Fizik Bölümü / Department of Physics
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Publication 1-Methylhydantoin: From the Matrix Isolated Single Molecule to H-Bond Patterns Defining Different Polymorphs of the Compound(2017) Nogueira, Bernardo, A.; Canotilho, Joa; Eusebio, M. E. S.; Paixao, Antonia; Rui, Fausto; ILDIZ, GÜLCE ÖĞRÜÇ; 107326Publication 4-Hydroxyquinolin-2(1H)-One Isolated in Cryogenic Argon and Xenon Matrices: Tautomers and Photochemistry(Elsevier, 2024) Secrieru, A.; Lopes, S.; Nikitin, T.; Cristiano, Maria L. S.; FAUSTO, RUI4-Hydroxyquinolin-2(1H)-one (4HQ2O) was synthesized, isolated in cryogenic matrices (argon and xenon), and studied by infrared spectroscopy. Quantum chemical calculations carried out at the DFT(B3LYP)/6-311++G (3df,3pd) level of theory were used to determine the conformational and tautomeric properties of the molecule. Two tautomeric forms were identified in the as-deposited matrices with the help of the theoretical data. To investigate the photochemistry of the compound, in situ broadband ultraviolet (lambda > 283 nm) irradiation of the asdeposited argon matrix was performed. This irradiation led to the generation of an additional tautomer, together with the products of fragmentation of the heterocyclic ring of the molecule, specifically isocyanic acid and carbon monoxide. Photoproducts such as 1,3-dihydro-2H-indol-2-one and cyclohepta-1,2,4,6-tetraene were also observed in the photolyzed argon matrix. A comprehensive assignment of the infrared spectra of all the species observed experimentally is presented.Publication Auxiliary Differential Diagnosis of Schizophrenia and Phases of Bipolar Disorder Based on the Blood Serum Raman Spectra(Wiley, 2020) ILDIZ, GÜLCE ÖĞRÜÇ; Bayari, Sevgi; Aksoy, Umut M.; Yorguner, Neşe; Bulut, Hüseyin; Yılmaz, Sultan S.; Halimoğlu, Gökhan; Kabuk, Hayrunnisa Nur; YAVUZ, GİZEM; Fausto, RuiSchizophrenia (SZ) and bipolar disorder (BP) are severe psychiatric disorders that are characterized by an extensive spectrum of symptoms and affect approximately 2% of the world population. BP exhibits three well-distinct phases, which are classified as manic and depressive episodes and euthymic phase. These disorders are of difficult differential clinical diagnosis due to the similarity of their symptoms. Diagnostic approaches for SZ and BP are based on constructed patient interviews and subjective evaluations of clinical symptoms, and there are still no molecular-based auxiliary diagnostic tools to support the clinical diagnosis. In this study, an analytical model for auxiliary differential diagnosis of SZ and BP, based on the analysis of patients' blood serum Raman spectra, is developed, which is able to account for the different BP phases and can also differentiate SZ and BP patients from healthy individuals. The model is based on a hierarchical sequence of four two-class PLS-DA steps where the Raman spectra are theX-predictor variables. It is concluded that the full 400-3,100 cm(-1)Raman spectroscopic range is a sensitive probe for the disorders, thus working as a general spectroscopic biomarker for the illnesses. The proposed methodology is reliable, fast, cheap, essentially minimal-invasive, and might be implemented easily in the clinical environment.Publication Benchmarking the Anisotropy of Nitroxyl Radical Solvation With IR Spectroscopy(The Royal Society of Chemistry, 2024) Bras, Elisa M.; Zimmermann, Charlotte; FAUSTO, RUI; Suhm, Martin A.Two simple nitroxyl radicals, di-tert-butyl nitroxyl (DTBN) and 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) are solvated by one or two water, methanol, tert-butyl alcohol or phenol molecules. The resulting low temperature IR spectra of the vacuum-isolated microsolvates in the OH stretching range are assigned based on harmonic DFT predictions for closed shell solvent dimers and trimers and their offset from experiment, to minimise theory-guided assignment bias. Systematic conformational preferences for the first and second solvent molecule are observed, depending on the conformational rigidity of the radical. These assignments are collected into an experimental benchmark data set and used to assess the spectral predicting power of different DFT approaches. The goal is to find inexpensive computational methods which provide reliable spectral predictions for this poorly explored class of microsolvates.Publication Blood