Mühendislik Fakültesi

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Credit Card Fraud Detection with Machine Learning Methods
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 01.01.2019) Goy, Gokhan; Gezer, Cengiz; Gungor, Vehbi Cagri; AGÜ, Mühendislik Fakültesi, Bilgisayar Mühendisliği Bölümü
With the increase in credit card usage of people, the credit card transactions increase dramatically. It is difficult to identify fraudulent transactions among the vast amount of credit card transactions. Although credit card fraud is limited in number of transactions, it causes serious problems in terms of financial losses for individuals and organizations. Even though large number of studies has been conducted to solve this problem, there is no generally accepted solution. In this paper, a publicly available data set is used. The unbalance problem of the data set was solved by using hybrid sampling methods together. On this data set, comparative performance evaluations have been conducted. Different from other studies, the Area Under the Curve (AUC) metric, which expresses the success in such data sets, has also been used in addition to standard performance metrics. Since it is also important to quickly detect credit card fraud transactions; the running time of different methods is also presented as another performance metric.
Planar MEMS Variable Optical Attenuators (VOAs) with Linear Attenuation-Voltage Characteristics
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 01.01.2019) Hah, Dooyoung; 0000-0002-1290-0597; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
Variable optical attenuators (VOAs) are essential components in wavelength division multiplexing (WDM) networks, light waveform generators, and optical fiber test equipment. Among various types of planar MEMS VOAs, a shutter type and a reflective type have been most frequently studied so far. In a shutter type, a knife-edge-like beam blocker is inserted in between the butt-coupled input and output fibers, partially obstructing the coupling between the fibers. In a reflective type, a mirror that is placed in the optical path controls the alignment between the fibers to result in attenuation. The movement of the shutter or the mirror is controlled by MEMS actuators, such as comb-drive actuators. In most of the planar MEMS VOAs reported, the relationship between the attenuation and the control voltage has been highly nonlinear. This nonlinearity results in uneven resolution throughout the attenuation range. Although this nonlinearity can be addressed by employing a control system, a structure-based solution is preferred, which can curtail the requirement of power consumption, and prevent control instability issues. In this study, shaped-finger comb-drive actuators are used to obtain a linear relationship between the control voltage and the attenuation in planar MEMS VOAs. Two types, i.e. shutter-type and reflective-type, of VOAs are examined. First, the objective differential equation is established based on attenuation-displacement relationships, electrostatic/mechanical force balance equation, and the design objective (linearity) equation. Then, the differential equation (in terms of 2-D comb capacitance) is solved by using the Euler's method, and the finger gaps are calculated by using a conformal mapping method. When a single comb-drive actuator is used, an excluded zone needs to be introduced around the region of small displacement. Effects of the width of the excluded zone to the device characteristics are studied. The issue of zone exclusion can be addressed by adopting dual (control and bias) combs. The effects of design parameters to the VOA performances are studied. It is shown that the planar MEMS VOAs with linear attenuation-voltage relationships can be designed successfully by using the proposed method.
Performance Evaluations of Active Subnetwork Search Methods in Protein-Protein Interaction Networks
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 01.01.2019) Gunter, Pinar; Bakir-Gungor, Burcu; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
Protein-protein interaction networks are mathematical representations of the physical contacts between proteins in the cell. A group of interconnected proteins in a protein-protein interaction network that contains most of the disease associated proteins and some interacting other proteins is called an active subnetwork. Active subnetwork search is important to understand mechanisms underlying diseases. Active subnetworks are used to discover disease related regulatory pathways, functional modules and to classify diseases. In the literature there arc many methods to search for active subnetworks. The purpose of this study is to compare the performance of different subnetwork identification methods. By using the Rheumatoid Arthritis dataset, the performances of greedy approach, genetic algorithm, simulated annealing algorithm, prize collecting steiner forest and game theory based subnetwork search methods are compared.
