Recent advances in additive manufacturing made it feasible to fabricate products with desired shapes and features. Herein, a new, photocurable 3D printer ink mainly based on pentaerythritol triacrylate (PETA) is reported. To achieve rapid curing needed for 3D printing process, high performance water‐soluble photoinitiator, lithium phenyl‐2,4,6‐trimethylbenzoylphosphinate (LAP), was emulsified in PETA monomers and this suspension was evaluated for its polymerization kinetics by exposing to 395 nm UV‐light. The distinct influences of LAP and triethanolamine (TEA) concentrations on photo‐polymerization and printability were examined and an optimum concentration for extrusion‐based 3D printing was found to be 10 mM and 1.62 M for LAP and TEA, respectively. Synthesized PETA‐based 3D printer ink was functionalized by dispersing magnetic particles/flakes into the mixture, and consequently, a magneto responsive ink was obtained to be used in specialized applications. A ring‐shaped structure embedded with micron sized iron flakes was printed as a prototype. This study presents a versatile photo‐curable polymer formulation with possible translation to high performance 3D printing of customizable shapes that can be utilized in a wide range of areas such as micro‐robotics and medical science.
The main objective of this study was to determine the removal mechanism of tetracycline (TC) and oxytetracycline (OTC) by microscale zerovalent iron (mZVI) and the formation of transformation products during their removal studies. Solution pH, iron dose, and reaction temperature were studied with a batch experimental series in order to evaluate the removal efficiency of TC and OTC and the adsorption kinetics. The results showed that pH was a key factor in removing both tetracycline compounds, although increasing the temperature and iron dose enhanced their removal efficiency. The optimal pH was similarly found as 3 for both tetracycline and oxytetracycline. The kinetics of adsorption fitted the pseudo-second-order model perfectly. The adsorption data was interpreted by the Langmuir model with the maximum adsorption capacity of 23.98 and 34.01 mg g(-1) (60 °C) of TC and OTC on mZVI, respectively. The main transformation product was 4-epi-tetracycline for TC which quickly sorbed onto mZVI within 15 min. β-Apo-OTC and α-Apo-OTC were found as OTC transformation products. The removal mechanism of TC and OTC using mZVI surface was due to the adsorption rather than the degradation process.
Intravitreally applied silicone oil undergoes no structural change. Wide relaxing retinotomy constitutes a risk factor for silicone oil emulsification, which can occur earlier than expected and before it can be observed clinically.
Son 15 yıla ait İngilizce dersi öğretim programlarının çeşitli ölçütler çerçevesinde incelendiği bu çalışmada, programlardaki gelişmelerin anlaşılması hedeflenmiştir. Çalışmada doküman analizi yöntemi kullanılmış, ulaşılabilen iki ilköğretim (2006 ve 2013) ve dört ortaöğretim (2002, 2011, 2014 ve 2016) İngilizce dersi öğretim programı, alanyazındaki program tasarım ilkeleri (kapsam, aşamalılık, süreklilik, kaynaşıklık, denge, kullanışlılık ve esneklik) çerçevesinde analiz edilmiştir. Bulgulara göre, ilköğretim ve ortaöğretim İngilizce dersi öğretim programlarında, dil eğitimi alanında dünyadaki gelişmelerin takip edildiği ve yeniliklerin programlara dâhil edilmeye çalışıldığı görülmüştür. İlköğretim programlarının, esneklik ilkesi dışında genel olarak tasarım ilkelerine uygun olduğu ancak önerilen sürelerin yetersiz kaldığı sonucuna varılmıştır. Ortaöğretim programlarının analizinden elde edilen bulgular ise, programlarda iletişimsel yaklaşımın benimsendiğini ancak araştırmalara göre bu yaklaşımın öğretmenler tarafından tam olarak anlaşılmadığını, dolayısıyla da uygulanamadığını göstermiştir. Bununla birlikte, tasarım ilkelerinden aşamalılık ve sürekliliğe özen gösterildiği ancak kapsam, denge, kullanışlılık ve esnekliğin göz ardı edildiği belirlenmiştir. Özellikle 2011 ortaöğretim programında hedefler ve içeriğin belirlenmesinde öğrencilerin ilgileri, ihtiyaçları ve hazırbulunuşluk düzeylerinin dikkate alınmaması, programın çok uzun ve karmaşık olması, önerilen sürenin yetersiz olması; denge, kullanışlılık ve esneklik ilkelerinin ihmal edildiğini düşündürmektedir. Bulgular ışığında kuram ve uygulamaya dönük öneriler sunulmuştur.
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