Designing Nanocomposite Materials For Catalyzing Electrochemical Reactions in Anion Exchange Membrane Fuel Cells

Fuel cells are considered to be one the most promising sustainable energy technologies for energy conversion and electric power generation. With the development of stable, conductive and high performance anion exchange membranes and ionomers, there has been an increased interest towards studying various electrochemical reactions in Anion Exchange Membrane Fuel Cells (AEMFC). This increased attention has been attributed to the comparatively facile reaction kinetics, minimized corrosion effects and reduced fuel crossover in alkaline media. However, the oxygen reduction reactions (ORR) taking place in the cathode compartment of fuel cells plays a crucial role in optimizing the electrochemical energy conversion efficiency, which is why it’s imperative to design electrocatalysts that can efficiently catalyze the electroreduction of oxygen in alkaline media. Various studies have demonstrated the improved intrinsic activity, stability and accessibility of Palladium/Graphene-based nanocomposites for ORR in alkaline electrolytes, although their integration into operating AEMFCs have been quite limited to date. This is mainly due to the challenges associated with (i) synthesizing Pd nanoparticles without surfactants and organic stabilizers (ii) fabricating porous graphitized supports with controlled morphologies that can form triple phase boundaries and (iii) a lack of standardization and optimization for integrating these nanocomposite materials into the membrane electrode assemblies of AEMFCs. This work addresses the current limitations and technical challenges by providing a synthetic strategy for designing Pd/Graphene nanocomposites with i) controlled surface to volume ratios for enhancing the solid-liquid-gas phase boundaries, ii) modified chemical properties for improving nanoparticle dispersion and electrochemical accessibility and iii) targeted tuning of active sites through nitrogen functionalization for oxygen electroreduction in alkaline media. In particular, stable size-controlled Pd nanoparticles were synthesized using surfactant free technique and deposited on hierarchically structured nitrogen doped 3D-Graphene nanosheets that were fabricated with varying levels of micro-, and macro-porosities developed using a sacrificial templating and pyrolytic methods. Using a synergetic combination of potentiodynamic, surface analysis and spectroscopic techniques, it was demonstrated that the porosity, surface functionalization, and the nature of nitrogen moieties doped into played a significant role in in modifying the size, dispersion, electrochemical accessibility as well as activity of the Pd nanoparticles for oxygen electroreduction in alkaline media. The Pd/3D-Graphene composite materials were also integrated into a catalyst coated membrane, optimized (assembly, activation, electrode fabrication) and analyzed for their performance in H2/O2 fed AEMFCs operating at 60°C. It was demonstrated that conditioning of the membranes was crucial for reducing ohmic losses, whereas porosity of the supports was imperative for facilitating mass transport kinetics. Overall, this work analyzes how the morphological and chemical properties of graphitized supports can be modified to play a key role in improving oxygen electroreduction pathways not only in the alkaline electrolytes, but also in minimizing concentration polarization losses in operating AEMFCs. The results in this study further highlights the importance of rationally designing nanomaterials for high-performance energy conversion devices, and can also be expanded to other energy storage and conversion applications such as electrodes for Li-air batteries and electrolyzers

EXPLORATION OF TM-NX ORR ELECTROCATALYSTS FROM FIRST PRINCIPLE CALCULATIONS

Fuel Cells are promising candidates for the energy conversion technologies in particular for non-stationary applications. However, current fuel cells rely on rare and expensive Platinum catalysts and the power generation is limited by the sluggish oxygen reduction reaction (ORR) at the cathode. An interesting alternative material set which continues to attract significant attention are TM-Nx (TM = Fe, Co, x = 2 - 4) based non-PGM electrocatalysts where the defect motifs are embedded in a carbon matrix during pyrolysis. By studying the material properties of individual defects we can determine how the chemistry and morphology of these TM-Nx motifs are interdependent. Additional focus will also be on XPS characterization for the identification of the nature of proposed catalytic site(s). Although XPS is a widely used experimental technique for this purpose, the unique identification of structural motifs from XPS observations alone remains challenging. vi First-principles computations can provide us with the missing link by predicting core-level shifts for candidate defect motifs. This ability enables us to establish structure/property relationships directly and provides us with information that is critical for the detailed interpretation of XPS spectra. The incentive of this research thesis resides in the understanding of the electrochemical performance and energetics of these TM-Nx catalysts and the quest for the design of suitable catalysts with improved performance

A Systematic Review of Mobile Apps for Child Sexual Abuse Education: Limitations and Design Guidelines

