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Fuel cell flow path design for improved efficiency and power density
No full textThermodynamic equipartitioning can improve the energy efficiency of a fuel cell at fixed size and fuel utilization by varying local cell potential to optimally distribute current density and electrochemical reaction rates over the electrode area. In practical systems however, potential across the end electrodes is fixed, resulting in higher current density near the inlet where reactant concentrations are highest. Here, a flow recirculation design for fuel and oxidizer streams is proposed to enable nearly uniform local current density distribution. The proposed configuration can achieve around 90 % of the thermodynamically feasible power enhancement, with higher improvement (up to 12 %) at a larger baseline system size. At a fixed power output, the design can also reduce area by 8 %–88 % through higher average current density operation. When cost-optimal system size is considered for both operating modes, a 2–6 % reduction in specific cost of energy can be achieved, with greater savings at higher fuel price compared to amortized cost of system area. Axial electrical conduction in the bipolar plates reduces energy efficiency improvements. Therefore, methods to limit axial conduction, such as reducing plate thickness or increasing its resistivity in the flow direction, are necessary to realize the full potential of the proposed design
Thap9 transposase cleaves dna via conserved acidic residues in an rnaseh-like domain
No full textThe catalytic domain of most �cut and paste� DNA transposases have the canonical RNaseH fold, which is also shared by other polynucleotidyl transferases such as the retroviral integrases and the RAG1 subunit of V(D)J recombinase. The RNase-H fold is a mixture of beta sheets and alpha helices with three acidic residues (Asp, Asp, Glu/Asp�DDE/D) that are involved in the metal-mediated cleavage and subsequent integration of DNA. Human THAP9 (hTHAP9), homologous to the well-studied Drosophila P-element transposase (DmTNP), is an active DNA transposase that, although domesticated, still retains the catalytic activity to mobilize transposons. In this study we have modeled the structure of hTHAP9 using the recently available cryo-EM structure of DmTNP as a template to identify an RNase-H like fold along with important acidic residues in its catalytic domain. Site-directed mutagenesis of the predicted catalytic residues followed by screening for DNA excision and integration activity has led to the identification of candidate Ds and Es in the RNaseH fold that may be a part of the catalytic triad in hTHAP9. This study has helped widen our knowledge about the catalytic activity of a functionally uncharacterized transposon-derived gene in the human genome. � 2021 Elsevier B.V., All rights reserved
Electrical Resistivity Testing of Concrete Cylinders: Bias, Precision, and Use in Process Control
No full textElectrical resistivity is increasingly used as a test method to assess the transport properties of concrete. This paper describes an interlaboratory study that was conducted to determine precision and bias for resistivity measurements made in surface and bulk configurations of concrete cylinders. Tests were performed following AASHTO T 358-22 and AASHTO T 402-23. A verification device is introduced with a known resistivity (and impedance) to aid in determining the bias associated with resistivity measurements. However, this device can also be used as a training tool and as a tool to evaluate the qualifications of those new to performing the test. Concrete cylinders were prepared, cured, and conditioned using three methods: immersed in simulated pore solution, sealed, and immersed in lime solution. The samples were tested to determine the precision in the resistivity measurements of the samples for the different curing conditions. The paper discusses how resistivity testing can be used for quality control testing as well as quality acceptance. The results were used to develop precision and bias statements for resistivity measurements, which have been adopted in the latest American Association of State Highway and Transportation Officials (AASTHO) standards
Equitable allocation for mixtures of goods and chores
