Photonic crystal based sensing using band edge modulation

A photonic crystal based structure is proposed for sensing exceptionally small refractive index changes of a background medium. In a typical photonic crystal, we show that the band edges and the defect band(s) (if present) are very sensitive to the dielectric contrast. Hence, a propagating electromagnetic wave at a particular frequency gains significant phase shift due to the index changes. When the phase shift is measured interferometrically, it is possible to infer refractive index changes as small as 10⁻¹¹ per lattice distance. We have mainly concentrated on the band edge shifts of the two lowest bands of a square lattice of dielectric rods. Calculations reveal that an optimized design of 100x100 rods could be utilized to sense an index modulation of ten to the power minus thirteen per square roots Hertz with a modulation bandwidth of 1 Hz, which is approximately 10⁵ times better than the resolution of novel waveguide based sensor configurations. We also report that defect modes in photonic crystals are even better candidates to be adapted for sensing applications. A further resolution enhancement on the order of 10 could be achived due to the high sensitivity of the defect bands. We have performed proof of principle experiments in the microwave regime with a photonic crystal wave of 7x7 alumina rods placed in a gas chamber, whose inner pressure can be adjusted with a nitrogen tank. Obtaining the index modulations by changing the inner pressure, we witnessed that the experimental results are in very good argeement with the theory at the band adges

Glyphosate inhibition of ferric reductase activity in iron deficient sunflower roots

Iron (Fe) deficiency is increasingly being observed in cropping systems with frequent glyphosate applications. A likely reason for this is that glyphosate interferes with root uptake of Fe by inhibiting ferric reductase in roots required for Fe acquisition by dicot and nongrass species. This study investigated the role of drift rates of glyphosate (0.32, 0.95 or 1.89 mM glyphosate corresponding to 1, 3 and 6% of the recommended herbicidal dose, respectively) on ferric reductase activity of sunflower (Helianthus annuus) roots grown under Fe deficiency conditions. Application of 1.89 mM glyphosate resulted in almost 50% inhibition of ferric reductase within 6 h and complete inhibition 24 h after the treatment. Even at lower rates of glyphosate (e.g. 0.32 mM and 0.95 mM), ferric reductase was inhibited. Soluble sugar concentration and the NAD(P)H oxidizing capacity of apical roots were not decreased by the glyphosate applications. To our knowledge, this is the first study reporting the effects of glyphosate on ferric reductase activity. The nature of the inhibitory effect of glyphosate on ferric reductase could not be identified. Impaired ferric reductase could be a major reason for the increasingly observed Fe deficiency in cropping systems associated with widespread glyphosate usage

Applications of electromagnetic phenomena in periodic structures

Ankara : The Department of Electrical and Electronics Engineering and the Graduate School of Engineering and Science of Bilkent Univetrsity, 2012.Thesis (Ph. D.) -- Bilkent University, 2012.Includes bibliographical references.Çakmak, Atilla ÖzgürPh.D

Introducing freshmen students to the practice of solid-phase synthesis

A one-semester laboratory project on solid-phase peptide chemistry was designed pedagogically to cater to freshman science students. The approach not only permitted multistep syntheses that would be considered impractical in solution, but also gave students insight into fundamental aspects of research at an early stage of development. Young scientists prepared Bz-Asn-Asn-Phe and Bz-Asn-Gln-Phe--peptides envisaged as potential competitive inhibitors of chymotrypsin. The synthesis, defined by an attachment-deprotection cycle, two elongation-deprotection cycles, and a benzoyl-capping protocol, was completed manually on Wang resin using Fmoc chemistry. Students quantified the yield of each condensation and deprotection reaction by measuring levels of dibenzylfulvene chromophore, a stoichiometrically afforded by-product. Benzoylation of the N-terminus was confirmed by employing a cadmium-ninhydrin reagent. The group also ascertained, through use of a chromogenic substrate, that chymotrypsin-catalyzed hydrolysis was impeded slightly when carried out in the presence of target peptides. Supplementary analyses supporting peptide purity and composition were given to students. Grading was based on laboratory participation, project proposals, reports, and a concluding slide-show presentation made to peers and colleagues. While the project was time-consuming overall, students acquired an impression of research work and an appreciation of the utility of solid-phase methods

Comparison of winter wheat genotypes differing in zinc efficiency and origin: the zinc uptake and enzyme activity

