Mahmoud Ahmed - Academia.edu (original) (raw)

Papers by Mahmoud Ahmed

One of the important contributions to the application of nanotechnology is the nanofluids techniq... more One of the important contributions to the application of nanotechnology is the nanofluids technique in which will be become a good alternative to the conventional heat transfer medium. This is done by addition of nano particles of high thermal conductivity to the base fluid of the low thermal conductivity. In the present paper, the performance of chilled-water air conditioning unit with and without alumina nanofluids has been experimentally investigated. The first method technique was used to prepare Al2O3water nanofluids.Al2O3 nano particles was added with water in the cooling tank through using different concentrations by weight varies from 0.1,0.2,0.3, and 1% wt. and the alumina nanofluids have been continuously supplied to the cooling coil. The experiments have been performed under operation conditions include a variation of flow rate of chilled water/ alumina nanofluids and the air through the cooling coil. The experimental results have been shown a less time is achieved to obt...

Polymers, 2021

In this paper, carbon aerogel (CA)-polyaniline (PANI) composites were prepared and first applied ... more In this paper, carbon aerogel (CA)-polyaniline (PANI) composites were prepared and first applied in the study of H2S gas sensing. Here, 1 and 3 wt% of as-obtained CA powder were blended with PANI to produce composites, which are denoted by PANI-CA-1 and PANI-CA-3, respectively. For the H2S gas-sensing studies, the interdigitated electrode (IDE) was spin-coated by performing PANI and PANI-CA composite dispersion. The H2S gas-sensing properties were studied in terms of the sensor’s sensitivity, selectivity and repeatability. IDE coated with PANI-CA composites, as compared with pristine PANI, achieved higher sensor sensitivity, higher selectivity and good repeatability. Moreover, composites that contain higher loading of CA (e.g., 3 wt%) perform better than composites with lower loading of CA. At 1 ppm, PANI-CA-3 displayed increased sensitivity of 452% at relative humidity of 60% with a fast average response time of 1 s compared to PANI.

Molecules, 2021

In this study, we successfully synthesized two types of meso/microporous carbon materials through... more In this study, we successfully synthesized two types of meso/microporous carbon materials through the carbonization and potassium hydroxide (KOH) activation for two different kinds of hyper-crosslinked polymers of TPE-CPOP1 and TPE-CPOP2, which were synthesized by using Friedel–Crafts reaction of tetraphenylethene (TPE) monomer with or without cyanuric chloride in the presence of AlCl3 as a catalyst. The resultant porous carbon materials exhibited the high specific area (up to 1100 m2 g−1), total pore volume, good thermal stability, and amorphous character based on thermogravimetric (TGA), N2 adsoprtion/desorption, and powder X-ray diffraction (PXRD) analyses. The as-prepared TPE-CPOP1 after thermal treatment at 800 °C (TPE-CPOP1-800) displayed excellent CO2 uptake performance (1.74 mmol g−1 at 298 K and 3.19 mmol g−1 at 273 K). Furthermore, this material possesses a high specific capacitance of 453 F g−1 at 5 mV s−1 comparable to others porous carbon materials with excellent columb...

Scholars Journal of Engineering and Technology, 2020

In this work a solar chimney with the aid of a humidifier located in opposite wall is applied as ... more In this work a solar chimney with the aid of a humidifier located in opposite wall is applied as a passive solar technique for cooling building in arid regions. A test room was made from wood material except for the south wall, Trombe Wall; it is composed of a commercial glass wall apart from masonry thick wall with 10 cm gap. The experiments were carried out on summer in the arid region along the day hours with and without humidification process. The experimental observations show a reduction in room temperature, reaches to 8 o C. The experimental results show an increase in natural air ventilation, with air velocity reaches to 1.6 m/s. Therefore, human thermally comfortable indoor environment for many hours during hot summers is achieved. The present study shows a Trombe wall with a movable air gap is recommended for the human comfortable along the day hours.

