The analysis of interlocking directors via hypergraphs

Since the dawn of the modern era, the associations that link companies together in the gathering and control networks have been interconnected. At the level of corporate governance, companies are linked by common stock directors, joint shareholders and joint directors (interlocking directors). Although often depicted as atomic, individual, unconnected market actors are actually embedded in such networks. In this study, we examine the network characteristics of interlocking directors of Turkish firms listed in ISO 500 and Borsa Istanbul Stock Exchange. To capture the higher order relations, we use hypergraphs to model interlocking directors and their relations. By introducing a simple graph representation based on the connectedness of agents in a hyper-network, we also give the community structure that is a cluster of densely connected nodes. The results we obtain in this study indicate that companies of Turkish market operating in global scale have central positions in their interlocking director network.Publisher's Versio

Diagnostic Value of Dynamic Contrast-Enhanced Magnetic Resonance Imaging in the Evaluation of the Biliary Obstruction

Purpose. In this study, our purpose was to investigate the diagnostic efficacy of the dynamic contrast-enhanced magnetic resonance imaging (MRI) method in the patients with bile duct obstruction. Materials and Methods. 108 consecutive patients (53 men, 55 women, mean age; 55.77 ± 14.62, range 18–86 years) were included in this study. All the patients underwent conventional upper abdomen MRI using intravenous contrast material (Gd-DTPA) and MRCP in 1.5 Tesla MRI scanner. MRCP images were evaluated together with the T1 and T2w images, and both biliary ducts and surrounding tissues were examined for possible pathologies that may cause obstruction. Results. MRI/MRCP findings compared with final diagnoses, MRI/MRCP in the demonstration of bile duct obstruction sensitivity 96%, the specificity 100%, and accuracy 96.3%, in the detection of presence and level of obstruction, the sensitivity 96.7%, specificity 100%, and accuracy 97.2%, in the diagnosis of choledocholithiasis, the sensitivity 82.3%, specificity 96%, and accuracy 91.7%, and in the determination of the character of the stenosis, sensitivity 95.6%, specificity 91.3%, and accuracy 94.5% were found. Conclusion. The combination of dynamic contrast-enhanced MRI and MRCP techniques in patients with suspected biliary obstruction gives the detailed information about the presence of obstruction, location, and causes and is a highly specific and sensitive method

Evaluation of self-esteem and dermatological quality of life in adolescents with atopic dermatitis

Background and Design: Atopic dermatitis is a chronic, inflammatory skin disease characterized by itchy skin lesions. Since adolescents are intensely interested in their physical appearance, chronic skin diseases in this period can adversely affect the development of self esteem. Atopic dermatitis is a skin disease that affects the appearance and there is an heightened attention to the body image in adolescence which is an important period of time in the development of self-esteem. Therefore, we aimed to investigate self-esteem and dermatological quality of life in adolescents with atopic dermatitis. Materials and Methods: Thirty-three patients with atopic dermatitis and 33 healthy controls were included in the study. The Piers-Harris Children’s Self-Concept Scale and the Children’s Dermatology Life Quality Index (CDLQI) were used for determining self-esteem and quality of life. The Scoring of Atopic Dermatitis (SCORAD) Index was used to assess the severity of atopic dermatitis. Results: It was found that patient group had lower self-esteem than healthy controls according to the Piers-Harris Children’s Self-Concept Scale. A statistically significant difference was observed in happiness/satisfaction and anxiety subscale scores between the patients and healthy controls while there was no significant difference between the other sub-scale scores. Mean value of dermatological quality of life in patients with atopic dermatitis was significantly lower than in healthy controls. A moderate negative correlation was found between self-esteem and CDLQI scores among adolescents with atopic dermatitis. Discussion: This study results have shown that self-esteem and dermatological quality of life were adversely affected in adolescents with atopic dermatitis irrespective of gender. These patients should be examined psychiatrically besides dermatological examination and treatment. We suggest that improvement will be observed in self-esteem and quality of life of adolescents with atopic dermatitis by providing the necessary psychosocial support

