Photovoltaic characteristics of Au/PVA (Bi-doped)/n-Si Schottky barrier diodes(SBDs) at various temperatures

H.G. Çetinkaya,H. Tecimer,H. Uslu,S. Altındal 한국물리학회 2013 Current Applied Physics Vol.13 No.6

The charge conduction properties of the Au/PVA (Bi-doped)/n-Si Schottky barrier diodes (SBDs) were investigated using currentevoltageetemperature (IeVeT) measurements in dark and under various illumination levels. For this purpose, the main diode parameters such as reverse-saturation current (Io),zero-bias barrier height (FBo), ideality factor (n), series resistance (Rs) and shunt resistance (Rsh) of diode were obtained as function of temperature and illumination level. Experimental results show that all of these electrical parameters are strong functions of illumination and temperature. The change in all electrical parameters becomes more important at low temperatures and illumination levels. While the n value decreases with increasing temperature and illumination level, FBo value increases. The fill factor (FF = Vm·Im/Voc·Isc) values were obtained as 0.34 at 80 K and 0.40 at 320 K under 50 Wand these values are near to a photodiode. Therefore, the fabricated diode can be used as a photodiode in optoelectronic applications. The forward bias IeV characteristics of the diode have also been explained by the space charge limited current (SCLC) model.

Frequency and voltage dependence of dielectric properties and electric modulus in Au/PVC þ TCNQ/p-Si structure at room temperature

A. Kaya,Ö. Vural,H. Tecimer,S. Demirezen,S¸ . Altındal 한국물리학회 2014 Current Applied Physics Vol.14 No.3

Au/PVC þ TCNQ/p-Si structure was fabricated and real and imaginary parts of the dielectric constant ( 3 0 , 3 00), loss tangent (tand), and the real and imaginary parts of the electric modulus (M0 , M00) and ac conductivity (sac) of this structure have been investigated in wide frequency a range of 1 kHze5 MHz at room temperature. All of these parameters were found strong function of frequency and voltage especially in the inversion and depletion regions at low frequencies due to interfacial polarization and charges at interface states (Nss). The decrease in 3 0 and 3 00 with increasing frequency indicated that the interfacial dipoles have less time to orient themselves in the direction of the alternate field. While the value of M0 increase with increasing frequency and reach a maximum, M00 shows a peak and the peak position shifts to higher frequency with increasing applied voltage. The ln(sac) vs ln(u) plot of the structure for 0.5 V has three linear regions (I, II and III) with different slopes which correspond to low, intermediate and high frequency ranges, respectively. Such behavior of ln(sac) vs ln(u) plot indicated that there are three different conduction mechanisms in the Au/PVC þ TCNQ/p-Si structure at room temperature.

Can Megestrol Acetate Induce Thrombosis in Advanced Oncology Patients Receiving Chemotherapy?

Ordu, Cetin,Pilanci, Kezban Nur,Koksal, Ulkuhan Iner,Okutur, Kerem,Saglam, Sezer,Tecimer, Coskun,Demir, Gokhan Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.23

Background: Megestrol acetate (MA) is a steroid origin medicine often used for control of cachexia in oncologic palliative care. Thrombosis is a common problem in oncology patients. One question is whether MA can cause thrombosis. This retrospective, registry-based analysis was therefore conducted to assess thrombotic processes in oncology patients using MA concurrent with chemotherapy. Materials and Methods: Data on oncology patients at the metastatic stage using MA were obtained from the archives of our center. Outcomes of patients were evaluated for thromboembolic events (VTEs) during treatment. Results: Ninety-seven oncology patients with a median age of 62 (33-84) years were included. During the median follow-up of 17 months, 58 (59.8%) died leaving 39 (31.2%) still alive. Median overall survival (OS) was 19 months (6-180). Mean time of MA use was 8.69 months(${\pm}3.53$), with a median dose of 160mg (range 160-480mg). Eleven VTEs were detected after MA use, 4 of these in pancreatic cancer cases. The patients with thrombosis non-significantly had worse OS, than those without thrombosis (p=0.106). Conclusions: This trial revealed that the 11.3% of all patients developed thrombosis,who had been treated with MA and chemotherapy concomittantly. There was no statistically significant difference regarding to occurrence of thrombotic process, among the patients receiving different chemotherapy regimens with MA concomittantly. Pancreatic cancer seemed to be related to thrombosis rather than MA use.

