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Biochemical regulation of cellular micromechanics is fundamental for many aspects of life, including development and disease. A better understanding of the principles of cellular information processing is therefore desirable. This thesis investigates how the stochastic micromechanis of bacteria on surfaces and thereby also surface-migrating bacterial cells perceive and adjust to their mechanical environment. We study the subject systematically from the single-cell level to the collective through analytical models, experiments, and simulations. Twitching is a mode of bacterial migration on biotic and abiotic surfaces driven by extracellular appendages called Type IV pili (T4P) that can extend and retract. We study the physics of twitching migration and the impact of mechanical properties of the substrates. To begin with, we employ mathematical modeling to find the conditions under which substrate-rigidity-dependent stick-slip motion of bacteria occurs. An idealized cell model is constructed, focusing solely on the mechanics of the migration. Migration is driven by stochastic extension-retraction dynamics of an active appendage modeled after T4P. A passive adhesion at the back of the cell allows for tension build-up in the system. The analytical calculations show that the migration speed depends non-linearly on the substrate rigidity on the condition that the attachment rates are an order of magnitude higher than the stochastic detachment rates of the appendages. We extend the model in simulations which allows us to obtain speed distributions. The results provide generic criteria for the emergence of substrate-rigidity-dependent stick-slip migration. Twitching is an intrinsically complex biological process that is only partially understood. It has been recently found that the extension-retraction dynamics of Pseudomonas aeruginosa's T4P result from stochastic binding of motor ATPases to a molecular transmembrane complex forming the pilus base. We investigate how such stochastic dynamics mediate twitching and explore the impact of substrate rigidity on T4P and twitching. Experiments done in collaboration, employing fluorescently labeled bacteria on two hydrogels with different chemical and mechanical properties, reveal that bacteria produce slightly shorter but twice as many pili on surfaces compared to the bacteria suspended in a liquid medium. An in-depth analysis of the empirical data shows no statistically significant change of these effects with different substrate rigidities. The experimental data also shows that only a small fraction of pili contributes to the migration, and bacteria retract their pili regardless of surface attachment. The fluorescent movies also reveal that passive adhesions on the cell body hinder twitching migration. A stochastic model describing the T4P dynamics is developed to study surface-associated migration of P. aeruginosa further. The model captures all measured T4P statistics quantitatively. By extending the T4P model with stochastic surface-bond dynamics, we simulate twitching bacteria. The simulations quantitatively explain the migration statistics of the ensemble. Moreover, the analysis of the measured mean-squared displacements suggests that the number of passive adhesions attaching P. aeruginosa to the substrate varies strongly. Using shear-flow experiments and simulations, we show that bacteria employ pili and passive adhesions together to balance migration and adherence to surfaces. Bacterial aggregation is an essential step towards biofilm formation. Hence, understanding aggregation dynamics is essential. Since we have explained the twitching dynamics of the individuals quantitatively, the next step is to study the collective behavior of twitching bacteria by taking into account our findings regarding T4P activity. For this purpose, a simulation framework is developed. The code is extended for investigating different twitching species by allowing for different bacterial shapes and T4P parameters. Moreover, a simplified bacterial gliding mechanism is implemented for bacteria that can glide and twitch. For rigid-rod-like bacteria that are strictly unipolar the simulations reveal a phase separation into dense clusters and areas with few bacteria, as previously shown. However, if bacteria twitch with the pilus distribution found in the experiments, without reversing the leading pole, the motion does not lead to phase separation. Even with a reversal of the leading pole every ~30 minutes, migration alone does not lead to clustering. These findings suggest that clustering of P. aeruginosa on surfaces is not purely driven by migration but that cell division, secretion of extracellular matrix proteins, or regulatory processes are essential for clustering. Finally, we investigate the effect of hydrogel-substrate composition on the microcolony formation of twitching and dividing bacteria by combining simulations with experimental data.