Genelleştirilmiş Atama Probleminin Hypergraf Çözümü ve Uzaysal Veri Kümelerine Uygulaması

In the simple task assignment problem, at most one task should be assigned to each agent; this constraint is relaxed in the multiple task assignment problems. The goal of the well-known Generalized Assignment Problem is to assign tasks to agents such that the capacity of the agent does not exceed its limits as it minimizes the total cost. In this study we present a novel approach to solve the general assignment problem by using the hypergraphs. Hypergraphs can be considered as the generalization of the graphs in such way that an edge can connect any number of vertices, and can be seen as the set systems. In the hypergraph multi-assignment problem, we are looking for a cost minimizing solution to tasks assignment to the agents which are the individual hyperedges. For this purpose, we first determine the tasks as hyperedges and then obtain the vertex cover of the simple graph representation of a hypergraph. Amongst the all possible covers, we choose the cost minimizing one as the solution.Basit atama probleminde, her bir etkene en fazla bir iş atanmaktadır; bu kısıtlanış genelleştirilmiş atama problemlerinde gevşetilmiştir. Oldukça iyi bilinen Genelleştirilmiş Atama Probleminin hedefi etkenlere iş atarken toplam minimum maliyeti minimumlaştırırken etkenlerin kapasitelerinin limitlerini geçmemesini sağlamaktır. Bu çalışmada Genelleştirilmiş Atama Probleminin çözümü için hypergraflar kullanılarak orijinal bir yöntem verilmiştir. Hypergraflar, bir ayrıt herhangi sayıda tepeyi içerecek şekilde grafların bir genelleştirilmesi olarak ele alınabilir ve küme sistemleri olarak görülebilir. Hypergraf multi-atama probleminde, etkenleri ayrı hyperayrıtlar olarak alıp maliyeti minimize eden çözümler aranmaktadır. Bu amaçla, ilk olarak işleri hyperayrıt olarak belirleyip daha sonra hypergrafın bir basit graf gösteriminde tepe örtü kümesini elde etmekteyiz. Bütün örtü kümeleri içerisinde maliyeti minimize edeni çözüm olarak kabul ederiz

Motor estetik kapaklarının araç iç ve dış gürültüsüne etkisinin incelenmesi

Günümüzde gelişen teknoloji ile otomotiv endüstrisinde araç sürüş konforu önemli hale gelmiş ve müşterilerin beklentileri de buna bağlı olarak artmıştır. Otomotiv üreticileri müşteri beklentilerinden taviz vermeden pazardaki zorlu rekabet şartlarında ayakta kalabilmek ve maliyetleri minimize edebilmek için fiyat/performans indeksini daha fazla ele almaya başlamışlardır. Fonksiyonel ve ekonomik parametrelerin seçim kriteri olmaktan zorunluluk olmaya doğru yol almasıyla birlikte sürüş konforu araç seçiminde ön plana çıkmaktadır. NVH kapsamında sürüş konforundan bahsedildiğinde ise; yol sesi, rüzgâr sesi, soğutma fan sesi, klima kompresörü sesi, alternatör sesi, araç rölanti titreşim ve gürültüsü, stop/start opsiyonu bulunan araçlarda stop ve start anlarında maruz kalınan titreşim gibi parametreler değerlendirilmektedir. Akustik konfor sadece sürücü ve yolcular için geçerli değildir. Dış gürültü de en az iç gürültü kadar önem taşımaktadır. Trafikte ışıkta dururken motor gürültüsü fazla olan bir araç, aracın dışında olan insanlar için de olumsuz anlamda dikkat çekecektir. Dış gürültü için en büyük gürültü kaynağı genellikle motor sesidir. Bu gürültüyü azaltabilmek için motor kapağı kullanılmaktadır. Motor bloğunun üzerinde bulunan motor estetik kapağı farklı yalıtım malzemelerinden yapılarak araç dış gürültüsünü önemli miktarda azaltmaktadır. Bu çalışmada binek bir araca ait motor estetik kapak değişiminin araç iç ve dış gürültüsüne etkisi incelenmiştir. Yapılan çalışma ile akustik performansı iyi olan motor kapağı tercih edilmiş ve son kullanıcıya iletimi yapılmıştır. Fiziksel test ortamı olarak yarı yankısız oda kullanılmış, test kurulumu gerçekleştirilmiş ve veri toplanması için de Simcenter TestLab programı kullanılmıştır. Objektif değerlendirmelerin ardından her bir durum için ayrıca sübjektif değerlendirmeler de yapılmıştır.Nowadays, with the developing technology, vehicle driving comfort has become important in the automotive industry and the expectations of the customers have increased accordingly. Automotive manufacturers have begun to consider the price/performance index more to survive in the harsh competitive conditions in the market and to minimize costs without compromising customer expectations. Driving comfort comes to the fore in vehicle selection, with functional and economic parameters moving from being a selection criterion to being a necessity. When it comes to driving comfort within the scope of NVH; parameters such as road noise, wind noise, cooling fan noise, air conditioning compressor noise, alternator noise, vehicle idling vibration and noise, and vibration during stop and start in vehicles if stop/start option are evaluated. Acoustic comfort is not just for the driver and passengers. External noise is just as important as internal noise. A vehicle with a high engine noise when stopped at a traffic light will also attract negative attention for people outside the vehicle. The biggest noise source for outside noise is usually engine noise. Engine beauty cover is used to reduce this noise. The engine beauty cover on the engine block is made of different insulating materials, significantly reducing the external noise of the vehicle. In this study, the effect of change of the engine beauty cover of a passenger car on the vehicle interior and exterior noise was studied. With the study, the material with good acoustic performance was preferred and the delivery was made to the customer. Semi-anechoic chamber was used as the physical test room, the test setup was carried out and Simcenter TestLab program was used for data collection. After the objective evaluations, subjective evaluations were also made for each situation

