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9 results on '"Kassim, C."'

1. Surface Driven Mn-Doping of Ge Quantum Dots - Mn-Interaction with the Ge QD{105} Facet and the Wetting Layer

Author

Kassim, C. A. Nolph. J. K., Floro, J. A., and Reinke, P.

Subjects
Condensed Matter - Materials Science
Abstract

The interaction of Mn with Ge quantum dots (QD), which are bounded by {105} facets, and the strained Ge wetting layer (WL), terminated by a (001) surface, is investigated with scanning tunneling microscopy (STM). Mn is deposited on the Ge QD and WL surface in sub-monolayer concentrations, and subsequently annealed up to temperature of 400 C. Bonding and surface topography were measured with STM during the annealing process. Mn forms flat islands on the Ge {105} facet, whose shape and position is guided by the rebonded step reconstruction. The images show a hybridization of Mn-d band and empty states of the Ge{105} facet. A statistical analysis of Mn-islands on the QD yields a slight preference for edge positions, whereas the QD strain field does not impact Mn-islands. The formation of ultra-small Mn-clusters dominates on the Ge(001) WL, which contrasts the Mn-interaction with unstrained Ge(001) surfaces. Annealing (<160 C) leaves the Mn-clusters on the WL unchanged, while the Mn-islands on the Ge{105} facet undergo a ripening process, followed by a volume gain attributable to the onset of intermixing with Ge. This is supported by a statistical analysis of island volume, and size distribution. Increasing the annealing temperature (220- 375 C) leads to a rapid increase in Mn-surface diffusion evidenced by the formation of nanometer size clusters, which are identified as germanide Mn5Ge3 by a mass balance analysis. This reaction is accompanied by the disappearance of the original Mn-surface structures completing Mn de-wetting. This study unravels the details of Mn-Ge interactions, and demonstrates the role of surface diffusion as a determinant in the growth of Mn-doped Ge materials., Comment: Images are 150 ppi in order to meet ArXiv size limit

Published
2012

2. Genetic algorithm for intrusion detection system in computer network

Author

Yuslinda Wati Mohamad Yusof, Afdallyna Fathiyah Harun, Saiful Izwan Suliman, Hamizan Suhaimi, Roslina Mohamad, and Murizah Kassim c

Subjects
Control and Optimization, business.product_category, Computer Networks and Communications, Process (engineering), business.industry, Computer science, Intrusion detection system, Authorization, Local area network, Genetic algorithm, Hardware and Architecture, KDD'99, Signal Processing, Benchmark (computing), Internet access, Computer network systems, Electrical and Electronic Engineering, business, Information Systems, Computer network, Hacker
Abstract

Internet connection nowadays has become one of the essential requirements to execute our daily activities effectively. Among the major applications of wide Internet connections is local area network (LAN) which connects all internet-enabled devices in a small-scale area such as office building, computer lab etc. This connection will allow legit user to access the resources of the network anywhere as long as authorization is acquired. However, this might be seen as opportunities for some people to illegally access the network. Hence, the occurrence of network hacking and privacy breach. Therefore, it is very vital for a computer network administrator to install a very protective and effective method to detect any network intrusion and, secondly to protect the network from illegal access that can compromise the security of the resources in the network. These resources include sensitive and confidential information that could jeopardise someone’s life or sovereignty of a country if manipulated by wrong hands. In Network Intrusion Detection System (NIDS) framework, apart from detecting unauthorized access, it is equally important to recognize the type of intrusions in order for the necessary precautions and preventive measures to take place. This paper presents the application of Genetic Algorithm (GA) and its steps in performing intrusion detection process. Standard benchmark dataset known as KDD’99 cup was utilized with forty-one distinctive features representing the identity of network connections. Results presented demonstrate the effectiveness of the proposed method and warrant good research focus as it promises exciting discovery in solving similar-patent of problems.

Published
2020

4. Nitrate reducing bacterial activity in concrete cells of nuclear waste disposal

Author

Albrecht A., Rafrafi Y., Sablayrolles C., Bertron A., Kassim C., Alquier M., and Erable B.

Subjects
Physics, QC1-999
Abstract

Leaching experiments of solid matrices (bitumen and cement pastes) have been first implemented to define the physicochemical conditions that microorganisms are likely to meet at the bitumen-concrete interface (see the paper of Bertron et al.). Of course, as might be suspected, the cement matrix imposes highly alkaline pH conditions (10

Published
2013
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5. Catalyse biotique et abiotique de la réduction des nitrates en milieu alcalin dans le contexte du stockage profond des déchets radioactifs

Author

Bertron, A., primary, Erable, B., additional, Alquier, M., additional, Jacquemet, N., additional, Kassim, C., additional, Sablayrolles, C., additional, Albasi, C., additional, Basseguy, R., additional, Strehaiano, P., additional, Vignoles, M., additional, Albrecht, A., additional, and Escadeillas, G., additional

Published
2013
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7. Binding of sigma-ligands to C57BL/6 mouse brain membranes: effects of monoamine oxidase inhibitors and subcellular distribution studies suggest the existence of sigma-receptor subtypes.

