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Periodicals - LEBANESE SCIENCE JOURNAL VOL.5, NO.1, 2004
Natural and Environmental Sciences
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Nutrient Fluxes from Sediments of the Northern Gulf of Aqaba
under Various Anthropogenic Activities
Mohammed Rasheed
Fluxes of inorganic nutrients and dissolved inorganic carbon (DIC)
from the sediments to the water column was investigated in sites
with various anthropogenic activities. Lab incubations of sediments
collected from four different sites were carried out under controlled
conditions. The sites were Marine Science Station (MSS), two industrial,
Phosphate Loading Berth (PLB) and Industrial complex (IC) and one
tourist site at Hotel Areas (H). Sediments at the MSS site were
composed mainly of carbonates while at the other sites, silicate
represented the dominant mineral. Fluxes of different solutes were
estimated from linear regressions of concentrations over incubation
time. Fluxes of ammonium, phosphate and dissolved inorganic carbon
(DIC) were higher for MSS sediments compared to fluxes for H, PLB,
and IC sediments (4.1, 1.7, 1.7 fold for ammonium, 3.3, 3.6, 1.6
fold for phosphate, and 1.2, 1.4, 1.2 fold for DIC respectively).
This was interpreted by the high permeability and the carbonate
content of the MSS sediments. Despite the higher organic content
in the PLB sediments, lower flux rates were estimated. This was
attributed to the refractory type (low degradable) of the organic
matter in the PLB sediments compared to a labile (degradable) organic
matter in the MSS sediments. These results demonstrated the probable
importance of the sediments as a sink for organic material and as
a suitable degradation environment for organic deposits. Back
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Spatial and Temporal Variations in Surface Zooplankton Biomass Distribution
in the Gulf of Aqaba, Red Sea
Tariq Al-Najjar
Surface zooplankton biomass (>150 µm) were examined in six
coastal stations and one offshore station along the Jordanian sector
of the Gulf of Aqaba during the period from January to December 2002.
The spatial variations of the total zooplankton biomass among stations
were not significant. Meanwhile, the temporal differences among months
were highly significant. Zooplankton biomass was highest in autumn
and winter (October - March) 19.34±3.4 mg .dry weight .m-3
and the average concentrations were lowest during summer (June - September)
5.45±0.20 mg .dry weight .m-3.
Size fractions >500 µm were dominating the sampled biomass
and represented 70 % of the total biomass. This was followed by the
size fraction 500-250 µm which was represented by 21 %. The
remaining fraction was for the 250-150 µm . Back
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Potato Cyst Nematodes Globodera spp. in Lebanon - Occurrence and Distribution
Said K. Ibrahim, Halim Abi Saad and Nisrin Mousa
The potato cyst nematodes (PCN) Globodera pallida (Stone) and G. rostochiensis
(Wollenweber) are economically important pests and distributed worldwide.
In Lebanon, the potato crop is economically important and cultivated
on a large scale. The current study confirms the recent discovery
of the potato cyst nematode G. rostochiensis in Lebanon and demonstrated
its distribution throughout the country. All 204 soil samples collected
from 38 different locations were infested with PCN. Of the samples
tested 72.5% contained live eggs. The population density ranged between
0.18-4.1 cyst/g soil and 0.13 -15.5 eggs/g soil. Of the infestation
found, 76.1% had a population density of less than 10 eggs/g soil.
The PCR results confirmed the presence of the potato cyst nematode
G. rostochiensis in Lebanon. The three set PCR primers readily identified
field samples in a single PCR reaction. PCR amplification of G. rostochiensis
gave a 265 base pair (bp) fragment, while G. pallida had a 434 bp
fragment. The origin of this infestation is unkown. No G. pallida
was found in the samples tested. The results of the occurrence and
distribution of G. rostochiensis in each area are discussed. Back
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Assainissement de la Pomme de Terre Infectée par le Virus PVY
NTN par Culture de Méristèmes
L. Chalak, A. Elbitar, W. Masaad, E. Choueiri
Ce travail a consisté en une mise au point technique d’un
protocole d’assainissement de 3 variétés de pommes
de terre Xantia, Odessa et Burren cultivées au Liban et infectées
par une souche du virus Y de la pomme de terre (PVYNTN)
et ceci par la culture de méristèmes. Les cultures ont
été établies sur le milieu de Murashige et Skoog
(1962) dépourvu de régulateurs de croissance avec des
taux de reprise variant de 89 à 99% selon les variétés.
