Ali Gelir

Istanbul Technical University · Department of Physics Engineering

Pulsed electromagnetic fields (PEMF) have been used in bone fracture healing for many years. However, it is still not clear which frequencies are more effective. Therefore, the aim of this study was to investigate the effect of single frequency of 4 Hz and a package of multiple frequencies (220 Hz, 727 Hz, 880 Hz and 10 kHz) on bone fractures of ra...

The determination of the sequence of two intersecting lines is still an ongoing and important issue in questioned document examination. In literature, scanning electron microscopy, optical profilometry, laser profilometry, and video reflectance spectroscopy were used for analyzing the intersecting lines. In this study, a cheap and easy-to-operate 3...

A new technique based on machine learning algorithms was introduced to detect internal wood defects. This technique relies on analyzing segmented propagation rays of stress waves and successfully generates the tomographic images of the defects by using the stress wave velocity. Utilizing a dual-stage methodology, the initial phase involves ray segm...

During the Covid-19 pandemic, one of the best means of personal protection was using face masks. In this context, the World Health Organization has declared the attempts to produce masks inactivating airborne virus species a welcome initiative. This preliminary study aimed to prove that airborne germs passing through a mask filter cartridge can be...

Solid‐state electrolytes such a further novel finding is going to have great importance because of the disadvantages of liquid electrolytes such as electrochemical instability, low ion selectivity, and interface contact. It is anticipated that the use of solid‐state electrolytes including supercapacitors (SCs) will become widespread with decreasing...

Upcycling of electronic waste is the efficient strategy to minimize the negative effect on environment. In the present study, e-waste (originating from small household appliances) was upcycled into the metal contented pyrolytic carbon (C-WPCB) through a simple pyrolysis without activation or any other additional processes. After crushing and fracti...

The motion of the ion pairs under the applied electric field is an important phenomenon in the storage properties of the capacitive devices. In this study, two different molecules, 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt hydrate (P4) and tetra-alkyl ammonium bromide (TAAB), were used as ionic groups in the PVA gel electrolytes. The counte...

Ahşaptaki stres dalgası hızının analiz edilmesi ve ahşap iç kusurlarının görüntülerinin oluşturulması amacıyla yeni bir algoritma önerilmiştir. Algoritma iki sensör arasında çizilen hız ışınını, eliptik komşuluk tekniğini kullanan bir ışın bölüntüleme (segmentasyon) yöntemi ile bölüntülendirilir. Yöntem ışınların elips biçimindeki etki alanlarının...

The spectral properties of the molecules depend on the matrix in which the interactions with other molecules inside the matrix affect the vibrational and rotational modes of the molecule. In this study, an absorption-based system was designed to show how the absorbance properties of the glucose change in polyacrylamide (PAAm) hydrogel when compared...

Supercapacitors (SC) with ionic liquid bis(trifluoromethanesulfonyl)imide (TFMS) trapped polyacrylamide (PAAM) hydrogel separator between graphene deposited nickel and copper foam electrodes were designed and assembled in CR2032 coin cell. The symmetric and asymmetric SCs were named as G‐NiF/G‐NiF, G‐CuF/G‐CuF, and G‐NiF/G‐CuF where G‐NiF, and G‐Cu...

Pen pressure is one of the important elements of handwriting and questioned document analysis which is also crucial to recognize forgery. In this paper, we present a new, non-contact, non-destructive, and relatively inexpensive technique to measure the width of the grooves made by the writing. Results demonstrate a clear difference in measured groo...

One of the challenging problems to solve in the design of high‐performance supercapacitors (SCs) is converting the surface of the electrodes to porous nature. Therefore, this study is aimed to increase the surface area of the NiZn electrodes by using a fast and low‐cost technique which is based on alloying/dealloying the metals. Nickel/Zinc (NiZn)...

Permanent facial scars cause serious trauma because the person has to live with a scar which s/he cannot easily hide. Conspicuous scar tissue will have a negative impact on psychology depending on how much importance they give to their appearance. Because of this reason, it is evaluated as an aggravated form of punishment in Turkish Criminal Law. I...

A hydrogel-based anodization system has been proposed, for the first time in the literature to our knowledge, to perform anodization. Here, the electrolyte solution is trapped inside the hydrogel, which makes the anodization process safer for the operators and environment. In addition, trapping the ions inside the hydrogel increases the reaction ra...

Pen pressure is one of the important elements of handwriting and questioned document analysis which is also crucial to recognize forgery. In this paper, we present a new, non-contact, nondestructive, and relatively inexpensive technique to measure the width of the grooves made by the writing. Results demonstrate a clear difference in measured groov...

The spectral properties of the molecules depend on the matrix in which it is present. The interaction of the molecule with the solute molecules affects the vibrational and rotational modes of the molecule. In this study, an absorption-based system was designed to show how the absorbance properties of glucose change in polyacrylamide hydrogel, and t...

Quantum dots (QDs) are significant fluorescent materials for energy transfer studies with phthalocyanines (Pcs) and phthalocyanine (Pc) like biomolecules (like chlorophylls). Especially, carbon based QDs are used in numerous studies concerning energy transfer studies with chlorophylls, but the number of studies concerning energy transfer between ph...

