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135 results on '"Sheikh, Saad"'

4. A study of the effects of kaolin, solid filler on the processing, mechanical, and dynamic properties of some industrial rubbers cured with novel sulphur cure system

Author

Sheikh, Saad H.

Subjects
620.1, Rubber, Kaolin, Viscosity, Cure properties, Mechanical properties
Abstract

Two novel methods for the sulphur vulcanisation of NR, BR and EPDM rubbers using N-tert-butyl-2-benzothiazole sulphenamide (TBBS) accelerator and zinc oxide (ZnO) activator have been developed. In one method, the optimum loading of TBBS and ZnO were measured for some sulphur-filled NR, BR and EPDM rubbers. The cure systems for the NR were (S/TBBS/ZnO), (1/1.5/0.2), (2/1.5/0.3), (3/1.5/0.25), and (4/3.5/0.2), for the BR, (0.5/1.75/0.2) and (1/3/0.2), and for the EPDM, (1/1/0.075). The cure was very efficient in spite of reducing the amount of TBBS and ZnO chemicals. In another method which used a single additive component in the form of a powder (TBBS/ZnO: 350mg/1g), the loading of the powder in NR was raised increasingly from 0.63 to 5.63 phr, the scorch time was unchanged and the optimum cure time reduced at 1.25 phr powder. The rate of cure accelerated at 1.25 phr powder. The crosslink density reached its maximum value at 5.63 phr powder. This method reduced the TBBS and ZnO requirement in the cure system by 85wt%. Solid kaolin filler pre-treated with a sulphur-bearing mercaptosilane was used to reinforce NR, BR and EPDM rubbers. For NR, to react the sulphur in the silane on the kaolin surface with the rubber chains and optimise the reaction between the two, 16 phr TBBS and 0.2 phr ZnO were added to the kaolin-filled rubber. The hardness and Young s modulus increased and compression set decreased when up to 3 phr elemental sulphur was included in the kaolin-filled rubber with 16 phr TBBS and 0.2 phr ZnO. The tensile strength, elongation at break, stored energy density at break, and tear energy of the rubber vulcanisate reduced when elemental sulphur was added. Notably, the inclusion of elemental sulphur was the key factor in controlling the rubber properties. In an extended work, 60 phr silane pre-treated kaolin was mixed with NR, BR and EPDM and the rubbers were cured using the novel cure systems developed earlier. The effect of 140 phr kaolin on the properties of NR was also investigated. For NR, the hardness increased by 64% when 60 phr kaolin was added and the trend continued rising by another 28% when the loading of kaolin reached 140 phr. Similarly, the Young s modulus rose by 170% with 60 phr kaolin and then by an extra 148% when the full amount of kaolin, i.e. 140 phr, was reached. The tensile strength and tear energy were unchanged and the elongation at break and stored energy density at break deteriorated by a total of 65% and 34%, respectively with 140 phr kaolin. The compression set of the unfilled rubber was 41%, and it then rose to 64% and 71%, when 60 and 140 phr kaolin was added, respectively. For BR, the hardness increased by 23% and for EPDM, by 34%, respectively when 60 phr kaolin was incorporated in the rubbers. For BR, the tensile strength, elongation at break and Young s modulus rose by 759%, 256% and 114%, respectively. The compression set of the unfilled BR was 9.4%, and subsequently rose to 26% when 60 phr kaolin was mixed with the rubber. For EPDM, the tensile strength, elongation at break and Young s modulus improved by 964%, 332% and 71%, respectively. For BR, the stored energy density at break and tear energy were increased by 2442% and 536%, respectively and for EPDM, by 3133% and 1479%, respectively. The compression set of the unfilled EPDM was 39%, and afterward increased to 48% with 60 phr kaolin. Kaolin was found to be extending or non-reinforcing filler for the strain-induced crystallising NR and highly reinforcing for the non-crystallising BR and EPDM.

Published
2017

18. Column-generation framework of nonlinear similarity model for reconstructing sibling groups

Author

Chou, Chun-An, Liang, Zhe, Chaovalitwongse, Wanpracha Art, Berger-Wolf, Tanya Y., DasGupta, Bhaskar, Sheikh, Saad, Ashley, Mary V., and Caballero, Isabel C.

Subjects
United States. National Science Foundation -- Analysis, Genetic markers -- Analysis, Algorithms -- Analysis, Algorithm, Computers, Science and technology
Abstract

Establishing family relationships, such as parentage and sibling relationships, is fundamental in biological research, especially in wild species, as they are often important to understanding evolutionary, ecological, and behavioral processes. [...]

