Digital Repository for University of Tripoli

Aims: The aim of the study was to characterize a spirochaete isolated from thelesions of a cow with digital dermatitis (DD).Methods and Results: The characterization was on the basis of its light andelectron microscopic appearance, enzymic profile and DNA sequence analysisof its flagellin and 16S rRNA genes. The spirochaete was 6–8-lm long and 0Æ2–0Æ3 lm in diameter, and possessed seven to eight periplasmic flagella, withthree to five helical turns. The enzymic profile of the bacterium resembles, butis not identical to that of Treponema brennaborense. Its flagellin gene sequencewas identical to that of Treponema phagedenis but distinct from that of anovine spirochaete. Analysis of a 1477-bp region of the 16S rRNA genes indica-ted that this is a Treponema species and that it is indistinguishable from someisolates made from cases of bovine DD in the United States. Finally, electronmicroscopy revealed the presence of myovirus-like bacteriophage particles in allcultures of the treponeme examined.Conclusions: The spirochaete isolate was identified as a Treponema species clo-sely related to some isolates from the United States (by 16S rDNA) and to T.phagedenis (by flagellin gene sequence) and is associated with bacteriophageparticles.Significance and Impact of the Study: The fact that the isolates with the sameor very similar 16S rDNA sequences have been obtained from cases of bovineDD in cattle in different countries at different times, lends further support tothe hypothesis that treponemes play a role in the pathogenesis of this disease arabic 10 English 72
Abdulgader Dhawi Alfitouri Dhawi(1-2021)

The transcriptional changes that occurred in Salmonella enterica serovar Enteritidis during colonization of the alimentary tract of newly hatched chickens were studied. A whole genome oligonucleotide microarray was used to compare the expression pattern with that from bacteria cultured in nutrient broth in vitro. Amongst other changes Salmonella Pathogenicity Island (SPI)-1, SPI-2 and SPI-5 genes were up-regulated in vivo suggesting a close association with the mucosa during colonization. Particular attention was paid to genes associated with metabolism of dicarboxylic acids and to responses to high osmolarity. Association between the colonization phenotype and gene mutations indicated that the latter was more important as a contribution to the colonization phenotype. arabic 12 English 89
Abdulgader Dhawi, Elazomi A, Jones M A, Lovell M A, Li H, Emes R D, Barrow P A(7-2011)

Bacterial pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) represent a well-known public health problem affecting both healthcare-associated and community populations. Past studies have clearly shown the value of characterizing problem organisms including MRSA through the use of molecular techniques (i.e. strain typing), with the aim of informing local, regional and national efforts in epidemiological analysis and infection control. The country of Libya represents a challenge for such analysis due to limited historical infectious disease information and major political unrest culminating in the Libyan Civil War (Libyan Revolution) in 2011. A MRSA study population of 202 isolates, cultured from patients in Tripoli Medical Center through this historical period (2008–2014), was characterized by both phenotypic and molecular methods. The results revealed a diversification of epidemic MRSA strains over time with generally increasing resistance to fluoroquinolone antibiotics. The study identified prevalent MRSA in comparison to known global epidemic types, providing unique insight into the change of strains and/or characteristics over time especially with reference to the potential influence of the political revolution (i.e. pre- and post-2011). arabic 17 English 111
Elloulu BenDarif, Asma Khalil , Abdunnabi Rayes , Emad Bennour , Abdulgader Dhawi, John J Lowe , Shawn Gibbs, Richard V Goering (12-2016)

This paper, emphasis different growth techniques of two-dimensional hole gas of strained germanium (sGe) heterostructure, molecular beam epitaxy (MBE) and chemical vapor deposition (CVD). sGe heterostructure has become an important material as a replacement material to Silicon in P-type devices because of its higher hole mobility and lower effective mass. Researchers study this material in terms of electrical and spintronic devices according to technology demands for devices with higher efficiency and low power consumption. High hole mobility up to 1×10cm/Vs at temperature of 1.5 K has been reported for normal structure declaring high quality samples with low density dislocation and low interface roughness. arabic 14 English 105
Adel Diyaf, A.H. A. Hassan , U. Elfurawi , A. E. Abubkr (6-2019)

