mohamed amr shalaby - Academia.edu (original) (raw)

Papers by mohamed amr shalaby

BMC Pregnancy and Childbirth, 2022

Background Objective to assess the value of preoperative tranexamic acid (TXA) in reduction of in... more Background Objective to assess the value of preoperative tranexamic acid (TXA) in reduction of intraoperative and postoperative blood loss in high-risk cesarean delivery (CD). Methods A double blind randomized controlled trial included 160 high risk women who underwent elective lower segment CD. They were equally randomized to receive either 1 g of TXA or placebo 15 min before surgery. The primary outcome was Intraoperative blood loss. Results The estimated blood loss was significantly higher in the placebo group when compared to TXA group (896.81 ± 519.6 vs. 583.23 ± 379.62 ml, P < 0.001). Both postoperative hemoglobin and hematocrit were lower (9.2 ± 1.6 and 27.4 ± 4.1 vs. 10.1 ± 1.2 and 30.1 ± 3.4, P values < 0.001and 0.012 respectively) and their change percentages (15.41 vs. 7.11%, P < 0.001) were higher in the placebo group when compared to TXA one. The need for further ecbolics was higher in placebo group when compared to TXA group (46.25 vs. 13.75%, P < 0.001). C...

Healthcare, 2021

Background: SARS-CoV-2 infection has a high mortality rate and continues to be a global threat, w... more Background: SARS-CoV-2 infection has a high mortality rate and continues to be a global threat, which warrants the identification of all mortality risk factors in critically ill patients. Methods: This is a retrospective multicenter cohort study conducted in five hospitals in the Kingdom of Saudi Arabia (KSA). We enrolled patients with confirmed SARS-COV-2 infection admitted to any of the intensive care units from the five hospitals between March 2020 and July 2020, corresponding to the peak of recorded COVID-19 cases in the KSA. Results: In total, 229 critically ill patients with confirmed SARS-CoV-2 infection were included in the study. The presenting symptoms and signs of patients who died during hospitalization were not significantly different from those observed among patients who survived. The baseline comorbidities that were significantly associated with in-hospital mortality were diabetes (62% vs. 48% among patients who died and survived (p = 0.046)), underlying cardiac dise...

The aim of this study was to determine the prevalence and predisposing conditions for atrial fibr... more The aim of this study was to determine the prevalence and predisposing conditions for atrial fibrillation (AF) in patients with atrial septal defect (ASD) and to evaluate the influence of age at surgical repair. The study population consisted of 35 patients with ASD (mean age 39.5 + 19 years). All patients had > 1 follow-up visit and a Doppler echocardiographic study. Twenty four of the patients underwent surgical closure 1 to 34 years before the study. Analyzed variables were entered into univariate (Mann-Whitney U) and multivariate (stepwise logistic regression) models to assess independent pre-dictors for AF. The prevalence of AF was similar in surgically treated patients (15.6%) and in the non surgical group (13.8%) (p = 0.69). Multivariate analysis showed that current age (RR 1.9 per each decade of age, 95% Confidence interval (CI) 1.3 to 2.7, p = 0.001), mitral regurgitation (RR 3.0 per each degree of regurgitation, 95% CI 1.6 to 5.8, p = 0.001), left atrial enlargement (RR...

Energies, 2021

Extensive studies are conducted to investigate the potential and techno-economic feasibility of b... more Extensive studies are conducted to investigate the potential and techno-economic feasibility of bioenergy routes in different countries. However, limited researches have been focused on the whole national agricultural bioenergy resources in Egypt. This research provides an assessment of the potential agricultural biomass resources for electric energy production in Egypt. It provides a strategic perspective for the design of a national network of biomass power plants to utilize the spatially available agricultural residues throughout a country. A comprehensive approach is presented and is applied to Egypt. First, the approach estimates the amount, type, and characteristics of the agricultural residues in each Egyptian governorate. Then, a techno-economic appraisal for locating a set of collection stations, and installing a direct combustion biomass power plant in each governorate is conducted. SAM simulation software is used for the technical and economic appraisals, and preliminary ...

Sustainability, 2020

The bullwhip effect reflects the variance amplification of demand as they are moving upstream in ... more The bullwhip effect reflects the variance amplification of demand as they are moving upstream in a supply chain, and leading to the distortion of demand information that hinders supply chain performance sustainability. Extensive research has been undertaken to model, measure, and analyze the bullwhip effect while assuming stationary independent and identically distributed (i.i.d) demand, employing the classical order-up-to (OUT) policy and allowing return orders. On the contrary, correlated demand where a period’s demand is related to previous periods’ demands is evident in several real-life situations, such as demand patterns that exhibit trends or seasonality. This paper assumes correlated demand and aims to investigate the order variance ratio (OVR), net stock amplification ratio (NSA), and average fill rate/service level (AFR). Moreover, the impact of correlated demand on the supply chain performance under various operational parameters, such as lead-time, forecasting parameter,...