In this thesis, we study the implications of multi-party pricing for both consumers and producers in different settings. Within most organizations, the final price of a product or service is usually the result of a chain of pricing decisions. This chain may consist of different departments of the same company as well as different companies in a specific industry. Understanding the implications of such chains on the final prices and on consumer and producer surplus is the key topic of this dissertation. In the first part of this thesis, we consider a network in which products consist of combinations of perishable resources. In this model, different revenue-maximizing "controllers" determine the resource prices and the price of the product is the sum of the prices of the constituent resources. For uncapacitated networks, we develop bounds on the "price of anarchy" -the loss from totally decentralized control versus centralized control- as the number of controllers increases. We present provably convergent algorithms for calculating Nash equilibrium prices for both the uncapacitated and capacitated cases and -using these algorithms- illustrate counterintuitive situations in which consumer surplus increases after decentralization. While we develop our model in the context of airline pricing, it is applicable to any service network such as freight transportation, pipelines, and toll roads as well as to the more general case of supply chain networks. In the rest of the dissertation, we focus on understanding and improving pricing decisions in the case when corporate headquarters set a list price for all products but local sales force is given discretion to adjust (or negotiate) prices for individual deals. This form of pricing is called list pricing with discretion (LPD) and it is commonly found in most business-to-business markets and in certain business-to-consumer settings, including consumer lending, insurance, and automobile sales. In the LPD setting, the question of how much (if any) pricing discretion should be granted to local sales force is crucial. In the second part of this thesis, we study this issue using two data sets - one from an online lender who sets all prices centrally and one from an indirect lender with local pricing discretion. We find strong evidence that the indirect sales force adjusts prices in a way that improves profitability. However, we also show that using a centralized, data-driven pricing optimization system has the potential of improving profitability further. In addition, using a control function approach, we show that the discretion applied by the local sales force introduces significant endogeneity into the indirect lender's pricing process. Ignoring this endogeneity can lead to severe underestimation of price sensitivity. These insights are valuable for any customized pricing market in which in-person interaction is part of the price-setting process. Finally, in the last part, we focus on the underlying negotiation process of the LPD setting and on the fact that not only buyers differ in their willingness-to-pay (WTP) but sellers also differ in the minimum prices (reservation prices) that they are willing to accept for the transaction. We develop a methodology based on the Expectation-Maximization (EM) algorithm to estimate both the WTP and the reservation price distributions given transactions data. The required data include information about both completed trades and failed trades, however price information is only available for completed trades (which is the most common situation in these markets). Using the same data from the auto lending industry, we show that our approach provides improved estimates of customer price-sensitivity over the approaches commonly used in practice. We also show how the WTP and reservation price estimates can be used to improve profits for the seller by optimally setting reservation prices on negotiations.

