ahmed Hassan | Hadramout - Academia.edu (original) (raw)

Papers by ahmed Hassan

Current Nanoscience, 2011

ABSTRACT Nanocrystalline hydroxyapatite (nHA) of 50 nm average diameter and length to diameter ra... more ABSTRACT Nanocrystalline hydroxyapatite (nHA) of 50 nm average diameter and length to diameter ratio of &gt; 3 was synthesized by biomimetic method. Non-isothermal sintering improved densification behavior and mechanical properties of apatite to 0.88 maximum fractional density, 70MPa bending strength, 148MPa compressive strength and 2.53GPa microhardness at sintering temperature of 1250° C. Higher sintering temperatures resulted in the decomposition of the apatite and in-situ biphasic calcium phosphate HAP/TCP formation. This process lowered apatite densification and weakened mechanical properties of the sintered specimen. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) helped to elucidate the structure/property correlations.

The Journal of Chemical Physics, 2015

The addition of carbon nanotubes (CNTs) and graphene sheets (GSs) into polymeric materials can gr... more The addition of carbon nanotubes (CNTs) and graphene sheets (GSs) into polymeric materials can greatly enhance the conductivity and alter the electromagnetic response of the resulting nanocomposite material. The extent of these property modifications strongly depends on the structural parameters describing the CNTs and GSs, such as their shape and size, as well as their degree of particle dispersion within the polymeric matrix. To model these property modifications in the dilute particle regime, we determine the leading transport virial coefficients describing the conductivity of CNT and GS composites using a combination of molecular dynamics, path-integral, and finite-element calculations. This approach allows for the treatment of the general situation in which the ratio between the conductivity of the nanoparticles and the polymer matrix is arbitrary so that insulating, semi-conductive, and conductive particles can be treated within a unified framework. We first generate ensembles of CNTs and GSs in the form of self-avoiding worm-like cylinders and perfectly flat and random sheet polymeric structures by using molecular dynamics simulation to model the geometrical shapes of these complex-shaped carbonaceous nanoparticles. We then use path-integral and finite element methods to calculate the electric and magnetic polarizability tensors (αE, αM) of the CNT and GS nanoparticles. These properties determine the conductivity virial coefficient σ in the conductive and insulating particle limits, which are required to estimate σ in the general case in which the conductivity contrast Δ between the nanoparticle and the polymer matrix is arbitrary. Finally, we propose approximate relationships for αE and αM that should be useful in materials design and characterization applications.

2012 Japan-Egypt Conference on Electronics, Communications and Computers, 2012

Oil and gas industrial plants and product pipelines belong to the largest and most sophisticated ... more Oil and gas industrial plants and product pipelines belong to the largest and most sophisticated structures to be protected against electrical shock, lightning strikes and electrostatic hazards. This paper is concerned with a typical ac substation ground grid design. The paper is distinct in presenting an integrated design method with a modern software package. This design takes into consideration the

Inorganic Chemistry, 1981

ABSTRACT Copper(I) halides react quantitatively with piperidine (Pip) in dioxygen-free methylene ... more ABSTRACT Copper(I) halides react quantitatively with piperidine (Pip) in dioxygen-free methylene chloride or nitrobenzene to form tetranuclear copper(I) complexes [(Pip)nCuX]4; n=1 or 2, X=Cl, Br or I. These complexes are very soluble and completely reduce dioxygen to dioxo bridging ligand, with stoichiometry, Δ[Cu(I)]/Δ[O2]=4.0. The stable oxo solids [(Pip)nCuX]4O2 mimic tyrosinase copper protein. They act as a homogeneous oxidative coupling catalysts for phenols. Electronic transition spectra in the near infrared with high molecular absorptivity are diagnostic for tetranuclear “Cu4X4” core structure. The electronic transitions are more likely due to charge transfer between a minimum of three halo ligands and copper(II) center. The room temperature EPR spectra of [(Pip)nCuX]4O2 in methylene chloride are isotropic with four hyperfine lines. The room temperature solid-state EPR spectra of [PipCuX]4O2 show an axial spectra with dx2−y2 ground state, suggesting square pyramidal arrangement of the five coordinated ligands around copper(II) centers. Cyclic voltammetry measurements show that they are more likely irreversible in character and show slight quasi-reversability when X=Br or I. Constant potential electrolysis indicate that the number of electrons consumed are equal to four electrons which will be due to the reduction of four copper(II) to copper(I).

Asian Journal of Chemistry, 2013

ABSTRACT This paper reports a new family of tetranuclear Cu complexes Pip4Cu4X8; Pip = piperidine... more ABSTRACT This paper reports a new family of tetranuclear Cu complexes Pip4Cu4X8; Pip = piperidine, X = Cl or Br. Two electron oxidant Br2 has been used to prepare Pip4Cu4Br8 from the respective [PipCuBr]4 complex. The dimeric complex, Pip4Cu2Cl4, is also prepared by the direct reaction of anhydrous CuCl2 with piperidine in O2-free CH2Cl2. These complexes are isolated as stable solids. They are easily soluble in aprotic solvents as CH2Cl2 or PhNO2. Cryoscopic measurements support tetranuclear core structure for Pip4Cu4X8.