Electrochemical properties of porous nickel (Ni) foam, electrodeposited zinc (Zn) on Ni foam (Ni–Zn) and electrodeposited reduced graphene oxide (rGO) on Ni–Zn foam electrodes (Ni–Zn-rGO) in 6 M KOH electrolyte were investigated. Cyclic voltammetry (CV) and galvanostatic charge–discharge cycling (GCD) techniques were used to carry out the redox int...

In conventional e / m experiments performed in undergraduate laboratories, generally a simple mechanical ruler is used to measure the radius of the circular trajectory of the electrons. But, the measurement error in this technique is mostly big and varies from one student to another. As an alternative to a mechanical ruler, we proposed a more accur...

Optical transmittance and electrical properties of polystyrene (PS)/reduced graphene oxide (rGO) composites were studied. Photon transmission technique was used to monitor the optical transmittance and two‐/four‐probe methods were used for the electrical conductivity measurements. Two separate experimental sets were prepared. In the first set, the...

New organometallic chemosensors which are based on triad molecules, ferrocenyl naphthoquinone linearly/angularly fused crown ethers (Fc–cnq–1a and Fc–cnq–1b) bearing ferrocene, quinone, and crown ether functional groups together, were synthesized and utilized for selective sensing trace amount of Be²⁺ ion (5.41 μM) among other metal cations. The UV...

A novel porphyrin-BODIPY dyad, where BODIPY acts as the central antenna, linked via the Sonogashira coupling reaction, and a novel porphyrin-o-carborane-BODIPY triad, where both porphyrin and BODIPY are covalently attached to the o-carborane, have been synthesised and characterised. X-ray crystallography confirmed a V-shaped triad molecule. Detaile...

Steady state photoluminescence technique is proposed for the measurement of the diffusion of oxygen into porous silicon (PS). In this work, the PS layers on n-type Si substrates were prepared by anodic etching in hydrofluoric (HF) acidic solution at a dc current under white light illumination. The PS layers with three different pore sizes (0.7, 1.9...

In this study, UV-visible(UVV) technique was used to probe the evolution of optical transmission during the film formation from composites of polystyrene (PS) latex particles and poly acrylamide (PAAm) films annealed by the infrared radiative heating (IRH) and convectional heating. Activation energies corresponding to the void closure and the inter...

The effect of washing with acidic and basic solutions on the internal structure (fluctuations in the density and the size of the polymer clusters through the gel) of the imprinted and the random PNIPA (polyN-isopropylacrylamide) hydrogels has been studied by using steady-state fluorescence technique, swelling kinetics and SEM images. When the gel i...

In this study, an ion conducting polymeric hydrogel (ICPH) is synthesized, characterized and used as a matrix for trapping the electrolyte solution to suppress the deterioration of cathode electrodes for dye-sensitized solar cells (DSSCs). Polymeric hydrogels are synthesized as free radical cross-linking co-polymerization of acrylamide (AAm) and me...

The present invention relates to a polymeric gel based anodic oxidation system (1) which is developed to realize the anodic oxidation process with a faster, safer and more compact system and essentially comprises at least one fixed platform (2) which carries the material to be subjected to anodic oxidation process, at least one polymeric gel layer...

In this study, poly(N-isopropylacrylamide) hydrogel is used as a matrix for synthesizing zinc oxide (ZnO) nanoparticles in the porous regions of the gel. When the gelation is completed, OH - ions of potassium hydroxide were diffused into the gel in which zinc acetate molecules were trapped previously during the gelation. The size of the nanoparticl...

The fluorescence spectra of the hydrophilic pyrene derivative 8-hydroxy-1,3,6-pyrenetri-sulfonate (pyranine) is firmly connected to the degree of ionization of the 8-hydroxyl group and hence to the pH of media, in the range of 0<pH<5. Once entrapped in a polyacrylamide (PAAm) hydrogel, pyranine does not readily leak out of the gel. The fluorescence...

In this study, the effect of the infrared radiative heating (IRH) was investigated on the film formation from composites of polystyrene (PS) latex particles and poly vinyl alcohol (PVA). The films were prepared as a pure PS and a mixture of PS and PVA particles at equal compositions at room temperature and they were annealed at elevated temperature...

Anodic oxidation is an electrochemical process used to increase the thickness of the natural oxide layer on the surface of a metal under an applied potential. In the traditional anodization studies, highly ordered pore structures can be obtained in acidic electrolytes, but this process takes a very long time such as hours or days. In addition, the...

In this study, Polyacrylamide (PAAm) hydrogels with different crosslinking molarity, such as 1/2, 3/2, 1, 6/4, 2 fold of stoichiometric ratio, synthesized by free radical polymerization. Synthesized hydrogels were used as hydrogel-based electrolyte which swollen in a suitable solvent was proposed for anodic oxidation of aluminum. It was aimed to in...

