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Papers by ZERIHUN GETAHUN WORKINEH

Orthopaedic Proceedings, 2024

Τα δενδριμερή είναι μία κατηγορία μονοδιάσπαρτων πολυμερικών μακρομορίων μεδενδρόμορφη τρισδιάστα... more Τα δενδριμερή είναι μία κατηγορία μονοδιάσπαρτων πολυμερικών μακρομορίων μεδενδρόμορφη τρισδιάστατη αρχιτεκτονική. Η μοριακή αρχιτεκτονική τους και ημονοδιασπορά τους καθιστούν τα δενδριμερή ιδανικά ως πολυλειτουργικά υπερ-μόρια μεεφαρμογές στην ιατρική και τη φαρμακολογία, την κατάλυση, την ηλεκτρονική καιοπτοηλεκτρονική κλπ. Τα Υγρό-Κρυσταλλικά Δενδριμερή (ΥΚΔ) είναι μια σχετικά νέακατηγορία υπερ-μορίων που βασίζονται στη χημική τροποποίηση των κοινώνδενδριμερών με μεσογόνες (υγρόκρυσταλλικές) μοριακές μονάδες. Ο συνδυασμός τωνιδιαίτερων μοριακών ιδιοτήτων των κοινών δενδριμερών με την κατευθυντικότητα τωνμεσογόνων έχουν οδηγήσει σε μια νέα κατηγορία υπερ-μεσογόνων (ΥΚΔ) με μοναδικέςμοριακές ιδιότητες που επιτρέπουν νέους τρόπους (υπερ)μοριακής αυτο-συναρμολόγησης και αυτο-οργάνωσης.Η εργασία αυτή ασχολείται με τη μοντελοποίηση και την υπολογιστική προσομοίωσηΥΚΔ. Εισάγονται οι αρχές για μια αδροποιημένη μοντελοποίηση ΥΚΔ που να λαμβάνειρητά υπόψη την ειδική αρχιτεκτονική, την εκτ...

Macromolecules, 2020

The ordering and kinetics of self-assembly of miktoarm star polymers of the form (A n) k −C−(B n)... more The ordering and kinetics of self-assembly of miktoarm star polymers of the form (A n) k −C−(B n) k in solution and confined between two surfaces are investigated using a coarse-grained molecular dynamics simulation, with the ultimate goal of developing predictive capabilities for these systems. By systematically changing the relative solvent-block interaction for one block, combined with the effect of confining substrate on one side and vapor on the other side, we observed a number of interesting morphologies for an inherently lamellar miktoarm star polymers in the absence of solvent. Furthermore, we also found that in solution the self-assembly kinetics of miktoarm star polymers into cylindrical and lamellar morphologies is completely different from the self-assembly kinetics of linear block copolymers. The findings from the present study can be used to tailor the film morphology of miktoarm star polymers, playing a leading role in guiding the experimentalists for designing this class of materials for different types of applications.

Physica A: Statistical Mechanics and its Applications, 2018

h i g h l i g h t s • We have calculated average time taken by a vacancy to complete six-jump cyc... more h i g h l i g h t s • We have calculated average time taken by a vacancy to complete six-jump cycle path (τ 6) in 2D order binary alloy. • Random Walk on Network technique has been used to calculate τ 6 as the function of local jump rates, p and q. • Later on, we calculated p and q in terms of energy barriers, E 1 , E 2 and temperature and substituted to have final expression for τ 6. • Variation of τ 6 with local jump rate and temperature has been reported. • From Einstein-Smoluchowski relation the connection between τ 6 and vacancy diffusion coefficient has also been described.

Computational Materials Science, 2019

Samarium (Sm 3+-doped LaF 3 nanoparticles (NPs) subsequently encapsulated with inert crystalline ... more Samarium (Sm 3+-doped LaF 3 nanoparticles (NPs) subsequently encapsulated with inert crystalline LaF 3 and amorphous silica layers were prepared by polyol and sol-gel chemical process, respectively. These surface modified core/shell/SiO 2-nanostructured were characterized by X-ray diffraction (XRD), FE-transmission electron microscopy (TEM), thermal analysis, FTIR, UV/Vis absorption, bang gap energy and photoluminescence spectroscopy. The FETEM, EDX and FTIR spectral studies clearly revealed that the silica layer has been formed surrounding the core-NPs. Comparative spectral analysis indicated that core/shell/SiO 2-NPs revealed high solubility in aqueous and nonaqueous solvents. The decrease in band gap energy after surface growth of an inert LaF 3 and silica shells is directly correlated to the increase in grain size. On comparing the emission intensity, a significant enhancement was observed after inert layer coating, whereas, it suppress after silica encapsulation due to the non-radiative transitions. The increase luminescent intensity after inert shell growth indicates that a significant amount of non-radiative centers existing on the surface of core/shell nanoparticles can be eliminated by the shielding effect of LaF 3 shells. These observed results indicate that the as-prepared core/shell/SiO 2-NPs could be highly useful in broad photonic based applications such as optical sensor/optical bio-probe and light emitting diode.

Liquid Crystals, 2017

Monte Carlo Simulation studies of different generation liquid crystalline dendrimers (LCDrs) (G n... more Monte Carlo Simulation studies of different generation liquid crystalline dendrimers (LCDrs) (G n D 3) under smectic-like mean field have been presented. Mean field-induced configurational and alignment properties of several LCDrs at different field strengths and layer spacing values were investigated. Tractable coarse-grained force fields to model both monomer-monomer and monomer-field interaction potentials have been formulated. Particularly, the effect of mean field on the shape, size and orientation of LCDrs was addressed. Depending on the generation of an LCDr, strength of the field and the layer spacing, on average spherically symmetric LCDrs were changed to either rod-or disc-like shapes. At a relatively strong field, smaller-generation LCDrs stretched to their maximum size at bigger values of layer spacing, whereas larger-generation LCDrs compressed to attain short-cylinder-/disc-like shape at smaller values of layer spacing. In addition to stretching and compression, sub-molecular partitioning has also been observed. Two layers of mesogenic units separated by populations of spherical beads were formed along the field direction. Those layers of mesogens are oriented along the field direction with intensity of orientability highly depending on the field strength.

Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2022

Materials Today Sustainability, 2021

Abstract Zinc-air batteries (ZABs) own a great consideration as a promising option for energy sto... more Abstract Zinc-air batteries (ZABs) own a great consideration as a promising option for energy storage technology because of their ideal energy density, eco-friendly, inexpensive, and abundant resource. However, the sluggish rates of oxygen reactions on the cathode of ZABs demand the preparation of durable, active, and cost-effective oxygen electrocatalysts. Thus, MnO2-based nanoparticles (NPs) have been investigated as potential oxygen electrocatalysts for ZABs, which have the advantages of high activity, cost-effectiveness, and excellent durability. Hence, this review aims to contribute a general outline of advancements in MnO2-based catalysts most recently. The types and structures of MnO2-based NPs, working mechanism, and electrochemistry of rechargeable ZABs are discussed. Then, different synthesis approaches for MnO2 NPs in rechargeable ZABs application are highlighted and summarized. The synthesis approaches of MnO2-based NPs addressed in this review refer to sol-gel, microemulsion, chemical coprecipitation, rheological phase reaction, solid-phase, template, microwave, redox, hydrothermal, and refluxing routes. The impact of the morphology and composition on MnO2-based NPs in their structural characteristics is summarized. Finally, the current challenges and possible strategies for improving the catalytic activity of MnO2-based NPs as air catalysts for ZABs are discussed in detail.

Journal of Physics: Condensed Matter, 2016

In this work we present results from NPT (isobaric-isothermal) Monte Carlo Simulation studies of ... more In this work we present results from NPT (isobaric-isothermal) Monte Carlo Simulation studies of Liquid Crystalline Dendrimer (LCDr) systems confined in a slit-pore made of two parallel flat walls. We investigate the substrate induced conformational and alignment properties of the system at different thermodynamic state points under uniform (unidirectional) anchoring condition. Tractable coarse grained force fields to model both monomer-monomer and monomer-substrate interaction potentials have been used from our previous work. In this anchoring condition, at lower pressure almost all the monomers are anchored to the substrates and mesogens are perfectly aligned with the aligning direction. This alignment is not uniformly transmitted to the bulk region as the pressure grows, instead, it decays with distance from the surface to the bulk region. Due to this reason, the global orintational order parameter decreases with increasing pressure (density). In the neighborhood (2 − 3 mesogenic diameter) of upper and lower walls, mesogenic units form smectic A like structure whose layers are separated by layers of spherical beads. In this region individual LCDrs possess a rod like shape.

Liquid Crystals, 2016

ABSTRACT Controlling microscopic or macroscopic alignment of liquid crystalline dendrimers (LCDrs... more ABSTRACT Controlling microscopic or macroscopic alignment of liquid crystalline dendrimers (LCDrs) in a porous media is an important feature for their possible potential applications. Here, we investigate structural and alignment behaviours of model LCDr system confined in a slit pore made of two parallel impenetrable walls. Isobaric–isothermal (NPT) Monte Carlo computational simulation method is used. A coarse-grained force field for inter-/intra-dendritic and LCDr-substrate interactions has been established. The inner surfaces of confining walls are made to induce homeotropic anchoring condition. According to simulation results, a variety of stable-ordered LCDr system states have been observed and analysed depending on the temperature and pressure. GRAPHICAL ABSTRACT

Polymers, 2014

The surface alignment of liquid crystalline dendrimers (LCDrs) is a key factor for many of their ... more The surface alignment of liquid crystalline dendrimers (LCDrs) is a key factor for many of their potential applications. Here, we present results from Monte Carlo simulations of LCDrs adsorbed on flat, impenetrable aligning substrates. A tractable coarse-grained force field for the inter-dendritic and the dendrimer-substrate interactions is introduced. We investigate the conformational and ordering properties of single, end-functionalized LCDrs under homeotropic, random (or degenerate) planar and unidirectional planar aligning substrates. Depending on the anchoring constrains to the mesogenic units of the LCDr and on temperature, a variety of stable ordered LCDr states, differing in their topology, are observed and analyzed. The influence of the dendritic generation and core functionality on the surface-induced ordering of the LCDrs are examined.

Liquid Crystals, 2019

In this work, we present results from (isobaric-isothermal) Monte Carlo Simulation studies of liq... more In this work, we present results from (isobaric-isothermal) Monte Carlo Simulation studies of liquid crystalline dimer systems confined in a slit pore. Liquid crystalline dimer systems of various spacer numbers have been considered. Surface-induced conformational and alignment properties of these systems at different pressures under homeotropic anchoring condition have been investigated. We have used easily manageable coarse grained force fields to model both monomer-monomer and monomer-substrate interaction potentials. According to the simulated result, the anchoring of dimers to the surface and orientation of mesogenic units with respect to the surface normal seem to depend on the spacer number for messogen attractive confinement. Dimers with lower spacer number are able be adsorbed to the surface and most of their mesogens are oriented along the surface normal even at lower pressure. Those with larger spacer number are distributed throughout the volume at lower pressure. In the case of mesogen repulsive confinement, most of the dimers are adsorbed to the surface and most mesogens are randomly oriented at low pressure. As the pressure gets higher, the adsorption and orientability increase depending on the type of confinement and spacer number. As a result, clear submolecular partitioning and smectic A like structure have been identified.