The International Journal of Advanced Manufacturing Technology, 2018

This work presents a developed thermal model of hard precision turning, in which the depth of the... more This work presents a developed thermal model of hard precision turning, in which the depth of the cut is made to be considerably smaller than the tool nose radius for final finishing. The required input data for this model was extracted from a previously published mechanistic model of precision turning. This mechanistic model is based on Merchant's analysis of 3D cutting, which was modified to adopt the precision turning operation. Calculations were obtained of the shear plane temperature rise at the primary deformation zone and the temperature rise of the chip due to the work done in overcoming friction at the secondary deformation zone (frictional temperature rise). The thermophysical properties of the workpiece and cutting tool materials as well as their variation under different shear plane and frictional temperatures were considered. After performing the required calibrations, the cutting temperatures were measured with the tool-workpiece thermocouple technique during machining of hardened HSS and D2 tool steel by PCBN and mixed alumina ceramic tools. The occurrence of secondary hardening during HSS machining was found to be dependent on the thermal conductivity of the tool material. The estimated cutting temperatures were found to be reasonably close to the measured ones.

Journal of Manufacturing and Materials Processing, 2018

High-speed machining (HSM) is used in industry to improve the productivity and quality of the cut... more High-speed machining (HSM) is used in industry to improve the productivity and quality of the cutting operations. In this investigation, pure alumina ceramics with the addition of ZrO 2 , and mixed alumina (Al 2 O 3 + TiC) tools were used in the dry hard turning of AISI 4340 (52 HRC) at different high cutting speeds of 150, 250, 700 and 1000 m/min. It was observed that at cutting speeds of 150 and 250 m/min, pure alumina ceramic tools had better wear resistance than mixed alumina ones. However, upon increasing the cutting speed from 700 to 1000 m/min, mixed alumina ceramic tools outperformed pure ceramic ones. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the worn cutting edges and analyze the obtained results. It was found that the tribo-films formed at the cutting zone during machining affected the wear resistances of the tools and influenced the coefficient of friction at the tool-chip interface. These observations were confirmed by the chip compression ratio results at different cutting conditions. Raising cutting speed to 1000 m/min corresponded to a remarkable decrease in cutting force components in the dry hard turning of AISI 4340 steel.

The International Journal of Advanced Manufacturing Technology, 2018

The Ti-6Al-4V aerospace alloy is a difficult-to-cut material due to its low thermal conductivity ... more The Ti-6Al-4V aerospace alloy is a difficult-to-cut material due to its low thermal conductivity and high strength. To reduce the total machining cost and meet environmental standards, dry machining of titanium alloys could present an attractive option to industry. This study seeks to compare and observe flood and dry finish turning of the Ti-6Al-4V using uncoated carbide and polycrystalline diamond (PCD) tools. Cutting with carbide tools was conducted at speeds of 150, 120, and 80 m/min, while PCD was at 150 m/min. Machining with uncoated carbide tools revealed that the tool life in flood cutting was remarkably longer than in dry cutting at 150 and 120 m/min. However, tool wear mechanisms were obviously different as indicated by the scanning electron microscope and the energy-dispersive spectroscopy (SEM/EDS). For the first time, it was proven that at 80 m/min, the wear resistance of the uncoated carbide tool was similar under flood and dry cutting. At the latter cutting speed, the formation of a V 2 O 5 tribofilm, a high-temperature liquid lubricant only created under dry cutting, could assist heat energy dissipation and prevent sticking of the workpiece material onto the cutting edge at such severe cutting conditions. TiC protective and W-O lubricant tribofilms were found at the lowest cutting speed (80 m/min) under flood and dry cutting. Formation of these tribofilms was confirmed by X-ray photoelectron spectroscopy (XPS). The same difference in tool life between flood and dry cutting was found with the PCD cutting tool at 150 m/min. XPS showed the presence of a high amount of TiC tribofilms at the worn cutting edge of this tool material under flood and dry conditions. This might be a cause of a longer tool life obtained during machining of Ti-6Al-4V with PCD cutting tools compared to carbide tools. As an indication of the frictional action at the tool-chip interface, chip compression ratio values did not show remarkable differences in neither flood nor dry cutting using the two tool materials. Moreover, the produced cutting forces were not affected by the application of cutting fluid.

