The Effect of Weekend Curfews on Epidemics: A Monte Carlo Simulation

The ongoing COVID-19 pandemic is being responded with various methods, applying vaccines, experimental treatment options, total lockdowns or partial curfews. Weekend curfews is one of the methods to reduce the amount of infected persons and this method is practically applied in some countries such as Turkey. In this study, the effect of weekend curfews on reducing the spread of a contagious disease, such as COVID-19, is modeled using a Monte Carlo algorithm with a hybrid lattice model. In the simulation setup, a fictional country with three towns and 26,610 citizens were used as a model. Results indicate that applying a weekend curfew reduces the active cases significantly and is one of the efficient ways to fight the epidemic. The results also show that applying personal precautions such as social distancing is important for reducing the number of cases and deaths.Comment: Published version, 14 pages, 6 figure

Posterior-Only Approach with Pedicle Screws for the Correction of Scheuermann's Kyphosis

Study DesignRetrospective study (level of evidence: level 3).PurposeThe purpose of this study was to evaluate the clinical and radiological results of the posterior-only approach with pedicle screws for the treatment of Scheuermann's kyphosis (SK).Overview of LiteratureThe correction of SK with instrumentation can be performed using posterior-only or combined anterior-posterior procedures. With the use of all-pedicle screw constructs in spine surgery, the posterior-only approach has become a popular option for the definitive treatment of SK. In a nationwide study involving 2,796 patients, a trend toward posterior-only fusion with lower complication rates was reported.MethodsWe retrospectively reviewed the data of patients who underwent posterior-only correction for SK between January 2005 and May 2013. Patients with a definite diagnosis of SK who fulfilled the minimum follow-up criterion of 24 months were included. The thoracic kyphosis (T5–T12), lumbar lordosis (L1–S1), and thoracolumbar junction (T10–L2) angles were measured from preoperative, postoperative, and last control radiographs. Sagittal balance, thoracic length, thoracic diameter, Voutsinas index and the sacral slope, pelvic tilt, proximal junction kyphosis, and distal junction kyphosis angles were also measured.ResultsForty-five patients underwent surgery for the treatment of SK between 2005 and 2013. After applying the exclusion criteria, 20 patients (18 males and 2 females) with a mean age of 19 years were included. The mean thoracic kyphosis angle was 79.8 degrees preoperatively, 44.6 degrees postoperatively, and 44.9 degrees at the last control. There were statistically significant differences between preoperative and postoperative values in the thoracic kyphosis and lumbar lordosis angles, thoracic length, thoracic diameter, and Voutsinas index (p<0.05).ConclusionsThe clinical and radiological results of the current study suggest that posterior-only fusion is an efficient technique for the treatment of SK

Katmanlı ve Kompozit Biyopolimerler: Mekanik, Fiziksel ve Antimikrobiyal Özellikleri