Swirl stabilised combustion is one of the most successful technologies for flame stabilisation in gas turbine combustors. Lean premixed combustion systems allow the reduction of NOx coupled with fair flame stability. The swirl mechanism produces an aerodynamic region known as central recirculation zone (CRZ) providing a low velocity region where the flame speed matches the flow velocity, thus anchoring the flame whilst serving to recycle heat and active chemical species to the root of the former. Another beneficial feature of the CRZ is the enhancement of the mixing in and around this region. However, the mixing and stabilisation processes inside of this zone have shown to be extremely complex. The level of swirl, burner outlet configuration and combustor expansion are very important variables that define the features of the CRZ. The complex fluid dynamics and lean conditions pose a problem for stabilization of the flame. The problem is even more acute when alternative fuels are used for flexible operation. Therefore, in this paper swirling flame dynamics are investigated using computational fluid dynamics (CFD) with commercial software (ANSYS). A new generic swirl burner operated under lean-premixed conditions was modelled. A variety of nozzles were analysed using isothermal case to recognize the the behavers of swirl . The investigation was based on recognising the size and strength of the central recirculation zones. The dimensions and turbulence of the Central Recirculation Zone were measured and correlated to previous experiments. The results show how the strength and size of the recirculation zone are highly influenced by both the shear layer surrounding the Central Recirculation Zones (CRZ) and outlet configurations. arabic 11 English 64
Adel Diyaf, Hesham Baej, Adel Akair, Salem Adeilla, Abdurahman Kraiem(9-2018)

Due to the global concerns on the depletion of fossil fuels and the negative effect of their use in environmental pollution and climate change, renewable energy resources are increasingly in demand. Global solar power generation has almost doubled during the last 2 years with countries, such as China, leading the way with huge investments. The first generation of solar cells are either single or multi crystalline silicon, and still have 59% market share; the second (amorphous silicon, copper indium gallium selenide, and cadmium telluride) is approaching in terms of cost and efficiency; and the third (dye sensitized solar cells, organic photovoltaic, quantum dots, and perovskite) all show promise yet are still to come to market. However, future solar cells (using copper oxide and zinc oxide) featuring the regular intrusion of one junction layer into the other in order to massively improve junction contact area are of particular promise. arabic 7 English 50
Adel Diyaf, Yahya Alajlani, Abed Alaswad, Frank Placido, Des Gibson(1-2018)

In this paper, considers a solution of Maxwell's curl equations by using the finite-difference time-domain (FDTD) method. We simulated electromagnetic waves propagation in free space. The electric and magnetic fields generated in two cases to make a comparison between the models. All models were computed using the same parameters. This study showed that the intensities of the fields affected when adding three excited sources pointed in three locations. However, it was noted that three sources placed in the same location improved the distributions of the fields. Therefore, this difference in excitation position leads to change the image intensity distribution. arabic 7 English 43
Adel G Diyaf, Sedig S. Farhat(4-2017)

Hybrid photovoltaic cells take the advantages of silicon in charge carrier separation and transport and organic dyes in strong complementary light absorption. Photovoltaic responses from a set of hybrid solar cells based on amorphous silicon and phthalocyanine dyes of double- or triple-layer heterojunction structures were investigated, which were found to have thickness dependence with the organic active layers. It was found that the photocurrent contributions from organic layers are limited, although they are strong light absorbers. The main photocurrent contributions are from the silicon counterpart. arabic 13 English 111
Adel Diyaf, Huan Zhao, Zhiqun He, Xiaojin Zhang, Zhi Zhang, John I B Wilson, Anna H N Lind(4-2015)