Polymers, 2020

High-molecular-weight PLA440-b-PEO454-b-PLA440 (LEL) triblock copolymer was synthesized through s... more High-molecular-weight PLA440-b-PEO454-b-PLA440 (LEL) triblock copolymer was synthesized through simple ring-opening polymerization (ROP) by using the commercial homopolymer HO-PEO454-OH as the macro-initiator. The material acted as a single template to prepare the large mesoporous carbons by using resol-type phenolic resin as a carbon source. Self-assembled structures of phenolic/LEL blends mediated by hydrogen bonding interaction were determined by FTIR and SAXS analyses. Through thermal curing and carbonization procedures, large mesoporous carbons (>50 nm) with a cylindrical structure and high surface area (>600 m2/g) were obtained because the OH units of phenolics prefer to interact with PEO block rather than PLA block, as determined by FTIR spectroscopy. Furthermore, higher CO2 capture and good energy storage performance were observed for this large mesoporous carbon, confirming that the proposed approach provides an easy method for the preparation of large mesoporous mate...

Journal of Thermal Science and Engineering Applications, 2020

Utilizing photovoltaic (PV) panels for generating electrical power is accompanied with a low elec... more Utilizing photovoltaic (PV) panels for generating electrical power is accompanied with a low electrical efficiency that is further reduced as its surface temperature surpasses an acceptable limit. In order to overcome this critical issue, it is necessary to maintain the PV panels relatively at low surface temperatures as possible as using appropriate cooling systems. The current implementation assesses experimentally the performance of a combined PV thermal (PV/T) system using a forced-air cooling system during April, May, June, and July of summer weather of Egypt. The results reveal that the highest values of the solar intensity and the ambient air temperature are obtained in July. Employing the forced-air cooling system reduces the average temperature on the front and back sides of the PV panel during July by 12% and 12.8%, respectively. In addition, the forced-air cooling system enhances noticeably the electrical power output of the PV panel by 3.3%, 4.3%, 4.5%, and 6.1% during A...

Thermophysical Properties of Complex Materials, 2019

Recently, nanotechnology has played a major part in multifields of heat transfer processes and de... more Recently, nanotechnology has played a major part in multifields of heat transfer processes and developed a remarkable progress in the energy applications. One of the most plausible applications of nanotechnology is to produce nanoparticles of high thermal conductivity and mixing with the base fluids that transfer energy forming what is called nanofluids. Adding of nanoparticles to the base fluid shows a remarkable enhancement of the thermal properties of the base properties. Nanotechnology has greatly improved the science of heat transfer by improving the properties of the energy-transmitting fluids. A high heat transfer could be obtained through the creation of innovative fluid (nanofluids). This also reduces the size of heat transfer equipment and saves energy.

$Research paper thumbnail of Isolation of anticancer constituents from Cucumis prophetarum var. prophetarum through bioassay-guided fractionation$

BMC complementary and alternative medicine, Jan 9, 2018

Cucumis prophetarum var. prophetarum is used in Saudi folk medicine for treating liver disorders ... more Cucumis prophetarum var. prophetarum is used in Saudi folk medicine for treating liver disorders and grows widely between Abha and Khamis Mushait City, Saudi Arabia. Bioassay-guided fractionation and purification were used to isolate the main active constituents of Cucumis prophetarum var. prophetarum fruits. These compounds were structurally elucidated using NMR spectroscopy, mass spectral analyses and x-ray crystallography. All fractions, sub-fractions and pure compounds were screened for their anticancer activity against six cancer cell lines. The greatest cytotoxic activity was found to be in the ethyl acetate fraction, resulting in the isolation of five cucurbitacin compounds [E, B, D, F-25 acetate and Hexanorcucurbitacin D]. Among the cucurbitacins that were isolated and tested cucurbitacin B and E showed potent cytotoxicity activities against all six human cancer cell lines. Human breast cancer cell lines were found to be the most sensitive to cucurbitacins. Preliminary struc...