Serum-Infrared Spectra-Based Chemometric Models for Auxiliary Diagnosis of Autism Spectrum Disorder(Elsevier, 2021) ILDIZ, GÜLCE ÖĞRÜÇ; Bayarı, Sevgi; Yorguner, Neşe; Fausto, RuiThis chapter focuses on the use of chemometric models developed from infrared (IR) spectroscopic data of blood serum as an auxiliary tool for autism spectrum disorder (ASD) diagnosis. In the introductory sections the fundamentals of IR spectroscopy are shortly reviewed and brief descriptions of the different chemometric methods used in the case study described in the last section of the chapter are presented. The last section deals with the application of the described strategy to the diagnosis of ASD in children and adolescents. © 2021 Elsevier Inc. All rights reserved.Publication Conformational Analysis of Milk Derived Tripeptides, IPP, VPP and LPP, and Investigation of Their Anti-COVID-19 Potentials by Molecular Docking and Molecular Dynamics Studies(Taylor & Francis Ltd., 2024) Çelik, Sefa; AKYÜZ, SEVİM; Agaeva, Gulshen; E. Özel, Ayşen; Qocayev, Niftali M.; Agaeva, UlkerMilk derived tripeptides IPP(Ile-Pro-Pro), VPP(Val-Pro-Pro) and LPP(Leu-Pro-Pro) have inhibitory effects on angiotensin converting enzyme, which plays a fundamental role in blood pressure systems. To discover the potentiality of the tripeptides as SARS-CoV-2 inhibitors, molecular docking analyses of IPP, VPP and LPP tripeptides with variety of SARS-CoV-2 enzymes, namely with Main protease, papain-like protease and Spike glycoprotein, were performed. Molecular dynamics simulations were performed to validate the stability of the IPP, LPP and VPP tripeptides docked into SARS-CoV-2 main protease within 50 ns time scale and ligand-receptor interactions were evaluated. Molecular docking and molecular dynamics studies showed that these food-derived tripeptides may be effective against COVID-19.Publication Conformational Analysis, Spectroscopy and Photochemistry of Matrix-Isolated 1H- and 2H- Tautomeric Forms of Ethyl Tetrazole-5-Carboxylate(Elsevier Science, 2021) ILDIZ, GÜLCE ÖĞRÜÇ; Fausto, RuiThe preferred conformations, infrared spectra and photochemistry of matrix-isolated 1H and 2H tautomers of ethyl tetrazole-5-carboxylate (ET5C) were investigated. Experimentally, isolated monomeric forms of the two tautomers were trapped in cryogenic argon matrices (15 K), and studied by infrared spectroscopy. Identification of the conformational species trapped in the matrices was undertaken by combining the experimental spectro-scopic data with results of quantum chemical calculations performed at the DFT(B3LYP)/6-311++G(d,p) level of theory. For each tautomer, two conformers were observed in the matrices, all forms exhibiting the ester group in the anti configuration (C-O-C-C dihedral equal to 180 degrees). In turn, the conformers having a gauche ester group that are predicted by the calculations to be significantly populated in the gas phase equilibrium (room temperature), were found to convert into the anti forms during matrix deposition (conformational cooling). Very interestingly, and contrarily to what is in general found for tetrazoles, the 1H tautomer is the most stable tautomer of ET5C, and strongly predominates in the studied matrices. Narrowband UV irradiation (lambda = 250 nm) was found to lead to tetrazole fragmentation, with release of molecular nitrogen and production of four isomeric photoproducts (diazirine, cyanamide, carbodiimide and nitrile imine), all of them being successfully identified through comparison of the experimental spectroscopic spectra of the irradiated matrices with the DFT(B3LYP)/6-311++G(d, p) predicted infrared spectra of these species. This study also stresses the structural relevance of the N-H//O = C intramolecular interaction between the ring hydrogen atom and the carbonyl group of the substituent in the 1H tautomer of ET5C.Publication Crystallization Kinetics: Relationship Between Crystal Morphology and the Cooling Rate-Applications for Different Geological Materials(MDPI, 2023-01-24) Aysal, Namık; Kurt, Yiğit; ILDIZ, GÜLCE ÖĞRÜÇ; Öztürk, Hüseyin; Yeşiltaş, Mehmet; Laçin, Davut; Öngen, Sinan; Nikitin, Timur; FAUSTO, RUICrystal morphology is controlled by several physicochemical parameters such as the temperature, pressure, cooling rate, nucleation, diffusion, volatile composition, and viscosity. The development of different crystal morphologies is observed as