Tribology Transactions, 2018

Tool wear is an important machinability criterion. For the sake of reduction of the total machini... more Tool wear is an important machinability criterion. For the sake of reduction of the total machining cost; this study demonstrates the wear and tribological performance of four ceramic tools in dry high speed turning of Ni-Co-Cr precipitation hardenable superalloy (Inconel 100). Wear of the tool materials and the structural and phase transformations at the tool/chip interface were investigated. Results obtained reveal that SiAlON ceramic outperformed other ceramic tool materials at different cutting speeds due to the formation large amount of mullite tribo-films on the tool face, which serve as a thermal barrier layer. Alumina ceramic with addition of ZrO 2 can be recommended for machining Inconel 100 at speeds above 150 m/min due its ability to form thermal barrier ZrO 2 tribo-films, which decrease of coefficient of friction at the tool chip/ interface. Mixed alumina and alumina matrix reinforced with SiC w were found to be not suitable for machining age-hardened Inconel 100 superalloy.

Pediatric nephrology (Berlin, Germany), Jan 5, 2018

Acute kidney injury (AKI) is common in neonates admitted to the neonatal intensive care unit (NIC... more Acute kidney injury (AKI) is common in neonates admitted to the neonatal intensive care unit (NICU). AKI is associated with increased morbidity and mortality and a greater long-term risk of chronic kidney disease. To study the incidence and outcome of neonatal AKI in a single Saudi Arabian center, level 2\3 NICU. This single-center prospective cohort study included all infants who received level II or III NICU care during 2015 (January to December). We excluded infants who survived less than 48 h after admission, had evidence of congenital renal anomalies, or had insufficient data. AKI was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Both AKI and non-AKI neonates were prospectively followed up until NICU discharge. Outcomes studied included mortality and length of NICU stay. The results of adjusted risk analyses were expressed as relative risk (RR) with 95% confidence interval (95% CI). The incidence of AKI (modified neonatal KDIGO stages) was...

Pediatric Nephrology, 2017

Background Acute kidney injury (AKI) is a common problem encountered in critically ill children w... more Background Acute kidney injury (AKI) is a common problem encountered in critically ill children with an increasing incidence and evolving epidemiology. AKI carries a serious morbidity and mortality in patients requiring admission to a pediatric intensive care unit (PICU). Methods We undertook a prospective cohort study of PICU admissions at three tertiary care hospitals in the Kingdom of Saudi Arabia over 2 years. The Kidney Disease Improving Global Outcomes (KDIGO) definition was used to diagnose AKI. Results A total of 1367 pediatrics PICU admissions were included in the study. AKI affected 511 children (37.4%), with 243 children (17.8%) classified as stage I (mild), 168 patients (12.3%) stage II (moderate), and 100 children (7.3%) were classified as stage III (severe). After adjustment for age, sex, and underlying diagnosis, in-hospital mortality was six times more likely among patients with AKI as compared to patients with normal renal function (adjusted OR: 6.5, 95% CI: 4.2-10). AKI was also a risk factor for hypertension (adjusted OR: 4.1, 95% CI: 2.8-5.9) and prolonged stay in the PICU and hospital, as it increased the average number of admission days by 10 (95% CI: 8.6-11) days in the PICU and 12 (95% CI: 10-14) days in the hospital. Conclusions One-third of PICU admissions were complicated with AKI. AKI was associated with increased hospital mortality and the length of stay in both PICU and hospital.

Virusdisease, 2017

The low pathogenic avian influenza (LPAI) H9N2 subtype has become the most prevalent and widespre... more The low pathogenic avian influenza (LPAI) H9N2 subtype has become the most prevalent and widespread in many Asian and Middle Eastern countries. It causes an enzootic situation in commercial poultry and known as a potential facilitator virus that can be transmitted to human from birds. The neuraminidase (NA) gene plays an important role the release and spread of the virus from infected cells and throughout the bird. The complete nucleotide sequences of the NA gene of seven H9N2 viruses collected from apparent healthy chicken and quail flocks in Egypt during 2014-2015, were amplified and sequenced. The phylogenetic relationships were investigated and all viruses were belonging to the A/Q/HK/G1/97 strain (G1-like). There were no insertions or deletions or shortening in NA stalk regions when compared to Y280-lineage and the human H9N2 isolates. No obvious changes NA interactions with antiviral drugs. We found that the Egyptian H9N2 viruses have seven glycosylation sites like the most re...

PloS one, 2017

Schimke immuno-osseous dysplasia (SIOD) is a rare multisystem disorder with early mortality and s... more Schimke immuno-osseous dysplasia (SIOD) is a rare multisystem disorder with early mortality and steroid-resistant nephrotic syndrome (SRNS) progressing to end-stage kidney disease. We hypothesized that next-generation gene panel sequencing may unsurface oligosymptomatic cases of SIOD with potentially milder disease courses. We analyzed the renal and extrarenal phenotypic spectrum and genotype-phenotype associations in 34 patients from 28 families, the largest SMARCAL1-associated nephropathy cohort to date. In 11 patients the diagnosis was made unsuspectedly through SRNS gene panel testing. Renal disease first manifested at median age 4.5 yrs, with focal segmental glmerulosclerosis or minimal change nephropathy on biopsy and rapid progression to end-stage kidney disease (ESKD) at median age 8.7 yrs. Whereas patients diagnosed by phenotype more frequently developed severe extrarenal complications (cerebral ischemic events, septicemia) and were more likely to die before age 10 years th...

