Efficient hydrogen generation from the NaBH4 methanolysis by waste material: banana peel

Elma Karakaş Duygu,Kaya Mustafa,Horoz Sabit 한국탄소학회 2022 Carbon Letters Vol.32 No.6

The aim and originality of our current study are to use the original biomass (activated carbon) obtained by functionalizing waste banana peels (commonly found in Turkey) with acid in NaBH4 methanolysis and to examine its contribution to the hydrogen generation rate (HGR). Our study consisted of three stages. In the first stage, the optimum conditions were determined by examining the catalyst under parameters such as different acid types, different carbonization temperatures, and different carbonization times. Thus, based on the maximum HGR value, the optimum conditions were determined as H3PO4, 600 °C, and 40 min. In the second step, the effects of parameters such as acid concentration, NaBH4 concentration, catalyst amount, and temperature on HGR were investigated. As a result of methanolysis experiments (condition: catalyst amount: 100 mg, acid amount: 30%, NaBH4 concentration: 2.5%, temperature: 30 °C, carbonization temperature: 400 °C, and carbonization time: 40 min.), the maximum HGR value, the reaction completion time and activation energy were found as 65,625 mLmin−1gcat−1, 0.233 min, and 4.56 kJ/mol, respectively. It was observed that the obtained activation energy was lower than that of some catalysts available in the literature. In addition, the structural and morphological examination of the banana peel (catalyst) with high HGR and low activation energy revealed that the acid functionalization process was successfully carried out.

Properties and Corrosion Resistance of AISI H13 Hot-Work Tool Steel with Borided B4C Powders

Ali Günen,İsmail Hakki Karahan,Mustafa Serdar Karakaş,Bülent Kurt,Yusuf Kanca,Vedat Veli Çay,Murat Yıldız 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9

In this study, the surface of AISI H13 steel was borided with powder blends of B4Cand NaBF4using the powder-pack methodat 800, 900 and 1000 °C for 2, 4 and 6 h. The structural and mechanical characteristics of the boride layers formed on thesurface were characterized using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, 2Dsurface profilometry, microhardness and electrochemical corrosion (3.5 wt% NaCl) tests. The boride layer exhibited a singlephase structure (Fe2B) in samples coated at 800 °C and a dual-phase structure (FeB + Fe2B) at higher boriding temperatures(900 and 1000 °C). The boride layers were compact and crack-free in all boriding conditions. Depending on boridingparameters, the thickness, hardness and average surface roughness (Ra) of the coatings were found to range between 5.81and 102.46 μm, 1635–1915 HV and 0.315–0.650 μm, respectively. The borided AISI H13 steel displayed up to 33.5 timesand 2.4 times higher corrosion resistance than untreated AISI H13 steel and martensitic AISI 431 steel, respectively. Thissuggests potential use of borided AISI H13 steel in the steam turbines and marine applications as an alternative to the morecostly martensitic and duplex stainless steel grades. The corrosion resistance depended on the phase structure (single- ordual-layer), density, thickness and surface roughness of the boride coatings.

Prognostic impact of p16 and p53 gene expressions in stage 1a epithelial ovarian cancer

( Emre Gunakan ),( Yusuf Aytac Tohma ),( Latife Atasoy Karakaş ),( Huseyin Akıllı ),( Asuman Nihan Haberal ),( Ali Ayhan ) 대한산부인과학회 2020 Obstetrics & Gynecology Science Vol.63 No.4

Objective Epithelial ovarian cancer (EOC) is rarely detected at stage 1a. Most of the patients have a good prognosis and there are limited factors that affect their survival. In the present study, we evaluated the p16 and p53 gene expressions of stage 1a EOC patients. Prognostic effects of these gene expressions, as well as those of other factors on short term survival were analyzed. Methods Our study included 29 patients. The specimens of the ovary with cancer were stained for p16 and p53. Gene expressions and other prognostic factors were evaluated. Results The median age of the patients was 51 years (27-84). The mean numbers of dissected pelvic and paraaortic lymph nodes were 27 and 12, respectively. The mean follow-up time was 33.7±18.9 months. During this period, recurrence occurred in two patients. One of the patients had grade 2 mucinous carcinoma and died of the disease at month 12 after the recurrence occurred at month 7. The second patient had clear cell carcinoma and recurrence occurred at month 34. p16 and p53 gene expressions or other factors were not associated with overall survival (OS) or diseasefree survival in the short term. The lower p16 positivity rate in the non-clear cell group was found to be statistically significant (P=0.003). Both p53 and p16 positivity rates were higher in the high-grade carcinoma. Conclusion The levels of none of the common prognostic factors, including those of p16 and p53 gene expression, were associated with the progression-free survival or OS of stage 1a in the short term. Appropriate surgical staging and non-omission of subclinical metastases seem to be of central importance.

