Local electromagnetic fields surrounding gold nano-cap particles

Using the discrete dipole approximation (DDA) the local electromagnetic fields surrounding gold nano-cap particles are investigated. Suitable k-vectors and polarization vectors of the incident light are used to determine the largest local electric field enhancement. The largest enhancement can be found for the 864 nm dipole resonance; where the field enhancement is approximately 30 000 times the applied field. The electric field contours surrounding the particle are used to assign the order of the surface plasmon resonances. © 2006 IEEE

Chemical analysis of the superatom model for sulfur-stabilized gold nanoparticles

The superatom model for nanoparticle structure is shown to be inadequate for the prediction of the thermodynamic stability of gold nanoparticles. The observed large HOMO-LUMO gaps for stable nanoparticles predicted by this model are, for sulfur-stabilized gold nanoparticles, attributed to covalent interactions of the metal with thiyl adsorbate radicals rather than ionic interactions with thiolate adsorbate ions, as is commonly presumed. In particular, gold adatoms in the stabilizing layer are shown to be of Au(0) nature, subtle but significantly different from the atoms of the gold core owing to the variations in the proportion of gold-gold and gold-sulfur links that form. These interactions explain the success of the superatom model in describing the electronic structure of both known and informatory nanoparticle compositions. Nanoparticle reaction energies are, however, found not to correlate with the completion of superatom shells

Fabrication of double nano-cup assemblies and their anomalous plasmon absorption

Double-cup assemblies of nanoscale gold semi-shells have been synthesized using a combination of thermal evaporation and chemical etching. The optical extinction of these structures peaked at 740 nm, but there was also evidence of additional extinction maxima at 560, 940 and 1110 nm. Numerical simulations of the optical properties revealed that the extinction was due mainly to scattering rather than to absorption In contrast, the extinction in simple single-shell nanocups was strongly absorptive in nature. Multiple plasmon resonances were identified in the double-cup structures, including an interesting quadrupole resonance in which oscillations of the inner and outer shells should operate 180° out-of-phase. © 2008 IEEE

Linear-scaling techniques for first principles calculations of stationary and dynamic systems

First principles calculations can be a computationally intensive task when studying large systems. Linear-scaling methods must be employed to find the electronic structure of systems consisting of thousands of atoms and greater. The goal of this thesis is to combine the linear-scaling divide-and-conquer (D&C) method with the linear-scaling capabilities of the SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) density functional theory (DFT) methodology and present this union as a viable approach to large-scale first principles calculations. In particular, the density matrix version of the D&C method is implemented into the SIESTA package. This implementation can accommodate high quality calculations consisting of atom numbers in the tens of thousands using moderate computing resources. Low quality calculations have been tested up to half million atoms using reasonably sized computing resources.The D&C method is extended to better handle atomic dynamics simulations. First, by alleviating issues caused by discontinuities in the potential energy surface, with the application of a switching function on the Hamiltonian and overlap matrices. This allows for a smooth potential energy surface to be generated. The switching function has the additional benefit of accelerating the self-consistent field (SCF) process. Secondly, the D&C frozen density matrix (FDM) is modified to allow for improved charge transfer between the active and constrained regions of the system. This modification is found to reduce both the number of SCF iterations required for self-consistency and the number of relaxation steps in a local geometry optimisation. The D&C paradigm is applied to the real-time approach of time-dependent density functional theory (TDDFT). The method is tested on a linear alkane molecule with varying levels of success.Divergences in the induced dipole moment occur when the external excitation field is aligned parallel to the axis of the molecule. The method succeeds in producing accurate dipole moments when the external field is aligned perpendicular to the molecule. Various techniques are tested to improve the proposed method. Finally, the performance and effectiveness of the current D&C implementation is evaluated by studying three current systems. The first two systems consist of two different DNA sequences and the last system is the large ZIF-100 zeolitic imidazolate framework (ZIF)

Anatomical and functional outcomes of scleral buckling versus primary vitrectomy in pseudophakic retinal detachment

Retinal detachment is the separation of the sensory retina from the retinal pigment epithelium by subretinal fluid. There are several types of retinal re-attachment surgery, including scleral buckling (SB), pneumatic retinopexy, and vitrectomy (with or without SB). The objective of this study was to compare anatomical and visual outcomes between patients with pseudophakic rhegmatogenous retinal detachment (RRD) who underwent pars plana vitrectomy (PPV) with silicone oil (SO) or perfluoropropane (C3F8) gas tamponade and pseudophakic RRD patients who underwent SB surgery. We evaluated retrospectively 101 pseudophakic RRD patients from a single center. The patients were classified into three groups according to the surgical procedure performed: PPV + Silicone - patients who underwent PPV with SO tamponade; PPV + Gas - patients who underwent PPV with perfluoropropane gas tamponade; and SB group - patients who underwent SB surgery. The groups were compared with regard to primary and final anatomical and visual outcomes. The number of patients in PPV + Silicone, PPV + Gas, and SB group was 39 (38.6%), 32 (31.7%), and 30 (29.7%), respectively. The mean follow-up period in PPV + Silicone, PPV + Gas, and SB group was 33.95 ± 23.58, 32.62 ± 10.95, and 33.76 ± 16.62 months, respectively. No significant difference was observed between the groups neither with regard to primary and final anatomical and visual success rates nor in relation to the recurrence rate of retinal detachment. According to our anatomical and visual outcome results, either of the three methods (i.e., PPV + Silicone, PPV + Gas, or SB) can be used in the treatment of pseudophakic retinal detachment