Pediatric Nephrology, 2016

Journal of virological methods, Jan 28, 2015

The 2006 outbreaks of H5N1 avian influenza in Egypt interrupted poultry production and caused sta... more The 2006 outbreaks of H5N1 avian influenza in Egypt interrupted poultry production and caused staggering economic damage. In addition, H5N1 avian influenza viruses represent a significant threat to public health. Therefore, the rapid detection of H5 viruses is very important in order to control the disease. In this study, a qualitative reverse transcription recombinase polymerase amplification (RT-RPA) assay for the detection of haemagglutinin gene of H5 subtype influenza viruses was developed. The results were compared to the real-time reverse transcription polymerase chain reaction (RT-PCR). An in vitro transcribed RNA standard of 970 nucleotides of the haemagglutinin gene was developed and used to determine the assay sensitivity. The developed H5 RT-RPA assay was able to detect one RNA molecule within 7min, while in real-time RT-PCR, at least 90min was required. H5 RT-RPA assay did not detect nucleic acid extracted from H5 negative samples or from other pathogens producing respir...

Applied Optics, 2014

In this work, we propose a numerical technique to compensate for errors due to dispersion effects... more In this work, we propose a numerical technique to compensate for errors due to dispersion effects in Fourier domain optical coherence tomography. The proposed technique corrects for errors in depth measurements and resolution loss due to dispersion. The results show that, by using this technique, errors in thickness measurement are reduced from about 5% to less than 0.1% depending on the sample length and the amount of dispersion. Also, an improvement in the resolution from about 50 μm to less than 10 μm is demonstrated.

World journal of gastrointestinal pharmacology and therapeutics, Jan 6, 2013

To study the possible interactions of metoclopramide, domperidone and erythromycin in streptozoto... more To study the possible interactions of metoclopramide, domperidone and erythromycin in streptozotocin-induced diabetic mice treated with insulin by various parameters. Effects of the individual as well as combined drugs were studied in diabetic mice via estimation of the blood glucose and serum insulin levels, small intestinal transit (SIT), gastric emptying (GE), xylose absorption and glucose tolerance tests. Groups were given insulin 2 IU/kg s.c., metoclopramide 20 mg/kg p.o., domperidone 20 mg/kg p.o. and erythromycin 6 mg/kg p.o. individually and in combination. There were also normal and diabetic control groups. The first set of experiments was carried out to investigate the subchronic effect on blood glucose and serum insulin levels in diabetic mice of one week of daily dose administration of the tested drugs individually as well as the combination of insulin with each prokinetic drug. The other five sets of experiments were carried out to investigate the acute effect of a sing...

2011 International Conference on Energy Aware Computing, 2011

Notebook and Laptop Original Equipment Manufacturers (OEMs) place great emphasis on creating uniq... more Notebook and Laptop Original Equipment Manufacturers (OEMs) place great emphasis on creating unique system designs to differentiate themselves in the mobile market. These systems are developed from the 'outside in' with the focus on how the system is perceived by the end-user. As a consequence, very little consideration is given to the interconnections or power of the devices within the system with a mentality of 'just make it fit'. In this paper we discuss the challenges of Notebook system design and the steps by which system floor-planning tools and algorithms can be used to provide an automated method to optimize this process to ensure all required components most optimally fit inside the Notebook system.

Robotica, 1996

SUMMARYThe main objective of this work is to study the performance of a flexible single hub-arm s... more SUMMARYThe main objective of this work is to study the performance of a flexible single hub-arm system. The equations of motion are derived using the extended Hamilton principle. The Liapunov functional is used as a condition for the stability analysis. The Liapunov functional is considered as the sum of the internal energy of the flexible beam. The required drive torque was obtained directly through the solution of the inverse dynamic problem. Although the flexible link is nonminimum phase in nature, the use of Liapunov and the PD controller guarantee the causality for the stable case. The effects of tip mass as well as its inertia in the case of stable and asymptotic stable systems were investigated to ensure the validity of this procedure.

Journal of the American Statistical Association, 1980

Page 1. Acceptance/Re jection Methods for Beta Variate Generation BRUCE W. SCHMEISER and MOHAMED ... more Page 1. Acceptance/Re jection Methods for Beta Variate Generation BRUCE W. SCHMEISER and MOHAMED A. SHALABY* The computer generation of pseudorandom variates from the beta distribution is discussed. Three ...