The objectives of this study are understanding the requirements of a CSA education app, identifying the limitations of existing apps, and providing a guideline for better app design. An electronic search across three major app stores(Google Play, Apple, and Microsoft) is conducted and the selected apps are rated by three independent raters. Total 191 apps are found and finally, 14 apps are selected for review based on defined inclusion and exclusion criteria. An app rating scale for CSA education apps is devised by modifying existing scales and used to evaluate the selected 14 apps. Our rating scale evaluates essential features, criteria, and software quality characteristics that are necessary for CSA education apps, and determined their effectiveness for potential use as CSA education programs for children. The internal consistency of the rating scale and the inter and intra-rater reliability among the raters are also calculated. User comments from the app stores are collected and analyzed to understand their expectations and views. After analyzing the feasibility of reviewed apps, CSA app design considerations are proposed that highlight game-based teaching approaches. Evaluation results showed that most of the reviewed apps are not suitable for being used as CSA education programs. While a few may be able to teach children and parents individually, only the apps "Child Abuse Prevention" (rate 3.89 out of 5) and "Orbit Rescue" (rate 3.92 out of 5) could be deemed suitable for a school-based CSA education program. However, all those apps need to be improved both their software qualities and CSA-specific features for being considered as potential CSA education programs. This study provides the necessary knowledge to developers and individuals regarding essential features and software quality characteristics for designing and developing CSA education apps

Air Breathing Cathodes for Microbial Fuel Cell using Mn-, Fe-, Co- and Ni-containing Platinum Group Metal-free Catalysts

© 2017 The Authors The oxygen reduction reaction (ORR) is one of the major factors that is limiting the overall performance output of microbial fuel cells (MFC). In this study, Platinum Group Metal-free (PGM-free) ORR catalysts based on Fe, Co, Ni, Mn and the same precursor (Aminoantipyrine, AAPyr) were synthesized using identical sacrificial support method (SSM). The catalysts were investigated for their electrochemical performance, and then integrated into an air-breathing cathode to be tested in “clean” environment and in a working microbial fuel cell (MFC). Their performances were also compared to activated carbon (AC) based cathode under similar conditions. Results showed that the addition of Mn, Fe, Co and Ni to AAPyr increased the performances compared to AC. Fe-AAPyr showed the highest open circuit potential (OCP) that was 0.307±0.001V (vs. Ag/AgCl) and the highest electrocatalytic activity at pH 7.5. On the contrary, AC had an OCP of 0.203±0.002V (vs. Ag/AgCl) and had the lowest electrochemical activity. In MFC, Fe-AAPyr also had the highest output of 251±2.3μWcm−2, followed by Co-AAPyr with 196±1.5μWcm−2, Ni-AAPyr with 171±3.6μWcm−2, Mn-AAPyr with 160±2.8μWcm−2and AC 129±4.2μWcm−2. The best performing catalyst (Fe-AAPyr) was then tested in MFC with increasing solution conductivity from 12.4 mScm−1to 63.1 mScm−1. A maximum power density of 482±5μWcm−2was obtained with increasing solution conductivity, which is one of the highest values reported in the field

Air breathing cathodes for Microbial Fuel Cell using Mn-, Fe-, Co- and Ni-containing platinum group metal-free catalysts

The oxygen reduction reaction (ORR) is one of the major factors that is limiting the overall performance output of microbial fuel cells (MFC). In this study, Platinum Group Metal-free (PGM-free) ORR catalysts based on Fe, Co, Ni, Mn and the same precursor (Aminoantipyrine, AAPyr) were synthesized using identical sacrificial support method (SSM). The catalysts were investigated for their electrochemical performance, and then integrated into an air-breathing cathode to be tested in “clean” environment and in a working microbial fuel cell (MFC). Their performances were also compared to activated carbon (AC) based cathode under similar conditions. Results showed that the addition of Mn, Fe, Co and Ni to AAPyr increased the performances compared to AC. Fe-AAPyr showed the highest open circuit potential (OCP) that was 0.307 ! 0.001 V (vs. Ag/AgCl) and the highest electrocatalytic activity at pH 7.5. On the contrary, AC had an OCP of 0.203 ! 0.002 V (vs. Ag/AgCl) and had the lowest electrochemical activity. In MFC, Fe-AAPyr also had the highest output of 251 ! 2.3 mWcm"2, followed by Co-AAPyr with 196 ! 1.5 mWcm"2, Ni-AAPyr with 171 !3.6 mWcm"2, Mn-AAPyr with 160 ! 2.8 mWcm"2 and AC 129 ! 4.2 mWcm"2. The best performing catalyst (Fe-AAPyr) was then tested in MFC with increasing solution conductivity from 12.4 mScm"1 to 63.1 mScm"1. A maximum power density of 482 ! 5 mWcm"2 was obtained with increasing solution conductivity, which is one of the highest values reported in the field

Comprehensive care of a patient with obesity of BMI >70 kg/m2

A 31-year-old woman, with a body mass index of 70.31 kg/m2 , presented with progressive worsening of dyspnoea for 3 days. She had multiple comorbidities, including obesity hypoventilation syndrome. The patient developed type II respiratory failure with respiratory acidosis along with multiorgan failure. She was intubated and put on a mechanical ventilator and treated with intravenous diuretics, subcutaneous low-molecularweight heparin and other supportive measures. Later, she was on noninvasive, continuous positive airway pressure ventilation overnight. She was prescribed a very-lowcalorie diet along with physiotherapy and exercise. The patient underwent bariatric surgery 2 months after resolution of acute illness. Ten months after surgery, her body weight reduced from 180 kg to 121 kg, and her general condition improved. Successful management before and after surgical intervention depends on multidisciplinary teamwork, which includes the dietician, physiotherapist, endocrinologist, pulmonologist, nursing care and other supportive care

