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1.
Noha M. Hassan Maher Y. Younan Hanadi G. Salem 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(10):38-42
The deformation behaviors of an Al-Li-Cu alloy (Aluminum 8090) during uniaxial and biaxial stress states were modeled using
the nonlinear finite element analysis package ABAQUS 5.8. Two different material models were used for the purpose of comparison and to propose a valid and accurate superplastic material
deformation behavior. Using a power law strain hardening model, the material was modeled with either constant or variable
properties of strain-rate sensitivity and strain-hardening exponent. Results from the numerical models were compared to experimental
results by Chen and Huang, who investigated the uniaxial and biaxial states of stress. Experimental data were primarily used
to acquire the needed uniaxial material parameters for the model. The strain-rate sensitivity and strain-hardening exponent
were dependent on the strain and strain rates. Comparing the two material models for both stress states indicated that the
material model with variable properties better represented the true behavior of the material when compared to the experimental
results.
For more information, contact Noha M. Hassan, the American University in Cairo, 113 Kasr El Aini St., P.O. Box 2511, Cairo
11511, Egypt; +202-797-5336; fax +202-797-7565; e-mail nhassan@vt.edu. 相似文献
2.
Tina M. Petersen Hanadi S. Rifai Monica P. Suarez A. Ron Stein 《Canadian Metallurgical Quarterly》2005,131(10):1414-1425
A pathogen impaired watershed in Houston, Tex., was studied to assess the spatial and temporal nature of point and nonpoint bacterial load contributions. End-of-pipe sampling at wastewater treatment plant effluent and storm sewers discharging under dry weather conditions was undertaken. Relatively low concentrations of E. coli were found in wastewater treatment effluent, with a geometric mean of 5 MPN/dL, while dry weather storm sewer discharges exhibited a geometric mean concentration of 212 MPN/dL. Loads from both point and nonpoint sources of E. coli were calculated and compared to in-stream bacteria loads. Nonpoint loads were estimated using an event mean concentration approach on an annual basis. Nonpoint source (NPS) loads were the primary source of bacteria loading to the bayou. Wastewater treatment plant and dry weather storm sewer loads, however, dominated in dry weather conditions. While NPS loads remained relatively constant from headwaters to the mouth of the bayou, point source loads exhibited greater spatial variability depending on the distribution of the discharging pipes. The study points to the need for spatial and temporal considerations in managing bacterial pollution in streams. 相似文献
3.
Howell NL Lakshmanan D Rifai HS Koenig L 《The Science of the total environment》2011,409(10):1867-1888
All 209 PCB congeners are quantified in water in both dry and wet weather urban flows in Houston, Texas, USA. Total water PCBs ranged from 0.82 to 9.4 ng/L in wet weather and 0.46 to 9.0 ng/L in dry. Wet weather loads were 8.2 times higher (by median) than dry weather with some increases of over 100-fold. The majority of the PCB load was in the dissolved fraction in dry weather while it was in the suspended fraction in wet weather. Dissolved PCB loads were correlated with rain intensity and highly developed land area, and a multiple linear regression (MLR) equation was developed to quantify these correlations. PCA generated five PCB components with nearly all positive loadings. They were interpreted as DOC-associated A1248, wet weather primarily suspended fraction A1254/A1260 likely from building sealants, truly dissolved-associated wastewater dechlorination, watershed-sourced PCB 11, and monochlorinated PCBs (likely connected to a different state or source of dechlorination). The PCB 11 component was statistically higher in wet versus dry weather when no other component showed such clear distinctions. Hierarchical cluster analysis (HCA) did not always group dry and wet weather samples from the same location together illustrating the different congener composition that often exists between dry and wet conditions. Four wet weather samples from high percentage developed land (> 90%) watersheds had nearly the same fingerprint suggesting a generic “urban” signature in runoff, which in this case was caused by residual A1254/A1260 PCB stocks and currently produced PCB 11 in consumer goods. 相似文献
4.