Pack-Boriding of Monel 400: Microstructural Characterization and Boriding Kinetics

Ali Günen,Mourad Keddam,Azmi Erdoğan,Mustafa Serdar Karakaş 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

Monel 400 was pack-borided in the temperature range of 1173–1273 K for exposure times of 2–6 h. The boride layersproduced on the surface of the alloy were examined by scanning electron microscopy and phase identification was carriedout by X-ray diffraction. The topmost layer on the borided Monel 400 was compact and contained the Ni2Bphase whilethe diffusion zone contained grain boundary precipitates of borides. Boride layers of 35–290 μm thickness and 1002–1476HV0.025hardness were obtained. SEM observations revealed a smooth interface between the boride layer and the diffusionzone. A kinetic model based on the integral method was applied to investigate the kinetics of Ni2Blayer. The boron activationenergy in the Ni2Blayer was estimated as equal to 300.7 kJ mol−1. An experimental validation of the model was madeby comparing the experimental layer thicknesses obtained, after boriding at 1198 K for 1 and 3 h, with predicted values.

Is There an Association between Restless Legs Syndrome and Urticaria?

Serpil Tuna,Sevil Alan,Nehir Samancı,Ayşe Akman Karakaş 대한의학회 2016 Journal of Korean medical science Vol.31 No.5

Restless legs syndrome (RLS) is a disease characterized by the urge to move the legs and sleep disturbances. Similarly, chronic spontaneous urticaria (CSU) is a dermatological disease characterized by pruritus and sleep disorders. In this study, we aimed to determine the prevalence and severity of RLS in patients with chronic spontaneous urticaria (CSU) and to compare the quality of sleep of patients with and without RLS in the CSU group using the Pittsburgh Sleep Quality Index. A total of 130 patients with CSU and 100 healthy controls were included in this study. The frequency of RLS, frequency of sleep disturbances, and average score of RLS in patients with CSU were statistically significantly higher than control groups (respectively P = 0.008, P = 0.009, P = 0.004). Subjective sleep quality, sleep latency and habitual sleep efficiency scores in patients with RLS were statistically significantly higher than patients without RLS (respectively P = 0.016, P = 0.007, P = 0.035). We claimed that pruritus of urticaria may decrease the quality of sleep in patients with RLS and it may trigger and worsen the restless legs syndrome. Furthermore, RLS and CSU may share a common etiology.

A consistent FEM-Vlasov model for hyperbolic cooling towers on layered soil under unsymmetrical wind load

Karakas, Ali I.,Ozgan, Korhan,Daloglu, Ayse T. Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.6

In this paper, the analysis of hyperbolic cooling tower on elastic subsoil exposed to unsymmetrical wind loading is presented. Modified Vlasov foundation model is used to determine the soil parameters as a function of vertical deformation profile within subsoil. The iterative parameter updating procedure involves the use of Open Application Programming Interface (OAPI) feature of SAP2000 to provide two way data flow during execution. A computing tool coded in MATLAB employing OAPI is used to perform the analysis of hyperbolic cooling tower with supporting columns over a hollow annular raft founded on elastic subsoil. The analysis of such complex soil-structure system is investigated under self-weight and unsymmetrical wind load. The response of the cooling tower on elastic subsoil is compared with that of a tower that its supporting raft foundation is treated as fixed at the base. The results show that the effect of subsoil on the behavior of cooling tower is considerable at the top and bottom of the wall as well as supporting columns and raft foundation. The application of a full-size cooling tower has demonstrated that the procedure is simple, fast and can easily be implemented in practice.