In this thesis, two oppositely charged biopolyelectrolytes –alginate and chitosan- were focused on. The interactions between these biopolymers and the effect of surfactants on these biopolymers were studied. Thesis is composed of three chapters. In first chapter. The changes in mechanical properties of the calcium and barium crosslinked alginate hydrogel beads, when sodium dodecyl sulfate (SDS) and Brij 35 were incorporated into the gel structure, were studied. SDS and Brij 35 are negatively charged and nonionic surfactants, respectively. Alginate concentration, types and concentrations of crosslinker and surfactant were found as parameters which affect the elastic properties of alginate hydrogel beads. Modulus of elasticity of the alginate gels increased when SDS was added and decreased in the presence of Brij 35. Therefore it is considered that SDS increases the negative charge density on alginate chain by binding to the chain via hydrophobic interactions. On the other hand, Brij 35 decreased the charge density. Second chapter focuses on the preparation of the alginate – chitosan polyelectroylte multilayer (PEM) films and the effect of surfactants on them by characterizing the samples using ellipsometry, X-ray reflectometry and atomic force microscopy. Results showed that SDS increased the thickness of the PEM films by increasing the adsorbed amount of mass of the alginate – chitosan system. In third chapter, it was aimed to develop a potent wound dressing agent by preparing cerium(III) crosslinked alginate-chitosan films. Mechanical and antimicrobial characterization of the samples indicated the potential of cerium(III) crosslinked alginate-chitosan as wound dressings. This graduate thesis project was derived from the results of the experiments and measurements, which were conducted within the scope of joint doctoral agreement between İstanbul Teknik Üniversitesi and Technische Universität Berlin. Graduate student was supported by Scientific and Technical Research Council of Turkey (TÜBİTAK) BİDEB 2214/B joint doctoral scholarship program.Die vorliegende Arbeit konzentriert sich auf die beiden entgegengesetzt geladenen Biopolyelectrolyte, Alginate und Chitosan. Die Wechselwirkungen zwischen diesen Biopolymeren und die Wirkung von Tensiden auf diese Biopolymere wurden untersucht. Die Arbeit besteht aus drei Teilen: Im ersten Teil der Dissertation wird die Änderungen der mechanischen Eigenschaften der Calcium- und Barium-vernetzten Alginat-Hydrogelperlen, wenn Natriumdodecylsulfat (SDS) und Brij 35 in die Gelstruktur eingearbeitet wurden, präsentiert. SDS und Brij 35 sind anionisches bzw. Nichtionisches Tensiden. Alginatkonzentration, Typen und Konzentrationen von Vernetzter und Tensid wurden als Parameter gefunden, die elastischen Eigenschaften von Alginat-Hydrogelperlen beeinflussen. Der Elastizitätsmodul der Alginatgele nahm zu, wenn SDS zugegeben und in Gegenwart von Brij 35 vermindert wurde. Daher wird davon ausgegangen, dass SDS die negative Ladungsdichte an der Alginatkette durch Bindung an die Kette über hydrophobe Wechselwirkungen erhöht. Der zweite Teil beschreibt auf die Herstellung der Alginat – Chitosan – Polyelektrolyt-Multischichten (PEMs) und die Wirkung von Tensiden auf sie durch die Charakterisierung der Proben mittels Ellipsometrie, Röntgenreflektometrie und Atomkraftmikroskop. Die Ergebnisse zeigten, dass SDS die Filmdicke der PEMs erhöhte, indem die adsorbierte Massenmenge des Alginat – Chitosansystems erhöht wurde. Im dritten Teil wurde darauf hingewiesen, ein potentielles Wundverband durch die Herstellung von Cer(III) vernetzten Alginat-Chitosan-Filmen zu entwickeln. Die mechanische und antimikrobielle Charakterisierung der Proben zeigte das Potential von Cer(III) vernetzten Alginat-Chitosan als Wundverbände an. Diese Dissertation wurde aus den Ergebnissen der Experimente und Messungen abgeleitet, die im Rahmen der gemeinsamen Promotionsvereinbarung zwischen der Technischen Universität Berlin und Technische Universität Istanbul durchgeführt wurden. Der Doktorand wurde von die Die Türkische Anstalt für Wissenschaftliche und Technologische Forschung (TÜBİTAK) BİDEB 2214/B gemeinsamen Doktorandenstipendium Programm unterstützt.Bu tez çalışmasında karşıt yüklü biyopolielektrolitler olan aljinat ve kitosanın, birbirleri ile ve yüzey aktif maddelerle olan etkileşimleri yapısal olarak aydınlatılmaya çalışılmış ve üç ayrı aşamada deneyler yapılmıştır. Birinci bölümde kalsiyum ve baryum katyonlarıyla çapraz bağlanmış aljinat hidrojellerinin, sırasıyla eksi yüklü ve yüksüz yüzey aktif maddeler olan sodyum dodesil sülfat (SDS) ve Brij 35 ile katkılandırıldığında mekanik özelliklerinin değişimini konu almaktadır. Bu kısımda, hidrojel kürelerinin esneklik katsayısına aljinat derişiminin, katyon derişiminin, yüzey aktif madde türünün ve derişiminin etkileri incelenmiş ve yüzey aktif maddelerin esneklik katsayısını ayarlanabilir biçimde değiştirdiği görülmüştür. SDS’nin aljinat zincirine hidrofobik etkileşimle bağlandığı ve yüzeydeki yük yoğunluğunu yükselterek, çapraz bağlanmayı artırdığı düşünülmektedir. Brij 35 ise ters etki göstererek yük yoğunluğunu azalttığı, dolayısıyla çapraz bağlanma yüzdesinin düştüğü anlaşılmaktadır. İkinci aşamada aljinat ve kitosan çoklu polielektrolit katmanları (PEM) hazırlanmış ve yüzey aktif maddelerin bu yapılara etkisi incelenmiştir. Deneysel olarak elipsometri, X-ışını yansıma ölçümü, atomik kuvvet mikroskopu ve kuvars kristal mikrodenge yöntemleri kullanılmıştır. Elde edilen sonuçlar, SDS varlığında filmlerin daha kalın olduğunu göstermektedir. SDS, aljinat – kitosan katmanlarının etkileşimini artırmaktadır. Elde edilen sonuçlar, SDS’nin aljinata hidrofobik etkileşimle bağlandığı savını desteklemektedir. Çalışmanın üçüncü bölümünde ise, potansiyel bir uygulama alanı olarak aljinat – kitosan filmleri seryum(III) iyonlarıyla çapraz bağlanmış, elde edilen filmlerin mekanik ve antimikrobiyal özellikleri incelenmiştir. Bu aşamadaki sonuçlar da yara örtüsü olarak kullanılabileceğini göstermektedir. Bu doktora tez çalışması, İstanbul Teknik Üniversitesi ve Berlin Teknik Üniversitesi arasında ortak doktora programı çerçevesinde her iki üniversitede yapılan deney ve ölçümlerin sonuçlarına dayanmaktadır. Doktora öğrencisi, Türkiye Bilimsel ve Teknolojik Araştırma Kurumu (TÜBİTAK) – BİDEB 2214-B yurtdışı müşterek doktora burs programı ile desteklenmiştir