a function of the cooling rate in many different rock types (i.e., glassy volcanic rocks, and archeometallurgical slags). Crystallization is a two-stage kinetic process that begins with the formation of a nucleus and then continues with the accumulation of ions on it. The shapes of the crystals depend on the degree of undercooling (& UDelta;T), and euhedral crystals, having characteristic forms that reflect their crystallographic internal structure, that grow just below their liquidus temperature. In this study, crystal morphologies in different minerals (e.g., quartz, sanidine, olivine, pyroxene, magnetite, etc.) that had developed in silicic volcanic rocks (spherulites) and slags from ancient mining were investigated and characterized using optical microscopy, X-ray diffraction, and Fourier-transform infrared (FTIR), Raman, and scanning electron microscope-energy dispersive X-ray fluorescence (SEM-EDX) spectroscopic techniques. Depending on the increase in the cooling rate, quartz, feldspar, olivine, pyroxene, and magnetite minerals were found to crystallize in subhedral, skeletal, dendritic, spherical, bow-tie and fibrous forms in glassy volcanic rocks and archeometallurgical slags.Publication Di-Alkyl Adipates as New Phase Change Material for Low Temperature Energy Storage(Springer/Plenum Publishers, 2023) Sequeira, Maria C. M.; Nogueira, Bernardo A.; Caetano, Fernando J. P.; Diogo, Herminio P.; Fareleira, Joao M. N. A.; FAUSTO, RUIThis work is a contribution to the thermal characterization of a selected binary system of two di-n-alkyl adipates that can be used as phase change material for thermal energy storage at low temperatures. The construction of the solid-liquid phase diagram using differential scanning calorimetry (DSC), complemented with Raman Spectroscopy studies for the system composed by diethyl and dibutyl adipates is presented. The solidus and liquidus equilibrium temperatures were determined by DSC for the pure components and 30 binary mixtures at selected molar compositions were used to construct the corresponding solid-liquid phase diagram. The binary system of diethyl and dibutyl adipates presents eutectic behaviour at low temperatures. The eutectic temperature was found at 240.46 K, and the eutectic composition was determined to occur at the molar fraction xdibutyl = 0.46. Additionally, the system shows a polymorphic transition, characteristic of dibutyl adipate, occurring at ca. 238 K, confirmed by optical microscopy. To the best of our knowledge, no reference to the phase diagram of the present system could be found in the literature. Raman spectroscopy was essential to complement the construction of the phase equilibrium diagram, enabling the identification of the solid and liquid phases of the system. Finally, the liquidus curve of the phase diagram was also successfully predicted using a suitable fitting equation, being the root mean square deviation of the data from the correlation equal to 0.54 K. In addition, this fitting operation enabled a correct prediction of the eutectic composition of the system.Publication The Effects of Conformation and Intermolecular Hydrogen Bonding on the Structure and IR Spectra of Flutamide; A Study Based on the Matrix Isolation Technique, Ab Initio and DFT Calculations(Pergamon-Elsevier Science Ltd., 2023) Arman, C.; Balcı, K.; Akkaya, Y.; AKYÜZ, SEVİM; Reaves-Mckee, T.; Frankamp, AH; Coates, JT; Collier, WB; Ritzhaupt, G.; Klehm, CE; Desman, P.In this study, stable conformers of flutamide referred to as an anticancer drug were searched through a relaxed potential energy surface scan carried out at the B3LYP/6-31G(d) level of theory. This was followed by geometry optimization and thermochemistry calculations performed with the HF-SCF, MP2, B3LYP methods and the 6-31G (d), 6-311++G(d,p), aug-cc-pvTZ basis sets for each of the determined minimum energy conformers. The results revealed that flutamide has at least five stable conformers and two of them provide the major contribution to the observed matrix isolation infrared (IR) spectra of the molecule. The effects of conformational variety and intermolecular hydrogen bonding interactions on the observed IR spectra of flutamide were interpreted in the light of the vibrational spectral data obtained for the most stable monomer and dimer forms of the molecule at the same levels of theory. Pulay's "Scaled Quantum Mechanical-Force