European journal of medicinal chemistry, Jan 15, 2018

Epidermal growth factor receptor (EGFR) signaling pathway has been previously investigated for it... more Epidermal growth factor receptor (EGFR) signaling pathway has been previously investigated for its significant role in the progression of different types of malignant tumors, where development of small molecules targeting EGFR is well known strategy for design of antitumor agents. Herein, we report the design and synthesis of two series of 6-(2-substitutedacetamido)-4-anilinoquinazolines (6a-x and 13a-d) as EGFR inhibitors. All the newly synthesized quinazoline derivatives were in vitro evaluated for their anti-proliferative activity towards MCF-7 (Breast Cancer) and HepG2 (Hepatocellular carcinoma) cell lines. In particular, compound 6n showed significant inhibitory activity against MCF-7 and HepG2 cell lines (IC = 3 and 16 μM, respectively), compared to that of Erlotinib (IC = 20 and 25 μM, respectively). Western blotting of 6n at MCF-7 cell line revealed the dual inhibitory activity of 6n towards diminishing the phosphorylated levels for EGFR and ERK. Also, ELISA assay confirmed ...

AAPS PharmSciTech, 2017

The present study planed to develop new fast dissolving tablets (FDTs) of torsemide. Solid disper... more The present study planed to develop new fast dissolving tablets (FDTs) of torsemide. Solid dispersions (SDs) of torsemide and sorbitol (3:1) or polyvinylpyrrolidone (PVP) k25 were prepared. The prepared SDs were evaluated for in-vitro dissolution. Fourier transform infrared spectroscopy and differential scanning calorimetry for SDs revealed no drug/excipient interactions and transformation of torsemide to the amorphous form. Torsemide/sorbitol SD was selected for formulation of torsemide FDTs by direct compression method. Box-Bhenken factorial design was employed to design 15 formulations using croscarmellose sodium and crospovidone at different concentrations. The response surface methodology was used to analyze the effect of changing these concentrations (independent variables) on disintegration time (Y 1), percentage friability (Y 2), and amount torsemide released at 10 min. The physical mixtures of torsemide and the used excipients were evaluated for angle of repose, Hausner's ratio, and Carr's index. The prepared FDTs tablets were evaluated for wetting and disintegration time, weight variation, drug content, percentage friability, thickness, hardness, and in vitro release. Based on the in-vitro results and factorial design characterization, F10 and F7 were selected for bioavailability studies following administration to Albino New Zealand rabbits. They showed significantly higher C max and (AUC 0-12) and shorter T max than those obtained after administration of the corresponding ordinary commercial Torseretic ® tablets. Stability study was conducted for F10 that showed good stability upon storage at 30°C/75% RH and 40°C/75% RH for 3 months.

Steroids, 2017

Growing evidence suggests that matrix metalloproteinases (MMP) are involved in thrombus dissoluti... more Growing evidence suggests that matrix metalloproteinases (MMP) are involved in thrombus dissolution; then, considering that new therapeutic strategies are required for controlling hemorrhage, we hypothesized that MMP inhibition may reduce bleeding by delaying fibrinolysis. Thus, we designed and synthesized a novel series of MMP inhibitors to identify potential candidates for acute treatment of bleeding. Structure-based and knowledge-based strategies were utilized to design this novel chemical series, α-spiropiperidine hydroxamates, of potent and soluble (>75 µg/mL) pan-MMP inhibitors. The initial hit, 12, was progressed to an optimal lead 19d. Racemic 19d showed a remarkable in vitro phenotypic response and outstanding in vivo efficacy; in fact, the mouse bleeding time at 1 mg/kg was 0.85 min compared to 29.28 min using saline. In addition, 19d displayed an optimal ADME and safety profile (e.g., no thrombus formation). Its corresponding enantiomers were separated, leading to the preclinical candidate 5 (described in drug annotations series, ref18).