Sustainable alginate-carboxymethyl cellulose superabsorbents prepared by a novel quasi-cryogelation method

The research in biopolymer-based superabsorbents is gaining importance in the green chemistry field thanks to their environmentally friendly properties. In this study, a biopolymer-based superabsorbent made of calcium ion crosslinked alginate/carboxymethyl cellulose composite was prepared by a new quasi-cryogelation process, where the complete ionic gelation takes place before the freezing step, in contrast to the conventional cryogelation technique in which gelation occurs under semi-frozen conditions. Thanks to the facile quasi-cryogelation method, the morphology of the gels changed and a significant increase in water absorption properties has been achieved. The swelling properties of the material were investigated in distilled water and different physiological fluids. Results show that the proposed material shows good water absorption property where a water absorption of 2343% was reached and even after five cycles this value was 1200%. As a result, this study reports a biopolymer-based sustainable superabsorbent which is appropriate for various applications such as the removal of pollutants from water or diaper production

A Biopolymer Superabsorbent Based on Alginate-Carboxymethyl Cellulose Quasi-cryogels

The research in biopolymer-based superabsorbents is gaining importance in the green chemistry field thanks to their environmentally friendly properties. In this study, a biopolymer-based superabsorbent made of calcium ion crosslinked alginate/carboxymethyl cellulose composite was prepared by a new quasi-cryogelation process, where the complete ionic gelation takes place before the freezing step, in contrast to the conventional cryogelation technique in which gelation occurs under semi-frozen conditions. Thanks to the facile quasi-cryogelation method, the morphology of the gels changed and a significant increase in water absorption properties has been achieved. The swelling properties of the material were investigated in distilled water and different physiological fluids. Results show that the proposed material shows good water absorption property where a water absorption of 2366% was reached and even after five cycles this value was 1200%. As a result, this study reports a biopolymer-based sustainable superabsorbent which is appropriate for various applications such as the removal of pollutants from water or diaper production