BMC Pregnancy and Childbirth, 2022

Background Objective to assess the value of preoperative tranexamic acid (TXA) in reduction of in... more Background Objective to assess the value of preoperative tranexamic acid (TXA) in reduction of intraoperative and postoperative blood loss in high-risk cesarean delivery (CD). Methods A double blind randomized controlled trial included 160 high risk women who underwent elective lower segment CD. They were equally randomized to receive either 1 g of TXA or placebo 15 min before surgery. The primary outcome was Intraoperative blood loss. Results The estimated blood loss was significantly higher in the placebo group when compared to TXA group (896.81 ± 519.6 vs. 583.23 ± 379.62 ml, P < 0.001). Both postoperative hemoglobin and hematocrit were lower (9.2 ± 1.6 and 27.4 ± 4.1 vs. 10.1 ± 1.2 and 30.1 ± 3.4, P values < 0.001and 0.012 respectively) and their change percentages (15.41 vs. 7.11%, P < 0.001) were higher in the placebo group when compared to TXA one. The need for further ecbolics was higher in placebo group when compared to TXA group (46.25 vs. 13.75%, P < 0.001). C...

Healthcare, 2021

Background: SARS-CoV-2 infection has a high mortality rate and continues to be a global threat, w... more Background: SARS-CoV-2 infection has a high mortality rate and continues to be a global threat, which warrants the identification of all mortality risk factors in critically ill patients. Methods: This is a retrospective multicenter cohort study conducted in five hospitals in the Kingdom of Saudi Arabia (KSA). We enrolled patients with confirmed SARS-COV-2 infection admitted to any of the intensive care units from the five hospitals between March 2020 and July 2020, corresponding to the peak of recorded COVID-19 cases in the KSA. Results: In total, 229 critically ill patients with confirmed SARS-CoV-2 infection were included in the study. The presenting symptoms and signs of patients who died during hospitalization were not significantly different from those observed among patients who survived. The baseline comorbidities that were significantly associated with in-hospital mortality were diabetes (62% vs. 48% among patients who died and survived (p = 0.046)), underlying cardiac dise...

The aim of this study was to determine the prevalence and predisposing conditions for atrial fibr... more The aim of this study was to determine the prevalence and predisposing conditions for atrial fibrillation (AF) in patients with atrial septal defect (ASD) and to evaluate the influence of age at surgical repair. The study population consisted of 35 patients with ASD (mean age 39.5 + 19 years). All patients had > 1 follow-up visit and a Doppler echocardiographic study. Twenty four of the patients underwent surgical closure 1 to 34 years before the study. Analyzed variables were entered into univariate (Mann-Whitney U) and multivariate (stepwise logistic regression) models to assess independent pre-dictors for AF. The prevalence of AF was similar in surgically treated patients (15.6%) and in the non surgical group (13.8%) (p = 0.69). Multivariate analysis showed that current age (RR 1.9 per each decade of age, 95% Confidence interval (CI) 1.3 to 2.7, p = 0.001), mitral regurgitation (RR 3.0 per each degree of regurgitation, 95% CI 1.6 to 5.8, p = 0.001), left atrial enlargement (RR...

Energies, 2021

Extensive studies are conducted to investigate the potential and techno-economic feasibility of b... more Extensive studies are conducted to investigate the potential and techno-economic feasibility of bioenergy routes in different countries. However, limited researches have been focused on the whole national agricultural bioenergy resources in Egypt. This research provides an assessment of the potential agricultural biomass resources for electric energy production in Egypt. It provides a strategic perspective for the design of a national network of biomass power plants to utilize the spatially available agricultural residues throughout a country. A comprehensive approach is presented and is applied to Egypt. First, the approach estimates the amount, type, and characteristics of the agricultural residues in each Egyptian governorate. Then, a techno-economic appraisal for locating a set of collection stations, and installing a direct combustion biomass power plant in each governorate is conducted. SAM simulation software is used for the technical and economic appraisals, and preliminary ...

Sustainability, 2020

The bullwhip effect reflects the variance amplification of demand as they are moving upstream in ... more The bullwhip effect reflects the variance amplification of demand as they are moving upstream in a supply chain, and leading to the distortion of demand information that hinders supply chain performance sustainability. Extensive research has been undertaken to model, measure, and analyze the bullwhip effect while assuming stationary independent and identically distributed (i.i.d) demand, employing the classical order-up-to (OUT) policy and allowing return orders. On the contrary, correlated demand where a period’s demand is related to previous periods’ demands is evident in several real-life situations, such as demand patterns that exhibit trends or seasonality. This paper assumes correlated demand and aims to investigate the order variance ratio (OVR), net stock amplification ratio (NSA), and average fill rate/service level (AFR). Moreover, the impact of correlated demand on the supply chain performance under various operational parameters, such as lead-time, forecasting parameter,...

