Bulunan: 32 Adet 0.001 sn
Koleksiyon [4]
Tam Metin [1]
Yazar [20]
Yayın Türü [2]
Konu Başlıkları [20]
Yayın Tarihi [15]
Dergi Adı [7]
Dil [1]
Yazar Departmanı [1]
Secondary metabolites from Sambucus ebulus

Atay, İrem | Kırmızıbekmez, Hasan | Yeşilada, Erdem | Gören, Ahmet Ceyhan

Other | 2015 | Turkish Journal of Chemistry39 ( 1 ) , pp.34 - 41

Abstract: A new nonglycosidic iridoid, sambulin B (1), was isolated from the methanol extract of Sambucus ebulus L. leaves along with a recently reported new nonglycosidic iridoid, 10-O-acetylpatrinoside aglycone (sambulin A) (2); 2 flavonoids, isorhamnetin-3-O-eta-D-glucopyranoside (3) and isorhamnetin-3-O-rutinoside (4); and a mixture of 2 flavonoids (5), quercetin-3-O-eta-D-glucopyranoside and quercetin-3-O-eta-D-galactopyranoside. Their structures were elucidated by 1-D and 2-D nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) experiments.

Neural Network Based Classification of Melanocytic Lesions in Dermoscopy: Role of Input Vector Encoding

Ertaş, Gökhan

Article | 2018 | Electrica18 ( 2 ) , pp.242 - 248

Melanocytic lesions are the main cause of death from skin cancer, and early diagnosis is the key to decreasing the mortality rate. This studyassesses the role of input-vector encoding in neural network-based classification of melanocytic lesions in dermoscopy. Twelve dermoscopicmeasures from 200 melanocytic lesions are encoded by compact encoding, ACD encoding, 1-of-N encoding, normalized encoding, and rawencoding, resulting in five different input-vector sets. Feed-forward neural networks with one hidden layer and one output layer are designedwith several neurons in the hidden layer, ranging from two to twenty-two for each type of . . .input-vector set, to classify a melanocytic lesion intocommon nevus, atypical nevus, and melanoma. Accordingly, 105 networks are designed and trained using supervised learning and then testedby performing a 10-fold cross validation. All the neural networks achieve high sensitivities, specificities, and accuracies in classification. However,the network with seven neurons in the hidden layer and raw encoded dermoscopic measures as the input vector realizes the highest sensitivity(97.0%), specificity (98.1%), and accuracy (98.0%). The practical use of the network can facilitate lesion classification by retaining the neededexpertise and minimizing diagnostic variability among dermatologists Daha fazlası Daha az


Utku, Feride Sermin | Basaran, Kubra | Sunar, Yagmur | Celebıoglu, Hulya | Kapıcı, Ibrahim

Article | 2017 | Istanbul University Journal of Electrical and Electronics Engineering17 ( 2 ) , pp.3439 - 3443

Mineralized natural protein based novel bone replacement materials are investigated for tissue engineering. Mineralized silk fibroin composite foams and films display excellent biocompatibility. In this study, the biomimetic and electrochemical mineralization of orderly oriented silk fibroin scaffolds was studied. Commercially obtained pure silk woven fabric was boiled in 0.02 M Na2CO3 for 20 min. Calcium phosphate was deposited at 37°C for twenty minutes in seven sequential immersion steps, using 250 mM CaCl2 2H2O and 120 mM K2HPO4, containing 0.15 M NaCl and 50mM TRIS-HCl, pH 7.4, followed by electrochemical treatment in modif . . .ied SBF solution at 40°C at a current density of -25mA/cm2 for 60 min. The amount of biomimetically deposited Ca-P increased with the number of immersion steps. SEM images and XRD analysis of the Ca-P deposit indicated the initial formation of brushite with its monoclinic crystal structure and characteristic peak at 11.76 2?, and electrochemical conversion of brushite to hydroxyapatite on silk after electrochemical cathodization as confirmed by XRD and SEM analysis. Thus, a silk-fibroin-hydroxyapatite composite material prepared as a xenograft consisting of biocompatible components, and easily prepared as an economical bone segment replacement material with highly oriented fibers Daha fazlası Daha az

