Effect of Graphene addition on the mechanical and tribological behavior of nanostructured AA2124 /Graphene self-lubricating metal matrix composite

In the current research, the mechanical and tribological behavior, and structural evolution of AA2124-3 and 5-wt.% graphene (G) composites prepared by a combination of ball milling and hot extrusion were investigated. Mixing followed by energy ball milling of the powders was conducted under argon atmosphere. Hot extrusion of the green compacts was carried out at 0.46 and 0.68 of the alloy melting temperature. Properties such as macro and micro-hardness, nanohardness, tensile and lattice strain were characterized. Wear rates, coefficient of friction (COF) were characterized using dry pin-on-disc test under loads of 50, 100N and 150N. Nanoscratch testing were employed to investigate the self-lubricating tribological behavior. X-ray diffraction, optical and scanning electron microscopy were used to determine the influence of the G-content on the crystallite size variation and the lattice strain for the ball milled powders compared to the hot extruded rods. Density measurements and optical microscopy (OM) were employed to investigate the consolidation degree and porosity variation as a function of increasing G- of the G and Al-matrices for the variable conditions. Bulk texture variation was analyzed to evaluate the influence of the extrusion temperature. AA 2124-3 wt.% G composites displayed the highest tensile properties, highest hardness and lowest wear rates and COF, as well as lowest scratch width and depth compared to the 5 wt.%G and the plain alloy. The uniform distribution of the G-particles within the Al-matrices for the 3wt.% containing composites hindered grain coarsening by the induced lattice strain compared to that of 5 wt% G ones. Moreover, addition of 3 wt.% G smeared thin uniform tribofilm on the surfaces of the worn composite rods. The formed layer reduced friction and wear. Increasing the G content up to 5 wt.% resulted in segregation and clustering of the G-particles within the Al-matrices, which caused microplouging and sever plastic deformation wear mechanism and excessive delamination. IV Lower consolidation temperatures of 300oC produced composites with lower wear rates due to the excessive strain hardening effect. Extrusion at 300oC produced a continuous G-encapsulating layer around the Al-matrix compared to an interrupted G-layer for the 450oC extrusions. The G-layer morphology influenced the dominating mechanism of the composite during deformation. Texture analysis of the AA2124-3 wt.%G extruded at low and high temperatures proved that both the Cu-and Shear are the dominating texture components, while increased texture intensities from 1.2-to-1.76 occurred with increasing the extrusion temperature

Geometric nonlinear analysis of plane flexible frame structures.

Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1978 .G439. Source: Masters Abstracts International, Volume: 40-07, page: . Thesis (M.A.Sc.)--University of Windsor (Canada), 1978

Cutaneous Toxicity of Gasoline as an Environmental Pollutant on Mice Skin: Histological and Ultrastrucural Studies

The present investigation was undertaken to determine whether gasoline with different octane number (90 and 80) exposure in healthy Swiss albino mice might affect the skin, in order to declare more recognition on the adverse changes that might occur as a result of exposure to this pollutant. Sixty Swiss albino mice were used and divided into 3 subgroups : control-subgroup, topically treated -subgroup with gasoline 90 and topically treated -subgroup with gasoline 80, both groups two and three treated with (0.5ml/kg B.W.) for 8 weeks.Determination of benzene concentration and some heavy metals in both types of gasoline (90 and 80), determination of some heavy metals bioaccumulation in skin after exposure to both types of gasoline (90 and 80),light and electron microscopical studies were performed.It was found that gasoline 80 contained more concentrations of benzene, lead , cadmium and nickel than gasoline 90. The accumulation of lead, cadmium and nickel in the skin have the following order lead > cadmium > nickel. The light microscopical examinations showed dermatitis such as epidermal hyperplasia, micro abscesses, hyperkeratosis and destruction of the dermis depending upon treatment duration from 4 to 8 weeks. After 8 weeks of topically treated mice with both gasoline type , the scanning electron microscope examination showed scales covering the mice skin and the transition electron microscope showed cytoplasmic vacuoles and mitochondrial degeneration in keratinocytes of all epidermal layers of the mice skin . Moreover, the spinosum keratinocytes of mice skin topically treated with gasoline 80 for 8 weeks had pyknotic nuclei,in addition to expansion of intercellular spaces in the stratum corneum