The International Journal of Advanced Manufacturing Technology, 2018

This work presents a developed thermal model of hard precision turning, in which the depth of the... more This work presents a developed thermal model of hard precision turning, in which the depth of the cut is made to be considerably smaller than the tool nose radius for final finishing. The required input data for this model was extracted from a previously published mechanistic model of precision turning. This mechanistic model is based on Merchant's analysis of 3D cutting, which was modified to adopt the precision turning operation. Calculations were obtained of the shear plane temperature rise at the primary deformation zone and the temperature rise of the chip due to the work done in overcoming friction at the secondary deformation zone (frictional temperature rise). The thermophysical properties of the workpiece and cutting tool materials as well as their variation under different shear plane and frictional temperatures were considered. After performing the required calibrations, the cutting temperatures were measured with the tool-workpiece thermocouple technique during machining of hardened HSS and D2 tool steel by PCBN and mixed alumina ceramic tools. The occurrence of secondary hardening during HSS machining was found to be dependent on the thermal conductivity of the tool material. The estimated cutting temperatures were found to be reasonably close to the measured ones.

Journal of Manufacturing and Materials Processing, 2018

High-speed machining (HSM) is used in industry to improve the productivity and quality of the cut... more High-speed machining (HSM) is used in industry to improve the productivity and quality of the cutting operations. In this investigation, pure alumina ceramics with the addition of ZrO 2 , and mixed alumina (Al 2 O 3 + TiC) tools were used in the dry hard turning of AISI 4340 (52 HRC) at different high cutting speeds of 150, 250, 700 and 1000 m/min. It was observed that at cutting speeds of 150 and 250 m/min, pure alumina ceramic tools had better wear resistance than mixed alumina ones. However, upon increasing the cutting speed from 700 to 1000 m/min, mixed alumina ceramic tools outperformed pure ceramic ones. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the worn cutting edges and analyze the obtained results. It was found that the tribo-films formed at the cutting zone during machining affected the wear resistances of the tools and influenced the coefficient of friction at the tool-chip interface. These observations were confirmed by the chip compression ratio results at different cutting conditions. Raising cutting speed to 1000 m/min corresponded to a remarkable decrease in cutting force components in the dry hard turning of AISI 4340 steel.

The International Journal of Advanced Manufacturing Technology, 2018

The Ti-6Al-4V aerospace alloy is a difficult-to-cut material due to its low thermal conductivity ... more The Ti-6Al-4V aerospace alloy is a difficult-to-cut material due to its low thermal conductivity and high strength. To reduce the total machining cost and meet environmental standards, dry machining of titanium alloys could present an attractive option to industry. This study seeks to compare and observe flood and dry finish turning of the Ti-6Al-4V using uncoated carbide and polycrystalline diamond (PCD) tools. Cutting with carbide tools was conducted at speeds of 150, 120, and 80 m/min, while PCD was at 150 m/min. Machining with uncoated carbide tools revealed that the tool life in flood cutting was remarkably longer than in dry cutting at 150 and 120 m/min. However, tool wear mechanisms were obviously different as indicated by the scanning electron microscope and the energy-dispersive spectroscopy (SEM/EDS). For the first time, it was proven that at 80 m/min, the wear resistance of the uncoated carbide tool was similar under flood and dry cutting. At the latter cutting speed, the formation of a V 2 O 5 tribofilm, a high-temperature liquid lubricant only created under dry cutting, could assist heat energy dissipation and prevent sticking of the workpiece material onto the cutting edge at such severe cutting conditions. TiC protective and W-O lubricant tribofilms were found at the lowest cutting speed (80 m/min) under flood and dry cutting. Formation of these tribofilms was confirmed by X-ray photoelectron spectroscopy (XPS). The same difference in tool life between flood and dry cutting was found with the PCD cutting tool at 150 m/min. XPS showed the presence of a high amount of TiC tribofilms at the worn cutting edge of this tool material under flood and dry conditions. This might be a cause of a longer tool life obtained during machining of Ti-6Al-4V with PCD cutting tools compared to carbide tools. As an indication of the frictional action at the tool-chip interface, chip compression ratio values did not show remarkable differences in neither flood nor dry cutting using the two tool materials. Moreover, the produced cutting forces were not affected by the application of cutting fluid.