A Comparison between the Thermomechanical and Structural Changes in Textured PET Yarns after Superheated Steam and Dry Heat Treatment

Karakas, Hale-Canbaz The Korean Fiber Society 2004 Fibers and polymers Vol.5 No.1

PET yarns textured at different texturing conditions were treated with superheated steam or dry heat at different temperatures for different times. The effects of the treatment conditions on the thermomechanical and structural changes of the yarn were examined by shrinkage, X-ray diffraction and birefringence measurements. With increase in superheated steam temperature, the crystalline orientation factor and birefringence decreased, whereas crystal size increased. Dry heat treatment had a smaller effect on shrinkage and structural properties in comparison with superheated steam treatment. The additional shrinkage after texturing process was investigated. The effect of heat-setting in both media was more significant at $200^{\circ}C$. The time dependence of the properties was not linear.

A novel reference model for dental scanning system evaluation: analysis of five intraoral scanners

Irina Karakas-Stupar,Nicola Ursula Zitzmann,Tim Joda 대한치과보철학회 2022 The Journal of Advanced Prosthodontics Vol.14 No.2

PURPOSE. The aim of this in vitro study was to investigate the accuracy (trueness and precision) of five intraoral scanners (IOS) using a novel reference model for standardized performance evaluation. MATERIALS AND METHODS. Five IOSs (Medit i500, Omnicam, Primescan, Trios 3, Trios 4) were used to digitize the reference model, which represented a simplified full-arch situation with four abutment teeth. Each IOS was used five times by an experienced operator, resulting in 25 STL (Standard Tessellation Language) files. STL data were imported into 3D software (Final Surface®) and examined for inter- and intra-group analyses. Deviations in the parameter matching error were calculated. ANOVA F-test and Kruskal-Wallis test were applied for inter-group comparisons (α = .05); and the coefficient of variation (CV) was calculated for intra-group comparisons (in % ± SD). RESULTS. Primescan (matching error value: 0.015), Trios 3 (0.016), and Trios 4 (0.018) revealed comparable results with significantly higher accuracy compared to Medit i500 (0.035) and Omnicam (0.028) (P < .001). For intra-group comparison, Trios 4 demonstrated the most homogenous results (CV 15.8%). CONCLUSION. The novel reference model investigated in this study can be used to assess the performance of dental scanning technologies in the daily routine setting and in research settings.

Acute Dystonia after Using Single Dose Duloxetine: Case Report

Gorkem Karakas,Ugurlu,Sinay Onen,Deniz BayindirLi,Ali Caykoylu 대한신경정신의학회 2013 PSYCHIATRY INVESTIGATION Vol.10 No.1

Duloxetine is a balanced and potent serotonin and noradrenaline reuptake inhibitor which is known to be effective in depression and anxiety disorders. The common adverse effects include dry mouth, nausea, insomnia, somnolence, dizziness and constipation. Reported adverse effects of the extra pyramidal symptoms (EPS) are rare. In this case, a patient who suffered from acute dystonia, after only one dose of 30 mg duloxetine is presented.

A consistent FEM-Vlasov model for hyperbolic cooling towers on layered soil under unsymmetrical wind load

Ali I. Karakas,Korhan Ozgan,Ayse T. Daloglu 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.22 No.6

In this paper, the analysis of hyperbolic cooling tower on elastic subsoil exposed to unsymmetrical wind loading is presented. Modified Vlasov foundation model is used to determine the soil parameters as a function of vertical deformation profile within subsoil. The iterative parameter updating procedure involves the use of Open Application Programming Interface (OAPI) feature of SAP2000 to provide two way data flow during execution. A computing tool coded in MATLAB employing OAPI is used to perform the analysis of hyperbolic cooling tower with supporting columns over a hollow annular raft founded on elastic subsoil. The analysis of such complex soil-structure system is investigated under self-weight and unsymmetrical wind load. The response of the cooling tower on elastic subsoil is compared with that of a tower that its supporting raft foundation is treated as fixed at the base. The results show that the effect of subsoil on the behavior of cooling tower is considerable at the top and bottom of the wall as well as supporting columns and raft foundation. The application of a full-size cooling tower has demonstrated that the procedure is simple, fast and can easily be implemented in practice.