On the Wiener disorder problem

In the Wiener disorder problem, the drift of a Wiener process changes suddenly at some unknown and unobservable disorder time. The objective is to detect this change as quickly as possible after it happens. Earlier work on the Bayesian formulation of this problem brings optimal (or asymptotically optimal) detection rules assuming that the prior distribution of the change time is given at time zero, and additional information is received by observing the Wiener process only. Here, we consider a different information structure where possible causes of this disorder are observed. More precisely, we assume that we also observe an arrival/counting process representing external shocks. The disorder happens because of these shocks, and the change time coincides with one of the arrival times. Such a formulation arises, for example, from detecting a change in financial data caused by major financial events, or detecting damages in structures caused by earthquakes. In this paper, we formulate the problem in a Bayesian framework assuming that those observable shocks form a Poisson process. We present an optimal detection rule that minimizes a linear Bayes risk, which includes the expected detection delay and the probability of early false alarms. We also give the solution of the ``variational formulation'' where the objective is to minimize the detection delay over all stopping rules for which the false alarm probability does not exceed a given constant.Comment: Published in at http://dx.doi.org/10.1214/09-AAP655 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Multisource Bayesian sequential change detection

Suppose that local characteristics of several independent compound Poisson and Wiener processes change suddenly and simultaneously at some unobservable disorder time. The problem is to detect the disorder time as quickly as possible after it happens and minimize the rate of false alarms at the same time. These problems arise, for example, from managing product quality in manufacturing systems and preventing the spread of infectious diseases. The promptness and accuracy of detection rules improve greatly if multiple independent information sources are available. Earlier work on sequential change detection in continuous time does not provide optimal rules for situations in which several marked count data and continuously changing signals are simultaneously observable. In this paper, optimal Bayesian sequential detection rules are developed for such problems when the marked count data is in the form of independent compound Poisson processes, and the continuously changing signals form a multi-dimensional Wiener process. An auxiliary optimal stopping problem for a jump-diffusion process is solved by transforming it first into a sequence of optimal stopping problems for a pure diffusion by means of a jump operator. This method is new and can be very useful in other applications as well, because it allows the use of the powerful optimal stopping theory for diffusions.Comment: Published in at http://dx.doi.org/10.1214/07-AAP463 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

The Serum Biomarkers in Ulcerative Colitis

Objective: In this study, the aim was to evaluate the diagnostic effectiveness of more easily applicable and cost-effective serum biomarkers, such as neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), C-reactive protein (CRP) to albumin ratio (CAR), and CRP-to-lymphocyte ratio (CLR), instead of the endoscopic activity index (EAI) used to determine disease activation in ulcerative colitis (UC) patients. Methods: Blood tests performed during the same period as colonoscopy were reviewed, and NLR, PLR, CAR, and CLR values were calculated. Based on the EAI score, patients with a score <4 were classified as having UC in remission, those with a score ≥4 as having active UC, and those with normal colonoscopy results as the control group. Results: The study included 66 patients with active UC, 31 with UC in remission, and 99 controls. The CLR and CAR values of active and remission UC patients were found to be higher compared with the control group (p<0.001), while no significant difference was found between the groups in terms of PLR and NLR values (p>0.05). The AUC calculated for CLR in diagnosing active UC was significant (p<0.001), and the best cut-off value was determined as >1,75. For CAR, the best cut-off value was calculated as >0.11. Conclusions: This study demonstrated that the CLR and CAR had high sensitivity and specificity for detecting UC activity, whereas the PLR and NLR had low diagnostic value

A rare case of fatal venous and cerebral air embolism

A venous air embolism can occur as a result of circumstances that include blunt head or chest trauma, thoracentesis, arterial catheterization, neurosurgery, cardiac surgery, and Caisson disease. The formation of a venous air embolism requires an air source, interaction between the air source and the vessel, and a pressure gradient supporting air migration into the vessel. Air enters through the impaired venous structure and travels to the right side of the heart and the pulmonary arteries, and depending on the amount of air, may occasionally be fatal. This report is the description of the case of a 3-year-old child who developed a fatal venous and cerebral embolism during neurosurgery for the treatment of skull fractures with epidural and subdural bleeding due to blunt head and chest trauma resulting from a television falling on her. The pathophysiology of death and notes regarding the medico-legal autopsy procedure in such cases are discussed. Meticulous autopsy techniques must be used to determine the presence of an air embolism in cases of blunt trauma, especially in patients with blunt trauma to the head who die during neurosurgery, and possible future malpractice claims should be kept in mind

Evaluation of socio-demographic characteristics of people was determined to use synthetic cannabinoids in Malatya and its surrounding cities / districts and LC-MS/MS analysis method

