Isolation, diversity, and biotechnological potential of rhizo- and endophytic bacteria associated with mangrove plants from Saudi Arabia.

Marine bacteria have been exceptional sources of halotolerant enzymes since decades. The aim of the present study was to isolate bacteria producing hydrolytic enzymes from seven different mangroves collected from the coastal area of Thuwal, Jeddah, Saudi Arabia, and to further screen them for other enzymatic and antifungal activities. We have isolated 46 different rhizo- and endophytic bacteria from the soil, roots, and leaves of the mangroves using different enzymatic media. These bacterial strains were capable of producing industrially important enzymes (cellulase, protease, lipase, and amylase). The bacteria were screened further for antagonistic activity against fungal pathogens. Finally, these bacterial strains were identified on the basis of the16S rDNA sequence. Taxonomic and phylogenetic analysis revealed 95.9-100% sequence identity to type strains of related species. The dominant phylum was Gammaproteobacteria (γ-Proteobacteria), which comprised 10 different genera - Erwinia, Vibrio, Psychrobacter, Aidingimonas, Marinobacter, Chromohalobacter, Halomonas, Microbulbifer, and Alteromonas. Firmicutes was the second dominant phylum, which contained only the genus Bacillus. Similarly, only Isoptericola belonged to Actinobacteria. Further these enzyme-producing bacteria were tested for the production of other enzymes. Most of the active strains showed cellulytic and lipolytic activities. Several were also active against fungal pathogens. Our results demonstrated that the mangroves represent an important source of potentially active bacteria producing enzymes and antifungal metabolites (bioactive products). These bacteria are a source of novel halophilic enzymes and antibiotics that can find industrial and medicinal use.

'Halomonas saudii' sp. nov., a new bacterial species isolated from marine plant Halocnemum strobilaceum.

We report here the main characteristics of 'Halomonas saudii' strain Saudii DR2 (CSUR P2512), a new species of the Halomonas genus that was isolated from a rhizosphere of Halocnemum strobilaceum in April 2015.

Field emission characteristics of regular arrays of carbon nanotubes.

The developments of electronic devices based on micron-sized vacuum electron sources during the last decades have triggered intense research on highly efficient carbon based thin film electron emitters. The synthesis of massive arrays of carbon nanotubes that are oriented on patterned Fe catalyst deposited on quartz substrates is reported. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotubes devices integrated into future technology. The emission from carbon nanotubes array is explained by Fowler-Nordheim tunneling of electrons from tip-like structures in the nanometer range, which locally amplify the applied field by the field enhancement factor beta. We found that the low pressure chemical vapour deposition (LPCVD) system can produce nanotubes capable of excellent emission currents at lower voltages. The carbon nanotubes array shows good field emission with turn on field E(alpha) = 1.30 V/microm at the current density of 3.50 mA/cm2 with enhancement factor beta = 1.22 x 10(2).

Synthesis and characterizations of ferrite nanomaterials for phenyl hydrazine chemical sensor applications.

This paper presents the synthesis, characterization and phenyl hydrazine chemical sensing applications of Cd0.5Mg0.5Fe2O4 ferrite nanoparticles. The nanoparticles were synthesized by facile and simple co-precipitation method and characterized in detail in terms of their morphological, structural, compositional and electrical properties. The detailed characterization studies revealed that the prepared nanoparticles are grown in high density, possessing Cd0.5Mg0.5Fe2O4 composition and exhibiting spinel cubic structure. Moreover, the prepared Cd0.5Mg0.5Fe2O4 ferrite nanoparticles were used as efficient electron mediators for the fabrication of high-sensitive, robust, reliable and reproducible phenyl hydrazine chemical sensor by simple I-V technique. The fabricated chemical sensor exhibits a highsensitivity of 7.01 microA mM(-1) cm(-2) with an experimental detection limit of 3.125 mM in a short response time of -10.0 s. This work demonstrates that Cd0.5Mg0.5Fe2O4 ferrite nanoparticles can efficiently be utilized for the fabrication of highly sensitive and reliable chemical sensors.

Spectroscopic ellipsometry of Zn(1-x)Cu(x)O thin films based on a modified sol-gel dip-coating technique.