Author

Itzhak, Y, Stein, I, Zhang, S H, Kassim, C O, and Cristante, D

Abstract

Our preliminary studies indicated that certain monoamine oxidase (MAO) inhibitors display high affinity for the sigma-binding sites labeled with (+)[3H]-3-(3-hydroxyphenyl)-N-1-(propyl)piperidine [(+)[3H]-3-PPP] in C57BL/6 mouse brain (Itzhak, Y., and Kassim, C. D.: Eur. J. Pharmacol. 176: 107-108, 1990). In the present study, the drug specificity and the subcellular distribution of (+)[3H]-3-PPP, (+)[3H]-N-allylnormetazocine [(+)[3H]SKF 10047] and [3H]1,3-di-o-tolyl-guanidine ([3H]DTG) binding sites in C57BL/6 mouse brain were investigated, and the properties of clorgyline interaction with the (+)-3-PPP/sigma-binding site(s) were examined. (+)[3H]-3-PPP binding, but not [3H]DTG binding, is inhibited by low concentrations (nM) of the dextrorotatory (+)-isomers of SKF 10047, 3-PPP and deprenyl and the type A MAO inhibitor, clorgyline. The haloperidol-sensitive/(+)[3H]SKF 10047 binding sites display virtually identical sensitivity towards the MAO inhibitors as (+)-3-PPP binding sites. These observations suggest a distinction between [3H]DTG and (+)[3H]-3-PPP/(+)[3H]SKF 10047 binding sites in the mouse brain. Clorgyline interaction with (+)-3-PPP/sigma-sites is competitive and reversible unlike the interaction of clorgyline with MAO-A. The sigma-ligands tested do not inhibit MAO activity and bind to sites that are apparently distinct from the MAO binding sites labeled with [3H]-N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. However, the mitochondrial fraction of the mouse brain that expresses MAO activity and high density of [3H]-N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine binding sites also comprises high density of (+)-3-PPP/(+)SKF 10047 binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Published
1991

8. Halomonas desiderata as a bacterial model to predict the possible biological nitrate reduction in concrete cells of nuclear waste disposals.

Author

Alquier M, Kassim C, Bertron A, Sablayrolles C, Rafrafi Y, Albrecht A, and Erable B

Subjects
Biodegradation, Environmental, Biological Availability, Denitrification, Hydrogen-Ion Concentration, Oxidation-Reduction, Halomonas growth & development, Halomonas metabolism, Nitrates metabolism, Radioactive Waste prevention & control, Waste Disposal, Fluid methods
Abstract

After closure of a waste disposal cell in a repository for radioactive waste, resaturation is likely to cause the release of soluble species contained in cement and bituminous matrices, such as ionic species (nitrates, sulfates, calcium and alkaline ions, etc.), organic matter (mainly organic acids), or gases (from steel containers and reinforced concrete structures as well as from radiolysis within the waste packages). However, in the presence of nitrates in the near-field of waste, the waste cell can initiate oxidative conditions leading to enhanced mobility of redox-sensitive radionuclides (RN). In biotic conditions and in the presence of organic matter and/or hydrogen as electron donors, nitrates may be microbiologically reduced, allowing a return to reducing conditions that promote the safety of storage. Our work aims to analyze the possible microbial reactivity of nitrates at the bitumen - concrete interface in conditions as close as possible to radioactive waste storage conditions in order (i) to evaluate the nitrate reaction kinetics; (ii) to identify the by-products (NO2(-), NH4(+), N2, N2O, etc.); and (iii) to discriminate between the roles of planktonic bacteria and those adhering as a biofilm structure in the denitrifying activity. Leaching experiments on solid matrices (bitumen and cement pastes) were first implemented to define the physicochemical conditions that microorganisms are likely to meet at the bitumen-concrete interface, e.g. highly alkaline pH conditions (10 < pH < 11) imposed by the cement matrix. The screening of a range of anaerobic denitrifying bacterial strains led us to select Halomonas desiderata as a model bacterium capable of catalyzing the reaction of nitrate reduction in these particular conditions of pH. The denitrifying activity of H. desiderata was quantified in a batch bioreactor in the presence of solid matrices and/or leachate from bitumen and cement matrices. Denitrification was relatively fast in the presence of cement matrix (<100 h) and 2-3 times slower in the presence of bituminous matrix (pH 9.7). The maximal rate of denitrification was approximately 0.063 mM h(-1) and some traces of nitrite were detected for a few hours (<2%). Overall, the presence of solid cement promoted the kinetics of denitrification. The inspection of the solid surfaces at the end of the experiment revealed the presence of a biofilm of H. desiderata on the cement paste surface. These attached bacteria showed a comparable denitrifying activity to planktonic bacterial culture. However, no colonization of bitumen was observed either by SEM or by epifluorescence microscopy., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Published
2014
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