Aim: Synthetic cannabinoids (SC) were initially developed in 1960s to target the cannabinoid receptors in medical therapy. However, in recent years, the developed SC derivatives by processing the plant-based material have been sold on websites under the name of natural drugs. The city of Malatya is located at the eastern part of Turkey and has an important location for the transfer and marketing of narcotic substances. In our study, presentation of the socio-demographic characteristics of the cases, the SC was determined in whose blood samples in the analyses, living in Malatya and the surrounding cities-districts were aimed. Materials and Methods: In the scope of study, 275 cases whose blood samples was sent to the Chemistry Department in Forensic Medicine Institute at Malatya Group Presidency in 2016 and were detected as SC-positive by the chemical analysis were investigated. Results: Out of 275 cases, 97.8% were male, 2.2% were female. Median age was 24, 66.5% (n=180) of them were primary school, 18% (n=51) were high school graduate and 0.7% (n=2) were university graduate. The educational status of 27 cases could not be obtained. Conclusion: SC derivatives are marketed with slogan of “the natural ones are harmless”, and their use among the young people is rapidly becoming widespread. In our study, it was determined that the SC users are in the young age group and have low educational status. In order to decrease the number of users, awareness meetings regarding the harmful effects of SC must be organized in the educational institutions

The Design And Analysis Of Piezoelectric Gripper

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1998Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1998Sonlu eleman metodu mühendislik problemlerinin birçoğunun nümerik olarak çözümlerinde önemli yer almaktadır. Bilgisayar teknolojisindeki ve bilgisayarla dizayn sistemlerindeki gelişmeler, karmaşık problemlerin bile kolayca modellenip çözülebilmesini sağlamaktadır. Örnek model üretilmeden önce, bilgisayar üzerinde değişik konfıgürasyonların denenerek en uygun modelin dizaynı gerçekleştirilir. Model sonlu eleman kurallarına göre küçük parçalara ayrılarak değişik yükleme durumları uygulanır. Elde edilen denklemler çözülerek gerçek durumdakine yakın sonuçlara ulaşılabilmesi sağlanır.Birleşik alan analizi bir sonlu eleman analiz yöntemidir. Bu yöntemde iki değişik fiziksel niceliğin etkileşimi İncelenmektedir. Örnek olarak bizim de bu çalışmada ele aldığımız piezoelektrik analizde; elektrik alan ile yapısal değişikliğin arasındaki etkileşim ele alınmaktadır. Termal-gerilme analizi, termal-elektrik analizi ve basınç-yapısal analiz gibi birçok örnek de bu analizin içindedir.Piezoelektrik malzeme birim çift kutupların dizilmesiyle ortaya çıkan bir malzemedir. Bu malzemenin uçlarına bir voltaj uygulandığında uçlardaki yük yoğunluğu değişecektir. Yük yoğunluğundaki bu değişiklik uygulanan voltajın yönünde malzemenin boyutlarında bir değişikliğin ortaya çıkmasına sebep olur.Piezoelektrik malzemenin bu özelliğinden faydalanarak geliştirdiğimiz tutucuyu analiz etmek için ANSYS analiz programından faydalandık. ANSYS’de piezoelektrik analiz için gerekli bilgiler ayrıntılı olarak tezin bölümlerinde ele alınmıştır.Sonuç bölümünde ANSYS’de analiz ederek bulduğumuz sonuçlarla, benzer şekilde dizaynlar üzerinde yapılmış çalışmalardan elde edilen sonuçlar karşılaştırılmıştır ve tutucunun kullanılabileceği sahalar belirtilmiştir.The smart structures field has grown rapidly over the last few years. One factor enabling this growth has been the development of small actuators based on smart materials such as piezoelectrics and shape memory alloys. Piezoelectric actuators are currently more widely used for smart structure applications because they are small, have low-power requirements, and respond quickly. However, commonly used piezoelectric actuators produce either high force coupled with small deflections (stacks) or large deflections coupled with low force (bimorphs). For piezoelectric actuation, this leaves a gap in force-deflection capabilities in which many smart structures applications operate.There exists an ongoing need in the area of robotics and prosthetics for light fast compact actuators. A review of current actuation systems such as electrical, hydraulic, and pneumatic systems that are commonly used for robotic and effectors reveals that these systems are too bulky, too heavy, too slow or too complex for use in lightweight anthropomorphic end effectors and prosthetic devices. Trimmer, defines a device in the range of 2 cm or smaller to be a microactuator. Many microactuator designs exist based upon shape memory alloy materials, electromagnetic materials, magnetic materials, electrostatic materials and piezoelectric materials. These devices were not applicable to the artificial hand problem because either they could not be combined to form a macroactuator, they were too slow or the additional equipment required to power the microactuator was too bulky or heavy. It became clear that the final microactuator would need to have a geometry that allowed it to be combined and also be capable of a direct electrical to mechanical energy conversion. Barium titanate and many other ceramic materials exhibit what is called the piezoelectric effect, illustrated schmetically in Figure 1. Let us consider a sample of a ferroelectric ceramic material which has a resultant dipole moment due to alignment of many small unit dipoles as indicated in Figure 1-a. In this material there will be an excess of positive charge at one and negative charge at the other end in the direction of the polarization. Now let us consider the sample when compressive stresses are applied, as shown in Figure 1-b. the compressive stresses reduce the length of the sample between the applied stresses and thus reduce the distance between the unit dipoles, which in turn reduces the overall dipole moment per unit volume of the material. The change in dipole moment of the material changes the charge density at the ends of the sample and thus changes the voltage difference between the ends of the sample if they are insulated from each other.Yüksek LisansM.Sc