On positive solutions of a reciprocal differenceequation with minimum } \iitem{}{\sc By and

Cengiz \c Cinar,Stevo Stevic,Ibrahim Yal\c cinkaya 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.17 No.1-2

In this paper we consider positive solutions of the following difference equation xn+1 = min A xn , B xn−2 , A,B>0. We prove that every positive solution is eventually periodic. Also, we present here some results concerning positive solutions of the difference equation xn+1 = min( A xnxn−1...xn−k , B xn−(k+2)....xn−(2k+2)), A,B>0.

Micro-CT – a digital 3D microstructural voyage into scaffolds: a systematic review of the reported methods and results

Ibrahim Fatih Cengiz,Joaquim Miguel Oliveira,Rui L. Reis 한국생체재료학회 2018 생체재료학회지 Vol.22 No.4

Background: Cell behavior is the key to tissue regeneration. Given the fact that most of the cells used in tissue engineering are anchorage-dependent, their behavior including adhesion, growth, migration, matrix synthesis, and differentiation is related to the design of the scaffolds. Thus, characterization of the scaffolds is highly required. Micro-computed tomography (micro-CT) provides a powerful platform to analyze, visualize, and explore any portion of interest in the scaffold in a 3D fashion without cutting or destroying it with the benefit of almost no sample preparation need. Main body: This review highlights the relationship between the scaffold microstructure and cell behavior, and provides the basics of the micro-CT method. In this work, we also analyzed the original papers that were published in 2016 through a systematic search to address the need for specific improvements in the methods section of the papers including the amount of provided information from the obtained results. Conclusion: Micro-CT offers a unique microstructural analysis of biomaterials, notwithstanding the associated challenges and limitations. Future studies that will include micro-CT characterization of scaffolds should report the important details of the method, and the derived quantitative and qualitative information can be maximized.

Investigation of Mass Transfer of Ozone in Jet Loop Reactor

Cengiz Ibrahim,Değermenci Nejdet,Yildiz Ergun,Barlak Melahat Semin 한국화학공학회 2024 Korean Journal of Chemical Engineering Vol.41 No.4

Mass transfer of ozone in a jet loop reactor was investigated in this study. Diff erent parameters such as ozone gas concentration, gas fl ow rate, circulation fl ow rate, and spray nozzle diameter were examined for their eff ect on mass transfer. In experiments with ozone gas concentrations ranging from 3.83 to 17.1 g/m 3 , the K L a values remained unchanged, with an average of 28.7 ± 2.2 h −1 . As the ozone gas concentration increased, the saturation values of ozone in the liquid phase also increased. Experiments were carried out with gas fl ow rates ranging from 50 to 250 L/h in the jet loop reactor, and increasing gas fl ow rates increased the K L a value up to fi ve times. When the eff ect of the liquid circulation fl ow rate was examined for a spray nozzle diameter of 15.5 mm, increasing the fl ow rate from 40 L/min to 80 L/min increased the K L a value by approximately 41%. However, the power consumed per reactor volume for this process increased 8 times and reached 2.65 kW/m 3 . K L a values in the JLR vary between 6.1 and 37.3 h −1 depending on operating parameters and it has been concluded that it performs well compared to its counterparts.

ON POSITIVE SOLUTIONS OF A RECIPROCAL DIFFERENCE EQUATION WITH MINIMUM

QINAR, CENGIZ,STEVIC, STEVO,YALQINKAYA, IBRAHIM 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.17 No.1

In this paper we consider positive solutions of the following difference equation $$x_{n+l}\;=\;min[{\frac{A}{x_{n}},{\frac{B}{x_{n-2}}}],\;A,B\;>\;0$$. We prove that every positive solution is eventually periodic. Also, we present here some results concerning positive solutions of the difference equation $$x_{n+l}\;=\;min[{\frac{A}{x_{n}x_{n-1}{\cdots}x_{n-k}},{\frac{B}{x_{n-(k+2)}{\cdots}x_{n-(2k+2)}}],\;A,B\;>\;0$$.

Comparison of Three Different Induction Regimens for Nasopharyngeal Cancer

Kertmen, Neyran,Aksoy, Sercan,Cengiz, Mustafa,Yazici, Gozde,Keskin, Ozge,Babacan, Taner,Sarici, Furkan,Akin, Serkan,Altundag, Kadri,Gullu, H. Ibrahim Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.1