Concentrations and Estimation of the Annual Effective Doses of Natural Radioactivity Uptake through Ingestion of Virgin and Extra Virgin Olive Oil

This study assesses the natural radioactive concentrations in virgin olive oil in Egypt. The presence and concentrations of naturally occurring radioactive materials (NORM) in 26 olive oil samples collected from different locations in Saini were conducted using two techniques: gamma spectroscopy using a high purity germanium detector (HPGe) and inductively coupled plasma-mass spectroscopy (ICP-MS). Because of their very low concentrations, the radioactivity of NORM was below the detection limits of the HPGe detector for the time of measurement, On the other hand ICP-MS results showed the concentrations of natural radioactive elements such as uranium and thorium in some examined samples. The concentrations of uranium and thorium elements were converted into specific activities using conversion factors recommended by the International Atomic Energy Agency (IAEA). The internal effective dose for individuals from the consumption of olive oil was estimated based on the calculated radionuclide contents and using dose coefficients given by the International Commission on Radiological Protection (ICRP). It was found the olive oil samples are considered radiologically safe for human consumption and dont contribute to any health problems

Improved charge storage performance of a layered Mo1.33C MXene/MoS2/graphene nanocomposite

The construction of nanocomposite electrodes based on 2D materials is an efficient route for property enrichment and for exploitation of constituent 2D materials. Herein, a flexible Mo1.33C i-MXene/MoS2/graphene (MOMG) composite electrode is constructed, utilizing an environment-friendly method for high-quality graphene and MoS2 synthesis. The presence of graphene and MoS2 between MXene sheets limits the commonly observed restacking, increases the interlayer spacing, and facilitates the ionic and electronic conduction. The as-prepared MOMG electrode delivers a volumetric capacitance of 1600 F cm(-3) (450 F g(-1)) at the scan rate of 2 mV s(-1) and retains 96% of the initial capacitance after 15 000 charge/discharge cycles (10 A g(-1)). The current work demonstrates that the construction of nanocomposite electrodes is a promising route towards property enhancement for energy storage applications

Cutaneous Toxicity of Gasoline as an Environmental Pollutant on Mice Skin: Histological and Ultrastrucural Studies

The present investigation was undertaken to determine whether gasoline with different octane number (90 and 80) exposure in healthy Swiss albino mice might affect the skin, in order to declare more recognition on the adverse changes that might occur as a result of exposure to this pollutant. Sixty Swiss albino mice were used and divided into 3 subgroups : control-subgroup, topically treated -subgroup with gasoline 90 and topically treated -subgroup with gasoline 80, both groups two and three treated with (0.5ml/kg B.W.) for 8 weeks.Determination of benzene concentration and some heavy metals in both types of gasoline (90 and 80), determination of some heavy metals bioaccumulation in skin after exposure to both types of gasoline (90 and 80),light and electron microscopical studies were performed.It was found that gasoline 80 contained more concentrations of benzene, lead , cadmium and nickel than gasoline 90. The accumulation of lead, cadmium and nickel in the skin have the following order lead > cadmium > nickel. The light microscopical examinations showed dermatitis such as epidermal hyperplasia, micro abscesses, hyperkeratosis and destruction of the dermis depending upon treatment duration from 4 to 8 weeks. After 8 weeks of topically treated mice with both gasoline type , the scanning electron microscope examination showed scales covering the mice skin and the transition electron microscope showed cytoplasmic vacuoles and mitochondrial degeneration in keratinocytes of all epidermal layers of the mice skin . Moreover, the spinosum keratinocytes of mice skin topically treated with gasoline 80 for 8 weeks had pyknotic nuclei,in addition to expansion of intercellular spaces in the stratum corneum

