This study aims at designing an ensemble Machine Learning Model to serve as a screening system to predict the potential of COVID-19 infection. according to specific parameters, it considers an online survey filled by 5966 participants from Khartoum City since Khartoum was under quarantine. Major statistical approaches were implemented as data cleaning, performing feature selection using Random Forest algorithm to elect the proper features, and finally, building the model on two parts: the first one used K-mode clustering algorithm whereas the second utilized Support Vector Classifier (SVC). The features included symptoms, age, underlying conditions, geographical location, the period of the symptoms, close contact with someone who has confirmed a case of coronavirus, and the number of deaths among the family members. The results indicated that the overall accuracy of the K-mode Part was 71 %; however, the sensitivity to predict cases as negative was 77%, while the accuracy of SVC Part was 76 %. The identity between predictions of the two Parts was 79%. The work concluded that the symptoms in the proposed Screen system – considering the highest weight- appeared as following: Fatigue, Headache, Fever, Gastrointestinal Disorders, Anosmia, Dry Cough, Short of Breath, and Chest Pain, respectively

Mie-Gans (MG) fitting model theoretical model utilizing the phenomena of scattering light to determine the morphologies, shape, and size of metallic nanoparticles in solution. In the present work, the average radius of biosynthesized silver nanoparticles (AgNPs) was evaluated based on the fitting of their Ultraviolet-visible (UV-Vis) spectra by the MG fitting model for spherical and non-spherical particles. Biosynthesis of AgNPs using Lemon (Citrus Limon) leaves extract as a reducing agent and Gum Acacia as a capping and stabilizing agent was studied for various concentrations of Citrus Limon leaves extract. The investigation of structural and optical properties was carried out for the synthesized samples using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV-Vis spectroscopy. XRD confirmed the structure of AgNPs and revealed that the structure of these nanoparticles was face-centered cubic (fcc). FTIR measurements indicate the presence of citric acid in Citrus Limon leaf extract which is responsible for reducing bioreduced AgNPs. UV-Vis spectroscopy determined the surface plasmon resonance (SPR) for AgNPs; the peaks of resonances of samples appear at 436-461nm range. MG fitting evaluations show that most of AgNPs were spherical in shape with an average radius in the range of 39-47nm. Moreover, this model allows the estimation of the fraction of nonspherical and aggregated AgNPs. These unique characteristics of AgNPs have made them applicable in a large number of fields like water treatment, biomedical, energy science, catalysis, etc.

Africa tends to be isolated and sometimes forgotten when it comes to scientific research and in particular physics. But the region has great potential, being home to the youngest population in the world, and despite a variety of issues, there has been steady, albeit uneven progress towards establishing a scientific infrastructure. Ten African researchers discuss the diverse challenges and opportunities faced by physicists across the continent.

This article aims to prepare high quality of TiO2 powder and study the effect of annealing temperature. TiO2 particles were synthesized by sol-gel method using titanium tetra chloride (TiCl4) as a precursor. The dried gel was annealed at temperatures of 500oC, 600oC, 700°C and 800 °C each for 4 hours. The as-prepared samples were further characterized using X-Ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray Fluorescence spectrometer (EDX), XRD showed anatase structure after annealing and its diffraction scattering intensity indicated the improvement in the crystal structure quality of TiO2 as the temperature increases. SEM micrographs showed a randomly distributed and non-uniform cluster of TiO2 that has a size increase with annealing temperatures. EDX indicated stoichiometric chemical composition between Ti and O enhanced by annealing.

This work aims to develop simple and cost-effective methods in reduction of Cr(VI) from water to less toxic and easy separated Cr(III) using Titanium dioxide (TiO_2 TiO_2 nanoparticles are prepared by a sol-gel method using titanium tetra-chloride and characterized using X-Ray Diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray Fluorescence spectrometer (EDX) and UV-visible spectroscopy. XRD shows Anatase structure of TiO_2 after annealing at 600^°C for four hours. The particles size is estimated to be 70 nm using SEM.UV-Visible spectroscopy indicated that TiO_2 nanoparticles played important role in decreasing the concentration of Cr (VI) in water samples for different pH range of 1 to 4. The decrease in Cr(VI) concentration after the treatment is ascribed to the reduction caused by the photocatalyst effect that resulted from the presence of TiO_2 nanoparticle in water samples under direct exposure to direct sunlight.

At Al Neelain University, Khartoum, Sudan, enrollment of female undergraduate physics students is significantly higher than that of males (double or more). However, most of the female staff in the Physics Department at this university hold lecturer positions because few women hold the necessary higher degrees. Sudanese students who seek higher qualifications must study abroad. Lack of financial support for such study affects both genders, but this situation imposes additional challenges on female students because of cultural and religious constraints that limit women's ability to study abroad.