Published
2015
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19. An analysis of a large multi-institutional database reveals important associations between treatment parameters and clinical outcomes for stereotactic body radiotherapy (SBRT) of oligometastatic colorectal cancer

Author

Sheikh, Saad, primary, Chen, Hanbo, additional, Sahgal, Arjun, additional, Poon, Ian, additional, Erler, Darby, additional, Badellino, Serena, additional, Dagan, Roi, additional, Foote, Matthew C., additional, Louie, Alexander V., additional, Redmond, Kristin J., additional, Ricardi, Umberto, additional, and Biswas, Tithi, additional

Published
2022
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21. Proton Beam Therapy for Locally Advanced Head and Neck Tumors

Author

Sheikh, Saad, primary, Kharouta, Michael Z., additional, Pidikiti, Rajesh, additional, Damico, Nicholas J., additional, Choi, Serah, additional, Dorth, Jennifer A., additional, Mansur, David B., additional, Machtay, Mitchell X., additional, Yao, Min, additional, and Bhatt, Aashish D., additional

Published
2021
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30. Predicting solid solubility in CoCrFeNiMx (M = 4d transition metal) high-entropy alloys.

Author

Sheikh, Saad, Mao, Huahai, and Sheng Guo

Subjects
*COBALT nickel alloys, *CHROMIUM iron alloys, *ENTROPY, *ATOMIC radius, *SOLUBILITY, *TRANSITION metal compounds
Abstract

CoCrFeMnNi is a prototype fcc-structured high-entropy alloy. Numerous efforts have been paid to strengthen CoCrFeMnNi, by replacing Mn with other elements for an enhancement of the solid solution strengthening. 4d transition metals, including Zr, Nb, and Mo, are of interest for this purpose, since they have much larger atomic radii than that of Mn. However, Nb and Mo are known to have a low solid solubility in fcc-structured CoCrFeNi. Compared to Nb and Mo, Zr has an even larger atomic radius. The solid solubility of Zr in fcc-structured CoCrFeNi was investigated in this work, combining both experimental studies and thermodynamic calculations. In addition, based on previous results and new results obtained here, methods to predict the solid solubility in CoCrFeNiMx (M=Zr, Nb, and Mo) alloys were developed. Particularly, the average d-orbital energy level, Md, was re-evaluated in the present work, for an improved predictability of the solid solubility in fcc-structured high entropy alloys containing 4d transition metals. [ABSTRACT FROM AUTHOR]

Published
2017
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31. Alloy design for intrinsically ductile refractory high-entropy alloys.

Author

Sheikh, Saad, Shafeie, Samrand, Qiang Hu, Ahlstróm, Johan, Persson, Christer, Veselý, Jaroslav, Zýka, Jiří, Klement, Uta, and Sheng Guo

Subjects
*REFRACTORY materials, *METALS, *ALLOYS, *ELECTRONS, *VALENCE (Chemistry)
Abstract

Refractory high-entropy alloys (RHEAs), comprising group IV (Ti, Zr, Hf), V (V, Nb, Ta), and VI (Cr, Mo, W) refractory elements, can be potentially new generation high-temperature materials. However, most existing RHEAs lack room-temperature ductility, similar to conventional refractory metals and alloys. Here, we propose an alloy design strategy to intrinsically ductilize RHEAs based on the electron theory and more specifically to decrease the number of valence electrons through controlled alloying. A new ductile RHEA, Hf0.5Nb0.5Ta0.5Ti1.5Zr, was developed as a proof of concept, with a fracture stress of close to 1 GPa and an elongation of near 20%. The findings here will shed light on the development of ductile RHEAs for ultrahigh-temperature applications in aerospace and power-generation industries. [ABSTRACT FROM AUTHOR]

Published
2016
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32. Combined Fluorescence-Guided Surgery and Photodynamic Therapy for Glioblastoma Multiforme Using Cyanine and Chlorin Nanocluster

Author

Teng, Clare W, primary, Amirshaghaghi, Ahmad, additional, Cho, Steve S, additional, Cai, Shuting, additional, De Ravin, Emma, additional, Singh, Yash, additional, Miller, Joann, additional, Sheikh, Saad, additional, Delikatny, Jim, additional, Cheng, Zhiliang, additional, Busch, Theresa, additional, Singhal, Sunil, additional, Dorsey, Jay, additional, Tsourkas, Andrew, additional, and Lee, John Y.K, additional