94.8 Km-Range Direct Detection Fiber Optic Distributed Acoustic Sensor
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 01.01.2019) Uyar, Faruk; Onat, Talha; Unal, Canberk; Unal, Canberk; Ozdur, Ibrahim; Ozbay, Ekmel; 0000-0003-3552-1650; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
This work demonstrates an ultra-long range direct detection fiber optic distributed acoustic sensor which can detect vibrations at a distance of 94.8 km with 10 m resolution along the sensing fiber. (C) 2019 The Author(s)
Use of laser-induced bubbles in intraocular pressure measurement: a preliminary study
(IOP PUBLISHING LTD, TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND, 01.01.2019) Altindis, Fatih; Ozdur, Ibrahim T.; Mutlu, Sait N.; Yilmaz, Bulent; 0000-0002-3891-935X; 0000-0001-6452-0804; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
This work investigates the feasibility of a novel approach for measuring intraocular pressure (IOP) by analyzing micron-level laser-induced bubble characteristics in the intraocular fluid. We believe that this concept may be used as a non-invasive alternative for measuring a patient's IOP by analyzing the laser-induced bubble volume in the intraocular fluid in the anterior chamber of the eye. The behavior of laser-induced bubbles was examined under differing fluid pressure levels and at differing laser pulse energy levels. An intraocular medium-like environment was imitated and an imaging system was designed in order to capture laser-induced bubbles with their movements. The video recordings of the bubbles were processed using custom software, and the volume of the bubbles was estimated using three different approaches. The bubble volumes were estimated more accurately by using the rising velocity of the bubble rather than its direct radii appearances on the images. An inversely proportional relationship was observed between the laser-induced bubble volume and the fluid pressure. IOP can be measured with a non-invasive technique using laser-induced bubble volume. Deeper and detailed studies, including clinical studies, may lead to the use of lasers for measuring IOP.
Software Defined Communication Framework for Smart Grid to Meet Energy Demands in Smart Cities
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 01.01.2019) Faheem, Muhammad; Umar, Muhammad; Butt, Rizwan Aslam; Raza, Basit; Ngadi, Md. Asri; Gungor, Vehbi Cagri; 0000-0003-4907-6359; AGÜ, Mühendislik Fakültesi, Bilgisayar Mühendisliği Bölümü
In smart cities, the electricity is an essential component since it preserves a certain level of residents' life quality and provisions the entire spectrum of their economic activities. Thus, a smart way is essential to develop cities without disregarding energy issues. In this scope, the smart grid paradigm offers power supply in an efficient, sustainable and economical manner with minimal impact on the environment and can meet the future energy demands. However, real-time monitoring and control of the smart grid (SG) for continuous and quality-aware power supply in smart cities (SCs) is challenging and requires an advanced quality of service (QoS)-aware communication framework. In this context, this research aims to present a novel data-gathering scheme by using the Internet of software-defined mobile sinks (SDMSs) and wireless sensor networks (WSNs) in the smart grid. The extensive simulation results conducted through the EstiNet9.0 indicate that the designed scheme outperforms existing approaches and achieves its defined goals for events-drive applications in the SG.
Optimizing nutrient content of microbial self-healing concrete
(CRC PRESS-TAYLOR & FRANCIS GROUP, 6000 BROKEN SOUND PARKWAY NW, STE 300, BOCA RATON, FL 33487-2742 USA, 01.01.2019) Ersan, Y. C.; Akin, Y.; 0000-0003-4128-0195; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü
Cracks in microbial self-healing concrete are autonomously sealed through microbial induced calcium carbonate precipitation (MICP). The biogenic production of dissolved inorganic carbon (i.e. CO2) is the main drive for MICP and it is limited by the bioavailability of the nutrients. When added as admixtures bioavailability of the nutrients becomes even more significant for crack sealing as they disperse in mortar and a considerable portion stays far from an individual crack. Therefore, determination of the nutrient bioavailability and optimization of the nutrient content is necessary to enhance self-healing performance of bioconcrete. This study defines an optimum nutrient content range for nitrate reduction based microbial self-healing concrete. Ca-formate and Ca-nitrate were used as nutrient admixtures and their wt/wt ratio was kept constant at 2.50: 1.00 while testing various nutrient doses. Variation in mortar properties and nutrient bioavailability was observed and the optimum nutrient content range was defined as 3.5% to 7% depending on the expectations.
The relationship of surface roughness and wettability of 316L stainless steel implants with plastic deformation mechanisms
(ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 01.01.2019) Cicek, S.; Karaca, A.; Torun, I.; Onses, M. S.; Uzer, B.; 0000-0001-6898-7700; 0000-0001-8778-1660; 0000-0001-9820-6565; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü
The wettability of the implant plays significant role in successful tissue-implant integration and shows strong dependence on the surface topography of the material. Recent studies showed that the plastic deformation mechanisms can improve cell response, and increase surface roughness and energy. In order to understand the effect of these mechanisms on wettability, 316L stainless steel samples were subjected to tensile test and deformed up to 15% to 35% of strain levels. Atomic force microscopy (AFM) presented approximately 22-fold greater average surface roughness on the 35% deformed sample compared to undeformed one. On the other hand, sessile drop test showed contact angle decrease from 82 degrees to 52 degrees as the deformation increased. This finding is significant since much higher contact angle value at similar surface roughness was presented in the literature. This demonstrates that the plastic deformation mechanisms can play significant role in enhancing the surface wettability without a need for a surface treatment technique. Hence, through the activation of these mechanisms, wettability and surface energy of the implant materials could be further increased which would result with enhanced cell response and lessened post-surgical complications. (C) 2018 Elsevier Ltd. All rights reserved.