Square wave voltammetric determination of valproic acid in pharmaceuticalPreparations

Acar, Ebru Türköz | Onar, Atiye Nur

Article | 2016 | Turkish Journal of Chemistry40 ( 1 ) , pp.106 - 116

The electrochemical behavior of valproic acid (VAL) was investigated using square wave voltammetry, cyclicvoltammetry, and sampled direct current polarography and a new square wave voltammetric method was developed fordetermination of VAL in pharmaceutical preparations. VAL showed two reduction peaks at about {0.2 V and {0.8 V vs.Ag/AgCl 3 M KCl with a hanging mercury drop electrode in 0.05 M pH 3.3 Britton{Robinson (BR) buffer. These peakswere named peak I and peak II, respectively. The types of limiting current of both peaks were determined as diffusioncontrolled based on cyclic voltammetry studies. A linear calibration graph was . . .obtained in the range 1.46104{1.0103M. The limit of detection (LOD) and limit of quanti cation (LOQ) were 1.09104M (21.05g/mL) and1.10104M (144.20g/mL), respectively. Recovery studies for the accuracy of the method were performed byadding known amounts of VAL and it was found to be 109.674.85%. The proposed method was successfully appliedto pharmaceutical products on the market Daha fazlası Daha az

Weak penetration and radiation through apertures in conducting bodies of revolution

Yeğin, Korkut

Article | 2009 | Turkish Journal of Electrical Engineering and Computer Sciences17 ( 3 ) , pp.231 - 239

The simplest way to solve for penetration through small apertures in conducting surfaces is to treat the body as a scatterer and determine the interior field as the sum of the incident field and the scattered field contributed by the current induced on the surface of the body. However, it is well known that, if the aperture is very small or if the penetrated field is very weak this method yields very inaccurate results, which, in turn, prohibits proper design of electronic systems, especially for electromagnetic compatibility and interference. Previously, alternative integral equations formulations were proposed to remedy this probl . . .em and applied to two-dimensional conducting cylinders with slots [1–2]. Application of these alternative techniques to threedimensional conducting bodies of revolution (BOR) is studied in this work. In addition, the reciprocity principle is used to recast a weak penetration problem into a weak radiation problem, and it is shown that the alternative formulations useful for weak penetration are also useful for weak radiation. The important features and relative accuracies of each formulation together with numerical results are detailed for mock missile-shape structures Daha fazlası Daha az

Molecular modeling and antimycobacterial studies of Mannich bases: 5-hydroxy-2-methyl-4H-pyran-4-ones

Berk, Barkın | Us, Demet | Öktem, Sinem | Kocagöz, Z. Tanıl | Çağlayan, Berrak | Kurnaz, Işıl Aksan | Erol, Dilek Demir

Article | 2011 | Turkish Journal of Chemistry35 ( 2 ) , pp.317 - 330

The World Health Organization lists tuberculosis among the top 3 leading causes of death from a single infectious agent, and reported cases of multidrug-resistant tuberculosis (MDR-TB) are on the rise. In an attempt to improve MDR-TB drug-directed therapy, we synthesized 11 4-substituted piperazine derivatives of 3-hydroxy-6-methyl-4H -pyran-4-one pharmacophore by reacting 5-hydroxy-2-methyl- 4H-pyran-4-one with suitable piperazine derivatives under Mannich reaction conditions. Inhibitory effects of the 11 compounds on Escherichia coli DNA gyrase were evaluated via DNA gyrase supercoiling assay. The minimum inhibitory concentrations . . . (MIC) of the 11 compounds and 41 compounds from our previous studies against Mycobacterium tuberculosis H37RV were assessed, in vitro, by a broth dilution method. To determine the interaction pattern between active site amino acids and all 52 compounds, homology modeling for the construction of M. tuberculosis DNA gyrase B subunit was performed, followed by a docking study. The data presented here could prove useful in future studies on interaction field analysis and high throughput virtual screening of the derivatives of the 3-hydroxy-6-methyl-4H -pyran-4-one pharmacophore toward the development of more clinically applicable compounds Daha fazlası Daha az