Variable laser power and temperature dependent photoluminescence (PL) measurements were used to identify some of the optical transitions and impurity-related emissions for chemically treated (Br-methanol, (NH4)(2)S + S or [(NH4)(2)S/(NH4)(2)SO4] + S solutions) or oxidised (annealed in oxygen) bulk n-InAs (111)A. A combination of PL and X-ray photoelectron spectroscopy (XPS) measurements before and after various treatments was used to identify the chemical nature of the impurities giving rise to bound exciton recombination in InAs (111). Band-to-band transitions have been observed at 0.4185 eV. In addition, two shallow neutral donor bound excitons ascribed to atomic oxygen (at 0.412 eV) and to sulphur (at 0.414 eV), have been detected after treatment

X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Raman and photoluminescence spectroscopy were used to evaluate the surface properties of n-type InAs (111)A etched in a 1% Br–methanol solution. Etching completely removes the native oxides from the surface and enhances the photoluminescence response. The adsorption of bromine onto the InAs surface leads to the formation of In–Brx and As–Brx bonds (x = 1, 2, 3) as inferred from changes in the In 3d3/2;5/2 and As 3d core level binding energies. The etch rate is found to decrease due to strong anisotropic effects and the high volatility of the bromine species. A 1 min Br–methanol etch was found to enhance the photoluminescence intensity by a factor of 3, probably due to a reduction in the surface state density upon de-oxidation of the surface. This is thought to be due to reductions in the surface state density. The presence of native oxides enhances both the surface accumulation layer and the surface state density.

A sulphur based chemical, [(NH4)(2)S/(NH4)(2)SO4] to which S has been added, not previously reported for the treatment of (1 0 0) n-GaSb surfaces, is introduced and benchmarked against the commonly used passivants Na2S center dot 9H(2)O and (NH4)(2)S. The surfaces of the treated material were studied by scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It has been found that the native oxides present on the GaSb surface are more effectively removed when treated with ([(NH4)(2)S/(NH4)(2)SO4] + S) than with (NH4)(2)S or Na2S center dot 9H(2)O, as evidenced by the ratio of the O-506 (eV) to Sb-457 eV AES peaks. XPS results reveal that Sb2S3/Sb(2)S5 "replaces" Sb2O3/Sb(2)O5, suggesting that sulphur atoms substitute oxygen atoms in Sb2O3/Sb(2)O5 to form Sb S. It seems sulphurization only partially removes Ga2O3. Treatment with ([(NH4)(2)S/(NH4)(2)SO4] + S) also results in a noteworthy improvement in the current-voltage (I-V) characteristics of Au/n-GaSb Schottky contacts compared to those fabricated on as-received material. (C) 2012 Elsevier B. V. All rights reserved.

Bulk (1 0 0) n-GaSb surfaces have been treated with a sulphur based solution ((NH4)2S/(NH4)2SO4) to which sulphur has been added, not previously reported for the passivation of GaSb surfaces. Au/n-GaSb Schottky barrier diodes (SBDs) fabricated on the treated material show significant improvement compared to that of the similar SBDs on the as-received material as evidenced by the lower ideality factor (n), higher barrier height (ϕb) and lower contact resistance obtained. Additionally, the reverse leakage current, although not saturating, has been reduced by almost an order of magnitude at −0.2 V. The sample surfaces were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The native oxide, Sb–O, present on the as-received material is effectively removed on treating with ([(NH4)2S/(NH4)2SO4]+S) and (NH4)2S. Analysis of the as-received surface by XPS, prior to and after argon sputtering, suggests that the native oxide layer is ≤8.5 nm.

An alternative sulphur blended [(NH4)2S04/(NH4)2S] solution is reported for stabilizing the bulk GaSb (100) surface. Scanning electron microscopy of treated surfaces shows a significant improvement in morphology over untreated surfaces. Dektak step profiling reveals that sulphurization causes a non-linear time dependent etching effect accompanied by smoothening of the surface while the photoluminescence is enhanced three-fold after a 30 minute treatment. The surface state density (Nss) distributions were calculated from forward IV characteristics of Au/n-GaSb Schottky structures. Surface state densities of 10cm, at midgap, were calculated, with treated surfaces showing about 3 times less than untreated. Treatment apparently unpins the fermi level in Au/n-GaSb Schottky structures as evidenced by a larger barrier height. Additionally, treatment also reduces the reverse leakage current. The reverse current however does not saturate with applied reverse bias. This may be attributed to either quantum mechanical tunnelling or near surface recombination via surface states not completely passivated (or removed) by the sulphurization.

The reaction of halogen-based etchants with n-InAs (111)A and the resulting surface morphology and surface electronic structure are investigated using field emission scanning electron microscopy and Raman spectroscopy. Using the intensity ratio of the unscreened longitudinal optical (LO) phonon to the transverse optical (TO) phonon in the Raman spectrum, a significant reduction in band bending is deduced after exposure of the InAs surface to HCl:H2O, Br–methanol and I–ethanol for moderate times and concentrations. These procedures also lead to smooth and defect-free InAs surfaces. The improvements in surface properties are reversed, however, if the concentrations of the etchants are increased or the etch time is too long. In the worst cases, pit formation and inverted pyramids with {111} side facets are observed. The influence of the etchant concentration and etch time on the morphological and electronic properties of the etched surfaces is reported.

A sulphur based chemical, ([(NH4)2S/(NH4)2SO4]) to which S has been added not previously reported for the treatment of (111)A InAs surfaces is introduced and benchmarked against the commonly used passivants Na2S·9H2O and ((NH4)2S+S), using Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It has been found that the native oxide layer present on the InAs surface is more effectively removed when treated with ([(NH4)2S/(NH4)2SO4]+S) than with ((NH4)2S+S) or Na2S·9H2O. AES depth profiles of the sulphurized layers revealed the formation of a thin (less than 8.5nm) In–S surface layer for both ((NH4)2SO4+S) and ([(NH4)2S/(NH4)2SO4]+S) treatments. No evidence for the formation of As―S bonds was found. Treatment with ([(NH4)2S/(NH4)2SO4]+S) also affected a significant improvement compared to the more established sulphur treatments in the surface morphology of the otherwise poor as-received n-InAs (111)A surface.