Le test ELISA, effectué sur l'ensemble des têtes de clones
régénérés à partir de méristèmes,
n'a décelé aucun virus. L'élimination du virus
a été confirmée plus tard au niveau des plantes
acclimatées en serre, aussi bien par test ELISA que par transmission
mécanique sur tabac. Back
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Assessing Soil Degradation by Landuse-Cover Change in Coastal Lebanon
Talal Darwish, Ghaleb Faour and Mohamad Khawlie
Change in landuse is rapid in Lebanon straining its narrow coastal
strip. Chaotic urban expansion in the last forty years resulted in
consumption of prime soils and degradation of most productive lands.
This study aims to show such expansion in Tripoli, the country’s
second largest city of 61.5 km2, and to evaluate the impact
of landuse change on soil sealing and degradation by integrating remote
sensing and GIS techniques. It will gear to more optimal landuse planning
based on assessing the result of chaotic landuse change. Social and
economic soil functions were involved and soil capability and land
suitability compared. Quantifying land cover/use change in the pilot
area was arrived at through analysis of multitemporal sources using
airborne-based detailed topographic maps (1:20000 scale) from 1962
and satellite imagery IRS-1C, 5-meter resolution from 2000. The topographic
maps contain detailed information on land use, like agriculture and
type of forest with corresponding borderlines, urban areas with real
geometric shapes and other info. This allowed identifying and grouping
the data and comparison with that gathered from the high-resolution
satellite images.
The resultant change showed an increase of 208% of urban area with
a decrease of 35% in agricultural lands. Secondary forest and shrubs
replaced the orchards on the abandoned lands. Concerning land capability,
32% of class 1 (prime land) and 26% of class 2 land, i.e. 971 ha,
were converted into urban area. Obviously, urban expansion occurred
at the expense of rare fertile soils with citrus orchards of the coastal
plain like Fluvisols, Luvisols and Cambisols belonging to the most
productive agricultural land.
Major structural changes in landuse between 1962 and 2000 occurred
in the agricultural and urban sectors. Analyzing current landuse pattern,
in view of requirements for sustainability, shows that about 10% of
prime lands were properly used. Overall, only 22.6% of land is fairly
used, while 46% is poorly used and 31.4% is misused. Providing a proper
management of water resources, the geographically isolated southeast
area with productive lands currently allocated for low-income olive
monoculture could be used for more balanced agricultural production.
Water harvesting and management will also provide adequate irrigation
water for perurban agriculture . Back
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Basic Sciences, Engineering and Technology
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Fractal Dimension of Transdermal-Delivery Drug Models
Francisco Torrens
Fractal percolating paths that exist in porous membranes are used
to deliver drugs. For a homologous series of phenyl alcohols, the
fractal dimension D is calculated as a model for transdermal-delivery
drugs. Our program TOPO is used for the calculation of the solvent-accessible
surface As, which is denoted by the centre of a probe,
which is allowed to roll on the outside while maintaining contact
with the bare molecular surface S. As depends on the probe
radius R. D is calculated as D=2-d(log As)/d(log R)
. For the phenyl alcohols, the quadrupole moment Θ is trebled.
The hydrophobic contribution to As is doubled while its
hydrophilic part remains constant. D increases 12%. The values of
all the geometric descriptors and topological indices are in agreement
with reference calculations. The 1-octanol-water partition coefficient
log P increases. The molar concentration of organic compounds
necessary to produce a 1:1 complex with bovine serum albumin via equilibrium
dialysis, log 1/C increases. The hydrophile-lipophile balance
(HLB) decreases. These results are in line with reference calculations.
The linear correlation between D and θ, and various non linear
correlations between D,log P, log 1/C , and HLB point not only
to a homogeneous molecular structure of the phenyl alcohols but to
the ability to predict and tailor drug properties. The latter is nontrivial
in pharmacology. Back
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Conséquences du Photovieillissement
sur le Comportement d’un Film Polyéthylène PEBd
F. Benkhenafou, M. Chikh-Bled, J. M. Lefebvre, M. Nait-Abdelaziz,
A. El-Achari
Le vieillissement photo-oxydatif du polyéthylène (PE)
est un mécanisme complexe d’oxydation radicalaire en
chaîne, amorcé par la photolyse des groupes du type hydropéroxyde
et des groupes de type carbonyles.
L’évolution structurale progressive du polymère
qui en découle se traduit au niveau macromoléculaire
par des réactions de coupure de chaînes et par des réactions
de réticulation.
Ces phénomènes entraînent une variation des propriétés
mécaniques et physico-chimiques qui conduit à une fragilisation
catastrophique en terme de diminution de l’allongement et de
l’énergie à la rupture, diminutions intervenant
après une période d’incubation plus ou moins longue.