Pneumococcal serotypes and serogroups causing invasive disease in Pakistan, 2005-2013

While pneumococcal conjugate vaccines have been implemented in most countries worldwide, use in Asia has lagged in part because of a lack of data on the amount of disease that is vaccine preventable in the region. We describe pneumococcal serotypes elicited from 111 episodes of invasive pneumococcal disease (IPD) from 2005 to 2013 among children and adults in Pakistan. Seventy-three percent (n = 81) of 111 IPD episodes were cases of meningitis (n = 76 in children 0-15 years and n = 5 among adults). Serotypes were determined by target amplification of DNA extracted from pneumococcal isolates (n = 52) or CSF specimens (n = 59). Serogroup 18 was the most common serogroup causing meningitis in children \u3c5 \u3eyears, accounting for 21% of cases (n = 13). The 10-valent pneumococcal conjugate vaccine (PCV 10) or PCV10- related serotypes were found in 61% (n = 47) of childhood (age 0-15 years) meningitis episodes. PCV-13 increased this coverage to 63% (one additional serotype 19A; n = 48). Our data indicate that use of PCVs would prevent a large proportion of serious pneumococcal disease

Population structure and antimicrobial resistance patterns of Salmonella Typhi isolates in urban Dhaka, Bangladesh from 2004 to 2016.

BACKGROUND: Multi-drug resistant typhoid fever remains an enormous public health threat in low and middle-income countries. However, we still lack a detailed understanding of the epidemiology and genomics of S. Typhi in many regions. Here we have undertaken a detailed genomic analysis of typhoid in urban Dhaka, Bangladesh to unravel the population structure and antimicrobial resistance patterns in S. Typhi isolated between 2004-2016. PRINCIPAL FINDINGS: Whole genome sequencing of 202 S. Typhi isolates obtained from three study locations in urban Dhaka revealed a diverse range of S. Typhi genotypes and AMR profiles. The bacterial population within Dhaka were relatively homogenous with little stratification between different healthcare facilities or age groups. We also observed evidence of exchange of Bangladeshi genotypes with neighboring South Asian countries (India, Pakistan and Nepal) suggesting these are circulating throughout the region. This analysis revealed a decline in H58 (genotype 4.3.1) isolates from 2011 onwards, coinciding with a rise in a diverse range of non-H58 genotypes and a simultaneous rise in isolates with reduced susceptibility to fluoroquinolones, potentially reflecting a change in treatment practices. We identified a novel S. Typhi genotype, subclade 3.3.2 (previously defined only to clade level, 3.3), which formed two localized clusters (3.3.2.Bd1 and 3.3.2.Bd2) associated with different mutations in the Quinolone Resistance Determining Region (QRDR) of gene gyrA. SIGNIFICANCE: Our analysis of S. Typhi isolates from urban Dhaka, Bangladesh isolated over a twelve year period identified a diverse range of AMR profiles and genotypes. The observed increase in non-H58 genotypes associated with reduced fluoroquinolone susceptibility may reflect a change in treatment practice in this region and highlights the importance of continued molecular surveillance to monitor the ongoing evolution of AMR in Dhaka. We have defined new genotypes and lineages of Bangladeshi S. Typhi which will facilitate the identification of these emerging AMR clones in future surveillance efforts

Direct detection of shigella in stool specimens by use of a metagenomic approach

The underestimation of Shigella species as a cause of childhood diarrhea disease has become increasingly apparent with quantitative PCR (qPCR)-based diagnostic methods versus culture. We sought to confirm qPCR-based detection of Shigella via a metagenomics approach. Three groups of samples were selected from diarrheal cases from the Global Enteric Multicenter Study: nine Shigella culture-positive and qPCR-positive (culture+ qPCR+) samples, nine culture-negative but qPCR-positive (culture- qPCR+) samples, and nine culture-negative and qPCR-negative (culture- qPCR-) samples. Fecal DNA was sequenced using paired-end Illumina HiSeq, whereby 3.26 × 108 ± 5.6 × 107 high-quality reads were generated for each sample. We used Kraken software to compare the read counts specific to Shigella among the three groups. The proportions of Shigella-specific nonhuman sequence reads between culture+ qPCR+ (0.65 ± 0.42%) and culture- qPCR+ (0.55 ± 0.31%) samples were similar (Mann-Whitney U test, P = 0.627) and distinct from the culture- qPCR- group (0.17 ± 0.15%, P \u3c 0.05). The read counts of sequences previously targeted by Shigella/enteroinvasive Escherichia coli (EIEC) qPCR assays, namely, ipaH, virA, virG, ial, ShET2, and ipaH3, were also similar between the culture+ qPCR+ and culture- qPCR+ groups and distinct from the culture- qPCR- groups (P \u3c 0.001). Kraken performed well versus other methods: its precision and recall of Shigella were excellent at the genus level but variable at the species level. In summary, metagenomic sequencing indicates that Shigella/EIEC qPCR-positive samples are similar to those of Shigella culture-positive samples in Shigella sequence composition, thus supporting qPCR as an accurate method for detecting Shigella