Tribology Transactions, 2018

Tool wear is an important machinability criterion. For the sake of reduction of the total machini... more Tool wear is an important machinability criterion. For the sake of reduction of the total machining cost; this study demonstrates the wear and tribological performance of four ceramic tools in dry high speed turning of Ni-Co-Cr precipitation hardenable superalloy (Inconel 100). Wear of the tool materials and the structural and phase transformations at the tool/chip interface were investigated. Results obtained reveal that SiAlON ceramic outperformed other ceramic tool materials at different cutting speeds due to the formation large amount of mullite tribo-films on the tool face, which serve as a thermal barrier layer. Alumina ceramic with addition of ZrO 2 can be recommended for machining Inconel 100 at speeds above 150 m/min due its ability to form thermal barrier ZrO 2 tribo-films, which decrease of coefficient of friction at the tool chip/ interface. Mixed alumina and alumina matrix reinforced with SiC w were found to be not suitable for machining age-hardened Inconel 100 superalloy.

Pediatric nephrology (Berlin, Germany), Jan 5, 2018

Acute kidney injury (AKI) is common in neonates admitted to the neonatal intensive care unit (NIC... more Acute kidney injury (AKI) is common in neonates admitted to the neonatal intensive care unit (NICU). AKI is associated with increased morbidity and mortality and a greater long-term risk of chronic kidney disease. To study the incidence and outcome of neonatal AKI in a single Saudi Arabian center, level 2\3 NICU. This single-center prospective cohort study included all infants who received level II or III NICU care during 2015 (January to December). We excluded infants who survived less than 48 h after admission, had evidence of congenital renal anomalies, or had insufficient data. AKI was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Both AKI and non-AKI neonates were prospectively followed up until NICU discharge. Outcomes studied included mortality and length of NICU stay. The results of adjusted risk analyses were expressed as relative risk (RR) with 95% confidence interval (95% CI). The incidence of AKI (modified neonatal KDIGO stages) was...

Pediatric Nephrology, 2017

Background Acute kidney injury (AKI) is a common problem encountered in critically ill children w... more Background Acute kidney injury (AKI) is a common problem encountered in critically ill children with an increasing incidence and evolving epidemiology. AKI carries a serious morbidity and mortality in patients requiring admission to a pediatric intensive care unit (PICU). Methods We undertook a prospective cohort study of PICU admissions at three tertiary care hospitals in the Kingdom of Saudi Arabia over 2 years. The Kidney Disease Improving Global Outcomes (KDIGO) definition was used to diagnose AKI. Results A total of 1367 pediatrics PICU admissions were included in the study. AKI affected 511 children (37.4%), with 243 children (17.8%) classified as stage I (mild), 168 patients (12.3%) stage II (moderate), and 100 children (7.3%) were classified as stage III (severe). After adjustment for age, sex, and underlying diagnosis, in-hospital mortality was six times more likely among patients with AKI as compared to patients with normal renal function (adjusted OR: 6.5, 95% CI: 4.2-10). AKI was also a risk factor for hypertension (adjusted OR: 4.1, 95% CI: 2.8-5.9) and prolonged stay in the PICU and hospital, as it increased the average number of admission days by 10 (95% CI: 8.6-11) days in the PICU and 12 (95% CI: 10-14) days in the hospital. Conclusions One-third of PICU admissions were complicated with AKI. AKI was associated with increased hospital mortality and the length of stay in both PICU and hospital.

Virusdisease, 2017

The low pathogenic avian influenza (LPAI) H9N2 subtype has become the most prevalent and widespre... more The low pathogenic avian influenza (LPAI) H9N2 subtype has become the most prevalent and widespread in many Asian and Middle Eastern countries. It causes an enzootic situation in commercial poultry and known as a potential facilitator virus that can be transmitted to human from birds. The neuraminidase (NA) gene plays an important role the release and spread of the virus from infected cells and throughout the bird. The complete nucleotide sequences of the NA gene of seven H9N2 viruses collected from apparent healthy chicken and quail flocks in Egypt during 2014-2015, were amplified and sequenced. The phylogenetic relationships were investigated and all viruses were belonging to the A/Q/HK/G1/97 strain (G1-like). There were no insertions or deletions or shortening in NA stalk regions when compared to Y280-lineage and the human H9N2 isolates. No obvious changes NA interactions with antiviral drugs. We found that the Egyptian H9N2 viruses have seven glycosylation sites like the most re...

PloS one, 2017

Schimke immuno-osseous dysplasia (SIOD) is a rare multisystem disorder with early mortality and s... more Schimke immuno-osseous dysplasia (SIOD) is a rare multisystem disorder with early mortality and steroid-resistant nephrotic syndrome (SRNS) progressing to end-stage kidney disease. We hypothesized that next-generation gene panel sequencing may unsurface oligosymptomatic cases of SIOD with potentially milder disease courses. We analyzed the renal and extrarenal phenotypic spectrum and genotype-phenotype associations in 34 patients from 28 families, the largest SMARCAL1-associated nephropathy cohort to date. In 11 patients the diagnosis was made unsuspectedly through SRNS gene panel testing. Renal disease first manifested at median age 4.5 yrs, with focal segmental glmerulosclerosis or minimal change nephropathy on biopsy and rapid progression to end-stage kidney disease (ESKD) at median age 8.7 yrs. Whereas patients diagnosed by phenotype more frequently developed severe extrarenal complications (cerebral ischemic events, septicemia) and were more likely to die before age 10 years th...

