B.1
THE OCCURRENCE OF ANOSTRACANS
VERNAL POOLS OF BAHRAIN
– FAIRY
SHRIMPS
Brachipus schaefferi
IN
Hashim Al-Sayed, Khadija Zainal*
Department of Biology, College of Science, University of Bahrain, Isa Town Campus,
P.O.Box 32038, Isa Town, The Kingdom of Bahrain
Journal of Arid Environments 61, 447-460 (2005)
Abstract
The occurrence of a native species of fairy shrimp (Anostraca) in the Kingdom of
Bahrain is documented for the first time. The appearance of adults depends on
rainfall events which are rare. These organisms survive by producing dormant cysts
that survive the dry period between rainfall events. The size of the population
differences between sexes, life cycle duration, tolerance to the fast retreating vernal
pools and survival under the laboratory conditions are discussed.
Multi-modal population density indicated two peak hatching events. Daily size
frequency distribution revealed the occurrence of smaller sized individuals throughout
the adult activity period.
From 1995 and 2001 salinity level in one pool increased. This may affect the
vegetation of this area.
B.2
BACTERIAL
COMMUNITY AND SOME PHYSICO-CHEMICAL CHARACTERISTICS IN A
SUBTROPICAL MANGROVE ENVIRONMENT IN BAHRAIN
Hasim A. Al-Sayed*, Essam H. Ghanem, Kareema M. Saleh
Department of Biology, College of Science, University of Bahrain, P.O.Box 32038,
Isa Town, of Bahrain
Marine Pollution Bulletin 50, 147-155(2005)
Abstract
A study of bacterial communities and some physico-chemical parameters of a
subtropical mangrove habitat in the Arabian Gulf (Bahrain) was carried out in 19931994. Six stations at different parts of the tidal channel were selected for sampling.
The mangrove habitat was found to harbor diverse bacterial communities, included
among them anoxygenic phototrophs (AP), oxygenic phototrops (OP), organotrophs
(OT), total coliforms (TC), faecal coliforms (FC) and haloalkaliphiles (HA). Spatial
and temporal variations in bacterial communities and environmental parameters were
found. Each of the OT, AP, TC and FC were dominant in the inner most stations (S1
& S2) and gradually decreased seaward. The HA community on the other hand, was
dominant at the seaward stations (S5 & S6) and was most likely to have originated
from the sea through the tidal flows. Both AP and OT were considered as part of the
mangrove native flora, whereas TC and FC were alien and believed to have been
introduced through partially treated sewage released at the upstream of the tidal
channel. Closely monitoring of the mangrove water revealed succession pattern in
bacterial communities. The AP community was predominant from November 1993
to March 1994, succeeded by dominance of OP from june 1994 to October 1994.
Both bacterial blooms gave water a pinkish, purple, or green color, respectively.
Although OT prevailed during Transitional period between AP and OP
eutrophication, it remained comparatively constant (not less than 2 x 105 cfu/ml)
through other periods. Frequent eutrophication phenomena of OP, which took place
in summer and autumn, coincided with increases in water temperature, chorophyll a,
1
and nutrients (NO 3 and PO 4 ). On the other hand, OT and AP were negatively
correlated with temperature, salinity and chorophyll a, but no specific pattern was
observed in relation to NO 3 and PO 4 .
In comparison with seawater, nutrients such as NO 3 and PO 4 were consistently
higher in the mangrove habitat. Partially treated sewage and farm drainage canals are
proposed to form additional sources of nutrients. Although, the mangrove habitat has
been demonstrated to possess self-cleaning properties, data obtained suggest that
anthropogenic pollution has a deleterious effect.
B.3
QUANTITY AND COMPOSITION OF SOLID WASTE
THE KINGDOM OF BAHRAIN, ARABIAN GULF
AT THE
BOTTOM
OF THE
K. Zainal, I. AL-Madany and W. Zainal
The University of Bahrain, P.O.Box 32038, State of Bahrain
4th International Conference on Marine Pollution
Ecotoxicology, 1-5 June 2004, Hong-Kong, O-92
SEA
IN
and
Abstract
The main objective of this investigation was to identify the type and quantity of heavy
solid waste at the bottom of the sea and removal of this waste was attempted
wherever possible. The locations of lost fishing gear were also identified. A total of
35 areas at the bottom of the sea were selected for the study according to their
importance to the fisherman and as pearl beds. Each area was subdivided into several
stations. The study was conducted during June 2001 to November 2001 and from
July 2002 to February 2003. A large amount of solid wastes (1,472 kg) were retrived
from the bottom of the sea. Forty different types of solid items were collected from
the sea bottom wheras only 36 different items were found along the shores (part two
of the study). Plastic waste comes at the top of the list of all other solid debris,
mainly fishing nets and gears. This fact highlighted the impact of fishermen on the
sea and the need for raising their awareness to this problem. Wooden debris
composed of only 2% of the total waste. This was attributed to the floatation
properties of these materials. Compared to other areas, larger amount of debris was
found accumulated in the fishing areas. Larger amount of solid debris also
accumulated along the eastern and northern sides of the main island compared to the
west and the southern sides. This has been correlated with higher human activites
along east and north coasts. The waste include shipwrecks, cars, pipes, iron bars, oil
exploration platforms and fuel tanks etc. These are mainly related to the major
economic activities in the Kingdom of Bahrain.
The present investigation finding is similar to many other studies carried out
elsewhere in the world in the following points:

High plastic content of waste composition

The source of most plastic pollution belonged to the fishing activities.

Higher percentage of wooden debris along the shores
Non-degradable solid wastes such as plastics affect negatively the water quality and
both marine habitat and organisms. Buoys were installed at sensitive areas such as
coral reef sites with the hope of protecting these delicate habitats from further
destructions.
In Bahrain, so far, most research studies have been targeting solid wates generated
from domestic and commercial sources on land. No previous work has been
conducted for the marine benthic environment. This study has filled a gap in our
2
understanding of solid wastes on the bottom of the sea in the territorial waters of the
Kingdom of Bahrain and provided valuable information to decision makers for an
appropriate management and protection of the marine habitat.
3
C.1
BENZO[a] PYRENE CONCENTRATIONS IN TOPSOILS OF NORTH BAHRAIN
Ameera Al Haddad
Department of Chemistry, University of Bahrain, Bahrain
Toxicological & Environmental Chemistry,
0,(0):1-7, 2005
Abstract
A comprehensive field study was conducted to determine the background
concentrations of benzo[a]pyrene (B[a]P) in soil samples collected at different points
on a grid covering most of the northern and middle parts of the Kingdom of Bahrain.
The average B[a]P concentration was 108.4 ngg-1 in winter and 73.0 ngg-1 in summer.
The capital city, Manama, and the industrial areas of the country showed the highest
levels of B[a]P.
C.2
INORGANIC CHEMICAL COMPOSITION OF AEROSOLS SETTLING
BAHRAIN FOLLOWING DUST HAZE STORMS
IN
HAMAD TOWN,
Ahmed Y. Ali-Mohamed
Department of Chemistry, College of Science, University of Bahrain, P.O.Box 32038,
Isa Town, Bahrain
Intern. J. Environ. Studies, 61(2), 161-171, April (2004)
Abstract
The inorganic chemical composition of settling particles from 10 dust storms in
Hamad Town, Bahrain has been determined. These storms occurred over a 3-year
period. Meteorological conditions during the storms were examined and the storms
classified, according to their trajectories, into two types: (a ) a low pressure system
from the Mediterranean, which traveled east into the Gulf and caused periods of
disturbed weather and causing of northwesterly winds; and (b) a low pressure over
Pakistan causing dry north-westerly wind, known locally as Al-Barah. After this
period, the low pressure system declined allowing the formation of south-easterly
winds known as the Kaus. The composition of the dust storms is montonic. The
settling particles are relatively enriched in Ca2+, K+, and SO 24  derived from local soil,
and Cl- from the sea.