Nanocrystalline Zn(1-x)Cu(x)O thin films (x=0, 0.01, 0.02, 0.03, 0.04 and 0.05) were synthesized by sol-gel dip-coating technique on a quartz substrate. These films were annealed at 350°C for 2 h. The X-ray diffraction showed a hexagonal crystal structure with high intensity peak for the (002) reflection plane indicating preferential growth along the c-axis of the crystal lattice. The peak position related to the (002) peak was shifted as a result of the copper ion incorporation, confirming the interstitial substitution of the zinc ions by the copper ions. This interstitial substitution leads to a decrease of an average crystallite size and lattice constants and an increase of the micro-strain up to 2 at.% of the copper amount. The surface morphology was explored by scanning electron microscopy which confirmed the homogenous distribution of nanoparticles in the deposited films along the quartz substrates. The energy dispersion X-ray spectroscopy revealed absence of impurities in the as-deposited films. The high resolution electron microscopy and selected area electron diffraction depicted that the films have polycrystalline nature. The film thickness and optical constants of the Zn(1-x)Cu(x)O thin films were estimated by fitting the spectroscopic ellipsometric data (ψ and Δ) using three different models. The refractive index was fitted using harmonic oscillator model from which the oscillator and the dispersive energies were found. The dielectric constant, dielectric loss, energy loss functions were also determined.

Effect of ethylene carbonate as a plasticizer on CuI/PVA nanocomposite: Structure, optical and electrical properties.

Layers of ethylene carbonate (EC) modified CuI/PVA polymer composites were prepared by growth of CuI nano-particles in an aqueous solution of PVA followed by casting at room temperature. The structural, thermal, optical, electrical and di-electrical characterization of polymer composites was investigated using different techniques. These investigations confirm the growth of CuI nano-particles and reduction of PVA crystallinity by increasing ethylene carbonate concentration. These results show that energy band gap and bulk conductivity increase while activation energy reduces with the increase of EC concentration in the composite. Moreover, the variation of the dielectric permittivity and dielectric loss with EC content are found to obey Debye dispersion relations.

Development of Fe/Fe3O4 core-shell nanocubes as a promising magnetic resonance imaging contrast agent.

Here, we report the synthesis, characterization, and properties of Fe/Fe3O4 core-shell nanocubes prepared via a simple route. It includes NaBH4 reduction of FeCl3 in an ethylene glycol solution in the presence of 2-mercaptopropionic acid (surfactant) and trisodium citrate (cosurfactant) followed by surface oxidation with trimethylamine N-oxide. The morphology and structure of Fe/Fe3O4 core-shell nanocubes were characterized using transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, X-ray powder diffraction, and X-ray photoelectron spectroscopy. All of the methods confirm a Fe/Fe3O4 core-shell structure of nanocubes. Magnetic measurements revealed that the Fe/Fe3O4 core/shell nanocubes are superparamagnetic at 300 K with a saturation magnetization of 129 emu/g. The T2 weighted imaging and the T2 relaxation time showed high MRI contrast and sensitivity, making these nanocubes viable candidates as enhanced MRI contrast agents.

Kinetics of phase transformation in nanostructured Ga-Se-Te glasses.

Bulk samples of Ga25Se(F5-x)Te(x) chalcogenides were prepared by melt quenching technique. The glassy nature of these alloys was verified by X-ray diffraction. The morphology of these as-prepared alloys was studied using field emission scanning electron microscopy. Kinetics of crystallization in these glassy alloys was studied under non-isothermal conditions at different heating rates (5, 10, 15, 20 and 25 K/min) using differential scanning calorimetry. The value of glass transition and crystallization temperature was found to be composition and heating-rate dependent. The value of order parameter indicates that the crystallization was due to volume nucleation with two dimensional growths. The activation energy of crystallization and activation energy of glass transition were determined from the heating rate dependence of glass transition and crystallization temperature. Both the activation energy for glass transition and the activation energy of crystallization were found to decrease from 130.05 to 102.99 kJ/mole and from 130.05 to 102.99 kJ/mole respectively with increasing Te content in Ga-Se system.