Proceedings of the 22nd international conference on World Wide Web - WWW '13, 2013

ABSTRACT

Traditional analysis techniques may not be sufficient for astronomers to make the best use of the... more Traditional analysis techniques may not be sufficient for astronomers to make the best use of the data sets that current and future instruments, such as the Square Kilometre Array and its Pathfinders, will produce. By utilizing the incredible pattern-recognition ability of the human mind, scientific visualization provides an excellent opportunity for astronomers to gain valuable new insight and understanding of their data, particularly when used interactively in 3D. The goal of our work is to establish the feasibility of a real-time 3D monitoring system for data going into the Australian SKA Pathfinder archive. Based on CUDA, an increasingly popular development tool, our work utilizes the massively parallel architecture of modern graphics processing units (GPUs) to provide astronomers with an interactive 3D volume rendering for multi-spectral data sets. Unlike other approaches, we are targeting real time interactive visualization of datasets larger than GPU memory while giving special attention to data with low signal to noise ratio - two critical aspects for astronomy that are missing from most existing scientific visualization software packages. Our framework enables the astronomer to interact with the geometrical representation of the data, and to control the volume rendering process to generate a better representation of their datasets.

Acm Transactions on the Web, Nov 6, 2014

The Australian SKA Pathfinder (ASKAP) will be producing 2.2 terabyte HI spectral-line cubes for e... more The Australian SKA Pathfinder (ASKAP) will be producing 2.2 terabyte HI spectral-line cubes for each 8 hours of observation by 2013. Global views of spectral data cubes are vital for the detection of instrumentation errors, the identification of data artifacts and noise characteristics, and the discovery of strange phenomena, unexpected relations, or unknown patterns. We have previously presented the first framework that can render ASKAP-sized cubes at interactive frame rates. The framework provides the user with a real-time interactive volume rendering by combining shared and distributed memory architectures, distributed CPUs and graphics processing units (GPUs), using the ray-casting algorithm. In this paper we present two main extensions of this framework which are: using a multi-panel display system to provide a high resolution rendering output, and the ability to integrate automated data analysis tools into the visualization output and to interact with its output in place.

The Egyptian Journal of Immunology Egyptian Association of Immunologists, 2010

Hepatitis C virus (HCV) which is one of the endemic viral infections in Egypt is not only hepatot... more Hepatitis C virus (HCV) which is one of the endemic viral infections in Egypt is not only hepatotropic, but also a lymphotropic virus and has many extrahepatic manifestations as mixed cryoglobulinemia and non-Hodgkin's lymphoma. We studied gene expression profile of 20 B-cell non-Hodgkin's lymphoma with HCV infection and 20 B-cell non-Hodgkin's lymphoma without HCV infection as a control group by c-DNA microarray. Out of the 15,500 studied genes, more than 1000 genes were differentially expressed; either upregulated or downregulated. We found that HCV may rescue B lymphocytes from apoptosis possibly through causing suppression of CASP1 and CASP4 and causing overexpression of the anti-apoptotic BCL2 gene. Also, HCV was associated with overexpression of the genes related to myeloid/lymphoid leukemia and B lymphoma as MLLT3, BAL, influences the overexpression of transcription regulator genes as TATA box binding protein (TBP) and may influence the overexpression of some immunoglobulin genes as immunoglobulin superfamily containing leucine gene in B cells resulting in overproduction of immunoglobulins in B-lymphocyte disorders. Moreover HCV was associated with reduced expression of MHC class II molecules in B lymphocytes, and therefore inhibition of antigen processing and presentation through downregulation of different MHC class II molecules genes. We conclude that the upregulated and the downregulated genes identified through the studied expression profiles of NHL with HCV infection may shed light on the mechanisms of HCV lymphomagenesis.

Proceedings of the 37th International Acm Sigir Conference, Jul 3, 2014

ABSTRACT Click dwell time is the amount of time that a user spends on a clicked search result. Ma... more ABSTRACT Click dwell time is the amount of time that a user spends on a clicked search result. Many previous studies have shown that click dwell time is strongly correlated with result-level satisfaction and document relevance. Accurate estimates of dwell time are therefore important for applications such as search satisfaction prediction and result ranking. However, dwell time can be estimated in different ways according to the information available about the search process. For example, a result reached for the query [Garfield] may involve 145s of "server-side" dwell time (observable to the search engine) and 40s of "client-side" dwell time (observable from the browser). Since search engines can only observe server-side actions (i.e., activity on the search engine result page), server-side dwell times are estimated by measuring the time between a search result click and the next search event (click or query). Conversely, more detailed information about page dwell times can be obtained via client-side methods such as Web browser toolbars. The client-side information enables the estimation of more accurate dwell times by measuring the amount of time that a user spends on pages of interest (either the landing page, or pages on the full navigation trail). In this paper, we define three different dwell times, i.e., server-side, client-side, and trail dwell time, and examine their effectiveness for predicting click satisfaction. For this, we collect toolbar and search engine logs from real users, and provide an analysis of dwell times for improving prediction performance. Moreover, we show further improvements in predicting click-level satisfaction by combining dwell times with other query features (e.g., query clarity).