Mannich base derivatives of 3-hydroxy-6-methyl-4H-pyran-4-one with antimicrobial activity

Us, Demet | Berk, Barkın | Gürdal, Ece | Aytekın, Nihan | Kocagöz, Tanıl | Layan, Berrak Çağ | Erol, Dilek Demir

Article | 2010 | Turkish Journal of Chemistry34 ( 3 ) , pp.447 - 456

A series of 3-hydroxy-6-methyl-2-[(substitutedpiperidine-1-yl)methyl]-4H -pyran-4-one structured compounds were synthesized by reacting 5-hydroxy-2-methyl-4H -pyran-4-one with suitable piperidine derivatives using Mannich reaction conditions. Antibacterial activities of the compounds for E. coli ATCC 25922, S. paratyphi ATCC BAA-1250, S. flexneri ATCC 12022, E. gergoviae ATCC 33426, and M. smegmatis ATCC 14468 were assessed in vitro by the broth dilution method for determination of minimum inhibitory concentration (MIC). In addition, their inhibitory effects over DNA gyrase enzyme were evaluated using a DNA gyrase supercoiling assay . . .. All the synthesized compounds showed a MIC value of either 8 or 16 μg/mL for M. smegmatis, whereas minimum to moderate activity was achieved for the others. Those tested in the supercoiling assay had at best a very mild inhibition of the enzyme. This series deserves further attention for testing over Mycobacterium species and topoisomerase II inhibition to develop new lead drugs to treat non-tuberculous mycobacterial infections Daha fazlası Daha az

4H-Pyran-4-one derivatives:; leading molecule for preparation of compounds with antimycobacterial potential

Us, Demet | Gürdal, Ece | Berk, Barkın | Öktem, Sinem | Kocagöz, Tanıl | Çağlayan, Berrak | Erol, Dilek Demir

Article | 2009 | Turkish Journal of Chemistry33 ( 6 ) , pp.803 - 812

A series of 3-hydroxy-6-methyl-2-((4-substitutedpiperazin-1-yl)methyl)-4H-pyran-4-one structured compounds were synthesized by reacting 5-hydroxy-2-methyl-4H-pyran-4-one with suitable piperazine derivatives using Mannich reaction conditions. Antibacterial activities of the compounds for E. coli, S. paratyphi, S. flexneri, E. gergoviae, and M. smegmatis were assessed in vitro by using broth dilution for determination of the minimum inhibitory concentration (MIC). In addition, their inhibitory effects over DNA gyrase enzyme were evaluated using a DNA gyrase supercoiling assay. Among the synthesized compounds; compound 7 showed a 4 &am . . .p;#956;g/mL MIC value for M. smegmatis, whereas the other compounds demonstrated moderate to high activity. Those tested in the supercoiling assay had at best a very mild inhibition of the enzyme. This series deserves further attention for testing over Mycobacterium species and topoisomerase II inhibition to develop new lead drugs Daha fazlası Daha az

Energy savings in simultaneous multi-threaded processors through dynamic resizing of datapath resources

Küçük, Gürhan | Mesta, Mine

Article | 2012 | Turkish Journal of Electrical Engineering and Computer Sciences20 ( 1 ) , pp.125 - 139