Bu çalışma, 2003-2004 Eğitim-Öğretim yılında Kırşehir il merkezinde bulunan Süleyman Türkmanî İlköğretim Okulu 5/B sınıfı öğrencileri ile hem nicel hem de nitel araştırma tekniklerine dayalı olarak yapılmış bir aksiyon araştırmasıdır. İlköğretim 5. sınıf öğrencilerinin tarihsel zaman kavramı ve kronoloji düşüncelerinin geliştirilmesine ilişkin bu çalışmada; kullanılan birçok öğretim yöntem ve materyaline (zaman çizelgeleri, geçmişe ilişkin fotoğraflar, eski ev aletleri, koleksiyonlar vs.) öğrencilerin ilgileri, tepkileri ile bu öğretim yöntem ve materyallerinin çocukların konuya ilişkin akademik başarılarına katkıları ele alınmıştır. Çalışmada hem ön test-son test deseni çerçevesinde tutum ve başarı testleri hem ses kayıt cihazıyla ders işleme sürecinin kayıtları hem de öğrencilerin öğrenme ürünlerinden hareketle veri toplanmıştır. Verilerin değerlendirilmesi; ön test-son test tutum ve başarı ölçekleri ve ders işlenişiyle ilgili öğrenci değerlendirme formunun istatistiki olarak tablolaştırılması, ders işlenişinin kaydedildiği ses kayıtlarının ve öğrenci öğrenme ürünleri ile öğrencilerin görüşlerini ortaya koydukları ders değerlendirme kompozisyonlarının çözümlenerek yorumlanmasıyla gerçekleştirilmiştir. Araştırmanın nicel verilerinin yorumlanmasında SPSS programı aracılığıyla t testi, Anova testi, yüzdelik dağılımlar ve korelasyon yöntemleri kullanılmış, nitel veriler ise ses kayıtlarının çözümlerinin analitik bir yaklaşımla değerlendirilmesi ve öğrenci ürünlerine yapılan içerik analizi teknikleri çerçevesinde ele alınmıştır. Araştırma bulgularına göre çocukların tarih şeritlerini kişisel yaşam çizelgelerinden hareketle hazırlamaları ve ailelerine ilişkin geçmişi anlatan eski fotoğraflar ile eski ev aletlerini inceleme etkinliklerinin, yalnızca onların tarihe yönelik ilgilerini çekmekle kalmayıp, tarihsel zaman ve kronoloji düşünceleri üzerinde akademik anlamda olumlu katkı sağladığı görülmüştür. Bu araştırma sonucunda çocuklarda tarihsel zaman kavramının uygun yöntem ve yaklaşımlarla çok erken yaşlardan itibaren öğretilebileceğini savunan konu merkezli düşünen araştırmacıların iddialarında olduğu gibi tarihsel zaman araçlarının etkili bir strateji ile kullanılmasının konunun çocuk tarafından kavranmasında çok etkili olduğunun görüldüğü söylenebilir. This study is an action research based on both quantitative and qualitative research techniques and this research was done with 5/B students of Süleyman Türkmani Elementary Education School which is at the city center of Kırşehir in 2003-2004 Education year. In this study related to the improvement of Primary School 5th grade students' historical time concept and chronology perceptions, students interest in, reaction to many education methods and materials (time tables, photographs related to past, old household tools, collections etc.) that are used, and the contributions of education methods and materials to the children's academic successes related to the subject have been studied. In the study, both attitude and success tests in the frame of pre-test & post-test design and the records of lesson processing period by the help of a tape recorder and the learning products gained during the lesson have been gathered. Evaluating the data has been carried out by statistically charting of pre-test & post-test attitude and success scales, and student evaluation form related to lesson process, interpreting with analyzing the lesson process's recorded voice, student learning products and lesson evaluation compositions that students have stated their opinions. In interpreting the quantitative data, t test through SPSS programme, ANOVA test, percentage distributions and correlation methods have been used, qualitative data on the other hand have been explained by evaluating voice records' analysis and in the frame of content analyze techniques carried out to the student products. According to the research findings; children's preparing historical timelines by the help of individual timelines, and that old photographs expressing their family's past and the activities of examining old household tools not only have attracted the interest of children towards history but also have provided positive contribution in academic aspect on their historical time and chronology perceptions have been observed. At the end of this research, it has been observed that as it has been in the claims of researchers thinking subject based who defend that historical time concept can be taught to children from the very early ages with the suitable methods and approaches, using historical time tools with an effective strategy is very effective in understanding the subject by child. Key Words historical time, chronological perception, historical timeline, historical building, artifact.