Field (SQM-FF)" method was used in the refinement of the calculated harmonic wavenumbers, IR intensities and potential energy distributions. This scaling method which proved its superiority to both anharmonic frequency calculations and other scaling methods helped us to correctly interpret the remarkable differences between the matrix IR spectra of flutamide in argon and the condensed phase IR spectra of the molecule in solvents such as KBr, H2O, D2O, ethanol and methanol.Publication Effects of Enol-Imine/Keto-Amine Tautomerism and Conformational Changes on the Electronic Spectra of a Novel 1,2,4-Triazole Ortho-Hydroxyaryl Schiff Base in Different Solvents(Elsevier, 2023) Sıdır, İsa; Sıdır, Yadigar Gülseven; Berber, Halil; FAUSTO, RUIIn this study, a novel o-hydroxyaryl Schiff base bearing the 1,2,4-triazole heterocyclic core, (E)-2-(((4H-1,2,4-triazol-4-yl)imino)methyl)-6-methoxyphenol, was synthesized and structurally characterized by NMR (1H-and 13C-) and IR spectroscopies as well as by Density Functional Theory (DFT) electronic structure calculations. The compound was then investigated by UV-Vis absorbance and fluorescence emission spectroscopies in different solvents. The wavelength shifts observed in the band corresponding to the lowest energy transition in the absorbance spectra upon changing the solvent, as well as in the emission bands observed in the fluorescence spectra (upon excitation at 310 nm) were explained considering the effects of solvent-induced conformational changes and photoinduced enol-imine/keto-amine tautomerism. The interpretation of the experimental results was supported by structural data calculated for the different isomeric forms of the compound and of their electronic spectra in the gas phase and in solvents of different polarity. Solvent effects were also evaluated at the light of the Kamlet-Taft and Catal & PRIME;an solvatochromic models.Publication Evaluation of Anti-Cancer and Anti-Covid-19 Properties of Cationic Pentapeptide Glu-Gln-Arg-Pro-Arg, From Rice Bran Protein and Its D-Isomer Analogs Through Molecular Docking Simulations(Elsevier Science Inc., 2021) Gasymov, Oktay K.; Çelik, Sefa; Ağaeva, Gülşen; AKYÜZ, SEVİM; Keçel-Gündüz, Serda; Qocayev, Niftali M.; Özel, Ayşen E.; Ağaeva, Ülker; Bakhishova, Matanat; Aliyev, Jamil A.Bioactive peptides derived from food proteins are becoming increasingly popular due to the growing awareness of their health-promoting properties. The structure and mechanism of anti-cancer action of pentapeptide GluGln-Arg-Pro-Arg (EQRPR) derived from a rice bran protein are not known. Theoretical and experimental methods were employed to fill this gap. The conformation analysis of the EQRPR pentapeptide was performed first and the obtained lowest energy conformer was optimized. The experimental structural data obtained by FTIR and CD spectroscopies agree well with the theoretical results. D-isomer introduced one-by-one to each position and all D-isomers of the peptide were also examined for its possible anti-proteolytic and activity enhancement properties. The molecular docking revealed avid binding of the pentapeptide to the integrins alpha(5)beta(1) and alpha(IIb)beta(3), with K-d values of 90 nM and 180 nM, respectively. Moreover, the EQRPR and its D-isomers showed strong binding affinities to apo-and holo-forms of M-pro, spike glycoprotein, ACE2, and dACE2. The predicted results indicate that the pentapeptide may significantly inhibit SARS-CoV-2 infection. Thus, the peptide has the potential to be the leading molecule in the drug discovery process as having multifunctional with diverse biological activities.Publication Fourier Transform Infrared Spectroscopy Based Complementary Diagnosis Tool for Autism Spectrum Disorder in Children and Adolescents(MDPI, 2020) ILDIZ, GÜLCE ÖĞRÜÇ; Bayari, Sevgi; Karadağ, Ahmet; Kaygısız, Ersin; Fausto, RuiAutism spectrum disorder (ASD) is a neurodevelopmental disorder that begins early in life and continues lifelong with strong personal and societal implications. It affects about 1%-2% of the children population in the world. The absence of auxiliary methods that can complement the clinical evaluation of ASD increases the probability of false identification of the disorder, especially in the case of very young children. In this study, analytical models for auxiliary diagnosis of ASD in children and adolescents, based on the analysis