C.3
MINERAL ION CONTENT OF
PALM (Phoenix dactylifera)
THE
SEEDS
OF
SIX CULTIVARS
OF
BAHRAINI DATE
Ahmed Y. Ali-Mohamed* and Ahmed S. H. Khamis
Department of Chemistry, College of Science, University of Bahrain, P.O.Box 32038,
Isa Town, Bahrain
J. Agric. Food CHEM. 52, 6522-6525(2004)
Abstract
The mineral ion composition of six different cultivars of Bahraini dates palm
(Phoenix dactylifera) seeds (Khálas, Murzban, Khunaizi, Khawajah, Khasaib Asfor,
and Khaseeb) were analyzed using flame atomic absorption spectroscopy (AA and
ICPS). Murzban was found to contain the higher mineral ion content. The essential
bulk metal ions in the six cultivars were found to be dominant, where [K+] was the
4
highest and [Ca2+] was the lowest. The decreasing order of essential trace metal ion
concentrations is Fe2+ > Mn2+ > Zn2+. Lead ion content was found to be higher than
cadium ion as metal ion pollutant. Mineral ion contents of Bahraini date palm seeds
and those of imported coffee grain and barley were studied, because date palm seeds,
coffee grain, and barley are used for coffee drinks.
C.4
SOLID STATE
IMPOSED VIBRATIONAL COUPLING BETWEEN
TETRADHEDRAL IONS
1
AND
3
MODE OF
Osama Abdulla Aljowder*
Department of Chemistry, College of Science, University of Bahrain, Isa Town,
Bahrain
Spectrochimica Acta Part A: 60, 2837-2841(2004).
Abstract
Raman spectra of the thiomolybdate ion in the compounds [CuNH4]MoS4] and
X2[MoS4], where X = NH 4 , Rb+ or Cs+, are reported and used to confirm the
hypothesis presented in an earlier paper [J. Chem. Phys. 94 (1991) 5946], that there is
solid state induced vibrational coupling between the 1 and 3 modes of tetrahedral
ions.
C.5
ANTIBACTERIAL ACTIVITY OF CERTAIN SPICE EXTRACTS
Q. Mandeel, A. Hassan and Z. Isa
College of Science, University of Bahrain, P.O.Box 32038, Isa Town Campus,
Kingdom of Bahrain
Journal of Spices and Aromatic Crops 12:146-153(2003)
Abstract
Seveteen raw spice samples were examined for phytochemical constituents and
antimicrobial properties. Qualitative phytochemical analysis of crude spice extracts
revealed the occurrence of alkaloids, coumarins, flavonoids, saponins, terpenes and
tannins. Turmeric, clove and bay leaf showed the highest frequency of occurrence of
these plant components among others. Terpenes were present in 94.12 % of the
samples evaluated. Ethanol extracts of spice samples were in vitro evaluated for their
antimicrobial properties using well diffusion assay against six Gram positive and
Gram negative bacteria. Results showed that all the spice extracts, except black
cardamom, possess biological activity on one or more of the test bacteria. Clove
extracts displayed the highest antibacterial activity (19.5 mm) against Escherichia
coli, followed by bay leaf (19 mm) against the same bacteria and cumin (19 mm)
against Pseudomonas aeroginosa, at 1000 l/100 l. Extracts of galangale, turmeric
and fennel also exhibited a broad spectrum biological activity. The most susceptible
bacteria, based on frequency values, were E. coli (76.4%), P. aeruginosa and Bacillus
subtilis (58.82%) and the least susceptible species were Salmonella arizonae
(23.52%) and Enterobacter aerogenes (17.64%) at 1000 g/100 l. Overall, the
presence of biologically active compounds and potent antimicrobial properties
elucidate the potential use of spices in small amounts, individually or in combination
in human therapy or folk medicine and as food preservative.
5
C.6
EVALUATION OF SOME METALS IN COMMONLY CONSUMED SPIECES IN BAHRAIN
A. M. Hassan, Q. A. Mandeel* and H. A. Nabi
College of Science, University of Bahrain, 32038, Isa Town Campus, Kingdom of
Bahrain
*Department of Biology, College of Science, University of Bahrain, 32038, Isa Town
Campus, Kingdom of Bahrain
Arab Gulf Journal of Scientific Research, 21(2), 7985(2003)
Abstract
Concentration of some heavy and essential metals were assayed in seventeen
commonly consumed spices in Bahrain using atomic absorption spectroscopy.
Samples were collected from different retail outlets in the local spice market (bazaar).
The data showed wide variation in metal content among the various spice samples.
The maximum mean level of elements among all spices based on plant parts fall in
the magnitude of the order: iron > zinc > copper > nickel > lead > cadimium, in
leaves, rhizomes, seeds, buds, fruits and barks, respectively. For heavy metals,
caraway contained the highest level of lead ( 2.2 g/g) and green cardamon exhibited
the highest cadmium level (0.9 g/g). With essential metals, concentration of iron,
zinc, copper and nickel were highest in cumin (13.6 g/g), black cumin (52.2g/g),
black pepper (17.3 g/g), and black cumin (4.9 g/g), in that order. The reliability of
the findings and approach was confirmed by analyzing data from the literature.
C.7
ASSESSMENT OF in vitro ANTIFUNGAL ACTIVITIES
INDIGENEOUS BAHRAINI MEDICINAL PLANTS
OF VARIOUS EXTRACTS OF
Qaher Mandeel1 and Ahmed Taha2
1
Department of Biology and 2Department of Chemistry, College of Science,
University of Bahrain, Kingdom of Bahrain
Pharmaceutical Biology, 43(2) 164-172 (2005)
Abstract
The in vitro antifungal activity of aqueous, ethanol, chloroform, petroleum ether, and
residue extracts from 10 indigenous Bahraini plants used in folk medicine for the
treatment of various diseases is reported. Extract efficacy was evaluated using the
agar well diffusion assay against four filamentous fungi and two yeasts monitored by
standard antifumgal disks. The results showed that all but, in particular, ethanol and
chloroform plant extracts reveal variable degrees of bioactivity against at least two of
the tested microbes. The highest ethanol extract activity was exhibited by Cressa
cretica (L.) against Penicillium citrinum Thom (32.2 mm) followed by Candida
albicans (C. P. Robin) Berkhout (25.7 mm). The diffusable metabolites of
Heliotropium curassavicum L. also demonstrated marked inhibitory effects against
the same microorganisms. Chloroform extracts of Emex spinosa Campd. displayed
an elevated potency against Alternaria alternata (Fries) Keissler (27.9 mm) and
Saccharomyces cerevisiae Meyen ex. E. C. Hansen (27.5 mm). Zone of inhibition
against other fungi varied from 19.9 to 25.9 mm. However, the highest growth
inhibition was encountered with Fagonia indica Burm F. against P. citrinum (29.3
mm). With the exception of chloroform extracts from cultivated soils, various
extracts of plants randomly collected from saline-affected soils exhibited higher
fungal radius inhibition than plants from cultivated soils. The significance of these
results in relation to ethnobotanical data is discussed.
6
M.1.
