Strain-gradient-induced magnetic anisotropy in straight-stripe mixed-phase bismuth ferrites: An insight into flexomagnetic phenomenon

Implementation of antiferromagnetic compounds as active elements in spintronics has been hindered by their insensitive nature against external perturbations which causes difficulties in switching among different antiferromagnetic spin configurations. Electrically-controllable strain gradient can become a key parameter to tune the antiferromagnetic states of multiferroic materials. We have discovered a correlation between an electrically-written straight-stripe mixed-phase boundary and an in-plane antiferromagnetic spin axis in highly-elongated La-5%-doped BiFeO$_{3}$ thin films by performing polarization-dependent photoemission electron microscopy in conjunction with cluster model calculations. Model Hamiltonian calculation for the single-ion anisotropy including the spin-orbit interaction has been performed to figure out the physical origin of the link between the strain gradient present in the mixed phase area and its antiferromagnetic spin axis. Our findings enable estimation of the strain-gradient-induced magnetic anisotropy energy per Fe ion at around 5$\times$10$^{-12}$ eV m, and provide a new pathway towards an electric-field-induced 90$^{\circ}$ rotation of antiferromagnetic spin axis at room temperature by flexomagnetism.Comment: 32 pages, 5 figure

Kıyı bölgeleri su basma alanlarının coğrafi bilgi sistemleri ( CBS ) ve uzaktan algılama ( UA ) teknikleriyle belirlenmesi

TÜBİTAK İNTAG Proje01.11.1999Hem sel hem deniz kabarması etkilerine açık olan bir kıyı bölgesinin su basma alanları saptanmıştır. Bu yapılırken alışılagelmiş tekniklerin yanı sıra coğrafi bilgi sistemleri (CBS) kullanılmıştır. Seçilen çalışma bölgesi olan Fethiye Çayboğazı havzası için çeşitli tekerrür sürelerine ait taşkın su basma haritaları elde edilmiştir. Çalışma birbirini tamamlar şekilde iki ayrı etkinlik sürecinden oluşmaktadır. Bunlardan birincisi, söz konusu akarsuyun değişik tekerrür sürelerine sahip taşkınlar sırasında oluşacak taşkın alanlarını konu edinmektedir. Diğeri, fırtına anında kıyı bölgesinde oluşacak deniz kaynaklı kabarmanın kıyı bölgesinde su altında bıraktığı alanı incelemektedir. Çalışmalar sonunda deniz kaynaklı kabarmanın 1 m civarında kaldığı ve iç bölgelere etkisinin olmadığı görülmüştür. Dolayısıyla, bölge için hidrolojik havzanın ürettiği taşkının kritik olduğu anlaşılmıştır. Taşkınlardan etkilenen, binalar, tarım alanları ve altyapı örneksel olarak saptanmıştır. Elde edilen sonuçlar söz konusu bölgenin taşkınlara karşı korunması ile ilgili kararların verilmesinde kullanılabilecektir

Investigation of the spontaneous emission rate of perylene dye molecules encapsulated into three-dimensional nanofibers via FLIM method

The decay dynamics of perylene dye molecules encapsulated in polymer nanofibers produced by electrospinning of polymethyl methacrylate are investigated using a confocal fluorescence lifetime imaging microscopy technique. Time-resolved experiments show that the fluorescence lifetime of perylene dye molecules is enhanced when the dye molecules are encapsulated in a threedimensional photonic environment. It is hard to produce a sustainable host with exactly the same dimensions all the time during fabrication to accommodate dye molecules for enhancement of spontaneous emission rate. The electrospinning method allows us to have a control over fiber diameter. It is observed that the wavelength of monomer excitation of perylene dye molecules is too short to cause enhancement within nanofiber photonic environment of 330 nm diameters. However, when these nanofibers are doped with more concentrated perylene, in addition to monomer excitation, an excimer excitation is generated. This causes observation of the Purcell effect in the threedimensional nanocylindrical photonic fiber geometry

Caprylic acid ameliorates rotenone induced inflammation and oxidative stress in the gut-brain axis in Zebrafish

Background Dysfunction of the gastrointestinal tract (GIT) is one of the most common non-motor symptom of Parkinson's Disease (PD). Pathological processes causing PD were suggested to initiate in the enteric nervous system (ENS) and proceed to the central nervous system (CNS). There are studies showing that low-carbohydrate ketogenic diets can improve motor symptoms of PD. Caprylic acid (C8) is the principal fatty acid component of the medium-chain triglycerides in the ketogenic diets. In this study, we aimed to evaluate the effects of caprylic acid, in neurotoxin exposed zebrafish focusing on the relationship between intestinal and brain oxidative stress and inflammation. Methods Adult zebrafish were exposed to rotenone (5 mu g/L) (R group) and caprylic acid (20 and 60 mg/mL) (L + HDCA and R + HDCA groups) for 30 days. At the end of 30 days locomotor activities were determined. Levels of lipid peroxidation (LPO), nitric oxide, glutathione and superoxide dismutase and glutathione S-transferase activities were determined by spectrophotometric methods and gene expressions of tnf alpha, il1, il6, il21, ifn gamma and bdnf were evaluated by RT-PCR in the brain and intestinal tissues of zebrafish. Results Caprylic acid ameliorated LPO, NO, SOD and the expressions of tnf alpha, il1, il6, il21, ifn gamma and bdnf in brain and intestines. Locomotor activities were only ameliorated in high dose R + HDCA group. Conclusions Caprylic acid ameliorated the neurotoxin-induced oxidative stress and inflammation both in the brain and intestines and enhanced locomotor activity in zebrafish