of patients' blood serum ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) spectra, were developed. The models use chemometrics (either Principal Component Analysis (PCA) or Partial Least Squares Discriminant Analysis (PLS-DA)) methods, with the infrared spectra being the X-predictor variables. The two developed models exhibit excellent classification performance for samples of ASD individuals vs. healthy controls. Interestingly, the simplest, unsupervised PCA-based model results to have a global performance identical to the more demanding, supervised (PLS-DA)-based model. The developed PCA-based model thus appears as the more economical alternative one for use in the clinical environment. Hierarchical clustering analysis performed on the full set of samples was also successful in discriminating the two groups.Publication Graphene-Assisted Chemical Stabilization of Liquid Metal Nano Droplets for Liquid Metal Based Energy Storage(Wiley, 2024) Sanati, Afsaneh L.; Nikitin, Timur; FAUSTO, RUI; Majidi, Carmel; Tavakoli, MahmoudEnergy storage devices with liquid-metal electrodes have attracted interest in recent years due to their potential for mechanical resilience, self-healing, dendrite-free operation, and fast reaction kinetics. Gallium alloys like Eutectic Gallium Indium (EGaIn) are appealing due to their low melting point and high theoretical specific capacity. However, EGaIn electrodes are unstable in highly alkaline electrolytes due to Gallium oxide dissolution. In this letter, this bottleneck is addressed by introducing chemically stable films in which nanoscale droplets of EGaIn are coated with trace amounts of graphene oxide (GO). It is demonstrated that a GO to EGaIn weight ratio as low as 0.01 provides enough protection for a thin film formed by GO@EGaIn nanocomposite against significantly acidic or alkaline environments (pH 1-14). It is shown that GO coating significantly enhances the surface stability in such environments, thus improving the energy storage capacity by over 10x. Microstructural analysis confirms GO@EGaIn composite stability and enhanced electrochemical performance. Utilizing this, a thin-film supercapacitor is fabricated. Results indicate that when coating the EGaIn with GO to EGaIn ratio of 0.001, the areal capacitance improves by 10 times, reaching 20.02 mF cm(-2). This breakthrough paves the way for advanced liquid metal-based thin-film electrodes, promising significant improvements in energy storage applications.Publication Hydrogen Tunneling Exhibiting Unexpectedly Small Primary Kinetic Isotope Effects(Wiley - VCH Verlag GmbH, 2024) Roque, Jose P. L.; Nunes, Claudio M.; Schreiner, Peter R.; FAUSTO, RUIProbing quantum mechanical tunneling (QMT) in chemical reactions is crucial to understanding and developing new transformations. Primary H/D kinetic isotopic effects (KIEs) beyond the semiclassical maximum values of 7–10 (room temperature) are commonly used to assess substantial QMT contributions in one-step hydrogen transfer reactions, because of the much greater QMT probability of protium vs. deuterium. Nevertheless, we report here the discovery of a reaction model occurring exclusively by H-atom QMT with residual primary H/D KIEs. 2-Hydroxyphenylnitrene, generated in N2 matrix, was found to isomerize to an imino-ketone via sequential (domino) QMT involving anti to syn OH-rotamerization (rate determining step) and [1,4]-H shift reactions. These sequential QMT transformations were also observed in the OD-deuterated sample, and unexpected primary H/D KIEs between 3 and 4 were measured at 3 to 20 K. Analogous residual primary H/D KIEs were found in the anti to syn OH-rotamerization QMT of 2-cyanophenol in a N2 matrix. Evidence strongly indicates that these intriguing isotope-insensitive QMT reactivities arise due to the solvation effects of the N2 matrix medium, putatively through coupling with the moving H/D tunneling particle. Should a similar scenario be extrapolated to conventional solution conditions, then QMT may have been overlooked in many chemical reactions.Publication The Importance of Polymers in Medicine and their FTIR and Raman Spectroscopic Investigations(IGI Global, 2023) Çelik, Sefa; AKYÜZ, SEVİM; Özel, Ayşen E.Polymers are macromolecules with a very high molecular weight that are formed as a result of one or more small molecules bonding to each other, typically by covalent bonds. The