Published
2020
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36. A Patient-Derived Glioblastoma Organoid Model and Biobank Recapitulates Inter- and Intra-tumoral Heterogeneity

Author

Jacob, Fadi, primary, Salinas, Ryan D., additional, Zhang, Daniel Y., additional, Nguyen, Phuong T.T., additional, Schnoll, Jordan G., additional, Wong, Samuel Zheng Hao, additional, Thokala, Radhika, additional, Sheikh, Saad, additional, Saxena, Deeksha, additional, Prokop, Stefan, additional, Liu, Di-ao, additional, Qian, Xuyu, additional, Petrov, Dmitriy, additional, Lucas, Timothy, additional, Chen, H. Isaac, additional, Dorsey, Jay F., additional, Christian, Kimberly M., additional, Binder, Zev A., additional, Nasrallah, MacLean, additional, Brem, Steven, additional, O’Rourke, Donald M., additional, Ming, Guo-li, additional, and Song, Hongjun, additional

Published
2020
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39. Stereotactic body radiotherapy (SBRT) for T2N0 (>3 cm) non-small cell lung cancer: Outcomes and failure patterns.

Author

Shamp, Stephen J., Sheikh, Saad, Chang, Tangel, Damico, Nicholas, Linden, Phillip, Dowlati, Afshin, Machtay, Mitchell, and Biswas, Tithi

Subjects
*NON-small-cell lung carcinoma, *STEREOTACTIC radiotherapy, *CANCER prognosis, *SURVIVAL rate, *LUNG cancer
Abstract

Purpose/objectives: Outcomes of T2N0 lung cancer patients treated with stereotactic radiotherapy are not well known. Methods and materials: We conducted a single institution retrospective review of patients with T2N0 NSCLC who were treated with SBRT. The local, regional, distant control rates were calculated from available clinical data. Survival outcomes were determined using the Kaplan Meier method. Results: Fifty-six patients met our selection criteria. The two-year local control rate was 84.2%. The two and 5-year disease-free survival (DFS) and OS were 31.9% and 15.3% and 39.9% and 12.1%, respectively. Centroid BED10 > 150Gy was associated with improved DFS, (p = 0.014), and OS on univariable analysis (p=0.0132). Conclusions: SBRT provides good local control for T2N0 NSCLC, but systemic failure remains problematic. [ABSTRACT FROM AUTHOR]

Published
2021

40. Predicting the solid solubility limit in high-entropy alloys using the molecular orbital approach.

Author

Sheikh, Saad, Klement, Uta, and Sheng Guo

Subjects
*IRREVERSIBLE processes (Thermodynamics), *THERMODYNAMIC molecular model, *ENTROPY (Information theory), *MOLECULAR physics, *TWO-dimensional materials (Nanotechnology), *ELECTROMAGNETIC theory
Abstract

High-entropy alloys (HEAs) are currently at the research frontier of metallic materials. Understanding the solid solubility limit in HEAs, such a highly concentrated multicomponent alloy system, is scientifically intriguing. It is also technically important to achieve desirable mechanical properties by controlling the formation of topologically or geometrically closed packed phases. Previous approaches to describe the solid solubilities in HEAs could not accurately locate the solubility limit and have to utilize at least two parameters. Here, we propose to use a single parameter, the average energy of d-orbital levels, Md, to predict the solid solubility limit in HEAs. It is found that Md can satisfactorily describe the solid solubilities in fcc structured HEAs containing 3 d transition metals, and also in bcc structured HEAs. This finding will greatly simplify the alloys design and lends more flexibility to control the mechanical properties of HEAs. When 4 d transition metals are alloyed, Md alone cannot describe the solid solubility limit in fcc structured HEAs, due to the large increase of the bond strength that can be gauged by the bond order, Bo. The potential opportunities and challenges with applying the molecular orbital approach to HEAs are discussed. [ABSTRACT FROM AUTHOR]

Published
2015
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42. A Patient-Derived Glioblastoma Organoid Model Maintains Intertumoral and Intratumoral Heterogeneity for Therapeutic Testing

Author

Salinas, Ryan, primary, Zhang, Daniel, additional, Jacob, Fadi, additional, Nguyen, Phuong, additional, Sheikh, Saad, additional, Prokop, Stefan, additional, Dorsey, Jay F, additional, Nasrallah, MacLean, additional, Brem, Steven, additional, O’Rourke, Donald M, additional, Ming, Guo-li, additional, and Song, Hongjun, additional

Published
2019
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