Model karmaşıklığının kontrolü

Model karmaşıklığı, modellerin başarısındaki en önemli ölçütlerden birisidir. Bu çalışmada bugüne dek model karmaşıklığının kontrolünde öne çıkan yaklaşımlar başlıklar halinde incelenmiştir. Bunlar Occam’ın usturası, Popper’ın yanlışlanabilirliği ve istatiksel öğrenme teorisidir. Occam’ın usturası ve Popper’ın yanlışlanabilirliği model karmaşıklığının kontrolünde, evet bir felsefi yaklaşım sağlamaktadırlar ve kabul de görmektedirler. Fakat model karmaşıklığının nasıl kontrol edileceği konusunda matematiksel bir formülasyon sağlamamaktadırlar. Fakat istatiksel öğrenme teorisi (diğer adıyla, VC teorisi) konuya yaklaşımı yalnızca felsefi bir düzeyde kalmamakta, aynı zamanda şimdiye dek geliştirilen modellerde kullanılan ampirik risk minimizasyonu (ARM) ilkesine VC katsayısını ilave ederek yeni bir risk minimizasyonu (yapısal risk minimizasyonu, YRM) ilkesi getirmektedir. Sonuç olarak Vapnik ve Chervonenkis tarafından geliştirilen VC teorisi bir kontrol modeli olarak, ispatlanmış matematiksel arka planı ve oldukça başarılı olan sonuçları itibariyle, model karmaşıklığının kontrolü konusunda, günümüz çerçevesinde, en tutarlı ve güvenilir bir yaklaşım olarak, model geliştiriciler için iyi bir ilham kaynağı olabilir

Tek Kademeli Bir Derin Kuyu Pompasının Karakteristiklerinin Belirlenmesi

A Major portion of electrical energy consumption is used by pumps and fans in buildings and in industrial applications in our world today. About 20% of the global electrical energy consumption is used by pumping systems and this rat

DEVELOPMENT OF CONSTITUTIVE EQUATIONS BASED ON CONTINUUM DAMAGE MECHANICS FOR MAGNETOELASTIC MATERIALS

Continuum Damage Mechanics deals with engineering materials which undergo structural weakening as a result of micro-crack formation or void growth. The general expressions of constitutive equations for isotropic magnetoelastic damaged materials were derived from the basic laws of continuum damage mechanics. This mathematical model represents a magnetoelastic media which has micro-voids and subjected to a mechanical loading. Due to micro-void distribution, overall structure attains a strong anisotropy, despite the fact that the material is otherwise isotropic. In this context the body will respond by means of stress, magnetization and strain-energy density release rate. In the conclusion, constitutive response functions for the stress, magnetization and strain-energy density release rate have been obtained in material coordinates

Does metoclopramide exposure alter endometrial receptivity and decrease pregnancy rates?

WOS: 000375027200028PubMed ID: 26421644Objective: The aim of this study was to investigate the effect of metoclopramide on endometrial receptivity with an immunohistochemical investigation of integrin beta 3 expression in pregnant rats. Materials and methods: In the present study, the pregnant mice administrated by different doses of metoclopramide were used to explore the effect of metoclopramide on embryo implantation, especially on the endometrial receptivity. Results: The statistical results showed that the number of implanted embryos was gradually declining along the increasing dose of metoclopramide. When the administrated dose of metoclopramide was 3 mg/kg per day, great changes were observed in the exposed uterine morphology and down-regulated integrin beta 3 were also found in high dose metoclopramide-exposed mice. Conclusion: Metoclopramide exposure, especially in high doses may alter endometrial receptivity by effecting integrin expression on decidual tissue which can decrease pregnancy rates. This drug should only be recommended for use during pregnancy when benefit outweighs the risk

Abortifacient effect of decreased decidual and placental galectin-1 expression due to metoclopramide exposure in pregnant rats

OBJECTIVE: To investigate the abortifacient effect of metoclopramide on decidual and trophoblastic tissues with immunohistochemical investigation of galectin-1 expression in pregnant rats. STUDY DESIGN: A total of 24 pregnant rats were selected for the study and divided into 3 groups as untreated, low-dose (1 mg/kg) metoclopramide applied, and high-dose (3 mg/kg) metoclopramide applied from days 5-15 of pregnancy. All rats were laparotomized on day 19 of pregnancy, and number of implantation sites, resorption, and dead or alive fetuses were recorded for evaluating abortifacient activity. Galectin-1 expression was investigated from decidual and trophoblastic tissues via immunohistochemical staining. RESULTS: The mean percentage of abortion was detected higher in the high-dose group than both control and low-dose groups. Galectin-1 staining was more intense and universal in the untreated group than both high- and low-dose metoclopramide exposed groups in labyrinth trophoblasts and decidual tissue. CONCLUSION: Metoclopramide exposure, especially in high doses, may cause abortion, and this drug should be recommended for use during pregnancy only when the benefit outweighs the risk

Presacral cyst: Case report

Bu makalede presakral bölgede nadir olarak görülen basit kist olgusu sunulmuştur. Altı ay önce başlayan karın ağrısı ve şişlik şikâyetiyle başvuran 30 yaşındaki erkek hastada presakral bölgede lokalize 11X17 cm ebatlarında kistik kitle saptandı. Kistik kitle abdominal insizyonla çıkartıldı. Kistik kitlenin histopatolojik incelemesinde basit kist tanısı konuldu.A rare case of simple cyst at presacral region is presented in this article. An 11X17 cm cystic mass localized at presacral area was established in a 30 year old male patient complaining of abdominal pain and swelling. Cystic mass was removed by abdominal incision. Histopathologic examination of the cyst mass was diagnosed as simple cyst

