Ramdhan Ramdhan - Academia.edu (original) (raw)

Papers by Ramdhan Ramdhan

European Physical Journal A, 1998

Beta decay of 58Zn has been studied for the first time. A new laser ion-source concept has been u... more Beta decay of 58Zn has been studied for the first time. A new laser ion-source concept has been used to produce mass-separated sources for beta and gamma spectroscopy. The half-life of 58Zn was determined to be 86(18) ms. Comparisons are made with previous data from charge-exchange reactions. Our Gamow–Teller strength to the 1+ state at 1051 keV excitation in 58Cu agrees well with the value extracted from a recent (3He, t) study. Extensive shell-model calculations are presented.

Macromolecular Chemistry and Physics, 2003

European Physical Journal A, 2003

The beta-decay of the N = Z, even-even nucleus 72Kr has been studied at the ISOLDE PSB facility a... more The beta-decay of the N = Z, even-even nucleus 72Kr has been studied at the ISOLDE PSB facility at CERN. Measurements of βγ and βγγ coincidences have enriched the decay scheme of the daughter nucleus 72Br with 27 new low spin levels. A more precise half-life of T 1/2 = 17.1(2) s has been determined. Strong feeding to the 72Br ground state is established yielding an unambiguous J π = 1+ assignment for this state. Candidates for the 72Br g.s. wave function are discussed in the framework of a self-consistent deformed mean-field calculation with SG2 Skyrme force and pairing correlations. A search for beta-delayed particle emission was made and an upper limit of 10-6 for this decay branch obtained. The cumulated experimental level density of 1+ states has been fitted with the constant temperature formula. The comparison indicates that most likely all 1+ levels up to 1.2 MeV have been observed in this investigation. The corresponding nearest-neighbour level spacing does not follow a Poisson distribution. The Gamow-Teller strength distribution is compared, in terms of nuclear deformation, with different calculations made in the framework of the quasiparticle random phase approximation.

Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2006

In recent years the k 0 -NAA method has been applied and developed at the 15 MW Es-Salam research... more In recent years the k 0 -NAA method has been applied and developed at the 15 MW Es-Salam research reactor, which includes: (1) the detection efficiency calibration of γ-spectrometer used in k 0 -NAA, (2) the determination of reactor neutron spectrum parameters such as α and f ...

Plant Molecular Biology, 2010

We describe here the isolation of a novel gene, designated AlSAP, from A. littoralis in a first s... more We describe here the isolation of a novel gene, designated AlSAP, from A. littoralis in a first step to exploit the potential of this halophyte grass as a genetic resource to improve salt and drought tolerance in plants and, particularly, in cereals. The Aeluropus genome contains a single AlSAP gene which has an intron at its 5’UTR. Sequence homology analysis showed that the AlSAP protein is characterized by the presence of two conserved zinc-finger domains A20 and AN1. AlSAP is induced not only by various abiotic stresses such as salt, osmotic, heat and cold but, also by abscisic acid (ABA) and salicylic acid (SA). Tobacco plants expressing the AlSAP gene under the control of the duplicated CaMV35S promoter exhibited an enhanced tolerance to abiotic stresses such as salinity (350 mM NaCl), drought (soil Relative Water Content (RWC) = 25%), heat (55°C for 2.5 h) and freezing (−20°C for 3 h). Moreover, under high salt and drought conditions, the transgenic plants were able to complete their life cycle and to produce viable seeds while the wild-type plants died at the vegetative stage. Measurements of the leaf RWC and of the root and leaf endogenous Na+ and K+ levels in AlSAP transgenic lines compared to wild-type tobacco, showed an evident lower water loss rate and a higher Na+ accumulation in senescent-basal leaves, respectively. Finally, we found that the steady state levels of transcripts of eight stress-related genes were higher in AlSAP transgenic lines than in wild-type tobacco. Taken together, these results show that AlSAP is a potentially useful candidate gene for engineering drought and salt tolerance in cultivated plants.

International Journal of Chemical Kinetics, 2008

A dynamic kinetic model for the oxidation of phenol in water by an UV/H2O2 process is developed. ... more A dynamic kinetic model for the oxidation of phenol in water by an UV/H2O2 process is developed. The model is based on the elementary chemical and photochemical reactions, initiated by the photolysis of hydrogen peroxide into hydroxyl radicals. The model is validated by using experimental data obtained from the open literature for an actual UV/H2O2 process. Using those data and the developed kinetic model, kinetic rate constants for phenol intermediates, catechol and hydroquinone, are estimated. Moreover, the optimum initial hydrogen peroxide concentration is estimated by means of the validated model. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 40: 34–43, 2008

Hyperfine Interactions, 2000

Resonance ionization laser ion source (RILIS) technique has been used in the β-decay studies of 5... more Resonance ionization laser ion source (RILIS) technique has been used in the β-decay studies of 59Mn and 58Zn. The importance of the RILIS for production of these elements is discussed. The properties of the low-lying levels of the studied nuclei are discussed.

Journal of Radioanalytical and Nuclear Chemistry, 2009

The k 0-standardization method of NAA is known as one of the most remarkable progress of NAA with... more The k 0-standardization method of NAA is known as one of the most remarkable progress of NAA with its many advantages. Recently, our laboratory is highly involved in various areas of application of k 0-NAA. This paper focuses on the application of the k 0-NAA method in Nutritional and Health-Related Environmental field. Tobacco holds a leading position among different commodities of human consumption. The adverse health effects of toxic and trace elements in tobacco smoke on smokers and non-smokers are a special concern. In the present study, the concentration of 24 trace elements in cigarette tobacco of five different brands of Algerian and American cigarettes have been determined by k 0-based INAA method. The results were compared with those obtained for samples from Iranian, Turkish, Brazilian and Mexican cigarettes tobacco. To evaluate the accurate of the results the SRM IAEA-140/TM was executed. The analytical results showed that the relative error of most of the elements was less than 10%.