Nowadays, all the designers of systems from high-performance servers to battery-operated handheld devices aim for reliability, high-performance and longevity. Central within these aims the issue of processor power consumption is becoming increasingly important. In this study, we aim to adapt our already-provenmethod for single-threaded superscalar processors to simultaneous multi-threaded (SMT) processors for energy savings. The original method focused on resizing datapath resources according to the demands of running applications. To achieve this, the targeted resources are physically divided into multiple partitions, and turned on . . . and off according to the needs of the applications. Since, the energy consumption of the turned-off datapath resources is quite low, as a result, it becomes possible to have great amount of energy savings within a processor. However, special care must be taken when there are multiple threads racing against each other to gain access to shared datapath resources. As a result, our proposed microarchitectural technique achieves 0.5% Instructions Per Cycle (IPC) and 3.2% Total number of instructions Per Cycle (TPC) improvement, while it turns off 45% of the Reorder Buffer (ROB), 59% of the Load-Store Queue (LSQ), 43% of the Issue Queue (IQ), 30% of the integer Physical Register Files (PRF) and, finally, 48% of the floating PRF, on the average across all simulated benchmarks. According to our estimates, the total processor power is reduced by 12%, on the average Daha fazlası Daha az

Design, optimization, and realization of a wire antenna with a 25:1 bandwidth ratio for terrestrial communications

Yeğin, Korkut

Article | 2014 | Turkish Journal of Electrical Engineering and Computer Sciences22 ( 2 ) , pp.371 - 379

Wire antennas can be made wideband if the antenna is loaded with passive elements and connected to a lossless matching network. However, realization of the load component values and matching network can easily become impractical. In this study, using only a surface mount and standard component values, antenna loads and a matching network are optimized using genetic algorithms. The optimized design achieves a 25:1 bandwidth ratio, from 20 MHz to 500 MHz, with a maximum voltage standing wave ratio (VSWR) of 3.5 and minimum system gain of --5 dBi. The antenna system gain at azimuth is taken as the objective function and an exact penalt . . .y function is formulated to take into account the VSWR over the design frequency band. A loaded antenna is built and measured to corroborate the simulations results. The realized antenna is only 0.14 lambda long at 20 MHz Daha fazlası Daha az

A short note on the application of Cholesky matrix factorisation using MATLAB

Keskin, Ali Ümit | Göker, İmran

Article | 2006 | Istanbul University Journal of Electrical and Electronics Engineering6 ( 1 ) , pp.113 - 115

One must first make sure that a given matrix subject to factorization is symmetric, and then use it in Cholesky algorithm, in MATLAB. This may cost machine time to check for symmetry, however, saves much more of it by preventing errors due to inherent structure of the built-in algorithm.

Fundamental noise studies in flame atomic magneto-optic rotation and atomic absorption spectrometry

İnce, Ahmet T. | Snook, Richard D. | Dawson, John B.

Other | 2000 | Turkish Journal of Chemistry24 ( 1 ) , pp.43 - 58

A study of inherent noise sources present in a purpose built flame atomic magneto-optic rotation (AMOR) spectrometer system was carried out with a view to identifying their sources. Two different optical configurations were employed, a crossed polariser and a 45° offset polariser configuration. The offset polariser configuration was operated in both an AMOR and atomic absorption (AA) mode for the noise measurements. Two main interference frequencies were found to occur in all the optical measurement modes. An interference flame feature frequency (15.5 Hz -39.0 Hz) which arose from an "organ-pipe" effect in the gas flow . . . through the flame cooling sheets. The second interference frequency (at 100 Hz) was thought, to arise due to modulation of the analytes magneto-optic properties due to ripple on the electromagnet d.c. power supply. Photon noise and fluctuation noise were found to be present as background noise. The fluctuation noise was dominant at. higher analyte concentrations. The characteristics and origins of fluctuation noise are discussed and investigated for each measurement mode. The noise spectra of the conventional AA measurements were compared with those of the contemporary AMOR measurements, to ascertain any differences in noise power spectra which may affect, the signal-to-noise ratio Daha fazlası Daha az

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