Ali Issa - Academia.edu (original) (raw)

Papers by Ali Issa

HAL (Le Centre pour la Communication Scientifique Directe), Jun 24, 2018

arXiv (Cornell University), Sep 15, 2014

This paper introduces a statistical treatment to use Cepheid variable stars as distance indicator... more This paper introduces a statistical treatment to use Cepheid variable stars as distance indicators. The expansion rate of the Universe is also studied here through deriving the value of the Hubble constant H0. A Gaussian function approximation is proposed to fit the absolute magnitude and period of Cepheid variables in our galaxy. The calculations are carried out on samples of Cepheids observed in 23 galaxies to derive the distance modulus (DM) of these galaxies based on the frequency distributions of their periods and intrinsic apparent magnitudes. The DM is the difference between the apparent magnitude for extragalactic Cepheids and the absolute magnitude of the galactic Cepheids at maximum number. It is calculated by using the comparison of the period distribution of Cepheids in our galaxy and in other galaxies. This method is preferred due to its simplicity to use and its efficiency in providing reliable DM. A linear fit with correlation coefficient of 99.68% has been found between the published distance modulus and that computed one in the present work. From the present sample, a value of H0 in the range of 66 to 80 ± 5 km s-1 Mpc-1 is determined. The present procedure of computation and its accuracy are confirmed by the high correlation found between our computed DM and that published in the literature.

Human Centred Intelligent Systems, 2020

This paper reports a comparative study of the most significant 4G mobile network open-source plat... more This paper reports a comparative study of the most significant 4G mobile network open-source platforms, namely: OAI and srsLTE. Moreover, this study includes 4G Amarisoft software, one of the promising commercial alternatives. The three alternatives were evaluated in the indoor environment of the university building in order to enhance LTE signal propagation and extend the capacity of preexisting WIFI solution. The carried out experimental measurements are compared and analyzed according to the Quality of Service (QoS) link and to the use of processing and/or computation resources. The results demonstrated that the commercial one outperforms the open-source alternatives, although the performance of the OAI solution appears to be fairly similar to the Amarisoft one.

For refugees seeking to reach Europe, the digital infrastructure is as important as the physical ... more For refugees seeking to reach Europe, the digital infrastructure is as important as the physical infrastructures of roads, railways, sea crossings and the borders controlling the free movement of people. It comprises a multitude of technologies and sources: mobile apps, websites, messaging and phone calling platforms, social media, translation services, and more. The smartphone is an essential tool for refugees because it provides access to a range of news and information resources that they depend on for their survival. Access to digital resources plays a crucial role in the planning and navigating of their perilous journeys, as well as in their protection and empowerment after arrival in Europe. But despite their utility, mobile phones have a paradoxical presence in the lives of refugees-they are both a resource and a threat. The digital traces that refugees' phones leave behind make them vulnerable to surveillance and other dangers. The research on which this report is based was conducted collaboratively by The Open University and France Médias Monde between October 2015 and April 2016. Our aim was to assess whether the provision of news and information for refugees was adequate to their needs. So much is written about refugees but little by or for them. Their voices often get drowned out in the cacophony of media and political debate about how to tackle "the refugee crisis". The problems are exacerbated by the lack of a pan-European approach to the provision of reliable, relevant and timely information. Policy and practice are uncoordinated and ineffective. There are many initiatives using apps but the field is fragmented and there is little or no collaboration. It is our common European problem. European member states alongside international news media need urgently to work together to find solutions to the worst humanitarian crises in recent history. There are significant ethical and practical difficulties in researching refugees, including privacy, security, trust, and informed consent. Our research team was very mindful of these problems. Most of us have had direct experience as researchers and/or workers in NGOs and refugees' support groups. The research was carried out on a shoestring budget offered by Centre for Research on Socio-Cultural Change at the Open University. We are very grateful to the researchers who gave their time generously, some on top of already heavy workloads. Professor Heaven Crawley and her colleagues generously shared with us a database of some 500 interviews conducted as part of the MEDMIG project. As a multidisciplinary team we are skilled in using a range of different research methods. Mixed methods enable us to offer diverse perspectives on the problem and to seek effective solutions to the information gaps that refugees face, and which often make the difference between life and death. We also involve refugees themselves in participatory research practices. We want to ensure that understanding the actual uses of technological, news and informational resources will direct any initiatives to create new resources and so contribute to their success. Refugees are not a homogenous group. The experiences of men, women and children in different places are profoundly different, as are their demographic characteristics and ideological positions as well as linguistic, social and cultural competences and digital literacy. All these factors need to shape the development of any resources for refugees. This report summarises the first of three planned phases of research. We hope this work will lead to the provision of valuable resources for refugees. This first phase feeds into plans to develop digital resources for refugees in Europe and to make recommendations to support such plans. The second and third phases will involve developing resources and monitoring and evaluating progress. Please get in touch if you wish to share information or comment on the report.

The Journal of Physical Chemistry C, 2022

American Journal of Infection Control, 2017

Pour comprendre les logiques de la constitutionnalisation de l'Islam dans les paysarabes, cet... more Pour comprendre les logiques de la constitutionnalisation de l'Islam dans les paysarabes, cette etude propose, dans la premiere partie, de mettre en evidence la permanence del'influence constitutionnelle de l'Islam. En effet, toutes les constitutions des Etats arabes, al'exception de celle du Liban, se referent a l'Islam. La place preeminente qu'occupe cettereligion dans les textes fondamentaux arabes influe effectivement sur la structure etl'organisation de l'Etat, mais egalement la protection des droits fondamentaux, en particuliercelle relative a la liberte religieuse.Dans la seconde partie, on a essaye de mettre en exergue les voies qui permettent aux Etatsarabes de depasser la vision theologique sur laquelle repose leur droit constitutionnel.L'accent est mis sur deux tendances : la secularisation progressive du pouvoir politique atravers la marginalisation du referent religieux et la consecration du pouvoir etatique d'unepart, et la ratio...