Typically, the dynamic error model for a terrestrial INS algorithm need for three position

Acl, 2010

... Alina Andreevskaia and Sabine Bergler. 2006. Min-ing wordnet for fuzzy sentiment: Sentiment t... more ... Alina Andreevskaia and Sabine Bergler. 2006. Min-ing wordnet for fuzzy sentiment: Sentiment tag ex-traction from wordnet glosses. In Proceedings of the 11th Conference of the European Chapter of the Association for Computational Linguistics (EACL 2006). Carmen Banea, ...

Coling, 2008

We introduce a technique for analyzing the temporal evolution of the salience of participants in ... more We introduce a technique for analyzing the temporal evolution of the salience of participants in a discussion. Our method can dynamically track how the relative importance of speakers evolve over time using graph based techniques. Speaker salience is computed based on the eigenvector centrality in a graph representation of participants in a discussion. Two participants in a discussion are linked with an edge if they use similar rhetoric. The method is dynamic in the sense that the graph evolves over time to capture the evolution inherent to the participants salience. We used our method to track the salience of members of the US Senate using data from the US Congressional Record. Our analysis investigated how the salience of speakers changes over time. Our results show that the scores can capture speaker centrality in topics as well as events that result in change of salience or influence among different participants.

Comptes Rendus Des Seances De La Societe De Biologie Et De Ses Filiales, 1991

Proceedings of the 22nd International Conference on Computational Linguistics Volume 1, Aug 18, 2008

Proceedings of the 49th Annual Meeting of the Association For Computational Linguistics Human Language Technologies Short Papers Volume 2, 2011

Proceedings of the 49th Annual Meeting of the Association for Computational Linguistics:shortpape... more Proceedings of the 49th Annual Meeting of the Association for Computational Linguistics:shortpapers, pages 592597, Portland, Oregon, June 19-24, 2011. cO2011 Association for Computational Linguistics ... Identifying the Semantic Orientation of Foreign Words

Journal of Applied Environmental Microbiology, Jan 23, 2014

The aim of this work was to evaluate the value of polymerase chain reaction (PCR) in rapid detect... more The aim of this work was to evaluate the value of polymerase chain reaction (PCR) in rapid detection of resistance to rifampin and isoniazid in TB patients. Sixty sputum specimens were collected from MDR-TB patients. In addition to 10 sputum samples from TB patients who were responders to treatment by first line anti-TB drugs. The isolates were identified, cultured and tested for detection of multidrug resistance mutations in ropB gene coding for RIF resistance and katG gene coding for INH resistance using PCR; and were compared to Lowenstein Jensen (LJ) culture drug susceptibility testing (DST) using the Proportion method as the 'gold standard'. By using proportion method on LJ all 60 sputum samples of MDR patients were resistant to both INH and RIF. By PCR; rpoB gene coding for RIF resistance was detected in 59 clinical isolates. The sensitivity and specificity of mutation of rpoB gene for the 60 specimens were 98.3% and 100% respectively. katG gene coding for INH resistance was detected in 56 clinical isolates. The sensitivity and specificity of mutation of KatG gene for the 60 specimens were 93.3 % and 100 % respectively. The 10 sputum samples of TB patients who were responders to treatment were susceptible to first-line anti-TB drugs on LJ culture DST and no MDR genes were detected by PCR. Our study demonstrated that PCR analysis was rapid, sensitive and specific approach for detection of rpoB and katG genes within 48 hours, which is more rapid than drug susceptibility testing after the culture.

Proceedings of the Sixth Acm International Conference on Web Search and Data Mining, Feb 4, 2013

ABSTRACT Understanding the characteristics of queries where a search engine is failing is importa... more ABSTRACT Understanding the characteristics of queries where a search engine is failing is important for improving engine performance. Previous work largely relies on user-interaction features (e.g., clickthrough statistics) to identify such underperforming queries. However, relying on interaction behavior means that searchers need to become dissatisfied and need to exhibit that in their search behavior, by which point it may be too late to help them. In this paper, we propose a method to generate underperforming query identification rules instantly using topical and lexical attributes. The method first generates query attributes using sources such as topics, concepts (entities), and keywords in queries. Then, association rules are learned by exploiting the FP-growth algorithm and decision trees using underperforming query examples. We develop a query classification model capable of accurately estimating dissatisfaction using the generated rules, and demonstrate significant performance gains over state-of-the-art query performance prediction models.