Thrombotic, fibrinolytic and proliferative activities of pulmonary vascular bed in secondary pulmonary hypertension

Amaç: Bu çalışma, sekonder pulmoner hipertansiyonda (SPH) sıklıkla izlenen in situ tromboz gelişimine ve vasküler yeniden biçimlenmeye pulmoner vasküler yatağın lokal katkısını araştırmak için planlanmıştır. Yöntemler: Kliniğimizde kalp kateterizasyonu yapılan 71 SPH hastası (38 kadın, 33 erkek; yaş ortalaması 40.36 1.05 yıl) çalışmaya dahil edilmiştir. Her hastanın pulmoner arter (PA) ve sol ventrikülünden (LV) alınan kan örneklerinde plazminojen aktivator inhibitör-1 (PAI-1), trombosit kökenli büyüme faktörü (PDGF), damar endoteli büyüme faktörü (VEGF), D-Dimer, von-Willebrand faktörü (vWF), protein-C, antitrombin-III, fibrinojen ve plazminojen düzeyleri bakılarak karşılaştırılmıştır. Ayrıca her parametrenin ortalama PA basıncı (MPAP) ile korelasyonu araştırılmıştır. Bulgular: Ortalama VEGF düzeyi LV’de PA’e göre daha yüksektir (p0.001); ancak, her iki değer de normal sınırlardadır. Ortalama PDGF ve D-dimer düzeyi LV'de PA'den daha yüksektir (p0.001 ve p0.001) ve her iki değer normalin üstündedir. Ortalama vWF düzeyi LV ve PA arasında benzerdir, ancak her iki değer normalin hafif üstündedir. Ortalama PAI-1 düzeyi PA'de LV 'e göre daha yüksektir (p0.012); ancak, her iki değer de normal sınırlardadır. Antitrombin-III, protein-C, plazminojen ve fibrinojen düzeyleri açısından PA ve LV arasında fark yoktur ve fibrinojen hariç diğer parametrelerin ortalama değerleri normal sınırlardadır. Fibrinojen düzeyi her iki boşlukta da hafif yüksektir. Gerek PA, gerekse LV'deki D-dimer düzeyi ile MPAP arasında anlamlı pozitif korelasyon mevcuttur. Sonuç: Sekonder pulmoner hipertansiyonda pulmoner dolaşımda lokal olarak artmış protrombotik, hipofibrinolitik ve proliferatif aktiviteler mevcuttur ve bu durum pulmoner hipertansiyonun şiddeti ile ilişkilidir.Objective: To determine whether pulmonary vascular bed contributes to the development of in situ thrombosis and vascular remodelling in secondary pulmonary hypertension (SPH) via changes in its local secretory activities. Methods: Seventy-one patients with the diagnosis of secondary pulmonary hypertension (38 females, mean age 40.36± 1.05 years) were included in the study. Selective right and left heart catheterization was performed to each patient for diagnostic purposes. Blood samples obtained from left ventricle (LV) and pulmonary artery (PA) of each patient were analyzed for levels of plasminogen activator inhibitor-1 (PAI-1), platelet derived growth factor (PDGF), vascular endothelial growth factor (VEGF), D-dimer, von Willebrand factor (vWF), protein-C, antithrombin-III, fibrinogen, and plasminogen. Results were compared between LV and PA. Correlation analysis between each parameter and mean pulmonary artery pressure (MPAP) was performed. Results: Although mean level of VEGF in LV and PA were found to be in normal range, it was significantly higher in LV than in PA (p<0.001). Mean PDGF and D-dimer levels, which remained in normal range were also higher in LV (p<0.001 and p<0.001, respectively) than in PA;.vWF showed similar degree of elevation in both LV and PA. Only one parameter, PAI-1, was found to be significantly higher in PA than in LV (p0.012). Antithrombin-III, protein C, plasminogen, and fibrinogen levels showed no significant differences between two chambers. They also remained in normal range, except for fibrinogen which was slightly elevated in both LV and PA. Correlation analysis revealed strong positive correlation between D-dimer level in both LV and PA and MPAP (r0.775, p<0.001 and r0.649, p<0.001, respectively). Conclusion: In SPH, pulmonary vascular bed shows increased thrombotic, hypofibrinolytic, and proliferative activities which are partially related to the severity of illness

Presacral cyst: Case report

Bu makalede presakral bölgede nadir olarak görülen basit kist olgusu sunulmuştur. Altı ay önce başlayan karın ağrısı ve şişlik şikâyetiyle başvuran 30 yaşındaki erkek hastada presakral bölgede lokalize 11X17 cm ebatlarında kistik kitle saptandı. Kistik kitle abdominal insizyonla çıkartıldı. Kistik kitlenin histopatolojik incelemesinde basit kist tanısı konuldu.A rare case of simple cyst at presacral region is presented in this article. An 11X17 cm cystic mass localized at presacral area was established in a 30 year old male patient complaining of abdominal pain and swelling. Cystic mass was removed by abdominal incision. Histopathologic examination of the cyst mass was diagnosed as simple cyst