ASYMPTOTIC
FORMULAE OF
LIOUVILLE – GREEN
TYPE FOR HIGHER EVEN-ORDER
EQUATIONS
A. S. A. Al-Hammadi
Department of Mathematics, College of Science, University of Bahrain, P.O.Box
32038, Bahrain
Communications
in
Nonlinear
Science
and
Numerical
Simulation 10, 643-652 (2005)
Abstract
Asymptotic formulae of Liouville – Green type of general linear ordinary differential
equations of an arbitary even-order 2 m are investigated. A theorem on asymptotic
behaviour at the infinity of 2m linearly independent solutions is proved. It is shown
that numerous results known in the literature are contained in this theorem as
particular cases.
M.2
EULER CASE FOR A GENERAL FOURTH – ORDER DIFFERENTIAL EQUATION
A. S. A. Al – Hammadi
Department of Mathematics, College of Science, University of Bahrain, P. O. Box 3238, Bahrain
IJMS 51, 2705-2717 (2004)
Abstract
We deal with an Euler case for a general fourth-order equation and under this case,
we obtain the general formula for the asymptotic form of the solutions.
M.3
THE CALIBRATION PROBLEM REVISITED
M. A. Ali and M. Y. Ashkar
Department of Mathematics, University of Bahrain, P.O.Box 32038, Isa Town,
Kingdom of Bahrain
Comunications in Statistics, Theory and Methods 31(10)
1733-1741(2002)
Abstract
This article examines the impact of correlation coefficient on the problem of
calibration. An estimator based on a 100(1 - )%, 0 <  < 1, calibration confidence
interval is obtained. This estimator dominates, in some sense, the available
estimators.
M.4
IMPACTS OF ERROR VARIANCE ON AN ASYMPTOTICALLY UNBAISED ESTIMATOR FOR
INVERSE REGRESSION
M. Y. Ashkar and M. A. Ali
Department of Mathematics, University of Bahrain, P.O.Box 32038, Bahrain.
Pak. J. Statist. 20(2), 263-275 (2004)
Abstract
7
Srivastava and Singh (1989) proposed a class of weighed average estimators for
inverse linear regression. They examined the asymptotic bias and the asymptotic
mean squared error (MSE) of this family of estimators. They found that a member of
this class is asymptotically unbaised to the order of their approximation. This article
compares the well known classical, inverse and the asymptotically unbaised weighted
average estimators of inverse linear regression by Monte Carlo methods. It is
observed that for small and moderate size samples the asymptotically unbaised
weighed average estimator is relatively interior to the inverse estimator from a mean
squared error point of view.
M.5
REFLECTION OF SOME QUASI-LOCAL DOMAINS
Ahmed Ayache1, David E. Bobbs2, and Othman Echi3*
Department of Mathematics, College of Science, University of Bahrain, P.O.Box
32038, Isa Town, Kingdom of Bahrain
Journal of Algebra and its Applications, (2005) in press.
Abstract
If (R,M) and (S,N) are quasi-loacl domains and ƒ : R → S is a ring homomorphism,
then ƒ is said to be a strong local homomorphism if ƒ(M) = N. Let PVD be the
category whose objects are the pseudo-valuation domains that are not fields and those
morphisms are the strong local homomorphisms; let VD be the full subcategory of
PVD whose objects are all the valuation domains that are not fields. Then VD is
shown to be a reflective subcategory of PVD. This result is extended in two ways:
by obtaining a reflective conclusion for a category whose class of objects properly
contains all pseudo-valuation domains; and by characterizing which pseudo-valuation
domains R are such that the inclusion map from R into the associated valuation
domain of R satisfies a universal mapping property in various categories of quasilocal domains and strong local homomorphisms.
M.6
A FORMULA ABOUT TREES
Ahmed Ayache1 and Walied H. Sharif2
1
University of Bahrain, Faculaty of Science, Department of Mathematics, P.O.Box
32038, Isa Town, Kingdom of Bahrain. aayche@sci.uob.bh
2
Department of Mathematics, College of Science, Qatar University, Doha, P.O.Box
2713, Qatar. W.sharif@qu.edu.qa
Vietnam Journal of Mathematics, (2005) in press.
Abstract
Let G be a tree. It is proved that for any vertex  of G
V+  [d (q)  2] l(,q) = 1,
qV
in which d(q) is the degree of the vertex q, and l(,q) is the distance between and q
in G. This result enable us to derive a formula concerning the average distance for
some particular trees.
M.7
CRITICAL
SLOWING DOWN IN A BISTABLE MODEL WITH SQUEEZED VACUUM
ENVIRONMENT
8
S. S. Hassan1,a and Y. A. Sharaby2
1,a
University of Bahrain, College of Science, Mathematics Department, P.O.Box
32038, Bahrain. E-mail: shoukryhassan@hotmail.com
2
Suez Canal University, Faculty of Education, Physics Department, Suez, Egypt.
Eur. Phys. J. D. 30, 393-401(2004)
Abstract
Critical slowing down effect in a bistable model of a two-level atomic medium in a
ring cavity and in contact with squeezed vacuum field is examined within the mean
field approximations in the high-, low- and arbitary-Q cavity cases. Depending on the
squeezed vacuum field phase parameter, the time response to linear perturbation of
the incident field near the switching – on point can be enhanced or reduced compared
with the normal vacuum case. In the low-Q cavity case with atomic collisional
broadening switching time is both increased and become insensitive to the phase of
the squeezed vacuum field. Analytical expressions are given and analysed for the
critical (extermal) values of the incident field. In the high-Q cavity, Gaussian field
features causes lesser-steep transition between the stable states in both the normal and
squeezed vacuum cases.
M.8
ENTROPIC
UNCERTAINTY IN THE
SECOND HARMONIC GENERATION
JAYNES-CUMMINGS
MODEL IN PRESENCE OF A
M. Sebawe Abdallaa.*, S. S. Hassanb, M. Abdel-Atyc
*
Mathematics Department, College of Science, King Saud University, P.O.Box 2455,
Riyadh 11451, Saudi Arabia.
b
Mathematics Department, College of Science, University of Bahrain, P.O.Box
32038, Bahrain
c
Mathematics Department, Faculty of Science, South Valley University, 82524 Sohag,
Egypt.
Optics Communications 244, 431-443(2005).
Abstract
In the present communication we investigate the usual Jaynes-Cummings
Hamiltonian model, describing two-level atom interacting with an electromagnetic
field, in the presence of the second harmonic generation (degenerate parametric
amplifer). Exact solutions of the wave function in the Schrodinger picture have been
obtained for two different cases. In the first case the field frequency  is not equal to
the splitting photon frequency , where the canonical transformation has been
invoked to obtain the solution of the wave function. In the second case, we
considered both frequencies are equal ( = ) and the system is taken to be at exact
resonance. Both solutions have been used to discuss the atomic inversion as well as
the entropy squeezing. It has been shown that the system is sensitive to any change in
the coupling parameter responses of the second harmonic generation as well as to the
atomic phase angle.
M.9
MESOSCOPIC MULTISTABILITY WITH TWO-PHOTON ATOMIC SYSTEM
Y. A. Sharaby1, S. S. Hassan2* and S. M. A. Maize3
1
Suez Canal University, Faculty of Education, Physics Department, Suez, Egypt.