Polymer Engineering and Science, 2009

The purpose of this work is to evaluate a new tetra-functional peroxide initiator and offer compa... more The purpose of this work is to evaluate a new tetra-functional peroxide initiator and offer comparisons with a di-functional peroxide commonly used in the production of controlled-rheology polypropylene (CRPP) resins. CRPP resins have been produced by reactive processing in a batch mixer by using various equivalent amounts of a tetra-functional and a conventional di-functional peroxide at two different temperatures. At a lower processing temperature (200°C), the chain length of CRPP decreases with increasing initiator concentration of the di-functional initiator, while in the case of tetra-functional initiator system, the change of chain length is larger than that in the di-functional initiator system. At a higher temperature (230°C), the observation is reversed. The molecular weight reduction increases with initiator concentration level for the tetra-functional initiator, while the di-functional initiator causes larger reduction in the molecular weight without any obvious relation to the initiator concentration level. Rheological measurements show results consistent with those from gel permeation chromatography (GPC). The observations are explained based on the competition between chain scission and chain extension caused by the single and multiple radicals generated from the initiators. No evidence of architectural change in the CRPP molecules such as branching and crosslinking has been observed in both GPC and rheological measurements. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Polymer Bulletin, 2006

This investigation examines the use of a tetrafunctional peroxide initiator in the bulk free radi... more This investigation examines the use of a tetrafunctional peroxide initiator in the bulk free radical homopolymerization of butyl acrylate and vinyl acetate. Rate of polymerization, molecular weights and in certain cases, gel fraction data were collected for selective experiments and compared to the results obtained with a monofunctional counterpart. In order to avoid the formation of insoluble gel material, further experiments were completed with varying concentrations of a chain transfer agent. Experimental results showed that when used at identical concentrations, the tetrafunctional initiator produced a faster rate in the polymerization of both butyl acrylate and vinyl acetate compared to the monofunctional initiator. Without the use of a chain transfer agent, runs with butyl acrylate produced significant amounts of gel material isolated by Soxhlet extraction. For a particular reaction time, the tetrafunctional initiator produced higher levels of gel compared to its monofunctional counterpart. When a chain transfer agent was used, the molecular weights were determined by its concentration and in turn, initiator functionality did not have an impact. In the polymerization of vinyl acetate, similar observations were made and no discernable difference could be seen between the molecular weight results of samples produced with either initiator.

Macromolecular Reaction Engineering, 2007

Canadian Journal of Chemical Engineering, 1998

A model consisting of three partial non-linear differential equations for describing the humidity... more A model consisting of three partial non-linear differential equations for describing the humidity and temperature of a thin sheet of material and of the temperature of the air flow as a function of time and position in an infrared dryer was reduced to a model more adaptable to direct digital control. To begin with the original model was discretized along the length of the dryer and then linearized. Models of orders ranging from 12 to 72 were analyzed for controllability and observability. Using Moore's method, the models thus obtained were further reduced to a controllable state space model of order 5 that produced satisfactory results and for which stability was preserved. Simulated open loop responses of the reduced model to discrete perturbations in emitter electrical power, inlet humidity and velocity of the web, produced satisfactory dynamic and steady-state responses when compared to responses of the original model subjected to similar perturbations. The steady-state responses showed absolute errors for humidity and temperature of the web less than 1.3% [g water/100 g] and 2.2°C, respectively.Un modèle décrit par trois équations différentielles partielles non-linéaires pour l'humidité et la température d'une nappe mince ainsi que la température de l'air en fonction du temps et de la position dans un séchoir infrarouge a été réduit à un modèle mieux adaptable à des fins de commande numérique. Le modèle original fut tout d'abord discrétisé suivant la longueur du séchoir puis linéarisé. Des modèles d'ordre 12 à 72 furent analysés sur les plans de la contrǒla-bilité et de l'observabilité. Les modèles d'état furent réduits davantage par la méthode de Moore afin d'obtenir un modèle d'ordre 5 pouvant produire des résultats satisfaisants tout en conservant la stabilité du modèle réduit. Des simulations de la réponse de ce modèle en boucle ouverte à des échelons dans la puissance électrique alimentée aux émetteurs radiants, dans l'humidité de la nappe entrant au séchoir ainsi que dans la vitesse de défilement de la nappe, indiquèrent des réponses satisfaisantes en régimes transitoire et permanent lorsque comparées aux réponses du modèle original soumis aux mêmes perturbations. Ainsi, en régime permanent, les erreurs absolues pour l'humidité et la température de la nappe à la sortie du séchoir furent inférieures à 1.3% [g eau/100g] et 2.2°C respectivement.

International Journal of Chemical Reactor Engineering, 2004

ABSTRACT

Physical Review Letters, 1996

Clinical Biochemistry, 2003

The present investigation was designed to distinguish prostate cancer and benign prostate hyperpl... more The present investigation was designed to distinguish prostate cancer and benign prostate hyperplasia by lectin-prostate specific antigen (PSA) binding. The quantitative precipitin method of concanavalin A (Con A)-carbohydrate interaction was explored with the serum PSA of patients suffering from prostatic complications. The carbohydrate content in the precipitate after binding of Con A with serum PSA of prostate cancer was significantly lower than that of benign prostate hyperplasia. This may be due to altered sugar chain structure or less glycosylation of PSA in prostate cancer. We conclude that a serum value &amp;amp;amp;lt;3.0 microg/ml of the carbohydrate content of Con A-PSA precipitate indicates strong suspicion for prostate cancer and this cut off level is effective in reducing the rate of unnecessary biopsies in men with total PSA value between 4.0 to 10.0 ng/ml.