Bu çalışma, öğrencilerin Sosyal Bilgiler ders içeriğinde nelerin bulunmasını, nelerin bulunmamasını istediklerine ilişkin yapılan bir araştırma üzerine kurulmuştur. Bununla, Sosyal Bilgiler ders içeriklerinin öğrencilerin ilgilerine ne derece cevap verebildiğini bulgulamak amaçlanmıştır. Kırşehir merkezinde bulunan Prof. Dr. Erol Güngör İ. Ö. O. ve Süleyman Türkmani İ. Ö. O.unda okuyan 4-7. sınıf öğrencilerinden rastgele birer şube öğrencinin örneklemini oluşturduğu bu araştırmada, açık uçlu sorulardan oluşan bir ölçme aracı ile veriler toplanmış ve içerik analizi tekniği ile çözümlenmiştir. Bulgular yüzdelik oranlarla ele alınarak değerlendirildiği için araştırmada, durum betimlemeyi amaçlayan nicel bir yöntem kullanılmıştır. 4-7. sınıf öğrencilerine Sosyal Bilgilerin içeriğine ilişkin sorulan; nelerin olmasını, nelerin olmamasını istedikleri ile neleri kolay, neleri zor buldukları sorularına farklı cevaplar alınmıştır. Yeni programın uygulandığı 4. ve 5. sınıflarda daha çok ünite adları olarak karşımıza çıkan bulgular, 6. ve 7. sınıflarda konu düzeyine inmiştir. Yine 4. ve 5. sınıflarda ilgili sorulara kitap dışından da cevaplar verilirken, 6. ve 7. sınıfların verdikleri cevapların tamamen kitap merkezli olduğu görülmüştür. 6. sınıflarda en çok istenmeyen konu olan Moğollar ve İlk Müslüman Türk devletleri ile 7. sınıflarda Osmanlı duraklama ve gerileme dönemlerini ele alan 17.,18.,19. ve 20. yy.daki gelişmeler konularının yeni programda farklı bir içerik ve formatta verilmesini yeni programın öğrenci isteklerine cevap verme noktasında olumlu değerlendirmek mümkündür. In this study, its been researched to "What are the children want in social studies".

Bu çalışmada, ilköğretimde tarih öğretiminin eğitimsel açıdan varolan problemlerine ve bu öğretimin nasıl olması gerektiğine, ilgili literatürden hareketle bir giriş yapılmıştır. Özellikle tarih konularının sosyal bilgiler dersi kapsamında ilköğretim 4. sınıftan itibaren kronolojik olarak öğretilmesinin sıkıntılarına değinilmiştir. Bu bağlamda, 1998 ve 2004 İlköğretim sosyal bilgiler öğretim programları ele alınmış ve karşılaştırılmıştır. Buna göre, 1998 Sosyal Bilgiler Öğretim Programında kronolojik tarih öğretiminin ilköğretim 4. sınıftan itibaren başlaması eleştirilmiştir. Ayrıca programdaki tarih konularının kronolojik açıdan tutarsızlıkları dile getirilmiştir. 2004 İlköğretim Sosyal Bilgiler Öğretim Programının beceri temelli olarak yapılandırmacı yaklaşıma göre oluşturulması ele alınmış, bu bağlamda tarih öğretiminin nasıl farklılaştığı belirtilmiştir. 2004 programı tarihi, çocuğun kendisi, ailesi, yakın çevresi, ilgileri doğrultusunda, kronolojik öğretimin dışında ele almıştır. Bu durum, çocukların tarihsel düşünce ve zaman algılarının gelişimi açısından oldukça olumlu bulunmuştur. In this study, the main purpose is to point out pedagogical problems of history education and to discuss how history should be taugth from the perspective of related literature. Especially, the difficulties in chronological history teaching which begins from 4th grade in Social Studies has been discussed. In this context, Social Studies curriculum of 1998 and 2004 have been compared. Chronological history teaching inbeginning of 4th grade in Social Studies curriculum has been criticized. Separately, the inconsistensy of historical subjects have been mentioned in chronological perspective. On the other hand, 2004 Social Studies curriculum which has been changed according to constructivist approch, has been examined to find out the innovations in the history teaching. This new curriculum seems to consider child, her/his family environment and interests arart from the chronological history teaching. This situation, have been founded very positive for children's historical thiking and developing sense of historical time perspective.

