The main goal of this paper is to introduce Durrmeyer modifications for the generalized Szász–Mirakyan operators defined in (Aral et al., in Results Math 65:441–452, 2014). The construction of the new operators is based on a function \(\rho \) which is continuously differentiable \(\infty \) times on \( \left[ 0,\infty \right) ,\) such that \(\rho \left( 0\right) =0\) and \( \inf _{x\in \left[ 0,\infty \right) }\rho ^{\prime }\left( x\right) \ge 1.\) Involving the weighted modulus of continuity constructed using the function \( \rho \), approximation properties of the operators are explored: uniform convergence over unbounded intervals is established and a quantitative Voronovskaya theorem is given. Moreover, we obtain direct approximation properties of the operators in terms of the moduli of smoothness. Our results show that the new operators are sensitive to the rate of convergence to f, depending on the selection of \(\rho .\) For the particular case \(\rho \left( x\right) =x\), the previous results for classical Szász-Durrmeyer operators are captured. 相似文献
Survival of small and medium-sized enterprises (SMEs) increasingly depends on their ability to exploit opportunities in foreign markets. Given their limited resources, exporting is one of the most viable modes of entry into foreign markets for SMEs. The present study is an attempt to contribute to the research that identifies the factors associated with SME export performance. Specifically, the association between top management team demographic composition and SME export performance was examined in an emerging market context and drawing from upper echelons perspective. Focusing on such commonly examined upper echelons attributes as age, education level, and tenure, the present research assessed whether top management team composition distinguished between SMEs in terms of their export levels. Data were collected from 128 SMEs operating in Ankara and Bursa regions of Turkey. Results obtained by a hierarchical regression analysis indicated that SMEs with lower mean industry tenure and higher age separation diversity had higher levels of export performance. 相似文献
The aim of the current study was to design a nucleotide-based radiopharmaceutical which could be labeled with 99mTc and to investigate its radiopharmaceutical efficiency and stability. GHA (glucoheptonate) was used as bifunctional chelate.
GHA was labeled with 99mTc by SnCl2 reduction method first, and then G (guanine) was conjugated with 99mTc-GHA at 90 °C. In order to determine its radiopharmaceutical stability, thin layer radio chromatography (TLRC) and electrophoresis
were employed. In addition, the results were confirmed using high performance liquid radio chromatography (HPLRC). Scintigraphic
imaging was performed on rats with mammary tumors, while tissue distribution was determined on Albino Wistar rats. Labeling
yield was found to be over 95% and the labeled complex maintained its stability during the study period. The lipophilicity
of the 99mTc-GHG was measured and the partition coefficient (logP) of the labeled compound calculated. The results demonstrated that the uptake of 99mTc-GHG (99mTc-glucoheptonate-guanine) reached its maximum at 3 hours p.i. in stomach and intestines. Main way of excretion was renal.
Hepatobiliary excretion was also observed. In conclusion, 99mTc-GHG may be useful as a nucleotide-based radiopharmaceutical for in vivo applications. 相似文献
The aim of the present study was to label acetaminophen (APAP) with I-131 and to determine its radiopharmaceutical potential in rats. Acetaminophen was labeled with I-131 using the iodogen method. The radiochemical purity of (131)I-APAP was determined by RTLC and paper electrophoresis. The labeling yield was 94 +/- 4%. The biodistribution studies of the labeled compound (specific activity; 56.60 GBq/mmol) were performed in male Albino Wistar rats. The uptake of (131)I-APAP in some organs were determined at different time after injection to the rats. The radioactivity in each organ was counted and the percentage of injected activity per gram of tissue weight (%ID/g) for each organ and blood was calculated. (131)I-APAP uptake in the lung, liver, kidneys, pancreas, blood, stomach and some brain region, were observed. Thus, (131)I-APAP may be radiopharmaceutical for the imaging of the brain. 相似文献
In this paper, a numerical approach is described to estimate escape times from attractor basins when a dynamical system is subjected to noise or stochastic perturbations. Noise can affect nonlinear system response by driving solution trajectories to different attractors. The changes in physical behavior can be observed as amplitude and phase change of periodic oscillations, initiation or annihilation of chaotic motion, phase synchronization, and so on. Estimating probability of transitions from one attractor to another, and predicting escape times are essential for quantifying the effects of noise on the system response. In this paper, a numerical approach is outlined where probability transition maps are generated between grids. Then, these maps are iterated to find the probability distribution after long durations, wherein, a constant escape rate can be observed between basins. The constant escape rate is then used to estimate the average escape times. The approach is applicable to systems subjected to low-intensity stochastic disturbances and with long escape times, where Monte Carlo simulations are impractical. Escape times up to \(10^{13}\) periods are estimated without relying on computationally expensive computations.