Seraj Yousef Abed

AN ECONOMETRIC ANALYSIS OF INTERNATIONAL AIR TRAVEL DEMAND IN SAUDI ARABIA

Air traffic analysis is an important task both for airlines and the concerned civil aviation authority. This paper addresses analyzing and forecasting international air travel market in Saudi Arabia using econometric models. In this study an attempt is made to develop several models for the air travel demand with different combinations of explanatory variables utilizing stepwise regression technique. The model with the two variables (i.e., total expenditures and population size) is the most appropriate model to represent the demand for international air travel in Saudi Arabia.

A quantitative comparison of three simulation languages: SLAM, GPSS/H, SIMSCRIPT

Abstract Three simulation languages are quantitatively compared in a manufacturing job shop environment. Both model size and model run length were varied to obtain data on compilation time, execution time. CPU time, memory time and the rate of change of these variables due to changes in the simulation period.

Cell cycle kinetics analysis of Hela cells exposed to aphidicolin: Computer simulation

A computer simulation model was developed and used to analyze the inhibitory effect of aphidicolin on the proliferation of Hela cells. Simulation results were compared with actual experimental results [Pedrali-Noy et al. (1980) Nuc. Acid Res. 8, 377] and were found to be in good agreement. Also, the simulation showed that aphidicolin caused cells to be accumulated at the G1/S boundary and that recruitment and synchrony occurred.

Regression models for estimating survival of patients with non-Hodgkin's Lymphoma

Abstract The life-table method is used for estimating the survivorship of 989 patients treated for non-Hodgkins Lymphoma at King Faisal Specialist Hospital and Research Center in Riyadh, Saudi Arabia. Estimates of various survival measures and their standard errors are obtained. Then, four common probability distributions namely; the exponential, Weibull, Gompertz, and the linear hazard are used to estimate the survivorship function, hazard function and the probability density function. Comparison between the log-likelihood values for the estimated data is also made to choose the best fitting model.

Cell growth simulation (CGS): the design philosophy

Cell Growth Simulation (CGS) is a software package that simulates the growth of cell cultures, and the effects of different types of agents on the cell populations in vitro. It is a stochastic simulation system based on the cell cycle kinetics. Experiments involving DNA synthesis blocking, mitosis inhibition, labelling and cell kill can be simulated by imitating agents such as thymidine, aphidicoline, hydroxyurea, vincristine, vinblistine, colcemid and others. The model to be simulated is described by the user according to his theoretical convictions, The system provides numerous facilities to help the user describe an experiment and examine the simulation results. A menu driven interactive scheme is used to communicate with the user. CGS has a modular structure and its general structure, design philosophy and capabilities are presented. The system has been developed through the cooperation of industrial engineering, cell biology, medical oncology and computer programming disciplines. It is implemented on...

Modeling Demand for Air Travel at Jeddah International Airport: an Empirical Study@@@بناء نموذج لطلب السفر الجوي في مطار جدة الدولي : دراسة تجريبية

The primary objective of the work was to suggest a suitable forecasting modeling demand for air travel at Jeddah International Air- port. A large amount of data was collected to provide the basis for the conclusions. Data on traffic intensity at Jeddah International Airport for a period ranging from 1975 to 1996 was used for the analysis. These voluminous figures were fitted to most forecasting models. Results in- dicate that data in all series are trended but non-seasonal. The growth rate was high in the 70s and fluctuating in early 80s and mid 90s. After the analyses, comparison and cross-checking, the authors ar- rived at the conclusion that the non-linear cubic model was the most suitable one for aviation planning in Jeddah city. An examination of the statistical performance measures calculated for all models conclu- sively points to the usefulness of the non-linear cubic model. A fur- ther extension of the work is possible with the development of a Deci- sion Support System (DSS) based on these models so that the aviation planning authority could use it for decision-making purposes as and when required.

Effect of colcemid on CHO cells progression: computer simulation

A computer model has been constructed to simulate the effects of the mitotic inhibitor colcemid on the Chinese hamster ovary (CHO) cells progression through the cell cycle. The simulation was implemented on personal computer. Colcemid treatment severely inhibits the progression of cells in mitosis and causes enrichment of cells into the M phase of the cell cycle. This blockage in M phase was reversible at the drug concentration used, and cells resumed cycle traverse following colcemid removal without any delay. The drug has no effect on the progression of cells from mitosis to G1 G1 to S, S to G2 and from G2 to mitosis.

A statistical study of prognostic factors influencing survival of patients with non‐hodgkin's lymphoma

Abstract Clinical data are obtained from the Oncology Department at King Faisal Specialist Hospital and Research Center in Riyadh, Saudi Arabia during 1971 to 1989 for 989 patients treated for Non‐Hodgkins Lymphoma. The cases are of different primary sites. The occurence is 227 in the head and neck, 164 gastric and intestinal, 204 in the bone, skin, breast, thyroid gland and CNS and 393 patients had multiple involvement. The patients are clinically staged according to Ann Arbor staging system. The histological material of the patients are graded according to the working formulation. 65% of the patients received combination chemotherapy,19% had surgery, 9 % had radiotherapy, 1% had surgery and chemotherapy, 1% had surgery and radiotherapy and the remaining 5% had a combination of chemotherapy and radiotherapy treatment. Seven factors have been investigated to determine their prognostic significance on survival. The results show that age, sex, initial stage, primary tumor site, histology and response to tr...