concept of macromolecules consisting of many repeating units are published in the article titled "Uber Polymerization," which was first published in 1920 by Hermann Staudinger. The idea of polymers, which have been in our lives for a long time, has thus become an important field of study. Polymers are commonly used in tissue engineering because of their properties such as biocompatibility and biodegradability. In addition, polymers have a wide range of applications in tissue regeneration, drug delivery, and wound healing. Polymers have varying structural properties based on their backbone structure, molecular weight, and crystallinity. For this cause, a great deal of study in the medicine has been based on this category of materials. This workfocuses on the importance of polymers in the medicine, 3D printed polymer composites and Fourier transform infrared, and Raman spectroscopic investigations of polymeric structures.Publication Interactions Mechanism of Commonly Used Drugs for the Treatment of COVID-19(Bulletin of the Chemical Society of Ethiopia, 2020) Çelik, Sefa; Demirağ, A. Demet; Özel, Ayşen E.; AKYÜZ, SEVİMIn this study conformation analysis of seven drugs commonly used in the treatment of COVID-19 was performed. The most stable conformers of the drug molecules were used as initial data for docking analysis. Using the Cavityplus program, the probable most active binding sites of both apo and holo forms of COVID-19 main protease enzyme (M-P(ro)) and spike glycoprotein of SARSCoV-2 receptors were determined. The interaction mechanisms of the 7 FDA approved drugs (arbidol, colchicine, dexamethasone, favipiravir, galidesivir, hydroxychloroquine, remdesivir) were examined using the AutoDock Vina program. The six of the seven drugs were found to be more stable in binding to apo form of COVID-19 M-P(ro) and spike glycoprotein. Moreover, a set of molecular mechanics (MM) Poisson-Boltzmann (PB) surface area (SA) calculations on the investigated drugs-protein systems were performed and the estimated binding free energy of remdesivir and the apo form of MP' system was found to be the best. The interaction results of FDA drugs with the apo form of COVID-19 M-P(ro) and spike glycoprotein can play an important role for the treatment of COVID-19.Publication Investigation of Menopause-Induced Changes on Hair by Raman Spectroscopy and Chemometrics(Pergamon-Elsevier Science Ltd., 2022) Brito, Anna Luiza B.; Brueggen, Carlotta; ILDIZ, GÜLCE ÖĞRÜÇ; Fausto, RuiThe ending of estrogen production in the ovaries after menopause results in a series of important physiologic changes, including hair texture and growth. In this study we demonstrate that Raman spectroscopy can be used successfully as a tool to probe menopause-induced changes on hair, in particular when coupled with suitable chemometrics approaches. The detailed analysis of the average Raman spectra (in particular of the Amide I and vS-S stretching spectral regions) of the hair samples of women pre- and post-menopause allowed to estimate that absence of estrogen in post-menopause women leads to an average reduction of similar to 12% in the thickness of the hair cuticle, compared to that of pre-menopause women, and revealed the strong prevalence of disulphide bonds in the most stable gauche-gauche-gauche conformation in the hair cuticle. From the analysis of the vS-S stretching spectral region it could also be concluded that the amount of alpha-helix keratin is slightly higher for post-menopause than for pre-menopause women. A series of statistical models were developed in order to classify the hair samples. Outperforming the traditional PCA-LDA (principal component analysis - linear discriminant analysis) approach, in the present study a GA-LDA (genetic algorithm - linear discriminant analysis) strategy was used for variable reduction/selection and samples' classification. This strategy allowed to develop of a statistical model (L16), which has exceptional prediction capability (total accuracy of 96.6%, with excellent sensitivity and selectivity) and can be used as an efficient instrument for the hair samples' classification. In addition, a new chemometrics approach is here presented, which allows to overcome the intrinsic limitations of the GA algorithm and that can be used to develop statistical models that use GA as the variable reduction/selection method, but superseding its