulants may cause hemorrhage’s in tissues and/or organs or may cause gastrointestinal symptoms withoutbleeding. It is also reported in the literature that it may lead to mental disorders, unwanted disorders in the urinary tract and skeletalmuscle system. However, when the literature is examined, there are no studies, which are of high-evidential value, evaluating theefficacy of apixaban on healthy, intact intervertebral disc tissue, and matrix-like structures. In this pharmaco-molecular study, itwas aimed to investigate the effects of a new oral anticoagulant agent containing the active ingredient apixaban on the intactintervertebral disc tissue cells, extracellular matrix (ECM) structure and to evaluate its positive and / or negative effects on geneexpressions of cartilage oligo matrix protein (COMP), chondroadherin (CHAD), and Matrix Metalloproteinase (MMP)s.Material and Methods: The primary cell cultures were prepared from the intact tissues of the patients with the traumatic intervertebraldisc herniation. Apixaban was administered to the cultures and molecular analyses were performed for 21 days. The data obtainedfrom the apixaban-administered and non-apixaban-administered samples were evaluated statistically and the significance valuewas accepted as P <0.05.Results: The changes were observed in the cell proliferation and the expressions of the mentioned genes in the apixabanadministered group. The suppression of COMP value and the increase in MMP-13 value may be indicative of the development ofmatrix degeneration in the apixaban-administered group, compared to the non-drug-administered control group.Conclusion: The selectivity is one of the most important features of the drugs. However, it should not be forgotten that no drug willonly produce the desired effect

A combined diagnosis and treatment algorithm for spine infection management: A single-center experience

Background and objectiveSpinal infection (SI) is an infectious disease affecting the vertebral column, spinal cord, and adjacent structures. The infection can occur following interventions or spontaneously. The aim of this study was to highlight the importance of employing a methodological approach for the accurate and rapid diagnosis of SI and to share information on the most effective treatment method, which involves using a diagnostic -treatment algorithm that can help with SI management.MethodologyThis study included 50 patients diagnosed with SI between 2016 and 2020. The treatment follow-up period was limited to six months, and the study was conducted as a retrospective cohort analysis. The sample consisted of 22 female patients and 28 male patients, and the mean age of the patients was 50.2 years. All patients received diagnosis and treatment according to the algorithm described in this article.ResultsIn the study group, 60% of patients had an infection in the lumbar spine, 4% in the thoracal spine, 12% in the cervical spine, and 8% in the sacral spine. Previously operated patients were diagnosed on the 30.16th day on average. A total of 19 patients (38%) had no history of undergoing surgery. Radiologically, the most common finding was spondylodiscitis/discitis (32%). Osteomyelitis was detected in one (2%) patient. Methicillin-sensitive Staphylococcus aureus (MSSA) was the most commonly isolated organism in culture results and was detected in 13 patients (26%). The culture results of 12 patients (24%) were negative. The number of patients with active SI who were unstable and stabilized at the time of diagnosis was 11 (22%), and stabilization materials were removed in two patients (4%). In the 6th month of control, the patients did not have any complaints, signs of an infection, or unstable vertebral column.ConclusionsWe conclude that the combined algorithm we recommend for the diagnosis and treatment of patients with SI can prevent negative deviation and is an effective treatment for this condition

Lumbar dynamic stabilization with 2-stage surgery: early results

Background: Screw loosening, which is a major problem in dynamic systems, can be easily overcome with 2-stage surgery. In this article, the clinical and radiological results of patients undergoing dynamic stabilization with a Dynesys device in 2 stages are discussed. Methods: A total of 10 male and 13 female adult patients were included in this single-center retrospective study conducted between 2018 and 2021. The mean age of the patients was 65.6 years. All of the patients had pain complaints that affected their daily lives. Bone density T scores were determined with the dual-energy x-ray absorptiometry method before patients were admitted for surgery. In the first surgery, Dynesys system pedicle screws were inserted. After 6 months of osteointegration, Dynesys system spacers and elastic bandages were placed. Preoperative, early postoperative, and late postoperative visual analog pain scale (VAS) scores and Oswestry Disability Index (ODI) scores were determined and statistically compared. Results: Patients were followed for an average of 30 months. Complications and recurrence were not observed. Neurological deficits were not observed after patients recovered from anesthesia. Significant improvement was observed in the ODI and VAS parameters in the preoperative (ODI: 66.2%, VAS: 7.8), early postoperative (ODI: 20.3%, VAS: 2.4), and late postoperative (ODI: 6.8% and VAS: 1.1) periods. Symptomatic improvement was seen in all patients. No screw breakage or loosening was detected by radiological evaluation in any of the patients during the 2-year follow-up period. Conclusions: In our experience, the insufficiency of the proximal and distal end screws is eliminated when 2 stages of dynamic system stabilizations are completed after osteointegration of the screws