No full textEquitable allocation of indivisible items involves partitioning the items among agents such that everyone derives (almost) equal utility. We consider the approximate notion of equitability up to one item (EQ1) and focus on the settings containing mixtures of items (goods and chores), where an agent may derive positive, negative, or zero utility from an item. We first show that -- in stark contrast to the goods-only and chores-only settings -- an EQ1 allocation may not exist even for additive {?1,1} bivalued instances, and its corresponding decision problem is computationally intractable. We focus on a natural domain of normalized valuations where the value of the entire set of items is constant for all agents. On the algorithmic side, we show that an EQ1 allocation can be computed efficiently for (i) {?1,0,1} normalized valuations, (ii) objective but non-normalized valuations, (iii) two agents with type-normalized valuations. We complement our study by providing a comprehensive picture of achieving EQ1 allocations under normalized valuations in conjunction with economic efficiency notions such as Pareto optimality and social welfare
Synthesis of Metal-Organic Framework (MOF) based composites for pH-responsive drug delivery
No full textEngineering mucoadhesive papaverine entrapped berberine microcrystals with enhanced bioactive functionalities for urinary tract infection
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Bioprospecting of Endolichenic Fungus Phanerochaetechrysosporium from Mangrove Associated Lichen Bactrosporamyriadea for Anticancer Leads
No full textEndolichenic fungi (ELF) are gaining attention as a promising source for novel cytotoxic compounds. In this study, lichens Bactrosporamyriadea and Arthoniaantillarum, collected from the mangroves of Negombo Lagoon in Sri Lanka, were examined to identify their associated ELFs. Phanerochaetechrysosporium, Lasiodiplodiatheobromae, and Xylariafeejeensis were isolated from B. myriadea, while Xylariapsidii, Daldiniaeschscholtzii, and Nodulisporium sp. were obtained from A. antillarum. The ethyl acetate extracts of these ELFs were screened for cytotoxic activity against the MCF-7 cell line, with P. chrysosporium extract showing potent cytotoxicity. The purified compounds from this extract were identified as spirolaxine (1), phanerosporic acid (2), and 5-(14-hydroxypentadecyl)-resorcinol (3). Their structures were determined using Fourier Transform Infrared, Nuclear Magnetic Resonance spectroscopy and Liquid Chromatography-High Resolution mass spectrometry, while their absolute configurations were established through circular dichroism and time-dependent density functional theory calculations. The compounds demonstrated moderate cytotoxic activity against human breast (MCF-7), oral (CAL-27), and lung (A549) cancer cell lines. Compound 1 exhibited the strongest cytotoxicity against oral cancer, with an IC50 value of 10.62 ± 0.02 µM. Compound 2 was effective against both MCF-7 and A549 cell lines, with IC50 values of 9.86 ± 0.02 µM and 6.66 ± 0.04 µM, respectively. This is the first report of compound 3 from a natural source, as it was previously documented only as a semi-synthetic derivative of compound 2. The study highlights the potential of the ELF P. chrysosporium to produce cytotoxic secondary metabolites
Bioimaging and therapeutic applications of multifunctional carbon quantum dots: Recent progress and challenges
No full textCarbon quantum dots (CQDs) have emerged as highly promising carbon-based nanomaterials in the field of nanomedicine. Their small size and unique physicochemical properties such as biocompatibility, tunable surface functionalities (such as amino, hydroxyl, carboxyl), stability and electron mobility, make them particularly advantageous for biomedical applications. CQDs show great potential as nanocarriers for drug delivery in the treatment of cancer, ophthalmic diseases, infectious diseases, cardiovascular diseases and neurological disorders. Additionally, their versatility has prompted growing interest in utilizing CQDs for gene therapy, vaccine development, stem cell therapy and tissue engineering. CQDs have also advanced bioimaging and biosensing due to their excellent optical properties, including high fluorescence, tunable emission, and photostability, making them ideal for in vivo imaging, cellular tracking, and biomolecule detection. Despite these promising applications, limitations such as non-biodegradability, potential cytotoxicity at higher concentrations, and inconsistent surface functionalization pose challenges to their efficacy and safety in biomedical applications. This review highlights recent advancements in the therapeutic use of CQDs, underscoring their potential to transform nanomedicine by offering precise and targeted drug delivery. In the future, CQD-based systems could facilitate more effective therapies with reduced off-target effects, paving the way for a new era of precision medicine