The Correlation between Changes in Biochemical Parameters and Central Macular Thickness in Patients with Non-Proliferative Diabetic Retinopathy

This study aimed at evaluating the correlation between changes in Hemoglobin A1c (HbA1c) and fasting serum lipids, and Central Macular Thickness (CMT) in patients with Non-Proliferative Diabetic Retinopathy (NPDR). In the current research, both eyes of 68 patients with mild or moderate NPDR, without clinically significant macular edema, were studied. Levels of fasting serum lipids, HbAlc, and CMT were measured during the first visit and at the end of the follow-up period (3 months). For statistical analysis, CMTs of each eye were studied and the correlation of changes was investigated. Additionally, the direction of changes in CMT for each eye was determined, and whether the changes in both eyes were symmetrical was investigated. Out of 68 patients, 24 were male and 44 were female. The mean CMT of all eyes was 290.05 ± 48.90 µm during the first visit and 286.80 ± 37.57 µm on the 3rd month follow-up. The mean HbAlc was 8.71 ± 1.82% at first visit to the hospital and the mean HbAlc was 8.39 ± 1.65% at the final visit. Although the changes in HbA1c and CMT during the follow-up period were statistically insignificant, the correlation of these 2 values was statistically significant (p=0.01). However, amongst l3 patients, the CMTs were asymmetrically changed in each eye during the follow-up period. To the best of the author’s knowledge, this was the first study, which indicated a significant correlation in changes of CMT and HbA1c, even amongst patients with low-grade diabetic retinopathy. Demonstration of asymmetric changes in CMT of each treatment-naive eye of the same patient, during changes in systemic conditions, was another important finding of this study

Institutional images of college of physical education and sports as perceived by studentsÖğrenci algılarına göre beden eğitimi ve spor yüksekokullarının kurumsal imajı

The purpose of this study is to identify the institutional image of physical education and sports schools as perceived by students. The study is a descriptive one. Data were captured by survey questionnaires. The population of the study consists of Physical Education and Sports Colleges students in Ankara. The survey instrument was administred to a total of 626 participants. Data on sex were analyzed by unpaired t-test, and data on class and school status by one-way analysis of variance. LSD Tests were applied in the post-hoc analysis to identify the sources of significant differences. According to the perceptions of students, the School (A) has a better institutional image than the school (B) and the School (B) has a better institutional image than the School (C). The level of institutional image was high in both the School (A) and the School (B), whereas it was medium in the School (C). ÖzetBu çalışmanın amacı, öğrenci algılarına göre beden eğitimi ve spor yüksekokullarının kurumsal imaj düzeyini belirlemektir.  Araştırma, var olan durumu ortaya koyan tarama türü bir çalışmadır. Verilerin elde edilmesinde hazırlanan ölçme aracı kullanılmıştır. Araştırmanın evreni, Ankara’da bulunan Beden Eğitimi ve Spor Yüksekokulu öğrencilerinden oluşmaktadır. Ölçme aracı toplam 626 kişiye uygulanmıştır. Cinsiyete ilişkin veriler, ilişkisiz t testi ile sınıf ve okul durumuna ilişkin veriler tek yönlü varyans analizi ile test edilmiştir. Tek yönlü varyans analizi sonucunda, anlamlı bulunan farklılığın kaynağını belirlemek için LSD Testi uygulanmıştır. Öğrenci algılarına göre, (A) okulu, (B) okuluna, (B) okulu da (C) okuluna göre daha iyi bir kurumsal imaja sahiptir. (A) ve (B) okullarında çok, (C) okulunda ise orta düzeyde kurumsal imaj olduğu saptanmıştır

Katarakt cerrahisi sonrası retina dekolmanına neden olan risk faktörlerinin değerlendirilmesi