ACS Applied Materials & Interfaces, 2015

The surface modification of semiconductor photoelectrodes with passivation overlayers has recentl... more The surface modification of semiconductor photoelectrodes with passivation overlayers has recently attracted great attention as an effective strategy to improve the charge-separation and charge-transfer processes across semiconductor-liquid interfaces. It is usually carried out by employing the sophisticated atomic layer deposition technique, which relies on reactive and expensive metalorganic compounds and vacuum processing, both of which are significant obstacles toward large-scale applications. In this paper, a facile water-based solution method has been developed for the modification of nanostructured hematite photoanode with TiO2 overlayers using a water-soluble titanium complex (i.e., titanium bis(ammonium lactate) dihydroxide, TALH). The thus-fabricated nanostructured hematite photoanodes have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Photoelectrochemical measurements indicated that a nanostructured hematite photoanodes modified with a TiO2 overlayer exhibited a photocurrent response ca. 4.5 times higher (i.e., 1.2 mA cm(-2) vs RHE) than that obtained on the bare hematite photoanode (i.e., 0.27 mA cm(-2) vs RHE) measured under standard illumination conditions. Moreover, a cathodic shift of ca. 190 mV in the water oxidation onset potential was achieved. These results are discussed and explored on the basis of steady-state polarization, transient photocurrent response, open-circuit potential, intensity-modulated photocurrent spectroscopy, and impedance spectroscopy measurements. It is concluded that the TiO2 overlayer passivates the surface states and suppresses the surface electron-hole recombination, thus increasing the generated photovoltage and the band bending. The present method for the hematite electrode modification with a TiO2 overlayer is effective and simple and might find broad applications in the development of stable and high-performance photoelectrodes.

Automation in Construction, 2015

There is a growing need for tools automating the processing of as-built 3D laser scanned data, an... more There is a growing need for tools automating the processing of as-built 3D laser scanned data, and more particularly the comparison of this as-built data with planned works. This paper particularly considers the case of tracking MEP components with circular cross-sections, which essentially include pipes, and some conduits and ducts. Discrepancies between the as-built and as-planned status of pipes, conduit and ductwork result from changes that occur in the field and that are either unnoticed (human error) or not reflected in the 3D model. Previous research has shown that the Hough transform, with judiciously applied domain constraints, is a practical and cost-effective approach to find, recognize and reconstruct cylindrical MEP works within point clouds automatically. Previous research has also shown that "Scanvs-BIM" systems that are based on the geometric alignment and comparison of as-built laser scans with as-designed BIM models can effectively recognize and identify MEP components as long as they are 2 constructed near their as-planned locations. The research presented in this paper combines the two techniques in a unified approach for more robust automated comparison of as-built and as-planned cylindrical MEP works, thereby providing the basis for automated earned value tracking, automated percent-built-as-planned measures, and assistance for the delivery of as-built BIM models from asdesigned ones. The proposed approach and its improved performance are validated using data acquired from an actual construction site. The results are very encouraging and demonstrate the added value of the proposed integrated approach over the rather simpler Scan-vs-BIM system. The two main areas of improved performance are: (1) the enabled recognition and identification of objects that are not built at their as-planned locations; and (2) the consideration for pipe completeness in the pipe recognition and identification metric.

Tunnelling and Underground Space Technology, 2012

Accurate estimation of tunnel face support pressure is necessary for economical and safe shield t... more Accurate estimation of tunnel face support pressure is necessary for economical and safe shield tunneling in cohesionless soils. This paper presents measurements of tunnel face support pressure and associated soil movements obtained using a transparent soil model that simulates shield tunneling in medium dense saturated sand. The use of a transparent soil surrogate permits measuring the internal soil deformations within the model soil. Soil deformations associated with various face support pressures are presented for 4 cover-to- ...