2
*University of Bahrain, College of Science, Mathematics Department, P.O.Box
9
32038, Bahrain
3
Menufia University, Faculty of Science, Physics Department, Shebin Elkom, Egypt
Nonlinear Optics, Quantum Optics, 33, 1-16(2005)
Abstract
Multistability that results from the interaction of a mesoscopic two-level two-photon
Rydberg atomic system, driven by coherent field, with a single cavity mode is
investigated in both absorber and amplifier regimes. The stark shift coefficient which
included in two-photon transition atomic systems, leads to a weaken Rabi oscillations
under certain parameters of the system. The effect of the stark shift is different in
both absorber and amplifer regimes. Transverse field effects, in addition to the stark
shift parameter leads to over-damped Rabi oscillations rather than strong nonlinear
oscillations that characterizing two-photon transition systems.
M.10
FIELD-DEPENDENT RELAXATION
TWO-LEVEL ATOM MODEL
AND QUANTUM INTERFERENCE IN A TWO-PHOTON
S.S. Hassan1 and M. A. El-Deberky2
1
University of Bahrain, College of Science, Mathematics Department, P.O.Box
32038, Bahrain ( shoukryhassan@hotmail.com )
2
Al-Azhar University, Faculty of Science, Mathematics Department (Women's
Section), Nasr City, Cairo, Egypt.
Nonlinear Optics, Quantum Optics, (2005), in press.
Abstract
The relaxation behaviour of the model of 2-photon transition 2-level atom is
investigated in the presence of intense coherent field excitations in Heisenberg
picture. Generalized forms for the Bloch-like equations for the net atomic coherence
are derived for arbitrary number of intermediate levels of the same parity and
approximately the same energy. The intense field excitations induce Fourier
harmonics (at the exciting field frequencies) in the atomic variables in the transient
regime and in some cases in the steady regime. For a single intermediate level (i.e.
two-level atom with one intermediate level) the obtained result are valid irrespective
of the atomic level structure. In the special case of 3-level ladder structure (i.e. twolevel atom with one intermediate level) the role of the quantum interference (cross
coupling) between the two transition channels is investigated in detail. Notably, the
case of two intense exciting fields induces steady oscillatory absorption coherence
due to quantum interference.
M.11
DIFFUSION RESONANCE FREQUENCY OF OSCILLATING SOLUBLE GAS BUBBLES
N. S. Khabeev
Department of Mathematics, University of Bahrain, Kingdom of Bahrain E-mail:
nail@sci.uob.bh
MORGAN X (The 10th International Conference in Modern
Group
Analysis),
Larnaca,
Cyprus
24-31
October,
pp.33,(2004)
Abstract
Soluble gas bubbles in a liquid experiencing radial oscillations created by an acoustic
filed are considered. It is shown that the resonance frequency of large soluble gas
10
bubbles practically coincides with the natural frequency of adiabatic gas bubbles as
determined by the Minnaert formula, while in the case of small gas bubbles, the
presence of capillary effects and solubility of the gas in the liquid leads to a new
resonance frequency that differs from the Minnaert frequency. A simple analytic
formula is obtained that relates the resonance frequency of a soluble gas bubble and
its radius. Ranges of dimensions of bubbles, and frequencies of the acoustic filed are
given, within which different approximations of the relations between resonance
frequency and bubble radius hold true.
M.12
SIMULATION
WELLS
OF
MICELLAR-POLYMERIC WATER-FLOODING
IN A
SYSTEM
OF
N. A. Inogamov and N. S. Khabeev*
*Department of Mathematics, University of Bahrain, Kingdom of Bahrain
Fluid Dynamics, 39(6), 953-960(2004)
Abstract
A mathematical model of the time-dependent two-dimensional flow of a two-phase
multicomponent incompressible fluid through a porous medium is proposed for the
micellar-polymeric flooding of oil reservoirs. The oil displacement process is
investigated numerically using an implicit first-order-accurate upwind scheme with
integration over the nonlinearity on a uniform grid under the assumption of planeradial motion in the neighborhood of the wells. The influence of the nonuniform
permeability of the porous medium on the efficiency of the proposed method of
improving oil recovery is analyzed using a five-point slug injection scheme.
M.13
A SIMPLE APPROXIMATION FOR JACOBI'S theta-FUNCTION
N. S. Khabeev*
Department of Mathematics, University of Bahrain, P.O.Box 32038, Bahrain, Email: nail@sci.uob.bh
Communications
in
Nonlinear
Science
and
Numerical
Simulation, (2005) in press.
Abstract
Solutions of heat transfer problems obtained by Fourier's method sometimes can be
expressed in terms of Jacobi's theta-functions. A simple analytic approximation of
high accuracy for Jacobi's theta-function is obtained.
M.14
COMPACT MANIFOLDS WITH POSITIVE EINSTEIN CURVATURE
M. –L. Labbi*
*Department of Mathematics, College of Science, Univeristy of Bahrain, Isa Town,
32038, Bahrain. E-mail: labbi@sci.uob.bh
Geometriae Dedicata, 108(1), 205-217(2004).
Abstract
In this paper we study positive Einstein curvature which is a condition on the
Riemann curvature tensor intermediate between positive scalar curvature and positive
sectional curvature. We prove some constructions and obstructions for positive
11
Einstein curvature on compact manifolds generalising similar well known results for
the scalar curvature. Finally, because our problem is relatively new, many open
questions are included.
M.15
DOUBLE FORMS, CURVATURE STRUCTURES AND THE (p,q)-CURVATURES
M. –L. Labbi*
*Department of Mathematics, College of Science, University of Bahrain, Isa Town,
P.O.Box 32038, Bahrain. E- mail: labbi@sci.uob.bh
Transactions of the American Mathematical Society. (2005)
Abstract
We introduce a natural extension of the metric tensor and the Hodge star operator to
the algebra of double forms to study some aspects of the structure of this algebra.
These properties are then used to study new Riemannian curvature invariants, called
the (p,q)-curvatures. They are a generalization of the p-curvature obtained by
substituting the Gauss-Kronecker tensor to the Riemann curvature tensor. In
particular, for p = 0, the (0,q)-curvatures coincide with the H. Weyl curvature
invariants, for p = 1 the (1,q)-curvatures are the curvatures of generalized Einstein
tensors and for q = 1 the (p,1)-curvatures coincide with the p-curvatures.
Also, we prove that for an Einstein manifold of dimension n > 4 the second H. Weyl
curvature invariant is nonegative, and that it is non-positive for conformally flat
manifold with zero scalar curvature. A similar result is proved for the higher H. Weyl
curvature invariants.
12
P.1
OPTICAL SWITCHING
IN HYDROGENATED AMORPHOUS SILICON-SULFUR ALLOY
PREPARED BY GLOW DISCHARGE
S. Al-Dallal*, F.Z. Henari, S.M. AL-Alawi, S.R. Arekat, H. Manaa
Department of Physics, University of Bahrain, P.O.Box 32038, Bahrain
Journal of Non-Crystalline Solids 345 and 346, 302-305
(2004)
Abstract
The third-order optical non-linearity of hydrogenated amorphous silicon-sulfur alloys
prepared by a plasma enhanced chemical vapor deposition process has been measured
using the z-scan technique. Intensity absorption dependence was observed and
attributed to reverse saturation absorption (optical limiting). The origin of the effect
was explained in term of defect states in the band gap. We demonstrate that the
reverse saturation absorption is responsible for the observed non-linearity and can be
utilized to generate all optical switching.
P.2
EMPIRICAL CORRELATIONS FOR THE CLIMATE DATA IN THE KINGDOM OF BAHRAIN
W.E. Alnaser*, M. K. Merzaa
Department of Physics, College of Science, University of Bahrain, P.O.Box 32038,
Isa Town, Bahrain. E-mail: waheeb@sci.uob.bh
Energy (2005), in press.