The effect of the internal morphology of polyacrylamide hydrogel as an electrolyte on the anodic oxidation of aluminum, which can be used for the rectification of current, was studied. Comparing with traditional electrolytes, the chemical reactions between the aluminum and the free ions (H+ and OH−) occur more effectively due to the trapping of the...

In Figure 1 current-potential characteristics of Polyacrylamide (PAAm) hydrogel-based electrolyte, sandwiched between platinum-platinum electrodes and platinum-aluminum electrodes, are represented. As seen from this figure when the platinum-platinum electrodes are used no rectification is observed but for the platinum-aluminum electrodes a consider...

Current-Potential (I-V) characteristics of Polyacrylamide (PAAm) hydrogel electrolyte and aluminum interface were studied. When the polyacrylamide hydrogel is used as filler between the parallel plate electrodes of the platinum, the I–V plots are symmetric on the contrary when a platinum electrode is replaced with aluminum; the I-V plots are asymme...

Introduction Experimental Methods Polymerization and Gelation Kinetics Sol–Gel Transition and Universality Discussion Imprinting the Gels Heterogeneity of Hydrogels Ionic p-Type and n-Type Semiconducting Gels Conclusions References

Metal-free, zinc (II) and nickel(II) phthalocyanines (3–5) with a 1-pyrenylmethoxy substituent on each benzo group were prepared from 4-(1-pyrenylmethoxy)phthalonitrile (2). The new compounds have been characterized by elemental analyses, IR, UV/vis, mass and 1H NMR spectroscopy. The electronic spectra exhibit an intense π–π∗ transition of pyrene u...

Multiple point interactions of pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt) fluoroprobe with the polymer chains during the free-radical polymerization of acrylamide (AAm) was studied using the steady state fluorescence measurements and also computer simulation based on Monte Carlo method. In recent literature it has been shown...

Polyacrylamide (PAAm)-Cobalt(II)acetate (Co) composite materials were synthesized with and without pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt; POH) anionic fluoroprobe having a reactive group, OH, and three ionic groups, SO, as peripheral. Magnetization and fluorescence measurements showed that addition of POH molecules into...

In this study, a new approach for in situ monitoring of the monomer conversion based on the chemical interaction of a fluoroprobe, pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt), with polymer chains during the free radical crosslinking copolymerization of acrylamide/bisacrylamide system (AAm/Bis) has been developed. Recently, we...

Poly(acrylamide-co-N,N′-methylenebisacrylamide) gels were synthesized in the presence of pyranine fluoroprobe (trisodium 8-hydroxypyrene-1,3,6-trisulfonate). Pyranine binds to polymer chains through its OH group via radical addition. Thus, the final gels were doped with the pyranines having SO ions as side groups and Na+ as counter-ions. The swelli...

Co-doped plain gels (PAAm) were prepared with and without pyranine fluoroprobe (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt; POH), which have a OH- reactive group and three SO-3 ionic groups. Magnetization and fluorescence measurements were used for characterization of the gels. It was observed that both the plain gel itself and the gel...

We have studied the multiple-point interactions of the pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt; 3sPyOH) fluoroprobe with polymer chains during the free-radical polymerization of acrylamide (AAm) by using the steady state fluorescence measurements. We observed a considerable blue shift from 515nm to 406nm in the emission spe...

New dioxomolybdenum(VI) complexes were prepared by reacting S-methyl/allyl-4-phenyl-thiosemicarbazones of 2-hydroxy-1-naphthaldehyde (L 1 H2 and L 2 H2) and [MoO2(acac)2] in methyl, ethyl and propylalcohols. In the complexes the doubly deprotonated ligands are coordinated to molybdenum as tridentate ONN-donors through phenolic-oxygen, azomethine-...

Real-time fluorescence measurements have been developed for measuring the fractal dimension d_{f} and critical exponents gamma and beta simultaneously during the sol-gel transition of acrylamide bisacrylamide cross-linking copolymerization. We observed that d_{f} passes through a minimum value of approximately 2.5 at a critical time t_{c} and cross...

A new approach based on fluorescence quenching of a chromophore, pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt, POH), was established for monitoring the synthesis of the pyranine-substituted phthalonitrile derivative POPht. 4-Nitrophthalonitrile binds to the POH through nitro elimination, by means of a nucleophilic aromatic subst...

Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide (PAAm) hydrogels during the swelling process. For the first time four distinct peaks (each corresponding to a different swelling stage) in the conductivity of the neutral gel...

A novel method based on the steady state fluorescence technique was used to study the sol–gel transition in the free radical crosslinking reaction between styrene (St) and divinyl benzene (DVB) with 2,2′-azobisisobutyronitrile (AIBN) as initiator. N-(4-(pyrenyl methylene)-oxycarbonyl phenyl)maleimide (Py-MI) was used as a fluorescence probe. The po...

The movements of the North Anatolian Fault Zone (NAFZ) caused two devastating earthquakes within an 87-day interval, epicentered on Gölcük-Izmit (17 August, 1999) and Düzce-Bolu (12 November, 1999). The Kuzuluk geothermal area (KGA) is located in the middle of the epicenters and the distance between the geothermal area and the fault zone is less th...