Saudi Pharmaceutical Journal, 2013

Emulsification/internal gelation has been suggested as an alternative to extrusion/external gelat... more Emulsification/internal gelation has been suggested as an alternative to extrusion/external gelation in the encapsulation of several compounds including non-steroidal anti-inflammatory drugs such as diclofenac sodium. The objective of the present study was a trial to formulate diclofenac sodium as controlled release microparticles that might be administered once or twice daily. This could be achieved via emulsification/internal gelation technique applying Box-Behnken design to choose these formulae. Box-Behnken design determined fifteen formulae containing specified amounts of the independent variables, which included stirring speed in rpm (X1), drug:polymer ratio (X2) and the surfactant span 80% (X3). The dependent variables studied were cumulative percent release after two hours (Y1), four hours (Y2) and eight hours (Y3). The prepared microparticles were characterized for their production yield, sizes, shapes and morphology, entrapment efficiency and Diclofenac sodium in vitro release as well. The results showed that the production yield of the prepared diclofenac sodium microparticles was found to be between 79.55% and 97.41%. The formulated microparticles exhibited acceptable drug content values that lie in the range 66.20-96.36%. Also, the data obtained revealed that increasing the mixing speed (X1) generally resulted in decreased microparticle size. In addition, scanning electron microscope images of the microparticles illustrated that the formula contains lower span concentration (1%) in combination with lower stirring speed (200 rpm) which showed wrinkled, but smooth surfaces. However, by increasing surfactant concentration, microspheres' surfaces become smoother and slightly porous. Kinetic treatment of the in vitro release from drug-loaded microparticles indicated that the zero order is the drug release mechanism for the most formulae.

Journal of Geotechnical and Geoenvironmental Engineering, 2011

Ground movements induced by shallow tunnels affect the safety of nearby underground and abovegrou... more Ground movements induced by shallow tunnels affect the safety of nearby underground and aboveground structures. Therefore, the reliable prediction of these movements is important. A transparent soil model is used to investigate not only the surface settlement profile induced by shield tunneling, but also the distribution of soil deformation within the soil mass near the tunnel. The observed surface settlements are consistent with the normal probability curve commonly used for predicting settlement, with only the inflection points or trough ...

Journal of Fluids Engineering, 2003

A theoretical investigation has been conducted for the prediction of the critical height at the o... more A theoretical investigation has been conducted for the prediction of the critical height at the onset of gas entrainment during single discharge from a stratified, two-phase region through a side branch with a finite diameter. Two different models have been developed, a simplified point-sink model and a three-dimensional finite-branch model. The two models are based on a new criterion for the onset of gas entrainment. The results of the predicted critical heights at the onset of gas entrainment showed that the finite-branch model approaches the physical limits at low Froude numbers. However, as the values of the Froude number increased, the predictions of both models eventually converged to the same value. Based on the results of the models, the critical height corresponding to the onset of gas entrainment was found to be a function of Froude number and fluid densities. The results of both models are compared with available experimental data. The comparisons illustrate a very good a...

Journal of Enzyme Inhibition and Medicinal Chemistry, 2013

Cucurbitacins (Cucs) have been classified as signal transducer and activator of transcription 3 i... more Cucurbitacins (Cucs) have been classified as signal transducer and activator of transcription 3 inhibitors. Kinase inhibition has been a validated drug target in multiple types of malignancies. B-RAF mutations are highly expressed in the melanoma. Our hypothesis is the Cucs can be a potential candidate to inhibit the signaling kinase pathway. The research presented is the evaluation of Cucs, as B-RAF and MEK1 kinase inhibitors. Virtual screening methods were employed to identify lead compounds. The hypothesis was tested on mutant B-RAF cell lines, A-375 and Sk-Mel-28 cell lines to determine the activity toward melanoma. A series of natural Cucs show an improved activity toward Sk-Mel-28 and A-375 cell lines. Cucs show potential inhibition for the total and phosphorylated ERK using ELISA kits. Cucs could be potential candidate for inhibiting cell growth.