Abstract
The Average yearly recorded weather data in the Kingdom of Bahrain over an
extended period ranging from 1902 to 2002 for the temperature and from 1962 to
2002 for the atmospheric pressure, the relative humidity, the wind speed and the
sunshine duration (i.e. long-term data), is statistically analyzed and empirically
modeled. Regression methods, including polynomial and sinusoidal models, are used
to fit the data. Polynominal fits are used in modeling the average yearly variations.
The obtained coefficients of determination (R2) of these fits are tabulated. In
addition, we empirically modeled the monthly variations of the climate parameters
using both polynominal as well as sinusoidal regression models. Our results were
compared with similar studies for nearby countries, i.e. Oman and Kuwait. The
values of R2 for both fits are also tabulated.
P.3.
CONSTRAINING COSMOLOGICAL PARAMETERS THROUGH GAMMA-RAY BURSTS
W. J. Azzam*, M. J. Alothman
Department of Physics, College of Science, University of Bahrain, P.O.Box 32038,
Isa Town, Kingdom of Bahrain
* e-mail address: wjazzam@hotmail.com (w.J.Azzam)
Advances in Space Research (2005) in press.
Abstract
Several independence gamma-ray burst luninosity indicators currently exist, two of
which were used in this study. One relates the variability, V, or spikiness of burst's
light curve to its luminosity, Lv; while the other relates the time lag, lag, between
peaks of hard and soft photons to the luminosity, Llag. Both relations have been
13
calibrated. If the redshift, z, photon flux, P and mean photon energy, , are known,
then the burst's luminosity L = 4Pd 2L , where dL is the luminosity distance for an
assumed cosmological model. By carrying out a minimization procedure one can
investigate the parameter space for certain cosmological parameters (for instance,
M), that bring L in agreement with Lv and Llag . The above procedure was carried
out for a small sample of burst for which z, V, lag and P are currently available.
Given the paucity of current data, this procedure should be considered more as a
proof of method. Our analysis indicates that at this stage it is very difficult to
distinguish among the different cosmological models. However, as data becomes
available from the Swift satellite, this procedure could prove a useful tool in probing
and investigating cosmological models.
P.4
DIELECTRIC AND OPTICAL PROPERTIES OF SAMARIUM OXIDE THIN FILMS
A.A. Dakhel
Dept. of Physics,College of Science, University of Bahrain, P.O.Box 32038, Bahrain
Journal of Alloys and Compounds 365, 233-239(2004)
Abstract
Samarium sesquioxide thin films were prepared by vacuum evaporation. Their
structural and optical properties have been obtained by X-ray diffractometry (XRD)
and optical spectrophotometry. The energy dispersion X-ray fluorescence (EDXRF)
spectroscopy method was used to study the composition of the deposited Sm2O3
films. Spectroscopic optical absorption coefficients () are evaluated in the
interband transition energy region. The obtained energy gap was 4.33 eV. Thin film
capacitors of Al/Sm2O3/Al structure have been prepared. The dc current – voltage
characteristics of the capacitor showed that the current transfer is via Schottky
emisson at high fileds (E>1 MV/cm). The leakage current density was 6 x 10-7 A/cm2
at an electric field of 106 V/m. The near electrode region (NER) has an effective
dielectric constant of 42.7 according to Schottky current formula. The dielectric
properties such as capacitance, ac conductance and dielectric loss factor were
investigated as a function of bias voltage, temperature and frequency in the range
from 60 Hz to 100 kHz. The measurements were performed in air at various
temperatures in the range from 297 to 483 k. The frequency dependence of
capacitance and conductance are consistent with the 'universal dielectric response law'
with exponent s = 0.6 at room temperature. The frequency behaviour of the dielectric
properties can be explained according to the dipoles-dipole interaction and screening
effect. The behavior of temperature dependence of ac conductivity suggests two
competing hopping mechanisms with dominating activation energies of 0.01 eV at
low-temperature range and of 0.04 eV at high-temperature range.
P.5
CHARACTERISATION OF Nd2O3 THICK GATE DIELECTRIC FOR SILICON
A.A. Dakhel
Dept. of Physics,College of Science, University of Bahrain, P.O.Box 32038, Bahrain
Phys.Sat.Sol.(a) 201, No.4, 745-755(2004)
Abstract
Thin neodymium films were prepared by the reactive synthesis method on Si(P)
substrates to form MOS devices. The oxide films were characterised by UV
14
absorption spectroscopy, X-ray fluorescence (EDXRF) and X-ray diffraction (XRD).
The ac conductance and capacitance of the devices were studied as a function of
frequency in the range 100 Hz – 100 kHz, of temperature in the range 293-473 K and
of gate voltage. It was proved that a suitable formalism to explain the frequency
dependence of the ac conductivity and capacitance of the insultator is controlled by a
universal power law based on the relaxation processes of the hopping or tunnelling of
the current carriers between equilibrium sites. The temperature dependence of the ac
conductance at the accumulation state shows a small activation energy of about 0.07
eV for a MOS device with amorphous neodymium oxide. The temperature
dependence of the accumulation capacitance for a MOS structure with crystalline
neodymium oxide shows a maximum at about 390 K; such a maximum was not
observed for the structure with amorphous neodymium oxide. The method of
capacitance –gate voltage (C-Vg) measurements was used to investigate the effect of
annealing in air and in vacuum on the surface density of states (Nss) at the
insulator/semiconductor (I/S) interface. It was concluded that the density of surface
states in the mid-gap increase by about five times while the density of the trapped
charges in the oxide layer decreases by about eight times when the oxide crystalises
into a polycrystalline structure.
P.6.
ELECTRICAL CONDUCTION PROCESSES
PREPARED ON Si(100) SUBSTRACTES
IN NEODYMIUM
OXIDE
THIN
FILMS
A.A. Dakhel
Dept. of Physics,College of Science, University of Bahrain, P.O.Box 32038, Bahrain
Journal of Alloys and Compounds 376, 38-42 (2004).
Abstract
Thin Nd oxide films were prepared on Si (P) substrates to form MOS structure. The
oxide films were annealed at different conditions and their crystal structure were
determined by X-ray diffraction (XRD). The dc electrical transport properties of the
devices with amorphous and crystalline Nd oxide were investigated. The currentvoltage J(Vg) and current-temperature J(T) characteristics suggest that the carrier
tranport through the device follows the space charge limited current mechanism
(SCLC) controlled by exponential or uniform distribution of localised levels in the
band gap, depending on the annealing conditions of the oxide. For the crystalline
oxide film annealed in air at 800ºC, the current transfer is governed by SCLC
mechanism characterised by uniform distribution of traps in the band gap while for
crystalline film annealed at 800ºC in vacuum of 10-4 Pa the current transfer follows
the SCLC mechanism characterised by exponential distribution of localised states in
the band gap. But, SCLC mechanism governs partially the current transfer in
amorphous oxide films. The effect of hygroscopic nature of Nd oxide is observed
only in the temperature dependence of current density of amorphous oxide sample.
P.7.