stochastic nature. Three suitable models for classification of the hair samples according to the menopause status of the women were developed using this novel approach (LV17, BLV20 and PLS7 models), which are based on the Fisher's and Bayers' LDA approaches and the PLS-DA method. The followed new chemometrics approach uses the results of a large set of GA-LDA runs over the full data matrix for the selection of the reduced data matrices. The criterion for the selection of the variables is their statistical significance in terms of number of occurrences as solutions of the whole set of GA-LDA runs. (C) 2022 Elsevier B.V. All rights reserved.Publication Investigation of the Magnetocaloric Effect and the Critical Behavior of the Interacting Superparamagnetic Nanoparticles of La0.8Sr0.15Na0.05MnO3(Elsevier Science Sa, 2022) Tozri, A.; Alhalafi, Sh.; Alrowaili, Ziyad A.; Horchani, Mongi; Omri, Aref; Skini, R.; Ghorai, S.; Benali, A.; Costa, Benilde F. O.; ILDIZ, GÜLCE ÖĞRÜÇWe report on structural, magnetic properties of Na-doped La0.8Sr0.15Na0.05MnO3 (LSNMO) nanoparticles (NP) with size about 50 nm elaborated via sol-gel route. The chemical composition was verified using the energy dispersive X-ray analysis (EDAX) and by X-ray photoelectron spectroscopy (XPS). Magnetic characterizations demonstrate that LSMNO exhibits a coexistence of interacting superparamagnetic (ISPM) phase with blocking temperature T-B = 194 K and a ferromagnetic phase with Curie temperature T-C = 255.5 K. At low temperatures, the SPM state undergoes a collective freezing state at T-f = 46 K. the high-temperature regime (well above TC) reveals that NP-LSNMO has a strengthened Griffiths-like phase compared to their bulk counterpart. An itemized investigation of the critical behavior of the material was carried out in the vicinity of T-C. The critical exponents [beta = 0.546(7), gamma = 0.972(6), and delta = 2.94 (5)] were found to be in close agreement with of the mean-field theory. The maximum magnetic entropy change (-Delta(pk)(M)) is about 1.41 Jkg(-1) K-1 and the refrigeration capacity (RC) is 288 Jkg(-1) for a field change of 5 T at T = 215 K. This magnetocaloric response is reasonably high for nanomaterials and, together with its cost-effectiveness, makes NP LSMNO a potential candidate material for active magnetic refrigerators. Besides, the ISPM properties are desirable for hyperthermia applications. Our findings suggest that the magnetic inhomogeneity and the dipolar interaction between the SPM and FM phases in the range T-B < T < T-C are crucial factors in determining the magnetic properties of NP-LSNMO. (C) 2021 Elsevier B.V. All rights reserved.Publication An Investigation on the Structure and Group Vibrations of Balenine Molecule by Matrix Isolation IR Spectroscopy, DFT and MP2 Based Calculations(Pergamon-Elsevier Science Ltd., 2022) Balcı, K.; Akkaya, Y.; Arman, C.; Gören, Y.; AKYÜZ, SEVİM; Hacker, AL; Van Vleet, HJ; Ritzhaupt, G.; Collier, W. B.Stable conformers of neutral balenine were scanned through molecular dynamics simulations and energy minimizations using Allinger's MM2 force field. For each of the found minimum-energy conformers, geometry optimization and thermochemistry calculations were performed by using B3LYP, MP2, G3MP2B3 methods, 6-31G(d), 6-311++G(d,p) and aug-cc-pvTZ basis sets. The calculation results have indicated that balenine has about twenty stable conformers whose relative energies are in the range of 0-9.5 kcal/mol. Three of these are thought to provide the major contribution to matrix isolation IR spectra of the molecule. Our solvent calculations using the polarized continuum model revealed the stable zwitterion structures which are predicted to dominate IR spectra of balenine in water and heavy water (D2O) solvents. Pulay's SQM-FF method was used in scaling of the harmonic force constants and vibrational spectral data calculated for the neutral and zwitterion structures. These refined calculation data together with those obtained from anharmonic frequency calculations enabled us to correctly interpret the matrix isolation IR spectrum of balenine and the tautomerism-based changes observed in its KBr IR and solution (D2O) IR spectra. The results revealed the crucial role of conformation and zwitterionic tautomerism on the structure and vibrational spectral data of the molecule.
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