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Background: Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. // Methods: We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung's disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. // Findings: We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung's disease) from 264 hospitals (89 in high-income countries, 166 in middle-income countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in low-income countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. // Interpretation: Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between low-income, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Acoustic Platform for MXene Synthesis and Electrochemical Behaviour of i-MXenes in Aqueous Electrolytes

Climate Change is believed to be the greatest global challenge and on its forefront is the topic of energy. While being of extreme importance, debates over energy have become a normality. The related field of material synthesis for energy storage applications has also been growing, as well as the demand for industrial electrification from renewable sources of energy. Water-based supercapacitors are a type of energy storage devices that can deliver high power densities while maintaining long term cyclability in an environmen-tally friendly media. However, their challenges include maintaining high per-formance in term of energy density, safety, and low cost of electrode manu-facturing.  MXene is family of two-dimensional transition metal carbides/nitrides that are terminated with H, OH and F groups. The material demonstrates superior physical and chemical properties related to energy applications in compari-son to its 3D parent material, the MAX phase. Since its discovery in 2011, MXene, such as Ti3C2Tz, has been widely investigated in the field of energy storage due to its high conductivity (20,000 S.cm-1) and a volumetric capac-itance that can reach 900 Fcm-3. However, reported synthesis processes for MXene are fraught with hazardous procedures that are time consuming. The first section of this thesis presents a new innovative method for Ti3C2Tz MXene synthesis, in which MXene was synthesized in a few milliseconds with the assistance of 30 MHz frequency surface acoustic waves (SAW) and 0.05M of LiF. The aluminium element in the Ti3AlC2 MAX phase was etched by so called “localized HF”, and the powder was converted to 2D Ti3C2Tz. This method showed resulting MXene comparable to that of previ-ously reported synthesis techniques, as demonstrated by the material’s elec-trochemical performance.   The second section of the thesis focuses on investigating the electrochemical performance of a comparatively new family of MXene, coined i-MXene, in aqueous electrolyte. i-MXene, reported in 2017, has the chemical formula Mo1.33CTz and is a product of chemical etching of the in-plane chemically ordered (Mo2/3Sc1/3)2AlC i-MAX phase. The Mo1.33CTz was studied in a sul-phuric acid electrolyte. This electrolyte sets a limit for the electrode potential window and capacitance, and therefore, post-synthesis treatment protocols was used to enhance the electrochemical performance. The Mo1.33CTz recorded a volumetric capacitance of 1050 Fcm-3 and1600 Fcm-3 for hydrogel treatment and heat-treated electrodes, respectively. Moreover, mixing Mo1.33CTz with MoS2 and graphene improved both the specific capacitance and the electrode stability even further.   The electrochemical properties of Mo1.33CTz were thereafter explored in dif-ferent sulfate-based aqueous electrolytes with univalent (Li+, Na+, and K+) and divalent (Mg2+ Mn2+ or Zn2+) cations. Mo1.33CTz exhibited a wider po-tential window without degradation, expanding the previously reported limit in sulphuric acid for both symmetric and asymmetric devices. Lithium chlo-ride gave the best results, being an electrolyte based on a natural salt that has high solubility at room temperature. It presented a large potential window, -1.2 to +0.3V (vs. Ag/AgCl), and a volumetric capacitance of ~800 Fcm−3 at a scan rate of 2 mVs−1. In addition, the performance of a Mo1.33CTz //MnxOn asymmetric device was tested in 5M LiCl electrolyte. The results showed a potential window of 2 V, a volumetric energy density of 58 mWhcm-3, and a 100% columbic efficiency after 10,000 charge/discharge cycles. A cyclic sta-bility is crucial for practical applications, and altogether, the promising re-sults motivate further exploration of i-MXenes for energy storage and be-yond.ISBN (PDF) saknas i den tryckta versionen och har lagts till i den digitala.Funding agencies: The Swedish Foundation for Strategic Research (SSF), Project EM16-0004.</p