MOTT-HOPPING PROCESSES
Si(100) SUBSTRATES
IN NEODYMIUM OXIDE THIN FILMS PREPARED ON
A.A. Dakhel
Dept. of Physics,College of Science, University of Bahrain, P.O.Box 32038, Bahrain
Crystal Research and Technology 39, 404-407 (2004)
15
Abstract
Thin Nd oxide films were prepared on Si(P) substrates to form MOS structure. The
oxide films were annealed at different conditions and their crystal structures were
determined by X-ray diffraction (XRD). The de electrical transport properties of the
devices with amprhous and crystalline Nd oxide were investigated. The currenttemperature J(T) characteristics suggest that the carrier transport through the insulator
follows Mott's variable-range hopping (VRH) mechanism and its results were
compared with the results obtained from X-ray diffraction.
P.8.
OPTICAL
AND DIELECTRIC PROPERTIES OF GADOLINIUM-INDIUM OXIDE FILMS
PREPARED ON Si(100) SUBSTRATES
A.A. Dakhel
Dept. of Physics,College of Science, University of Bahrain, P.O.Box 32038, Bahrain
Chem. Phys. Lett. 393, 528-534 (2004).
Abstract
Samples of thin (Gd-In) oxide film were prepared on quartz and Si(P) substrates for
optical and electrical investigations. These samples were annealed at different
conditions and and characterised by UV-Vis absorption spectroscopy, X-ray
fluorescence (XRF) and X-ray diffraction (XRD). The AC-conductance and
capacitance were studied as a function of frequency, temperature, and gate voltage.
The 'corrected barrier hopping' CBH model controls the frequency dependence of the
conductivity and capacitance. Good oxide-Si interface properties due to low midgap
interface state density was observed for (Gd-In) oxide sample annealed in vacuum.
P.9.
DIELECTRIC
PROPERTIES OF EUROPIUM-INDIUM OXIDE SOLID SOLUTION FILMS
PREPARED ON Si(100) SUBSTRATES
A.A. Dakhel
Dept. of Physics,College of Science, University of Bahrain, P.O.Box 32038, Bahrain
J. Phys. Chem. Solids, 65, 1765-1771(2004)
Abstract
Thin Eu-In solid solution oxide films (SS) were grown on Si(P) substrates to form
MOS devices. The samples were characterised by X-ray fluorescence and X-ray
diffraction techniques. The ac-conductance and capacitance of the devices were
studied as a function of frequency in the range 500 Hz to 100 kHz, temperature in the
range 293-400 K and gate voltage. The investigation established that: (1) the
prepared SS exhibit a sudden reversible structural change at about 370 K, (2) the
frequency dependence for ƒ> 10 kHz of the ac-conductivity and capacitance of the
insulator at room temperature is controlled by the 'corrected barrier hopping' CBH
model, (3) the temperature dependence of the ac-conductance which shows a small
activation energy characterises the hopping process of current carriers between
equilibrium sites, and (4) the prepared transparent SS have a sufficiently high relative
permittivity , around 30, which suggests they are promising candidates for high-
dielectric applications.
P.10.
CHARACTERISTICS
OF DEPOSITED
Eu2O3
16
FILM AS A THICK GATE DIELECTRIC FOR
SILICON
A.A. Dakhel
Dept. of Physics,College of Science, University of Bahrain, P.O.Box 32038, Bahrain
Eur. Phys. J. Appl. Phys. 28, 59-64 (2004)
Abstract
Thin Eu2O3 films were prepared on Si(P) substrates to form MOS devices. The oxide
films were characterised by X-ray fluorescence (EDXRF) and X-ray diffraction
(XRD). The ac conduction mechanism and the dielectric properties of the oxide
layers were studied at room temperature and in the temperature range of 290-420 K.
we have also investgated the effect of the oxide-crystal structure on the surface
density of states (Nss) at the insulator/semiconductor (I/S) interface. The method of
capacitance-voltage (C-V) measurements was used to determine the Nss. It was
concluded that the density of surface states in the mid-gap increases by about 30
times when the oxide Eu2O3 crystallises in polycrystalline form. Also, the density of
the trapped charges in the oxide layer decreases by about 12 times when the oxide
crystallises. The infrared studies inform us about the humidity incorporaton in the
oxide film in form of chemisorbed hydroxyl (OH) groups that leave the film for T >
373 K.
P.11
ELECTRICAL
AND TRANSPORT PROPERTIES OF EUROPIUM-INDIUM OXIDE FILMS
PREPARED ON Si(100) SUBSTRATES
A.A. Dakhel
Dept. of Physics,College of Science, University of Bahrain, P.O.Box 32038, Bahrain
Physica B: Physics of Condensed Matter 353, 255-262
(2004)
Abstract
Thin EU-In binary oxide films were prepared by alternating deposition method on
Si(P) substrates to form metal-oxide-Si(MOS) devices. These films were annealed at
different conditions and characterised by X-ray fluorescence (EDXRF) and X-ray
diffraction (XRD). The capacitance-gate voltage (C-Vg) dependence was used to
investigate the effect of annealing conditions on the trapped-fixed charge
concentration in the oxide and on the relative permittivity of the film sample. It was
observed that the prepared crystalline-dielectric Solid Solution (SS) of EU-In oxide
has a sufficiently high relative permittivity , around 30. This suggests that it is
promising candidate for high- dielectric applications.
The DC electrical properties of EU-In binary oxides insulator were investigated. The
current-voltage J(Vg) and current – temperature J(T) characteristics refer to different
current transfer processes depending on the annealing conditions, i.e., on the structure
and trap concentration. The current transfer in the oxide film sample with mixed
amorphous Eu oxide and polycrystalline In2O3 is governed by Poole-Frenkel (PF)
mechanism of barrier height 0.15 eV while in the oxide film with mixed
polycrystallines Eu2O3 and In2O3 follows the trap-charge-limited space-chargelimited conductivity (TCLC-SCLC) mechanism characterised by exponential
distribution of traps of temperature parameter of 512.8 K and total trap concentration
(Nt) of 4.2 x 1022m-3. The current transfer in MOS device with dielectric solid
solution of EU-In oxide follows the TCLC-SCLC mechanism with temperature
parameter of 427.8 K and Nt of 2.2 x 1023 m-3. It was concluded that the carrier traps
17
in those crystalline films are distributed exponentially in energy within the band gap.
These concentrations Nt were compared with the concentrations of the fixed charges
in the films calculated from the capacitance measurements, which was around 1022
charges/m3.
P.12
TEXTURE EFFECTS IN PARTICULATE MEDIA
M. A. Gonzalez-Fernandeza, G. Blocksidgea, C. Buncea, K. O'Gradya, M. ElHilob, M. P. Sharrockc, and D. M. Seftickc
a
Department of Physics, The University of York, Heslington, York YO10 5DD, UK
b
Physics Department, University of Bahrain, Isa Town, 32038, Bahrain.
c
Imation Corporation, Oakdale, Minnesota, 55128-3414, USA.
Journal of Magnetism and Magnetic Materials Vol. 290-291,
part I, 498-501 (2004).
Abstract
In this paper, we report on a study of the switching field distribution of the particles in
a tape that has been fabricated with different easy axes orientations along its length.
The samples are composed of acicular metal particles dispersed within binders and
solvents coated onto a plastic film. We observed a broadening of the switching field
distribution in samples with a wide easy axes distribution.
P.13
MAGNETIC VISCOSITY EFFECTS ON THE DETERMINATION OF THE SWITCHING FIELD
DISTRIBUTION IN CoNiCr THIN FILMS
B. A. Jonesa, M.El-Hilob, K. O'Gradya,*
a
Physics Department, University of York, Heslington, York, YO10 5DD, UK
b
University of Bahrain, College of Science, PO Box 32038, Isa Town, Bahrain
Journal of Magnetism and Magnetic Materials 272-276,
e517-e519(2004).