Bu çalışmada, Atatürk'ün Türk milletine bıraktığı mirastan ne anlaşılması gerektiği, bu mirasın korunması ve geliştirilmesinde örgün eğitimin rolünün ne olduğu / olması gerektiği ele alınmaya çalışılmıştır. Osmanlı'dan Türkiye Cumhuriyeti'ne ve günümüze kadar geçen süreçte, genelde eğitimden, özeldeyse öğretmenden beklenilen rollere kısaca değinilmiştir. Atatürk'ün Türk milletine bıraktığı mirasın aktarılmasında öğretim kademelerindeki yaşanan problemleraksaklıklar dikkate alınarak, öğretmenlerin bu konudaki rollerinin geçmişte ve bugün ne durumda olduğu tartışılmıştır. In this study, it was brought up what to understand in the inheritance of Atatürk which he left to Turkish people, what the formal education is role in protecting and improving this inheritance was. It was briefly touched on the roles expected in general on education and in special on teacher in the period from Ottoman to Turkish Republic and to present. Considering the problems which take place/occurs in teaching grades, in transferring the inheritance that Atatürk, it was discussed what the roles of the teachers were in the past and what they today.

Bu araştırmada, ilköğretim Sosyal Bilgiler dersini yürüten öğretmenlerin tarihsel hikâyeye yönelik tutumları, çeşitli değişkenlere göre değerlendirilmiştir. Bu amaçla; 2002-2003 öğretim yılında, Kırşehir ili merkez ilköğretim okullarında Sosyal Bilgiler dersini yürüten 35 öğretmene tutum ölçeği uygulanmıştır. Öğretmenlerin tarihsel hikâyeye yönelik düşünceleri; cinsiyet, kıdem (meslekte hizmet yılı), asıl branş, süreli yayın takip etme ve kitap okuma değişkenlerine göre ele alınmıştır. Elde edilen bulguların çözümlenmesinde t testi ve anova testleri kullanılmıştır. Araştırma sonunda, Sosyal Bilgiler dersini yürüten öğretmenlerin tarihsel hikâyeye yönelik tutumlarının yüksek derecede olumlu olduğu bulgulanmıştır. In this study, the attitutes to historical story of Social Study teachers of elemantary school have been evaluated with different variables. For this purpose; attitute criterion has been applied to 35 Social Study teachers of elemantary schools in Kırşehir in 2002-2003 scholl year. This teachers' opinions to historical story; have been evaluated in gender, seniority, orginal branch, periodical reading and books reading variables. For the analyzes of datas, t test and anova test has been used in. Finally in this study, it is founded that Social Study teacher's attitutes to historical story are highly positive.

Bu çalışmada, tarih öğretiminde iki boyutlu görsel materyalin kullanımı konusu ele alınmıştır. Öğretim materyallerinin öğretim sürecine katkılarından bahsedilmiş, tarih öğretiminde daha önceden yapılmış genel bir materyal sınıflamasına değinilmiştir. Çalışmanın asıl kısmını; tarih öğretiminde iki boyutlu görsel materyal ve özelde resim-fotoğraf ikilisiyle, haritanın kullanımı üzerine zihinsel kritikler, önerilen düşünce, teknik ve modeller oluşturmuştur. In this study, using two dimension visual materials in teaching history is considered. The addition of teaching materials on teaching process is discussed and clasification of materials which are used in teaching history is mentioned. The origin of the study is formed on suggested opinion, technicals and models about mentional critics on using two dimension visual materials especially picture-photo dualty, maps in teaching history.

Bu çalışmada, İnkılâp Tarihi derslerinin gerekçeleri ortaya konularak, ilk verildiği günden bugüne kadar dersin içeriğinde meydana gelen değişikliklerin devrin siyasî iktidarının kültürel ve sosyal yaklaşımları ile ilgisi kısaca ele alınmaya çalışılmıştır. Okuyucu böylelikle İnkılâp Tarihi derslerinin temel felsefî anlayışı üzerine sahip olduğu düşünceleri ve değer yargılarını tekrar gözden geçirebilecektir. In this study the relationship between social and cultural approach throught the changes in the content of realities about the origin of revolution history. So the reader will have an oportunity to review his or her own ideas and beliefs which are about the history.