Predictive and Prognostic Significance of p27, Akt, PTEN and PI3K Expression in HER2-Positive Metastatic Breast Cancer

Okutur, Kerem,Bassulu, Nuray,Dalar, Levent,Aydin, Kubra,Bozkurt, Mustafa,Pilanci, Kezban Nur,Dogusoy, Gulen Bulbul,Tecimer, Coskun,Mandel, Nil Molinas,Demir, Gokhan Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.7

Background: The phosphatidylinositol 3'-kinase/Akt (PI3K/Akt) pathway is a key regulator for HER2-overexpressing breast cancer, but data about whether activation of PI3K/Akt is associated with poor prognosis and resistance to trastuzumab therapy is controversial. In this study we investigated predictive and prognostic significance of expression of p27, Akt, PTEN and PI3K, which are components of the PI3K/Akt signaling pathway, in HER2-positive metastatic breast cancer (MBC), retrospectively. Materials and Methods: Fifty-four HER2-positive MBC patients who had received first-line trastuzumab-based therapy were recruited for the study group. All of the patient's breast tissue samples were examined for p27 and Akt expression. In addition, twenty-five patients with sufficient amount of tumor tissue were also examined for PTEN and PI3K expression. p27, Akt, PTEN and PI3K were evaluated by immunohistochemistry and their relationship with patient demographic features, tumor characteristics, response to trastuzumab-based treatment and survival outcomes were analyzed. Results: p27, Akt, PTEN and PI3K were positive in 25.9%, 70.4%, 24% and 96% of the cases, respectively. Nomne were significantly associated with response to trastuzumab and time to progression (TTP). A trend toward statistical significance for longer overall survival (OS) was found for PTEN-positive patients (p=0.058); there was no significant relationship between the other immunohistochemical variables and OS. When we analyzed groups regarding co-expression, the PTEN-negative/Akt-negative group had a significantly lower objective response rate (ORR) (20% vs 80%, p=0.023) and the PTEN-negative/p27-negative and PTEN-negative/Akt-negative groups had significantly lower median OS compared to other patients (26.4 months vs 76.1 months, p=0.005 and 25.6 months vs 52.0 months, p=0.007, respectively). Conclusions: p27, Akt, PTEN and PI3K expression is not statistically significantly associated with ORR, TTP and OS, individually. However, the combined evaluation of p27, Akt and PTEN could be helpful to predict the response to trastuzumab-based therapy and prognosis in HER2-positive MBC.

Vitamin D Levels in Patients with Breast Cancer: Importance of Dressing Style

Alco, Gul,Igdem, Sefik,Dincer, Maktav,Ozmen, Vahit,Saglam, Sezer,Selamoglu, Derya,Erdogan, Zeynep,Ordu, Cetin,Pilanci, Kezban Nur,Bozdogan, Atilla,Yenice, Sedef,Tecimer, Coskun,Demir, Gokhan,Koksal, G Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.3

Background: Vitamin D deficiency is a potentially modifiable risk factor that may be targeted for breast cancer (BC) prevention. It may also be related to prognosis after diagnosis and treatment. The aim of our study was to determine the prevalence of vitamin D deficiency as measured by serum 25-hydroxy vitamin D (25-OHD) levels in patients with BC and to evaluate its correlations with life-style and treatments. Materials and Methods: This study included 186 patients with stage 0-III BC treated in our breast center between 2010-2013. The correlation between serum baseline 25-OHD levels and supplement usage, age, menopausal status, diabetes mellitus, usage of bisphosphonates, body-mass index (BMI), season, dressing style, administration of systemic treatments and radiotherapy were investigated. The distribution of serum 25-OHD levels was categorized as deficient (<10ng/ml), insufficient (10-24 ng/ml), and sufficient (25-80 ng/ml). Results: The median age of the patients was 51 years (range: 27-79 years) and 70% of them had deficient/insufficient 25-OHD levels. On univariate analysis, vitamin D deficiency/insufficiency was more common in patients with none or low dose vitamin D supplementation at the baseline, high BMI (${\geq}25$), no bisphosphonate usage, and a conservative dressing style. On multivariate analysis, none or low dose vitamin D supplementation, and decreased sun-exposure due to a conservative dressing style were found as independent factors increasing risk of vitamin D deficiency/insufficiency 28.7 (p=0.002) and 13.4 (p=0.003) fold, respectively. Conclusions: The prevalence of serum 25-OHD deficiency/insufficiency is high in our BC survivors. Vitamin D status should be routinely evaluated for all women, especially those with a conservative dressing style, as part of regular preventive care, and they should take supplemental vitamin D.