A new large - Scale synthesis of magnesium oxide nanowires: Structural and antibacterial properties.

Large-scale one-dimensional magnesium oxide (MgO) nanowires with diameters of 6 nm and lengths of 10 µm have been successfully synthesized by a new facile and simple reaction. This production was performed via a microwave hydrothermal approach at low temperature growth of 180 °C for 30 min. The structure of as synthesized MgO nanowires were investigated by means of X-ray diffraction (X-ray), Fourier Transformation Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED) and Energy Dispersive X-ray (EDS). The antibacterial behavior of MgO nanowires concentration in solid media against Gram negative and Gram positive for different bacteria has been tested in details. The results show that the MgO nanowires have bacteriostatic activity against Escherichia coli and Bacillus sp. The antibacterial activity increases with increasing MgO nanowires concentration. Furthermore, the presence of one-dimensional MgO nanowires has high antibacterial efficacy and damages the membrane wall of bacteria. Finally, this study offered the prospect of developing ultrafine nanoscale devices utilizing MgO nanowires and implementing their useful potential in biological control.

Growth and properties of ultra-violet emitting aligned zinc oxide nanocones with hexagonal caps.

Ultraviolet-emitting, single-crystalline aligned zinc oxide (ZnO) nanocones with hexagonal caps were grown on silicon substrate via simple non-catalytic thermal evaporation process. High-purity metallic zinc powder and oxygen were used as source materials for zinc and oxygen, respectively. The detailed structural characterizations confirmed that the formed products are single-crystalline, possess a wurtzite hexagonal phase and grown along the c-axis direction. Raman-active optical-phonon E2(high) mode at 437 cm(-1) with sharp and strong UV emission at 385 nm in room-temperature photoluminescence (PL) spectrum demonstrated that the as-grown ZnO nanocones with hexagonal caps possess good-crystal quality with the excellent optical properties. Finally, a plausible growth mechanism for the formation of as-grown ZnO nanocones with hexagonal caps was also proposed.

Direct growth of ZnO nanosheets on FTO substrate for dye-sensitized solar cells applications.

ZnO nanosheets were directly grown on fluorine-doped tin oxide (FTO) substrate via simple solution process at low temperature by using zinc chloride and hexamethylenetetramine (HMTA). The morphological characterizations by SEM and TEM confirmed that the deposited structures are nanosheets in which some are assembled in flower-shaped morphologies. The detailed structural investigations revealed that the deposited nanosheets are pure and crystalline ZnO and composed of Zn and O only. The obtained ZnO nanosheets on FTO substrate were used as a photoanode to fabricate the dye sensitized solar cells (DSSCs). The fabricated DSSCs exhibited an overall light-to-electricity conversion efficiency of 1.45%. A short-circuit current of 4.51 mA/cm2, open-circuit voltage of 0.610 V, and a fill factor of 0.53 were achieved from the fabricated ZnO nanosheets-based DSSCs.

Effect of Composition on Electrical and Optical Properties of Thin Films of Amorphous Ga(x)Se(100-x) Nanorods.

We report the electrical and optical studies of thin films of a-Ga(x)Se(100-x) nanorods (x = 3, 6, 9 and 12). Thin films of a-Ga(x)Se(100-x) nanorods have been synthesized thermal evaporation technique. DC electrical conductivity of deposited thin films of a-Ga(x)Se(100-x) nanorods is measured as a function of temperature range from 298 to 383 K. An exponential increase in the dc conductivity is observed with the increase in temperature, suggesting thereby a semiconducting behavior. The estimated value of activation energy decreases on incorporation of dopant (Ga) content in the Se system. The calculated value of pre-exponential factor (sigma(0)) is of the order of 10(1) Omega(-1 )cm(-1), which suggests that the conduction takes place in the band tails of localized states. It is suggested that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. On the basis of the optical absorption measurements, an indirect optical band gap is observed in this system, and the value of optical band gap decreases on increasing Ga concentration.

Incidence of tuberculosis in people living with the human immunodeficiency virus in Saudi Arabia.