Production of precipitated calcium carbonate particles from gypsum waste using venturi tubes as a carbonation zone
(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 01.01.2019) Altiner, Mahmut; Top, Soner; Kaymakoglu, Burcin; Seckin, Ismail Yigit; Vapur, Huseyin; 0000-0002-7428-5999; 0000-0003-3486-4184; 0000-0003-4438-3982; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
In this study, we investigated the production of precipitated calcium carbonate (PCC) particles from desulfurization gypsum (DG) waste using a new experimental apparatus that is divided into two main parts: carbonation and stabilization zones. The solution was circulated via a pump from the stabilization zone to the carbonation zone where different types of Venturi tube were used for the reaction of CO2 with solution to produce PCC particles. The effects of CO2 flow rate, circulation rate, and Venturi types on the properties of the produced PCC particles were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analyses. The conductivity and pH values of the solution were monitored during the carbonation. In addition, the reactivity of selected PCC was determined to evaluate its use as a sorbent in a desulfurization unit. The experimental results indicate that the Venturi tube had a strong effect on the reaction time and properties of PCC particles. The use of a Venturi tube resulted in a decrease in the time required for producing PCC particles, which were smooth, well-crystallized, and nano-sized cubic crystals. However, when no Venturi tube was used, hollow spherical crystals formed along with cubic crystals. It was found that the reactivity of selected PCC particles produced using Venturi tube was rather higher (52x10(-4) min(-1)), indicating that the PCC can be used as a sorbent in the desulfurization unit.
Parameter investigation of topological data analysis for EEG signals
(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 01.01.2021) Altindis, Fatih; Yilmaz, Bulent; Borisenok, Sergey; Icoz, Kutay; 0000-0002-0947-6166; 0000-0002-3891-935X; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
Topological data analysis (TDA) methods have become appealing in EEG signal processing, because they may help the scientists explore new features of complex and large amount of data by simplifying the process from a geometrical perspective. Time delay embedding is a common approach to embed EEG signals into the state space. Parameters of this embedding method are variable and the structure of the state space can be entirely different depending on their selection. Additionally, extracted persistent homologies of the state spaces depend on filtration level and the number of points used. In this study, we showed how to adapt false nearest neighbor (FNN) test to find out the suitable/optimal time embedding parameters (i.e., time delay and embedding dimension) for EEG signals, and compared their effects on different types of artefacts and motor intention waves that are commonly used in brain-computer interfaces. We extracted and compared persistent homologies of state spaces that were reconstructed with four different sets of parameters. Later, the effect of filtration level on extracted persistent homologies was compared, and statistical significance levels were computed between leftand right-hand movement imaginations. Finally, computational cost of the discussed methods was found, and the adaptability of this method to a real-time application was evaluated. We demonstrated that the discussed parameters of the TDA approach were highly crucial to extract true topological features of the EEG signals, and the adapted testing approaches depicted the applicability of this approach on real-time analysis of EEG signals.