Abstract
In this work we examine the effect of magnetic viscosity on the determination of the
switching field distribution (SFD) in hard magnetic materials. We find that
measuring at a slower rate broadens the measured SFD and leads to larger values of
the Néel fluctuation field. The effect of intergranular exchange coupling is also
discussed.
P.14
INTERACTIONS EFFECTS IN GRANULAR POWDER SYSTEMS
M. El-Hiloa*, I. Bsoulb, A. Rousanc, A. Hudeishc
a
*Physics Department, College of Science, University of Bahrain, P.O.Box 32038, Isa
Town, Bahrain. E-mail: mhilo@rocketmail.com
b
Department of Physics, Al al-Bayt University, P.O.Box 130040, Mafraq, Jordan
c
Department of Physical Science, Jordan University of Science and Technology,
P.O.Box 3030, Irbid, Jordan
Journal of Magnetism and Magnetic Materials 272-276, 327329(2004).
18
Abstract
In this paper the effects of interactions in doped barium ferrite powder system at
different concentrations are examined. At low concentrations (Ms<2emu/g), the
coercivity is observed to decrease linearly with increasing particle concentration. In
addition, the measured M curves for all samples examined showed negative profiles,
which indicates that, the predominant dipolar interactions are negative. The linear
decrease in coercivity is attributed to be due to the increase in the strenght of the
negative dipolar interactions.
P.15
TIME-DEPENDENT COERCIVITY IN PARTICULATE RECORDING MEDIA
M. El-Hilo
*Physics Department, University of Bahrain, P.O.Box 32038, Isa Town, Bahrain. Email: mhilo@rocketmail.com
Journal of Magnetism and Magnetic Materials 272-276, 1700
- 1702(2004).
Abstract
In this paper, the time dependence of coercivity (Hc) in particulate systems in the
thermal relaxation regime is calculated. The calculations were made for an aligned
system of poly dispersed particles. In the thermal regime, the calculations show that
the Brown's model for relaxation times gives better results than the Arrhenius-Néel
model, due to the field dependence of the attempt frequency in the Brown's model.
P.16
MAGNETIZATION REVERSAL IN GRANULAR POWDER SYSTEMS
M. El-Hiloa*, A. Rousanb, A. Al-Hattabb
a
* Department of Physics, University of Bahrain, P.O.Box 32038, Isa Town, Bahrain.
E-mail: mhilo@rocketmail.com
b
Department of Physical Science, Jordan University of Science and Technology,
P.O.Box 3030, Irbid, Jordan
Journal of Magnetism and Magnetic Materials 272-276,
e493-e495(2004).
Abstract
In this paper, the magnetization reversal in substituted BaFe12-2xCoxTixO19
nanoparticles is examined. Measurements of fluctuation field (Hf) have shown that
the behaviour of Hf is greatly influenced by the substitution level (x). At x = 0.71, Hf
is observed to be slowly varying with field, which is expected for a particulate system
when both distributions (anisotropy fileds and particle volumes) have comparable
standard deviations. Hence a constant behaviour of Hf with field cannot be used as an
indication of single activation energy in the system.
P.17.
GAIN MEASUREMENTS IN A DYE-DOPED POLYVINYL-PYRROLIDONE POLYMER
F.Z. Henari
Physics Department, College of Science, University of Bahrain, P.O.Box 32038, Isa
Town, Kingdom of Bahrain
Laser Physics, 15(3), 419-421(2005)
19
Abstract
We report on optical-gain measurements in a glass-clad polymer optical fiber that
uses dye-doped polyvinyl pyrrolidone. The optical gain is determined from amplified
spontaneous emission intensity, which is dependant on the stripe excitation length.
Net gains of 3 to 6.5 cm-1 for input energies of 15 to 62 J, respectively, were
measured. A slope effciency as high 7% is an indication of the possible use of the
compound as a laser medium.
P.18
Picosecond pulse generation from passively mode-locked vertical cavity diode
laser at up to 15 GHz pulse repetition rate
K. Jasim, Q. Zhang, A. V. Nurmikko, E. Ippen, A. Mooradian, G. Carey and W. Ha
K. Jasim, Q. Zhang, and A. V. Nurmikko (Department of Physics, Division of
Engineering, Brown University, Providence, RI 02912 USA).
A. Mooradian, G. Carey and W. Ha (Novalux, Inc., Sunnyvale, CA 94086 USA).
E. Ippen (Department of Electrical Engineering and Computer Science, MIT,
Cambridge, MA 02139 USA).
IEEE Electronics Letters 40(1),34-36 (2004).
Abstract
The generation of ultrashort pulses (~15 ps) from a passively mode-locked InGaAs
multiple quantum well (MQW) vertical cavity surface emitting diode laser is reported
at a repetition rate up to 15 GHz, utilising a cavity configuration that incorporates a
reverse-baised quantum well devie as a fast saturable absorber. Pulsing at up to 20
GHz rate has been observed on a continuous-wave background.
P.19
Operation of a Passively Mode-locked extended-cavity surface-emitting diode
laser in multi-GHz regime
Qiang Zhang, Khalil Jasim, A. V. Nurmikko, Fellow, IEEE, Arm Moodradian,
Member IEEE, Glen Carey, Wonill Ha, and Erich Ippen, Fellow, IEEE
Q. Zhang, K. Jasim, and A. V. Nurmikko are with Division of Engineering, Brown
University, Providence, RI 02912 USA (e-mail: Qiang_Zhang@brown.edu ).
A. Mooradian, G. Carey and W. Ha are with the Novalux, Inc., Sunnyvale, CA 94086
USA.
E. Ippen is with the Department of Electrical Engineering and Computer Science,
MIT, Cambridge, MA 02139 USA.
IEEE Photonics Technology Letters, 16(3),885-887 (2004)
Absract
We report on passive mode-locking of vertical cavity surface-emitting diode lasers at
980-nm wavelength, applied to different extended resonator configurations. Stable
mode-locking producing pulses of approximately 50 ps in duration at up to 6-GHz
repition rate has been achieved. The use of external feedback results in pronounced
harmonic pulse generation, extending the operational range of these new devices.
P.20.
EFFECTIVE STIMULATED EMISSION CROSS-SECTIONS
VINYLENE) COPOLYMERS IN TOLUENE SOLUTION
20
OF
POLY(PHENYLENE
H. Manaa1*, Fryaz Z. Henari1, Ahmed Al-Saie1, Stefanie Maier2 and Werner J.
Blau2
1
Department of Physics,College of Science, University of Bahrain, P.O.Box 32038,
Kingdom of Bahrain
2
Material Ireland Research Center, Department of Physics, Trinity College, Dublin
2, Ireland
Optical and Quantum Electronics 36 819-826(2004)
Abstract
We report optical gain measurements in four different copolymers poly{p-phenyleneco-[2,5-dioctyloxy-p-phenylene-bis-2(4-nonylphenyl)vinylene]}
nonyl-PpPV,
poly{m-phenylene-co-[2,5-dioctyl-oxy-p-phenylene-bis-2(4-methylphenyl)
vinylene]} methyl-PmPV,poly[p-phenylene-co-[2,5-dioctyloxy-p-phenylene-bis-2(4methyl-phenyl) vinylene]}methyl-PpPV, poly{p-phenylene-co-[2,5-dioctyloxy-pphenylene-bis-2(4-methylphenyl)vinylene]}methyl-PpPV,poly{p-phenylene-co-[2,6naphthy-lene-bis-2(4-nonylphenyl)vinylene]}nonyl-PpPV-NV in toluene. The
copolymers are related to poly(phenylene vinylene) and have been synthesized via
Horner-Emmons polycondensation reaction. The optical gain determined from the
amplified spontaneous emission (ASE) intensity is dependent on the excited stripe
length. The net optical gain coefficients are found to vary between 0.1 cm-1 in nonylPpPV to 2.5 cm-1 in methyl-PmPV under nanosecond pulse excitation. The gain for
Rodamine 6G was also measured under the same experimental condition and was
used to determine the stimulated emission cross-sections for the four polymers and
found to be SE (peak) = 6.7 x 10-20 cm2 for nonyl-PpPV, SE (peak) = 1.7 x 10-18 cm2
for methyl-PmPV, SE (peak) =1.4 x 10-18 cm2 for methyl-PpV, and SE (peak) = 1.5
x 10-18 cm2 for nonyl-PmPV-NV.