Pediatric Nephrology, 2016

Journal of virological methods, Jan 28, 2015

The 2006 outbreaks of H5N1 avian influenza in Egypt interrupted poultry production and caused sta... more The 2006 outbreaks of H5N1 avian influenza in Egypt interrupted poultry production and caused staggering economic damage. In addition, H5N1 avian influenza viruses represent a significant threat to public health. Therefore, the rapid detection of H5 viruses is very important in order to control the disease. In this study, a qualitative reverse transcription recombinase polymerase amplification (RT-RPA) assay for the detection of haemagglutinin gene of H5 subtype influenza viruses was developed. The results were compared to the real-time reverse transcription polymerase chain reaction (RT-PCR). An in vitro transcribed RNA standard of 970 nucleotides of the haemagglutinin gene was developed and used to determine the assay sensitivity. The developed H5 RT-RPA assay was able to detect one RNA molecule within 7min, while in real-time RT-PCR, at least 90min was required. H5 RT-RPA assay did not detect nucleic acid extracted from H5 negative samples or from other pathogens producing respir...

Applied Optics, 2014

In this work, we propose a numerical technique to compensate for errors due to dispersion effects... more In this work, we propose a numerical technique to compensate for errors due to dispersion effects in Fourier domain optical coherence tomography. The proposed technique corrects for errors in depth measurements and resolution loss due to dispersion. The results show that, by using this technique, errors in thickness measurement are reduced from about 5% to less than 0.1% depending on the sample length and the amount of dispersion. Also, an improvement in the resolution from about 50 μm to less than 10 μm is demonstrated.

World journal of gastrointestinal pharmacology and therapeutics, Jan 6, 2013

To study the possible interactions of metoclopramide, domperidone and erythromycin in streptozoto... more To study the possible interactions of metoclopramide, domperidone and erythromycin in streptozotocin-induced diabetic mice treated with insulin by various parameters. Effects of the individual as well as combined drugs were studied in diabetic mice via estimation of the blood glucose and serum insulin levels, small intestinal transit (SIT), gastric emptying (GE), xylose absorption and glucose tolerance tests. Groups were given insulin 2 IU/kg s.c., metoclopramide 20 mg/kg p.o., domperidone 20 mg/kg p.o. and erythromycin 6 mg/kg p.o. individually and in combination. There were also normal and diabetic control groups. The first set of experiments was carried out to investigate the subchronic effect on blood glucose and serum insulin levels in diabetic mice of one week of daily dose administration of the tested drugs individually as well as the combination of insulin with each prokinetic drug. The other five sets of experiments were carried out to investigate the acute effect of a sing...

2011 International Conference on Energy Aware Computing, 2011

Notebook and Laptop Original Equipment Manufacturers (OEMs) place great emphasis on creating uniq... more Notebook and Laptop Original Equipment Manufacturers (OEMs) place great emphasis on creating unique system designs to differentiate themselves in the mobile market. These systems are developed from the 'outside in' with the focus on how the system is perceived by the end-user. As a consequence, very little consideration is given to the interconnections or power of the devices within the system with a mentality of 'just make it fit'. In this paper we discuss the challenges of Notebook system design and the steps by which system floor-planning tools and algorithms can be used to provide an automated method to optimize this process to ensure all required components most optimally fit inside the Notebook system.

Robotica, 1996

SUMMARYThe main objective of this work is to study the performance of a flexible single hub-arm s... more SUMMARYThe main objective of this work is to study the performance of a flexible single hub-arm system. The equations of motion are derived using the extended Hamilton principle. The Liapunov functional is used as a condition for the stability analysis. The Liapunov functional is considered as the sum of the internal energy of the flexible beam. The required drive torque was obtained directly through the solution of the inverse dynamic problem. Although the flexible link is nonminimum phase in nature, the use of Liapunov and the PD controller guarantee the causality for the stable case. The effects of tip mass as well as its inertia in the case of stable and asymptotic stable systems were investigated to ensure the validity of this procedure.

Journal of the American Statistical Association, 1980

Page 1. Acceptance/Re jection Methods for Beta Variate Generation BRUCE W. SCHMEISER and MOHAMED ... more Page 1. Acceptance/Re jection Methods for Beta Variate Generation BRUCE W. SCHMEISER and MOHAMED A. SHALABY* The computer generation of pseudorandom variates from the beta distribution is discussed. Three ...