Turner syndrome and associated problems in turkish children: A multicenter study

Objective: Turner syndrome (TS) is a chromosomal disorder caused by complete or partial X chromosome monosomy that manifests various clinical features depending on the karyotype and on the genetic background of affected girls. This study aimed to systematically investigate the key clinical features of TS in relationship to karyotype in a large pediatric Turkish patient population. Methods: Our retrospective study included 842 karyotype-proven TS patients aged 0-18 years who were evaluated in 35 different centers in Turkey in the years 2013-2014. Results: The most common karyotype was 45,X (50.7%), followed by 45,X/46,XX (10.8%), 46,X,i(Xq) (10.1%) and 45,X/46,X,i(Xq) (9.5%). Mean age at diagnosis was 10.2±4.4 years. The most common presenting complaints were short stature and delayed puberty. Among patients diagnosed before age one year, the ratio of karyotype 45,X was significantly higher than that of other karyotype groups. Cardiac defects (bicuspid aortic valve, coarctation of the aorta and aortic stenosi) were the most common congenital anomalies, occurring in 25% of the TS cases. This was followed by urinary system anomalies (horseshoe kidney, double collector duct system and renal rotation) detected in 16.3%. Hashimoto’s thyroiditis was found in 11.1% of patients, gastrointestinal abnormalities in 8.9%, ear nose and throat problems in 22.6%, dermatologic problems in 21.8% and osteoporosis in 15.3%. Learning difficulties and/or psychosocial problems were encountered in 39.1%. Insulin resistance and impaired fasting glucose were detected in 3.4% and 2.2%, respectively. Dyslipidemia prevalence was 11.4%. Conclusion: This comprehensive study systematically evaluated the largest group of karyotype-proven TS girls to date. The karyotype distribution, congenital anomaly and comorbidity profile closely parallel that from other countries and support the need for close medical surveillance of these complex patients throughout their lifespan. © Journal of Clinical Research in Pediatric Endocrinology

Urban Landscapes

The issue focuses on philosophies and designs that shape our cities on a broader scale; exploring different approaches between architecture, built environment, and nature; from material to medicinal plants, from plant scale to urban and social sciences. The issue examines the natural and built environment in Istanbul through the relationship between urban planning, urban space, architecture, and landscape architecture. It focuses on designs made in different parts of Istanbul between natural areas and built areas in the city. The urban landscape is an effective and important design process that includes the interaction of architecture, city planning, and landscape architecture disciplines and creates the living environment of people within and between buildings. It has a complementary and important effect in the process of providing and maintaining the physical, physiological, psychological, and social needs of its users. It covers structural design and furniture location selection and design as well as planting. The special issue on Urban Landscape covers this concept; It has a content setup that starts from the upper scale and shrinks towards the building scale.info:eu-repo/semantics/publishedVersio

Shear and Fracture Characteristics of Nano-silica and GNP Hybrid Nanoparticle Reinforced Single Lap Joints

In the current study, the effects of hybrid nanoparticles on the shear and fracture behaviours of adhesively bonded single lap joints (SLJs) using Aluminum substrates were investigated. To this aim, nano-silica and graphene nanoplatelet (GNP) particles were used as filler materials in Araldite 2014-2 epoxy-based adhesive. The SLJ samples prepared at seven different configurations were subjected to lap shear tests. Additionally, macro and SEM views taken from damaged surfaces of the samples were examined to understand the influence of nanoparticle addition on the fracture characteristics of the joints. The experimental findings showed that all nanoparticle-doped samples, whether single or hybrid, exhibited remarkable improvements in shear strength compared to pure ones. The maximum improvements were obtained from the H2 sample having 1 wt.% nano-silica and 0.5 wt.% GNP. The maximum shear strength was 13.62 MPa which was 213% higher than pure samples (4.35 MPa). It was determined that some toughening mechanisms such as crack deviation, crack bridging and plastic void formations had a crucial role in the enhancements of the samples. However, higher amounts of nanoparticle inclusion such as H4 (1.5 wt.% nano-silica+1 wt.% GNP) showed a decrease in shear strength, compared to the maximum one, due to the material degradation caused by agglomerations. In conclusion, nano-silica and GNP particles proved they could be used together by exhibiting a synergetic effect in the adhesive joints