Background: The standard treatment of local advanced nasopharyngeal cancer is chemoradiotherapy. There is a lack of data concerning induction therapy. In this study we retrospectively examined patients treated with induction therapy and chemoradiotherapy. Materials and Methods: Locally advanced nasopharyngeal cancer patients treated between 1996 and 2013 in our clinic were included in the study. Three different induction regimens were administered to our patients in different time periods. The regimen dosages were: CF regimen, cisplatin $50mg/m^2$ 1-2 days, fluorouracil $500mg/m^2$ 1-5 days; DC, docetaxel $75mg/m^2$ 1 day, cisplatin $75mg/m^2$ 1 day; and DCF, docetaxel $75mg/m^2$ 1 day, cisplatin $75mg/m^2$ 1 day, 5-Fu $750mg/m^2$ 1-5 days. Most of the patients were stage III (36.4%) and stage IV (51.7%). Results: Median follow-up time was 50 months (2-201 months). Three-year progression-free survival (PFS) was 79.3%, and 5-year PFS 72.4% in all patients. Three-year overall survival (OS) was 87.4% and 5-year OS 76% in all patients. In terms of induction therapies, 3-year OS was 96.5% in the DCF group, 86.6% in the DC group and 76.3% in the CF group (p=0.03). Conclusions: There was no significant differences in response rate and PFS between the three regimens. OS in the DCF group was significantly higher than in the other groups. However, this study was retrospective and limited toxicity data were available; the findings therefore need to be interpreted with care.

Ifosfamide and Doxorubicin Combination Chemotherapy for Recurrent Nasopharyngeal Carcinoma Patients

Dede, Didem Sener,Aksoy, Sercan,Cengiz, Mustafa,Gullu, Ibrahim,Altundag, Kadri Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.5

Background: We assessed the efficacy and toxicity of ifosfamide and doxorubicin combination chemotherapy (CT) regimen retrospectively in Turkish patients with recurrent or metastatic nasopharyngeal carcinoma (NPC) previously treated with platinum-based chemotherapy. Methods: A total of thirty patients who had received cisplatin based chemotherapy/chemoradiotherapy as a primary treatment received ifosfamide 2500 $mg/m^2$ days 1-3, mesna 2500 $mg/m^2$ days 1-3, doxorubicin 60 mg/m2 day 1 (IMA), repeated every 21 days. Eligible patients had ECOG PS< 2, measurable recurrent or metastatic disease, with adequate renal, hepatic and hematologic functions. Results: Median age was 47 (min-max; 17-60). Twenty six (86.7 %) were male. Median cycles of chemotherapy for each patient were 2 (range:1-6). Twenty patients were evaluable for toxicity and response. No patient achieved complete response, with nine partial responses for a response rate of 30.0% in evaluable patients. Stable disease, and disease progression were observed in five (16.7%) and six (20.0%) patients, respectively. Clinical benefit was 46.7%. Median time to progression was 4.0 months. Six patients had neutropenic fever after IMA regimen and there were one treatment-related death due to tumor lysis syndrome in first cycle of the CT. No cardiotoxicity was observed after CT and treatments were generally well tolerated. Conclusion: Ifosfomide and doxorubicin combination is an effective regimen for patients with recurrent and metastatic NPC. For NPC patients demonstrating failure of cisplatin based regimens, this CT combination may be considered as salvage therapy.

Increased Neutrophil/Lymphocyte Ratio in Patients with Depression is Correlated with the Severity of Depression and Cardiovascular Risk Factors

Esra Aydin Sunbul,Murat Sunbul,Omer Yanartas,Fatma Cengiz,Mehmet Bozbay,Ibrahim Sari,Huseyin Gulec 대한신경정신의학회 2016 PSYCHIATRY INVESTIGATION Vol.13 No.1

ObjectiveaaChronic inflammation is associated with cardiovascular (CV) risk factors and psychiatric disorders. The neutrophil to lymphocyte ratio (NLR) has been investigated as a new biomarker for systemic inflammatory response. The aim of the study is to investigate the relation of NLR with severity of depression and CV risk factors. MethodsaaThe study population consisted of 256 patients with depressive disorder. Patients were evaluated with the Hamilton Rating Scale for Depression (HAM-D). Patients were classified into four groups according to their HAM-D score such as mild, moderate, severe, and very severe depression. Patients were also evaluated in terms of CV risk factors. ResultsaaPatients with higher HAM-D score had significantly higher NLR levels compared to patients with lower HAM-D score. Correlation analysis revealed that severity of depression was associated with NLR in depressive patients (r=0.333, p<0.001). Patients with one or more CV risk factors have significantly higher NLR levels. Correlation analysis revealed that CV risk factors were associated with NLR in depressive patients (r=0.132, p=0.034). In logistic regression analyses, NLR levels were an independent predictor of severe or very severe depression (odds ratio: 3.02, 95% confidence interval: 1.867–4.884, p<0.001). A NLR of 1.57 or higher predicted severe or very severe depression with a sensitivity of 61.4% and specificity of 61.2%. ConclusionaaHigher HAM-D scores are associated with higher NLR levels in depressive patients. NLR more than 1.57 was an independent predictor of severe or very severe depression. A simple, cheap white blood cell count may give an idea about the severity of depression.