Slim M Durisic N Grutter P Sleiman HF 《Chembiochem : a European journal of chemical biology》2007,8(7):804-812
We report the first example of a small molecule that can noncovalently cross-link DNA with streptavidin and streptavidin-labeled materials. Molecule 1 possesses a ruthenium dipyridophenazine DNA-intercalating moiety and a biotin unit; these two units are adequately separated to ensure efficient cross-linking of DNA with protein. Complex 1 is essentially nonemissive in aqueous solution and when bound to streptavidin, however, its luminescence is turned "on" when it binds to DNA. We have used these properties to establish that this complex can simultaneously bind to DNA and streptavidin, and can thus bring these two biomolecules together. We also synthesized a related molecule, 3, in which the biotin and DNA-intercalating moieties are covalently bound. While complex 3 can intercalate into DNA through a threading mechanism, luminescence experiments show that it cannot simultaneously bind DNA and streptavidin, most likely due to the proximity of its two molecular-recognition units. The cross-linking ability of molecule 1 was used to template the assembly of streptavidin molecules on circular plasmid DNA, as visualized by atomic force microscopy. In addition, using 1, we show the organization of discrete groups of gold nanoparticles labeled with streptavidin on a linear DNA template of finite size, with transmission electron microscopy. In these experiments the DNA template acted as a "molecular ruler" that dictated the number of particles in the assembly. 相似文献
5.
Amal M.K. Esawi Hanadi G. Salem Hanady M. Hussein Adham R. Ramadan 《Polymer Composites》2010,31(5):772-780
Carbon nanotube‐reinforced polymer composites are being investigated as promising new materials having enhanced physical and mechanical properties. With regards to mechanical behavior, the enhancements reported thus far by researchers are lower than the theoretical predictions. One of the key requirements to attaining enhanced behavior is a uniform dispersion of the nanotubes within the polymer matrix. Although solvent mixing has been used extensively, there are concerns that any remaining solvent within the composite may degrade its mechanical properties. In this work, a comparison is carried out between solvent and “solvent‐free” dry mixing for dispersing multiwall carbon nanotubes in polypropylene before further melt mixing by extrusion. Various weight fractions of carbon nanotubes (CNTs) are added to the polymer and their effect on the mechanical properties of the resulting composites is investigated. Enhancements in yield strength, hardness, and Young's modulus when compared with the neat polymer, processed under similar conditions, are observed. Differences in mechanical properties and strain as a function of the processing technique (solvent or dry) are also clearly noted. In addition, different trends of enhancement of mechanical properties for the solvent and dry‐mixed extrudates are observed. Dry mixing produces composites with the highest yield strength, hardness, and modulus at 0.5 wt% CNT, whereas solvent mixing produces the highest mechanical properties at CNT contents of 1 wt%. It is believed that this difference is primarily dependent on the dispersion of CNTs within the polymer matrix which is influenced by the processing technique. Field emission scanning electron microscopy analysis shows the presence of clusters in large wt% CNT samples produced by dry mixing. Samples produced by solvent mixing are found to contain homogeneously distributed CNTs at all CNT wt fractions. CNT pull‐out is observed and may explain the limited enhancement in mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers 相似文献
6.
Abeer Dagher Hanadi G. Salem Tarek M. Moustafa Eman Bellah Mettawee Ehab Abdel-Rahman 《International Journal of Hydrogen Energy》2014
A first investigation into the production of amorphous and nanostructured Ti-based alloys with nominal compositions Ti41.5Zr41.5Ni17, Ti61Zr22Ni17, Ti41.5V41.5Ni17 and Ti61V22Ni17 by mechanical alloying (MA) technique is presented. This technique was adopted to produce alloys' powders with high fresh surface area that were active for hydrogen storage. Hydrogen absorption characteristics and structure changes in the alloys after hydrogenation were investigated. Gas phase hydrogenation of the Ti–Zr–Ni alloys, at 573 K and an initial hydrogen pressure of 2 MPa, exhibited good hydriding properties and started at a maximal rate without induction period with a hydrogenation capacity up to 1.2 wt%. However, hydriding of Ti–V–Ni alloys at the same conditions exhibited slower rates. The Ti61V22Ni17 composition showed high hydrogen absorption capacity of 1.8 wt% and exceeded 4 wt% at 345 K. In addition, the Ti–V–Ni alloys showed structure stability after hydrogenation and retained the amorphous structure. 相似文献
7.