There are several indicators suggesting that Near Field Communication (NFC) is about to have a ma... more There are several indicators suggesting that Near Field Communication (NFC) is about to have a major breakthrough in the market. In this paper we explore the feasibility of implementing an NFC event ticketing system and investigate potential future functionality while answering our research question: How could NFC be used to better apply to the field of event ticketing, as compared to existing NFC ticketing solutions? We answered this question by using a design research approach in order to implement and evaluate an event ticketing prototype which transfers information through NFC using peer-to-peer mode. Our findings imply that implementing a system in this way makes NFC more applicable for event ticketing purposes as compared to existing

This paper describes obtaining some potential antibacterial imidazoles using QSAR method. Highly ... more This paper describes obtaining some potential antibacterial imidazoles using QSAR method. Highly substituted imidazoles were synthesized and studied their bacterial activities. Some of the compounds showed considerable bactericidal activities against S. aureus. MLR models for various ring substituted imidazoles were derived to elucidate their structure-activity relationships. The descriptors used in the model relate to surface area, volume, dipole moment and the properties of molecule. Both the training set and test set compounds were modeled to the established procedures and were aligned. There were good correlations between the predicted and experimental activities for both the test set and training set compounds by MLR models. The derived MLR models have a very good predictability (q2 > 0.81). According to this study, six new imidazoles having high biological activity against S. aureus were suggested.

ACS Applied Nano Materials, 2021

Three-dimensional (3D) photoluminescent crypto-images can be created by nanopatterning quantum do... more Three-dimensional (3D) photoluminescent crypto-images can be created by nanopatterning quantum dots (QDs) within a polymeric micro-object. A UV-sensitive photoresist, doped with (CdSe)ZnS core–shell QDs, is employed to fabricate fluorescent devices, by two-photon polymerization direct laser writing (TPP-DLW). In this work, we report on the expulsion of the majority of QDs from the irradiated area, caused by the cross-linking of the monomers, determining their accumulation on the photopolymer surface. At the same time, QDs get excited and trigger a surrounding thermal polymerization, leading to a variation of the spatial resolution of the fabricated structures. By opportunely combining these physical phenomena, it is possible to control the local density of QDs with nanometric resolution and, as a consequence, to tune the local photoemission of the fabricated polymeric structure. A photopolymer doped with five different concentrations of (CdSe)ZnS core–shell QDs is analyzed and tested. We define the best conditions to create nanostructures containing only few QDs to be integrated in optical devices, as well as to create 3D photoluminescent micro crypto-images. By TPP-DLW and one-photon lithography, a 3D fluorescent design can be concealed inside a polymeric microstructure that is swiftly fabricated using a photoresist. An example of a 3D crypto-image is shown to illustrate the technique.

Nature Communications, 2020

Hybrid plasmonic nano-emitters based on the combination of quantum dot emitters (QD) and plasmoni... more Hybrid plasmonic nano-emitters based on the combination of quantum dot emitters (QD) and plasmonic nanoantennas open up new perspectives in the control of light. However, precise positioning of any active medium at the nanoscale constitutes a challenge. Here, we report on the optimal overlap of antenna’s near-field and active medium whose spatial distribution is controlled via a plasmon-triggered 2-photon polymerization of a photosensitive formulation containing QDs. Au nanoparticles of various geometries are considered. The response of these hybrid nano-emitters is shown to be highly sensitive to the light polarization. Different light emission states are evidenced by photoluminescence measurements. These states correspond to polarization-sensitive nanoscale overlap between the exciting local field and the active medium distribution. The decrease of the QD concentration within the monomer formulation allows trapping of a single quantum dot in the vicinity of the Au particle. The la...

Soft Matter, 2020

Gold nanocubes with tunable size and interparticle gap were produced by altering the spin-coating... more Gold nanocubes with tunable size and interparticle gap were produced by altering the spin-coating speed of PMMA/gold precursor dispersion on silicon substrate. Then, their optical properties were provided by spectroscopic ellipsometry measurements.

SPE Kuwait Oil & Gas Show and Conference, 2019

With the increase in Plug and Abandonment activities worldwide, Oil and Gas Exploration and Produ... more With the increase in Plug and Abandonment activities worldwide, Oil and Gas Exploration and Production Companies are always looking for ways to reduce rig time and overall costs involved in such activities. One of the plug and abandonment objectives is to seal the well and isolate permanently. This requires milling a window inside the casing to set a cement plug to seal the reservoir and prevent hydrocarbon leakage to surface or hydrocarbon movement between different formations, as well as preventing contaminations of aquifers. In most of the wells, where the cement plug is to be set there are two overlapping casing strings. In standard Plug and Abandonment applications, this will need pilot milling of the inner casing string from surface (couple of 100s to 1000s meters) to the required depth and then section milling a window in the outer casing string, then opening the formation to set a cement plug and seal the reservoir. Responding to such application, the plug and abandonment re...