Objective: The Algan Hemostatic Agent (AHA) is a novel herbal originated blood stopper. The aim of this study is to investigate the effect of AHA on wound healing on excisional wound model in rats. Methods: In this study, 54 adult Wistar albino rats were used. Rats were divided into 3 groups (saline, Madecassol and AHA). Each group was then divided into 3 subgroups as 3rd, 7th and 14th days. Two wounds were created in the dorsal thoracic region of the rats. One of the lesions was used for histopathological examinations and the other for hydroxyproline measurement. In order to evaluate the wound healing, wound area were measured during the whole treatment period and animals were sacrificed at the end of 3rd, 7th and 14th days and tissue samples were taken for the determination of hydroxyproline levels. Results: AHA treatment did not cause significantly difference in hydroxyproline level on days 3, 7, 14. The contraction percentage of wound area was higher in the AHA group on day 7 than control group. However, the difference was not statistically significant (p> 0.05). On days 3 and 14, no significant difference was detected in the contraction percentage of wound area between the control and AHA groups. AHA and Madecassol results of epidermis regeneration on the 14th day, neutrophil infiltration on the 7th day and edema on the 3rd, 7th and 14th days were different in terms of histopathological parameters compared to the control group. Conclusion: Despite good histological findings, AHA did not significantly accelerate wound healing. but did not adversely affect on wound healing. AHA may be used safely on excisional wounds.

Bacterial pathogenicity relies on both firm surface adhesion and cell dissemination. How twitching bacteria resolve the fundamental contradiction between adhesion and migration is unknown. To address this question, we employ live-cell imaging of type-IV pili (T4P) and therewith construct a comprehensive mathematical model of Pseudomonas aeruginosa migration. The data show that only 10% to 50% of T4P bind to substrates and contribute to migration through random extension and retraction. Individual T4P do not display a measurable sensory response to surfaces, but their number increases on cellular surface contact. Attachment to surfaces is mediated, besides T4P, by passive adhesive forces acting on the cell body. Passive adhesions slow down cell migration and result in local random motion on short time scales, which is followed by directionally persistent, superdiffusive motion on longer time scales. Moreover, passive adhesions strongly enhance surface attachment under shear flow. Δ pilA mutants, which produce no T4P, robustly stick to surfaces under shear flow. In contrast, rapidly migrating Δ pilH cells, which produce an excessive number of T4P, are easily detached by shear. Wild-type cells sacrifice migration speed for robust surface attachment by maintaining a low number of active pili. The different cell strains pertain to disjunct regimes in a generic adhesion-migration trait space. Depending on the nature of the adhesion structures, adhesion and migration are either compatible or a trade-off is required for efficient bacterial surface colonization under different conditions.

Fluid flow is thought to prevent bacterial adhesion, but some bacteria use adhesins with catch bond properties to enhance adhesion under high shear forces. However, many studies on bacterial adhesion either neglect the influence of shear force or use shear forces that are not typically found in natural systems. In this study, we use microfluidics and single-cell imaging to examine how the human pathogen Pseudomonas aeruginosa interacts with surfaces when exposed to shear forces typically found in the human body (0.1 pN to 10 pN). Through cell tracking, we demonstrate that the angle between the cell and the surface predicts if a cell will depart the surface. We discover that at lower shear forces, type IV pilus retraction tilts cells away from the surface, promoting surface departure. Conversely, we show that higher shear forces counterintuitively enhance adhesion by counteracting type IV pilus retraction-dependent cell tilting. Thus, our results reveal that P. aeruginosa exhibits behavior reminiscent of a catch bond, without having a specific adhesin that is enhanced by force. Instead, P. aeruginosa couples type IV pilus dynamics and cell geometry to tune adhesion to its mechanical environment, which likely provides a benefit in dynamic host environments.