Overlooked Strategies in Exploitation of Microorganisms in the Field of Building Materials
(SPRINGER-VERLAG SINGAPORE PTE LTD, 152 BEACH ROAD, #21-01/04 GATEWAY EAST, SINGAPORE, 189721, SINGAPORE, 01.09.2019) Ersan, Yusuf Cagatay; 0000-0003-4128-0195; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü
Resource efficiency reports released in the last decade point out construction industry as one of the key sectors that needs improvement in terms of ecological sensitivity. Being aware of this unfavorable reputation of construction industry, researchers embarked on replacing the ongoing conventional methods with more sustainable and environmentally friendly ones. One of the approaches for the latter is incorporating microorganisms into construction industry. Popularly investigated strategies can be listed as biocementation, biomasonry, biorepair, and bioconsolidation. Most of these processes are the outcome of a single approach, namely microbial-induced calcium carbonate precipitation (MICP) which was mostly investigated by means of axenic cultures and through one single microbial process, ureolysis. The state of the art about the latter is close to saturation. Moreover, approaching from the ecological wisdom perspective it can be said that some promising microbial strategies to achieve green building materials were overlooked and drawing attention to these strategies became necessary. This review study reveals the overlooked promising microbial strategies in the field of construction biotechnology. The context mainly discusses the potential of five overlooked microbial strategies: (i) heterotrophic and autotrophic MICP pathways, (ii) microbial strategies for surface treatment, (iii) microbial-induced corrosion inhibition, (iv) microbial sequestration of greenhouse gases, and (v) microbial- produced polymers, for their application in the field of construction materials. Further suggestions aim to integrate the microbial resource management approach and non-axenic cultures into the relevant fields of research for the development of environmentally friendly building materials.
Selective removal of cationic micro-pollutants using disulfide-linked network structures
(ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND, 207-05-15) Atas, Mehmet Sahin; Dursun, Sami; Akyildiz, Hasan; Citir, Murat; Yavuz, Cafer T.; Yavuz, Mustafa Selman; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü;
Micropollutants are found in all water sources, even after thorough treatments that include membrane filtration. New ones emerge as complex molecules are continuously produced and discarded after used. Treatment methods and sorbent designs are mainly based on non-specific interactions and, therefore, have been elusive. Here, we developed swellable covalent organic polymers (COP) with great affinity towards micropollutants, such as textile industry dyes. Surprisingly, only cationic dyes in aqueous solution were selectively and completely removed. Studies of the COPs surfaces led to a gating capture, where negatively charged layer attracts cationic dyes and moves them inside the swollen gel through diffusive and hydrophobic interaction of the hydrocarbon fragments. Despite its larger molecular size, crystal violet has been taken the most, 13.4 mg g(-1), surpassing all competing sorbents. The maximum adsorption capacity increased from 12.4 to 14.6 mg and from 8.9 to 11.4 mg when the temperature of dye solution was increased from 20 to 70 degrees C. The results indicated that disulfide-linked COPs are attractive candidates for selectively eliminating cationic dyes from industrial wastewater due to exceptional swelling behaviour, low-cost and easy synthesis.
Magnetic micro/nanoparticle flocculation-based signal amplification for biosensing
(DOVE MEDICAL PRESS LTD, PO BOX 300-008, ALBANY, AUCKLAND 0752, NEW ZEALAND, 07.07.2016) Mzava, Omary; Tas, Zehra; Icoz, Kutay; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
We report a time and cost efficient signal amplification method for biosensors employing magnetic particles. In this method, magnetic particles in an applied external magnetic field form magnetic dipoles, interact with each other, and accumulate along the magnetic field lines. This magnetic interaction does not need any biomolecular coating for binding and can be controlled with the strength of the applied magnetic field. The accumulation can be used to amplify the corresponding pixel area that is obtained from an image of a single magnetic particle. An application of the method to the Escherichia coli 0157: H7 bacteria samples is demonstrated in order to show the potential of the approach. A minimum of threefold to a maximum of 60-fold amplification is reached from a single bacteria cell under a magnetic field of 20 mT.
Cation exchange mediated synthesis of bright Au@ZnTe core-shell nanocrystals
(IOP PUBLISHING LTD, TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND, 08.01.2021) Sadeghi, Sadra; Melikov, Rustamzhon; Sahin, Mehmet; Nizamoglu, Sedat; 0000-0002-8569-1626; 0000-0003-2214-7604; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
The synthesis of heterostructured core-shell nanocrystals has attracted significant attention due to their wide range of applications in energy, medicine and environment. To further extend the possible nanostructures, non-epitaxial growth is introduced to form heterostructures with large lattice mismatches, which cannot be achieved by classical epitaxial growth techniques. Here, we report the synthetic procedure of Au@ZnTe core-shell nanostructures by cation exchange reaction for the first time. For that, bimetallic Au@Ag heterostructures were synthesized by using PDDA as stabilizer and shape-controller. Then, by addition of Te and Zn precursors in a step-wise reaction, the zinc and silver cation exchange was performed and Au@ZnTe nanocrystals were obtained. Structural and optical characterization confirmed the formation of the Au@ZnTe nanocrystals. The optimization of the synthesis led to the bright nanocrystals with a photoluminescence quantum yield up to 27%. The non-toxic, versatile synthetic route, and bright emission of the synthesized Au@ZnTe nanocrystals offer significant potential for future bio-imaging and optoelectronic applications.