Zinc (Zn)-efficient wheat genotypes yield well on Zn-deficient soil. In this study, two Chinese wheat genotypes, Kenong9204 and Han6172, and two reference genotypes, Bezostaja (Zn efficient) and BDME10 (Zn inefficient), from Turkey were conducted to measure their physiological responses to Zn deficiency in the greenhouse. Results showed obvious genetic variation among the genotypes with Zn efficiency from 76% to 105%. Bezostaja and Kenong9204 had greater shoot dry weight and accumulated more shoot Zn content than BDME10 and Han6172 without Zn application. In one aspect of enzyme activities, Bezostaja and Kenong9204 presented significantly greater activities of superoxide dismutase while maintaining similar activities of catalase, ascorbate peroxidase, and glutathione reductase compared with inefficient genotypes BDME10 and Han6172 under Zn-deficient condition. Zinc-efficient genotypes are recommended to satisfy the sustainable grain yield in China and other areas, where Zn deficiency in soil is spread and multiple stresses may happen at times

Genel cerrahi uzmanlık eğitimine farklı bir bakış

Aim: We planned a trial to establish the realities on the suggestion which included the idea that there is loss of interest to General Surgery residency or it is not among the top choices. Material and Method: We performed a questionairre on 202 residents who studied general surgery residency in 9 state universities in Ankara, Istanbul, Izmir and Bursa. The residents were asked about which medical school they have graduated from, how many times they joined residency examination, in which examination they succeede to start residency and the order of their choice of general surgery residency was in their list. Results: Among those 202 residents, only 40 of them preferred general surgery residency as the first choice in their list (19.8 %). Most of residents who were successful in the first examination period preferred Ankara University General Surgery Department (44.4%). The residents who preferred general surgery residency as the first choice were found mostly in Hacettepe University General Surgery Department (37.5 %). Most residents who preferred general surgery residency in their first 3 choice in their list were found in Uludag University General Surgery Department (64.3 %). Examination for medical doctor residency April 2009 results have shown that general surgery residency was chosen in the 24th level among 25 branches. Conclusion: As a result general surgery residency was found to be placed at the end of the choices in residency examination among other branches in our trial.Amaç: Son yıllarda Genel Cerrahi Uzmanlık Eğitimi'ne ilginin azaldığı veya ilk sıralarda tercih edilmediği şeklinde ortaya çıkan bir görüşün gerçek boyutunu saptamak amacıyla bir çalışma planladık. Yöntem: Ankara, İstanbul, İzmir ve Bursa'daki 9 Devlet Üniversitesi Tıp Fakültesi Genel Cerrahi Anabilim Dalları'nda uzmanlık eğitimi yapan 202 asistana bir anket uyguladık. Bu anketimizde halen eğitim gören asistanların hangi Tıp Fakültesi'nden mezun oldukları, Tıpta Uzmanlık Sınavına kaç kez girdikleri, hangi sınavda başarılı oldukları, Genel Cerrahi uzmanlık alanını hangi sırada tercih ettikleri ve kazandıkları soruldu. Bulgular: Genel Cerrahi uzmanlık alanını 1. sırada, 202 asistanın ancak 40'ı (%19,8) tercih etmiştir. İlk girdikleri Tıpta Uzmanlık Sınavı'nda başarılı olanlar arasında Ankara Üniversitesi Tıp Fakültesi Genel Cerrahi Anabilim Dalı'nı tercih edenlerin %44,4 ile 1. sırada yer aldığı izlenmiştir. Genel cerrahiyi ilk sırada tercih edenlerin analizi yapıldığında %37,5 ile Hacettepe Üniversitesi Tıp Fakültesi Genel Cerrahi Anabilim Dalı ilk sırada yer almaktadır. Genel cerrahiyi ilk 3 sırada tercih edenlerin sonuçları incelendiğinde Uludağ Üniversitesi Tıp Fakültesi Genel Cerrahi Anabilim Dalı %64,3 ile 1. sırada yer almaktadır. ÖSYM-Tıpta Uzmanlık Sınavı 2009 Nisan Dönemi tüm uzmanlık alanlarının tavan puan sıralamasında 25 uzmanlık alanı içerisinde Genel Cerrahi 24. sırada yer almaktadır. Sonuç: Sonuç olarak uzmanlığa giriş sınavında tercih sırasında Genel Cerrahi'nin son sıralarda yer aldığı bu sonuçlarda da çarpıcı bir şekilde ortaya koyulmaktadı