Cobalt(II) Alginate as a Precursor for Green Synthesis of Cobalt Oxide Nanoparticles

There is an increasing scientific interest in environmentally friendly methods in nanoparticle synthesis. In this study, cobalt oxide nanoparticles were prepared by thermal decomposition of cobalt crosslinked alginate gel, where alginate acts as a precursor. The resulting material was characterised using X-ray diffraction (XRD). The size of nanocrystals was 32 nm as calculated by the Scherrer equation and the size of nanocrystals varied between 1 and 60 nm according to grain size distribution (GSD). Transmission electron microscopy (TEM) was used to observe nanocrystals. Thermogravimetric analysis (TGA) was studied to elucidate the formation of cobalt oxides from cobalt crosslinked alginate beads. An easy and cost-effective method was reported for the synthesis of Co3O4 nanoparticles

Electric-field induced phase transitions in capillary electrophoretic systems

The movement of particles in a capillary electrophoretic system under electroosmotic flow was modeled using Monte Carlo simulation with the Metropolis algorithm. Two different cases with repulsive and attractive interactions between molecules were taken into consideration. Simulation was done using a spin-like system, where the interactions between the nearest and second closest neighbors were considered in two separate steps of the modeling study. A total of 20 different cases with different rates of interactions for both repulsive and attractive interactions were modeled. The movement of the particles through the capillary is defined as current. At a low interaction level between molecules, a regular electroosmotic flow is obtained; on the other hand, with increasing interactions between molecules, the current shows a phase transition behavior. The results also show that a modular electroosmotic flow can be obtained for separations by tuning the ratio between molecular interactions and electric field strength

Carboxymethyl Cellulose-Zinc Alginate Hydrogels as Antibacterial Wound Dressings

Wound dressings need to have strong physical capabilities, good antibacterial qualities, and, more importantly, natural material components. In this study, zinc alginate and carboxymethyl cellulose were combined to obtain a novel wound dressing film based on natural materials. Film samples were characterized by Fourier transform infrared spectroscopy (FTIR), light transmittance, scanning electron microscopy (SEM), swelling experiments, and water vapor transmittance tests. Wound dressing based on zinc crosslinked alginate and carboxymethyl cellulose films gained antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and had a good swelling capability in pure water and isotonic solution (0.9% NaCl), had UV-protective character and had a high value of water vapor transmission rate (WVTR) thanks to their porous structure. Results indicate that the presented formulation is a novel and promising wound dressing material

COVID-19 modeling based on real geographic and population data

Background/aim: Intercity travel is one of the most important parameters for combating a pandemic. The ongoing COVID-19 pandemic has resulted in different computational studies involving intercity connections. In this study, the effects of intercity connections during an epidemic such as COVID-19 are evaluated using a new network model. Materials and methods: This model considers the actual geographic neighborhood and population density data. This new model is applied to actual Turkish data by means of provincial connections and populations. A Monte Carlo algorithm with a hybrid lattice model is applied to a lattice with 8802 data points. Results: Around Monte Carlo step 70, the number of active cases in Türkiye reaches up to 8.0% of the total population, which is followed by a second wave at around Monte Carlo step 100. The number of active cases vanishes around Monte Carlo step 160. Starting with İstanbul, the epidemic quickly expands between steps 60 and 100. Simulation results fit the actual mortality data in Türkiye. Conclusion: This model is quantitatively very efficient in modeling real-world COVID-19 epidemic data based on populations and geographical intercity connections, by means of estimating the number of deaths, disease spread, and epidemic termination