Conjunctival Flora in Diabetic and Nondiabetic Individuals

Objectives: To evaluate the conjunctival bacterial flora in diabetic patients and nondiabetic subjects. Materials and Methods: Fifty-three diabetic patients and 43 nondiabetic healthy individuals were included in the study. A specimen was taken from each participant for the study by rubbing a sterile cotton-tipped swab on the inferior palpebral conjunctiva of the right eye. Samples were incubated in blood agar, chocolate agar, eosin methylene-blue lactose sucrose agar and sabouraud 4% dextrose agar. Isolated microorganisms were identified using routine microbiological methods. Results: Rates for bacterial isolations were determined as 38.5% in diabetic patients and 34.9% in nondiabetic controls. Staphylococcus aureus was isolated in 30% of cases in the diabetic patient group, while 20% tested positive for Escherichia coli, 10% for coagulase-negative Staphylococcus, 10% for Klebsiella pneumoniae and 30% for multiple bacteria. In the non-diabetic group, 53.3% of patients were positive for Staphylococcus aureus while coagulase-negative Staphylococcus was isolated in 26.7%, Klebsiella pneumoniae in 6.7% and multiple bacteria in 13.3% of patients. Although there was no statistically significant difference in the number of isolated bacteria between the diabetic and nondiabetic groups, gram-negative bacterial colonization was significantly higher in diabetic patients (χ2=0.129, p=0.719 and χ2=5.60, p=0.018, respectively). Conclusion: Gram-negative bacteria are more common in the conjunctival flora of diabetic patients. This should be considered by clinicians when treating ocular infections in diabetic patients. (Turk J Ophthalmol 2015; 45: 193-196

Average edge-distance in graphs

The average edge-distance of a connected graph G is the average of the distance between all pairs of edges of G. In this work we give the average edge-distance of a graph, a new vulnerability measure. We also find sub and upper bounds for average edge-distance and give a polynomial time algorithm which calculates the average edge-distance of a graph.The average edge-distance of a connected graph G is the average of the distance between all pairs of edges of G. In this work we give the average edge-distance of a graph, a new vulnerability measure. We also find sub and upper bounds for average edge-distance and give a polynomial time algorithm which calculates the average edge-distance of a graph