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    The iterative stein rule estimator of the disturbance variance in a linear regression model when the proxy variables are used
    (Selcuk University Research Center of Applied Mathematics, 2006) Ünal, Deniz; Akdeniz, Fikri
    In case of the existence of the unobservable relevant regressors, a way of estimating the model is to use the proxy variables as regressors. Here we consider the estimator of the disturbance variance in a linear regression model with the proxy variables when the Stein-rule(SR) estimator of this model is used in place of the ordinary least square estimator (OLSE). Our aim is to examine the effect of the proxy variables on disturbance variance in a regression models with proxy variables. For this purpose we define the iterative SRP (SR in a linear regression model with the proxy variables) and iterative PSRP (Positive part SR in a linear regression model with the proxy variables) estimators of the disturbance variance in a regression model with proxy variable and analyze them by using MSE (Mean square error) criterion.
  • Küçük Resim Yok
    Öğe
    Protective effect of L-carnitine in a rat model of retinopathy of prematurity
    (2014) Keleş, Sadullah; Caner, İbrahim; Ateş, Orhan; Çakıcı, Özgür; Saruhan, Fatih; Mumcu, Uğur Yılmaz; Ünal, Deniz
    Aim: To investigate the effects of L-carnitine (LC) on rats with oxygen-induced retinopathy. Materials and methods: The study was conducted on 40 Sprague Dawley rat pups. The rat pups were randomly divided into 4 groups: group 1 (n 10), the healthy control group with intraperitoneal 0.1 mL/day physiological saline injection; group 2 (n 10), exposed to hyperoxygen, did not receive LC but received 0.1 mL/day physiological saline intraperitoneally; group 3 (n 10), exposed to hyperoxygen and received 100 mg/kg/day LC intraperitoneally; group 4 (n 10), exposed to hyperoxygen and received 200 mg/kg/ day LC intraperitoneally. After postnatal day 20, the rat pups were killed and an histological examination was performed on the eyes, in addition to the detection of plasma malondialdehyde (MDA) levels. Results: The retinal and choroidal histopathological changes due to hyperoxygen were less in group 3 and minimal in group 4 compared with group 2. Compared with the healthy control group, the increase in the MDA levels in group 2 was significant (P < 0.05). Compared with group 2 there was a significant (P < 0.05) decrease in the MDA levels in groups 3 and 4. Conclusion: LC has beneficial effects on oxygen-induced retinopathy in rats in terms of histopathological changes and MDA levels.