Amaç: Çalışmanın amacı katarakt cerrahisi geçirmiş hastalarda gelişen psödofakik retina dekolmanı risk faktörlerini değerlendirmektir.Gereç ve Yöntem: Çalışmamız retrospektif özellikte olup, çalışmaya 2010 ile 2018 yılları arasında katarakt cerrahisi uygulanan 212 hastanın 212 gözü dahil edilmiştir. Cerrahi sonrası retina dekolmanı gelişen 106 hasta retina dekolmanı grubuna dahil edildi. Retina dekolmanı grubundaki hastalarla aynı dönemde katarakt cerrahisi geçiren ve retina dekolmanı gelişmeyen 106 hasta, kontrol grubuna dahil edildi. Hastaların dosyaları taranarak cerrahi ve cerrahi sonrası komplikasyonlar, refraksiyon bozukluğu, aksiyel uzunluk ve hastalık öyküsü not edildi. Elde edilen veriler analiz edilerek risk faktörleri incelendi.Bulgular: Gruplar arasında ortalama yaş ve cinsiyet dağılımı açısından istatistiksel bir fark izlenmedi (p=0,213, p=0,192 sırasıyla).Psödofakik retina dekolmanı riskinin arka kapsül yırtığı olan gözlerde 5,5 kat, ön vitrektomi yapılan gözlerde 6,5 kat, künt travma hikayesi olan gözlerde 3,1 kat, diğer gözde retina dekolmanı hikayesi olan gözlerde 4,8 kat ve miyopik refraksiyon kusuru olan gözlerde 2,2kat daha fazla olduğu tespit edilmiştir (p<0,05). Aksiyel uzunluğun 26 mm’den büyük olmasının psödofakik retina dekolmanı riskini 4kat arttırdığı tespit edildi (p=0,013). Neodymium-doped yttrium aluminum garnet lazer kapsülotomi uygulamasının retina dekolmanı gelişimine bir etkisinin olmadığı gözlenmiştir (p=0,853).Sonuç: Miyopik refraksiyon kusuru, arka kapsül yırtığı, ön vitrektomi, künt travma ve diğer gözde retina dekolmanı hikayesi kataraktcerrahisi sonrası retina dekolmanı gelişim riskini arttırmaktadır. Bu faktörlerin bulunduğu hastalar cerrahi sonrasında retina dekolmanı gelişim açısından daha dikkatle izlenmelidir.Objective: To determine the pseudophakic retinal detachment risk factors following cataract surgery. Material and Method: 212 eyes of 212 patients that underwent cataract surgery between 2010 and 2018 were included in this retrospective study. 106 patients with postoperative pseudophakic retinal detachment were included in the retinal detachment group. 106 patients that underwent cataract surgery at the same time with those in the retinal detachment group were included in the control group. Medical records of the patients were investigated and surgical and postsurgical complications, refraction errors, axial length and disease history were noted for each patient. Data of the patients were analyzed to reveal the risk factors. Results: No significant difference was observed between groups regarding age and gender (p=0.213, p= 0.192 respectively). Retinal detachment development risk was 5.5 fold higher with posterior capsule rupture, 6.5 fold higher with anterior vitrectomy, 3.1 fold higher with blunt ocular trauma history, 4.8 fold higher with retinal detachment history in contralateral eye and 2.2 fold higher with myopic refraction error respectively (p<0.05). Retinal detachment development risk was 4 fold higher in eyes with axial length higher than 26 mm (p=0.013). Performing neodymium-doped yttrium aluminum garnet laser capsulotomy after cataract surgery had no effect on pseudophakic retinal detachment development (p=0.853). Conclusion: Pseudophakic retinal detachment risk is higher in patients with myopic refraction error, posterior capsule rupture, anterior vitrectomy, blunt ocular trauma, and retinal detachment history in the contralateral eye. Patients with those risk factors should be screened frequently with great caution

Temperature and pH-dependent behaviors of mAb drugs: A case study for trastuzumab

The distortions in the high-order structure of therapeutic monoclonal antibodies (mAbs) under different environmental conditions acutely affect mAb stability, resulting in altered safety, efficacy, and shelf-life profiles. The overall stability of mAbs depends on many factors, and it requires complementary techniques for an in-depth analysis. The stability of mAbs can be characterized by differential centrifugal sedimentation (DCS), differential scanning calorimetry (DSC), differential scanning fluorimetry (DSF), and size exclusion chromatography (SEC) techniques. In this report, temperature-ramped dynamic light scattering (DLS), and circular dichroism (CD) spectroscopy were employed as complementary tools to show how temperature and pH affect the aggregation of a model mAb, trastuzumab, in solution. The results showed that the aggregation onset temperature of trastuzumab defined by DLS was 75 degrees C, which decreases the amount of beta-sheets and causes a slight increase in helix structures. Moreover, the melting temperature of trastuzumab was determined to be between 80-83 degrees C by temperature-ramped CD spectrophotometry, which is in line with the Tm of trastuzumab's Fab region tested with DSC. Thus, unfolding and aggregation of trastuzumab start simultaneously at 75 degrees C, and unfolding triggers the aggregation. The temperature-ramped CD and DLS methods are robust tools to determine the thermal behavior of biosimilars in various solution conditions. Their complementary usage provides solid scientific background for regulatory applications and a better understanding of mAb instability and its relationship with structural changes