A New Method to Identify Affected Pathway Subnetworks and Clusters in Colon Cancer
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 11.09.2019) Goy, Gokhan; Yazici, Miray Unlu; Bakir-Gungor, Buren; AGÜ, Mühendislik Fakültesi, Bilgisayar Mühendisliği Bölümü
Nowadays new technological developments that play an important role in the production of big data have brought about the interpretation, sharing and storage of data related to complex diseases. Combining multi-omic data in different molecular levels is potentially important for understanding the biological origin of complex diseases. One of these complex diseases is cancer of different types, which has one of the highest causes of death worldwide. The integration of multiple omic data in the framework of a comprehensive analysis and identification of relevant pathways contribute to the development of therapeutic approaches related to disease. In this study, RNA and methylation data (genes and p values) of colon adenocarcinoma were obtained from TCGA data portal and combined with Fisher's method. While protein subnetworks affected by the disease were identified by using subnetwork algorithm, pathways related to the disease and genes associated with these pathways were determined by functional enrichment analysis. Using gene-pathway relationship matrix, kappa scores of pathways were determined by similarity calculation. In this way, the pathways were clustered according to the hierarchically optimal number, as a result, the most important pathway clusters and related genes that are effective in disease formation identified.
Effect of Granulated Blast Furnace Slag and fly ash addition on the strength properties of lightweight mortars containing waste PET aggregates
(ELSEVIER SCI LTD, 2011) Akcaozoglu, Semiha; Atis, Cengiz Duran; 0000-0003-3459-329X; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Atis, Cengiz Duran
In this work, the effect of Granulated Blast Furnace Slag (GBFS) and fly ash (FA) addition on the strength properties of lightweight mortars containing waste Poly-ethylene Terephthalate (PET) bottle aggregates was investigated. Investigation was carried out on three groups of mortar specimens. One made with only Normal Portland cement (NPC) as binder, second made with NPC and GBFS together and, third made with NPC and FA together. The industrial wastes mentioned above were used as the replacement of cement on mass basis at the replacement ratio of 50%. The size of shredded PET granules used as aggregate for the preparation of mortar mixtures were between 0 and 4 mm. The waste lightweight PET aggregate (WPLA)–binder ratio (WPLA/b) was 0.60; the water–binder (w/b) ratios were determined as 0.45 and 0.50. The dry unit weight, compressive and flexural–tensile strengths, carbonation depths and drying shrinkage values were measured and presented. The results have shown that modifying GBFS had positive effects on the compressive strength and drying shrinkage values (after 90 days) of the WPLA mortars. However, FA substitution decreased compressive and flexural–tensile strengths and increased carbonation depths. Nevertheless a visible reduction occurred on the drying shrinkage values of FA modifying specimens more than cement specimens and GBFS modified specimens. The test results indicated that, GBFS has a potential of using as the replacement of cement on the WPLA mortars by taking into consideration the characteristics. But using FA as a binder at the replacement ratio of 50% did not improve the overall strength properties. Although it was thought that, using FA as binder at the replacement ratio of 50% for the aim of production WPLA concrete which has a specific strength, would provide advantages of economical and ecological aspects.
The Effects of Different Types of Fly Ash on the Compressive Strength Properties of Briquettes
(HINDAWI LTD, ADAM HOUSE, 3RD FLR, 1 FITZROY SQ, LONDON, W1T 5HF, ENGLAND, 2011) Sola, Ozlem Celik; Yayla, Murat; Sayin, Baris; Atis, Cengiz Duran; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü;
The aim of this study is to evaluate the effect of the different types of fly ash on the compressive strength properties of sintered briquettes. Thermal gravimetric (TG) analysis was carried out. The chemical composition and physical properties of the materials used were determined. Particle size distribution and microstructure elemental analyses of the materials used were carried out by a particle size analyzer (Mastersizer) and a scanning electron microscope (SEM-EDS). Following the characterization of the materials, briquettes were prepared by sintering at different temperatures. Compressive strength test results of the briquette samples indicated that briquettes with a compressive strength value of 47.45 N/mm(2) can be produced. The results obtained exceed the Turkish standard (TS EN 771-1) requirements (9.8-23.54 N/mm(2)). SEM-EDS results showed that briquette samples made with Tuncbilek (T) fly ash had a higher percentage of the glassy phase than the other briquette samples. Due to this microstructure, it results in higher compressive strength value.