P.21
NONLINEAR OPTICAL PROPERTIES
HEXA-ALUMINATE LaMgAl11O19
OF
Cr3+ -DOPED
LANTHANUM-MAGNESIUM
H. Manna*
*Physics Department, University of Bahrain, Isa Town, 32038, Kingdom of Bahrain
e-mail: hacene@sci.uob.bh
Laser Phys. Lett. DOI 10.1002510005/ 1-4(2005).
(Published online: 17 February, 2005)
Abstract
A single beam Z-Scan technique is used to characterize the nonlinear optical
properties of Cr3+ -doped lanthanum-magnesium hexa-aluminate LaMgAl11O19 with
c.w.laser radiation at 514.5 nm. The real part n'2 = 2.6 x 10-8 cm2/W and the
imaginary part n''2 = - 1.1 x 10-9 cm2/W of the laser induced complex refractive index
are measured. The excited state absorption cross-section is deduced and found to be 3
x 10-20 cm2 at the same wavelength.
P.22
Z-SCAN
MEASUREMENTS
PERYLIMIDE DYES
IN
POLY(METHYL
METHRACRYLATE)
DOPED
WITH
H. Manna*
*Physics Department, University of Bahrain, Isa Town, 32038, Kingdom of Bahrain
e-mail: hacene@sci.uob.bh
Laser Phys. Lett.1(5),259-263 (2004).
21
(Published online : 8 April, 2004)
Abstract
Optical limiting with reverse absorption saturation is reported on plastic bulk of
poly(methyl methacrylate) (PMMA) doped with two different perylimide molecules,
KF 241 and BASF 339. The non-linear absorption coefficient  was measured at
three wavelengths using the open z-scan technique.  was used to calculate the value
of imaginary component of the third order non-linear susceptibility X(3). The
nonlinear behaviour is explained in terms of a six-level model of electronic structure.
P.23
SELF-ABSORPTION AND LIGHT
POLY(METHY-METHACRYLATE)
AMPLIFICATION IN PERYLIMIDE DYES-DOPED
Hacene Manaa*
*Physics Department, University of Bahrain, Isa Town, 32038, Kingdom of Bahrain
e-mail: hacene@sci.uob.bh
Journal of Alloys and Compounds 393/1-2, 219-222(2005)
Abstract
Optical properties of poly(methyl-methacrylate)(PMMA) doped with perylimide
molecules are studied. The self –absorption of perylimide BASF 339 (red) and KF
241 (yellow) is investigated by measuring the emission spectrum in the sample as a
function of the distance traveled by the emitted light, after being excited with a
continuous laser. The effect of this phenomenon on the shape of the emission
spectrum and consequently on the wavelength tunability range is found to be
important. The optical gain coefficient is measured using a simple set-up based on
only one exciting laser beam, and the detection of a single-pass amplified light
emitted along the length of an optically excited sample. The presence of stimulated
emission is determined by the exponential increase of the photoluminescence output
intensity, when the only length of the excited region is varied. Under moderate
pumping intensities, a net laser gain of 53 cm-1 and 36 cm-1 is measured for yellow
KF 241 and red BASF 339, respectively. The increase of the emission spectra as the
length of the excited region of the sample is increased is found to be wavelength
dependent.
P.24
EFFECTS OF STATIC MAGNETIC FIELDS ON EARLY EMBROYONIC DEVELOPMENT OF
THE SEA URCHINS Echinometra mathaei
Lama Sakhnini and Maheen Dairi
L.Sakhnini is with the Physics Department, College of Science, University of Bahrain,
Isa, Kingdom of Bahrain (e-mail: l_sakhnini@yahoo.com )
M. Dairi is with the Biology Department, College of Science, University of Bahrain,
Isa, Kingdom of Bahrain.
IEEE: Transactions on Magnetics, 40(4),2979-2981(2004)
Abstract
The influence of static magnetic fields with intensity of 30-50 mT on the early
cleavage division of the sea urchin Echinometra mathaei was investigated. The
exposure of fertilized eggs to 30,40, and 50 mT of magnetic fields delayed the onset
of early cleavage division. A delay in the first cleavage of 15, 30 and more than 60
22
min was caused by application of 30,40, and 50 mT, respectively. The data also
showed a significant decrease in cleaved cells for the exposed embryos. Moreover,
the exposed eggs to magnetic fields showed more abnormalities compared to the
control group. As the intensity of the magnetic field is increased, earlier appearances
of abnormalities were observed. That is, deformed fertilization membrane appeared
after only 15 min of exposure to 50 mT compared to 30 min in 30 and 40 mT
exposures and 90-105 min in the control group.
P.25
THE MECHANICAL PROPERTIES OF SKIN USING LIGHT REFLECTION TECHNIQUE
L. Sakhnini1, Muneer Excel1, M. Dairi2
University of Bahrain, College of Science, 1 Department of Physics,
2
Department of Biology.
The International Symposium on Optical Science and
Technology, San Diego Convention Center, San Diego,
California, USA. 3-8 August, 2003. Proceedings of SPIE's
vol.5212-46.(2003).
Abstract
The experimental method is designed to measure small changes that take place in the
reflection characteristics of the skin as a function of applied stretch. Pieces of rabbit
skin were stretched and light reflection was measured. Different moisturing creams
which known to increase the elasticity of the skin were applied to some of the skin
samples.
P.26
MATHEMATICAL MODELLING
OF TWO PHASE FLOW IN A VERTICAL WELL
CONSIDERING PARAFFIN DEPOSITS AND EXTERNAL HEAT EXCHANGE
V. Sh. Shagopova , N.G. Musakaevb, N. S. Khabeevc and S. S. Bailey c
a
Sterlitamak State, Pedagogical Institute,Sterlitamak 453103, Russia
b
Tyumen Insitute of Mechanics of Multiphase Systems, Tyumen 625000, Russia.
C
Department of Mathematics, College of Science, University of Bahrain, P.O.Box
32038, Isa Town, Bahrain
International Journal of Heat and Mass transfer , 47(4),
843-851(2004) (Appeared online 7 October 2003)
Abstract
Processes, occuring during exploration of gas-oil wells in frozen rock are simulated.
A system of differential equations, describing hydro and thermal dynamics of an
ascending two-phase flow of a hydrocarbon system in a vertical channel taking into
account phase transitions and structure of a flow is developed. Kinetics of paraffin
deposits on internal walls of an elevating column of a well are considered. The effect
of the heat exchange of a well within frozen rock is developed using differential
equations that describe the evolution of the radius of thermal influence of the well and
the radius of the melting zone. We conclude with numerical research of some
preventive ways of dealing with paraffin deposits.
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