Tahreem Tanweer Nosheen Fatima Rana Iqra Saleem Iqra Shafique Sultan M. Alshahrani Hanadi A. Almukhlifi Amenah S. Alotaibi Sohad Abdulkaleg Alshareef Farid Menaa 《International journal of molecular sciences》2022,23(24)
Antibacterial restorative materials against caries-causing bacteria are highly preferred among high-risk patients, such as the elderly, and patients with metabolic diseases such as diabetes. This study aimed to enhance the antibacterial potential of resin composite with Magnesium-doped Zinc oxide (Mg-doped ZnO) nanoparticles (NPs) and to look for their effectiveness in the alloxan-induced diabetic model. Hexagonal Mg-doped ZnO NPs (22.3 nm diameter) were synthesized by co-precipitation method and characterized through ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. The Mg-doped ZnO NPs (1, 2.5 and 5% w/w) were then evaluated for antibacterial activity using a closed system in vitro biofilm model. Significant enhancement in the antibacterial properties was observed in composites with 1% Mg-doped ZnO compared to composites with bare ZnO reinforced NPs (Streptococcus mutans, p = 0.0005; Enterococcus faecalis, p = 0.0074, Saliva microcosm, p < 0.0001; Diabetic Saliva microcosm, p < 0.0001). At 1–2.5% Mg-doped ZnO NPs concentration, compressive strength and biocompatibility of composites were not affected. The pH buffering effect was also achieved at these concentrations, hence not allowing optimal conditions for the anaerobic bacteria to grow. Furthermore, composites with Mg-doped ZnO prevented secondary caries formation in the secondary caries model of alloxan-induced diabetes. Therefore, Mg-doped ZnO NPs are highly recommended as an antibacterial agent for resin composites to avoid biofilm and subsequent secondary caries formation in high-risk patients. 相似文献
8.
Hanadi Ananbeh Petr Vodicka Helena Kupcova Skalnikova 《International journal of molecular sciences》2021,22(8)
Huntington’s disease (HD) is a rare hereditary autosomal dominant neurodegenerative disorder, which is caused by expression of mutant huntingtin protein (mHTT) with an abnormal number of glutamine repeats in its N terminus, and characterized by intracellular mHTT aggregates (inclusions) in the brain. Exosomes are small extracellular vesicles that are secreted generally by all cell types and can be isolated from almost all body fluids such as blood, urine, saliva, and cerebrospinal fluid. Exosomes may participate in the spreading of toxic misfolded proteins across the central nervous system in neurodegenerative diseases. In HD, such propagation of mHTT was observed both in vitro and in vivo. On the other hand, exosomes might carry molecules with neuroprotective effects. In addition, due to their capability to cross blood-brain barrier, exosomes hold great potential as sources of biomarkers available from periphery or carriers of therapeutics into the central nervous system. In this review, we discuss the emerging roles of exosomes in HD pathogenesis, diagnosis, and therapy. 相似文献
9.
Encapsulation of Gold Nanoparticles into DNA Minimal Cages for 3D‐Anisotropic Functionalization and Assembly
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Xin Luo Pongphak Chidchob Janane F. Rahbani Hanadi F. Sleiman 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(5)
Gold nanoparticles (AuNPs) endowed with anisotropic DNA valency are an important class of materials, as they can assemble into complex structures with a minimal number of DNA strands. However, methods to encode 3D DNA strand patterns on AuNPs with a controlled number of unique DNA strands in a predesigned spatial arrangement remain elusive. In this work, a simple one‐step method to yield such DNA‐decorated AuNPs is demonstrated, through encapsulating AuNPs into DNA minimal nanocages. The AuNP@DNA cage encapsulation complex inherits the 3D anisotropic molecular information from the DNA nanocage with enhanced structural stability. The DNA nanocage can be further functionalized and used as a building block for the self‐assembly of complex architectures, such as dimers and trimers, programmed assemblies with sequential growth DNA backbones and DNA origami. 相似文献
10.
Monica P. Suarez Hanadi S. Rifai Jennifer Schimek Michael Bloom Paul Jensen Larry Koenig 《Canadian Metallurgical Quarterly》2006,132(12):1633-1643
Concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans in runoff were measured at 10 small flood control drainage channels in the Houston area. Total toxicity equivalent concentrations in runoff ranged from 0.01?to?0.11?pg/L for the dissolved phase and from 0.02?to?0.88?pg/L for the suspended phase. The dissolved concentrations were lower than their respective suspended concentrations, with average suspended/dissolved ratios between 5 and 152 for individual congeners. Average observed logs of organic-carbon (OC)-normalized suspended sediment-dissolved partitioning coefficients (log?KOC) varied between 5.47 and 7.83?L/kg OC. Dioxin concentrations in runoff were generally at the same level or lower than those measured in the receiving water body. Principal component analyses indicated that the signatures for dissolved runoff match those observed in dissolved ambient water in the channel, while the suspended-sediment runoff signatures are similar to those observed in dry air deposition in the Houston area. 相似文献