OBJECTIVE: To identify the incidence of tuberculosis (TB) in people living with the human immunodeficiency virus (HIV) (PLWH) followed at an HIV referral and care facility. DESIGN: Observational longitudinal cohort. METHODS: Data were collected longitudinally as patients were admitted to the HIV programme and included demographics, TB diagnosis and treatment, CD4+ T lymphocyte count and TB treatment outcomes. The TB-free follow-up period of all patients was used to calculate TB incidence rates. RESULTS: Between 1997 and 2007, 217 new adult patients joined the HIV programme. TB was diagnosed in 16 patients (7.4%), all of whom had acquired immune-deficiency syndrome at the time of TB diagnosis. Seven developed extra-pulmonary disease (44%), six had pulmonary TB (37%), while three had both (19%). The TB incidence rate was 1354 per 100,000 person-years (py) among the HIV-infected cohort. The incidence rate of pulmonary TB was 762/100,000 py and for extra-pulmonary TB it was 592/100,000 py. Seven patients (44%) died despite early diagnosis and treatment for TB. CONCLUSION: Among PLWH in Saudi Arabia, TB incidence is 30 times higher than in the general population, with significant mortality despite early diagnosis, treatment and tertiary care support.

Clinical features of culture-proven Mycoplasma pneumoniae infections at King Abdulaziz University Hospital, Jeddah, Saudi Arabia.

OBJECTIVE: This retrospective chart review describes the epidemiology and clinical features of 40 patients with culture-proven Mycoplasma pneumoniae infections at King Abdulaziz University Hospital, Jeddah, Saudi Arabia. METHODS: Patients with positive M. pneumoniae cultures from respiratory specimens from January 1997 through December 1998 were identified through the Microbiology records. Charts of patients were reviewed. RESULTS: 40 patients were identified, 33 (82.5%) of whom required admission. Most infections (92.5%) were community-acquired. The infection affected all age groups but was most common in infants (32.5%) and pre-school children (22.5%). It occurred year-round but was most common in the fall (35%) and spring (30%). More than three-quarters of patients (77.5%) had comorbidities. Twenty-four isolates (60%) were associated with pneumonia, 14 (35%) with upper respiratory tract infections, and 2 (5%) with bronchiolitis. Cough (82.5%), fever (75%), and malaise (58.8%) were the most common symptoms, and crepitations (60%), and wheezes (40%) were the most common signs. Most patients with pneumonia had crepitations (79.2%) but only 25% had bronchial breathing. Immunocompromised patients were more likely than non-immunocompromised patients to present with pneumonia (8/9 versus 16/31, P = 0.05). Of the 24 patients with pneumonia, 14 (58.3%) had uneventful recovery, 4 (16.7%) recovered following some complications, 3 (12.5%) died because of M pneumoniae infection, and 3 (12.5%) died due to underlying comorbidities. The 3 patients who died of M pneumoniae pneumonia had other comorbidities. CONCLUSION: our results were similar to published data except for the finding that infections were more common in infants and preschool children and that the mortality rate of pneumonia in patients with comorbidities was high.

Fluorescence anisotropy by use of optical kerr gating with incoherent laser light.

Incoherent fluorescence optical Kerr gating can in principle be used to measure fluorescence anisotropies and determine molecular reorientational times. A novel method for fluorescence anisotropy by use of optical Kerr gating with incoherent laser light is presented. Incoherent optical Kerr signals have been obtained for parallel and perpendicular fluorescence polarization for a 10(-3)-M solution of Rhodamine 6G in ethanol.

Human papillomavirus DNA and TP53 mutations in lung cancers from butchers.

To investigate whether the high frequency of human papillomavirus infection in butchers may be linked to their higher than average incidence of lung cancer, we have examined lung cancers from 40 butchers and 26 controls for the presence of DNA from both HPV type 7, which is found almost uniquely in hand warts from butchers and fishermen, and for those HPV types associated with laryngeal and genital cancers. No HPV 7, and only a low frequency of HPV DNA was found, suggesting that HPV infection does not make an important contribution to the elevated levels of lung cancer in meat handlers. In addition, the frequency of p53 mutation was shown to be slightly lower than previously reported in lung cancers.