Infrared multiple photon dissociation spectroscopy of protonated histidine and 4-phenyl imidazole
(ELSEVIER, 2012) Hinton, Christopher S.; Oomens, Jos; Citir, Murat; Steill, Jeffrey D; Armentrout, P. B.; 0000-0002-6666-4980; AGÜ; Citir, Murat
The gas-phase structures of protonated histidine (His) and the side-chain model, protonated 4-phenyl imidazole (PhIm), are examined by infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light generated by the free electron laser FELIX. To identify the structures present in the experimental studies, the measured IRMPD spectra are compared to spectra calculated at a B3LYP/6–311+G(d,p) level of theory. Relative energies of various conformers are provided by single point energy calculations carried out at the B3LYP, B3P86, and MP2(full) levels using the 6–311+G(2d,2p) basis set. On the basis of these experiments and calculations, the IRMPD action spectrum for H+(His) is characterized by a mixture of [N,N] and [N,CO] conformers, with the former dominating. These conformers have the protonated nitrogen atom of imidazole adjacent to the side-chain (N) hydrogen bonding to the backbone amino nitrogen (N) and to the backbone carbonyl oxygen, respectively. Comparison of the present results to recent IRMPD studies of protonated histamine, the radical His•+ cation, H+(HisArg), H2 2+(HisArg), and M+(His), where M+ = Li+, Na+, K+, Rb+, and Cs+, allows evaluation of the vibrational motions associated with the observed bands.
Alkali activation of mortars containing different replacement levels of ground granulated blast furnace slag
(ELSEVIER SCI LTD, 2012) Bilim, Cahit; Atis, Cengiz Duran; 0000-0003-3459-329X; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Atis, Cengiz Duran
The aim of the present study is to investigate some properties of alkali-activated mortars containing slag at different replacement levels. Ground granulated blast furnace slag was used at 0%, 20%, 40%, 60%, 80% and 100% replacement by weight of cement, and liquid sodium silicate having three different Na dosages was chosen as the alkaline activator. In this research, carbonation resistance measurements and compressive and flexural strength tests were performed on the mortar specimens with size of 40 40 160 mm. The findings obtained from the tests showed that carbonation depth values of the mortars decreased with the increase of activator dosage. Additionally, compressive and flexural strength values increased with the increase in activator concentration and slag replacement level. Portland cement/slag mortars activated by liquid sodium silicate exhibited lower strength than the slag alone activated by the same activator.
Thermochemistry of alkali metal cation interactions with histidine: Influence of the side chain
(American Chemical Society, 2012) Armentrout, P. B.; Citir, Murat; Chen, Yu; Rodgers, M. T.; 0000-0002-7957-110X; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Citir, Murat
The interactions of alkali metal cations (M+ = Na+ , K+ , Rb+ , Cs+ ) with the amino acid histidine (His) are examined in detail. Experimentally, bond energies are determined using threshold collision-induced dissociation of the M+ (His) complexes with xenon in a guided ion beam tandem mass spectrometer. Analyses of the energy dependent cross sections provide 0 K bond energies of 2.31 ± 0.11, 1.70 ± 0.08, 1.42 ± 0.06, and 1.22 ± 0.06 eV for complexes of His with Na+ , K+ , Rb+ , and Cs+ , respectively. All bond dissociation energy (BDE) determinations include consideration of unimolecular decay rates, internal energy of reactant ions, and multiple ion-neutral collisions. These experimental results are compared to values obtained from quantum chemical calculations conducted previously at the MP2(full)/6-311+G(2d,2p), B3LYP/6-311+G(2d,2p), and B3P86/6-311+G(2d,2p) levels with geometries and zero point energies calculated at the B3LYP/6-311+G(d,p) level where Rb and Cs use the Hay−Wadt effective core potential and basis set augmented with additional polarization functions (HW*). Additional calculations using the def2-TZVPPD basis set with B3LYP geometries were conducted here at all three levels of theory. Either basis set yields similar results for Na+ (His) and K+ (His), which are in reasonable agreement with the experimental BDEs. For Rb+ (His) and Cs+ (His), the HW* basis set and ECP underestimate the experimental BDEs, whereas the def2-TZVPPD basis set yields results in good agreement. The effect of the imidazole side chain on the BDEs is examined by comparing the present results with previous thermochemistry for other amino acids. Both polarizability and the local dipole moment of the side chain are influential in the energetics.

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