La compréhension de l’évolution structurale du
polymère est approfondie par l’intermédiaire de
l’application des tests mécaniques statiques (contrainte
et allongement à la rupture, module de Young ; D.S.C (température
de transition vitreuse Tg, paramètre énergétique
ΔH) ; infra-rouge (densité optique, taux de cristallinité)
. Back
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Behaviour of Space Charge Distribution in Air-Aged Samples of Poly(Methyl
Methacrylate)
H. Guermazi, S. Guermazi, Y. Mlik,
S. Agnel, A. Toureille
Polymeric materials are used in various environments in which they
are subjected to different stresses. In this setting, samples of poly(methyl
methacrylate) were treated in aqueous salt solutions at 100 °C
for 20 min. The Thermal Step Method (T S M) and the Thermally Stimulated
Discharge Current method (T S D C) were used to characterize the electrical
state of these samples.
In order to study the influence of ageing process on polarization
and space charge distribution, air-aged samples were left for one
year on aluminium paper at room temperature. The TSM and the TSDC
measurements were then applied on aged samples.
The comparison between space charge distributions and TSDC currents
measured before and after ageing, shows that the ageing process affects
the space charge distribution.
PACS numbers: 81.90.+c, 81.40.Tv, 77.22.Ej . Back
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Etude Générale des Transformations Conservant le
Tenseur Métrique de l'Espace de Minkowski
S. Melki, M. Kobeissi, I. Rachidi
On donne les conditions satisfaites par une transformation qui conserve
le tenseur métrique de l'espace de Minkowski. En résolvant
ces conditions, on montre que la transformation considérée
s'écrit sous la forme d'une transformation de Lorentz suivie
ou précédée d'une rotation d'espace. Back
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Calculations of Different Physical Parameters by 2D Simulations
of the Ising Model for Different Geometrical Lattices
J.P. Atanas, C. Elzoghbi , J. Bechara and M. Ajaka
This work presents a theoretical simulation of the dependencies
of different physical parameters (internal energy, magnetization,
specific heat, magnetic susceptibility and others) on the temperature
for a two-dimensional Ising model and for different geometrical
lattices (square, triangular, rhombohedral). These different geometrical
lattices allow the determination of the dependency of the critical
temperature on the coordination number (number of nearest neighbors).
The linear behavior of the maximum values for the specific heat
and for the magnetic susceptibility as a function of different geometrical
lattice dimensions was obtained. Back
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Data Forum
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Nouvelles Recherches sur des Espèces Végétales
Citées pour la Premiere Fois du Liban
Georges Tohmé & Henriette Tohmé
Dans cette note, les auteurs dressent une liste de 14 plantes non
citées encore du Liban et en donnent une brève description.
Certaines existent en Syrie, d’autres sont mentionnées
de l’Asie occidentale en général ou de la Turquie
en particulier. Back
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Review Article
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Taxonomie du Genre Pseudomonas : Rétrospective et Actualité
Idir Meghdas, Monzer Hamze, Fouad Dabboussi, Nader Baida et Daniel
Izard
Les bactéries du genre Pseudomonas appartiennent à
la famille des Pseudomonadaceae. Elles sont ubiquitaires et présentent
un intérêt particulier en microbiologie médicale,
alimentaire, aquatique et environnementale ainsi qu'en agronomie.
Certaines espèces sont potentiellement utilisables en agriculture
et pour l'assainissement des écosystèmes pollués
par des composés xénobiotiques. Le travail magistral
de Palleroni et de son équipe, basé sur la similarité
de l'ARN ribosomal (ARNr), a révélé l'extrême
hétérogénéité du genre Pseudomonas
et a permis le remaniement de celui-ci en 5 groupes d'homologie
d'ARNr. Cette restructuration a été par la suite confirmée
notamment par l'analyse numérique des caractères phénotypiques,
l'étude des ubiquinones, la détermination du profile
des acides gras cellulaires 3-hydroxy et le séquençage
de l'ARNr 16S. Les bactéries considérées à
tort comme membres du genre Pseudomonas (groupes II à V de
Palleroni) ont été assignées soit à
des genres préexistants soit à des genres nouveaux.
Les Pseudomonas «sensu stricto» ou les «Pseudomonas
vrais» correspondent au groupe I de Palleroni. Ce genre rassemble
une soixantaine d’espèces isolées de milieux
différents. Celles-ci synthétisent ou non des pyoverdines
(pigments fluorescents) et se distinguent des genres apparentés
par la présence de l'ubiquinone 9 et des acides gras cellulaires
caractéristiques [acides 3-hydroxydécanoique (3-OH
10:0) et 3-hydroxydodécanoique (3-OH 12:0)] ainsi que par
l'absence d'accumulation de poly-ß-hydroxybutyrate. Back
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