Partially Fluorinated Multiblock Poly(arylene ether sulfone) Membranes for Fuel Cell Applications

Sulfonated poly(arylene ether sulfone) (SPAES‐F series) membranes, which are partially fluorinated multiblock polymers containing Bisphenol 6F (6F‐BPA), are synthesized. The membranes exhibit less water uptake and higher ion conductivity at similar ion exchange capacity (IEC) values compared to previous SPAES membranes containing identical hydrophilic blocks. This is attributed to the presence of 6F‐BPA in the hydrophobic block, which enhances hydrophobicity and promotes phase separation, as observed through transmission electron microscopy analysis. F4 (IEC = 2.4 meq g^?1) shows superior ion conductivity than Nafion NRE212 membrane irrespective of the humidity level. Furthermore, the SPAES electrolyte membrane of 1.5 meq g^?1 produces better performance than NRE212, yielding a current density of 488 mA cm^?2 at 80 °C, 80% RH, and 0.6 V. In 50% RH at 80 °C, SPAES with 1.5 meq g^?1 exhibits a cell resistance and fuel cell performance comparable to those of NRE212; clearly, regulating hydrophobicity and hydrophilicity is crucial for enhanced performance.     

Dual growth factor-releasing nanoparticle/hydrogel system for cartilage tissue engineering

In order to induce the chondrogenesis of mesenchymal stem cells (MSCs) in tissue engineering, a variety of growth factors have been adapted and encouraging results have been demonstrated. In this study, we developed a delivery system for dual growth factors using a gelation rate controllable alginate solution (containing BMP-7) and polyion complex nanoparticles (containing TGF-β₂) to be applied for the chondrogenesis of MSCs. The dual growth factors (BMP-7/TGF-β₂)-loaded nanoparticle/hydrogel system showed a controlled release of both growth factors: a faster release of BMP-7 and a slower release of TGF-β₂, ca., approximately 80 and 30% release at the end of an incubation period (21 days), respectively, which may be highly desirable for chondrogenic differentiation of MSCs. On the contrary, the release of each growth factor from the dual growth factors-loaded hydrogel (without the nanoparticles) was much slower than that of the nanoparticle/hydrogel system, approximately 36% (BMP-7) and 16% (TGF-β₂) for 21 days, and this is more than likely attributed to the aggregation between growth factors during the hydrogel fabrication step. The nanoparticle/hydrogel system with separate growth factor loading may provide desirable growth factor delivery kinetics for cartilage regeneration, as well as the chondrogenesis of MSCs.     

Evaluation of Brining Ingredients and Antimicrobials for Effects on Thermal Destruction of Escherichia coli O157:H7 in a Meat Model System

ABSTRACT: Escherichia coli O157:H7 may become internalized during brine injection of meat. This study evaluated the effect of brining ingredients on E. coli O157:H7 in a meat model system after simulated brining, storage, and cooking. Fresh knuckles (5.3 ± 2.4% fat) or beef shoulder (15.3 ± 2.2% fat) were ground individually, mixed with an 8-strain composite of rifampicin-resistant E. coli O157:H7 (7 log CFU/g) and brining solutions. Treatments included no brining, distilled water, sodium chloride (NaCl, 0.5%), sodium tripolyphosphate (STP, 0.25%), sodium pyrophosphate (SPP, 0.25%), NaCl + STP, NaCl + SPP, NaCl + STP + potassium lactate (PL, 2%), NaCl + STP + sodium diacetate (SD, 0.15%), NaCl + STP + PL + SD, NaCl + STP + lactic acid (0.3%), NaCl + STP + acetic acid (0.3%), NaCl + STP + citric acid (0.3%), NaCl + STP + EDTA (20 mM) + nisin (0.0015%) or pediocin (1000 AU/g), NaCl + STP + sodium metasilicate (0.2%), NaCl + STP + cetylpyridinium chloride (CPC; 0.5%), and NaCl + STP + hops beta acids (0.00055%). Samples (30 g) were analyzed for pH, and total microbial and rifampicin-resistant E. coli O157:H7 (inoculum) populations immediately after mixing, storage (24 h at 4 °C), and cooking to 65 °C. Fat and moisture contents and water activity were measured after storage and cooking only; cooking losses also were determined. The effect of beef type on microbial counts, pH, and water activity was negligible. No reductions in microbial counts were obtained by the brining solutions immediately or after storage, except for samples treated with CPC, which reduced (P < 0.05) pathogen counts after storage by approximately 1 log cycle. Cooking reduced pathogen counts by 1.5 to 2.5 logs, while CPC-treated samples had the lowest (P < 0.05) counts compared to any other treatment. These data may be useful in developing/improving brining recipes for control of E. coli O157:H7 in moisture-enhanced beef products.     

Atmospheric Trace Molecule Spectroscopy (ATMOS) Experiment Version 3 data retrievals

Version 3 of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment data set for some 30 trace and minor gas profiles is available. From the IR solar-absorption spectra measured during four Space Shuttle missions (in 1985, 1992, 1993, and 1994), profiles from more than 350 occultations were retrieved from the upper troposphere to the lower mesosphere. Previous results were unreliable for tropospheric retrievals, but with a new global-fitting algorithm profiles are reliably returned down to altitudes as low as 6.5 km (clouds permitting) and include notably improved retrievals of H2O, CO, and other species. Results for stratospheric water are more consistent across the ATMOS spectral filters and do not indicate a net consumption of H2 in the upper stratosphere. A new sulfuric-acid aerosol product is described. An overview of ATMOS Version 3 processing is presented with a discussion of estimated uncertainties. Differences between these Version 3 and previously reported Version 2 ATMOS results are discussed. Retrievals are available at http://atmos.jpl.nasa.gov/atmos.     

An adaptive redundancy control method for erasure-code-basedreal-time data transmission over the Internet

We propose an adaptive redundancy control method for erasure-code-based real-time data transmission over the Internet. The loss rate is an important quality of service (QoS) parameter for real-time data transmission. However, real-time data transmission over best-effort networks, such as the Internet, suffers from a frequent packet loss due to traffic congestion. Erasure-code-based loss recovery scheme is widely used for loss recovery on the Internet. We propose a redundancy estimation algorithm which considers consecutive losses since the loss recovery rate depends on the amount of redundancy data. A continuous time Markov chain is used for modeling the loss process and adjusting the number of redundant packets. Measurements and simulation results show that the proposed scheme can be used as an efficient loss recovery algorithm for real-time data transmission over the Internet     

Accelerated Sulfur Evolution Reactions by TiS2/TiO2@MXene Host for High-Volumetric-Energy-Density Lithium–Sulfur Batteries (Adv. Funct. Mater. 35/2023)

The poor cycling stability and low volumetric energy density of lithium–sulfur batteries compared with lithium-ion batteries are hindering their practical applications. Here, it is demonstrated that a dense sulfur electrode containing heavy TiS₂/TiO₂@MXene heterostructures can tackle these issues. It is observed that the TiO₂ part functionally anchors the lithium polysulfides through the strong chemical affinity, and the TiS₂ part serves as an efficient electrocatalyst to enhance the kinetics of sulfur evolution reactions. Benefitting from these synergistic effects, the TiS₂/TiO₂@MXene heterostructures effectively suppress the shuttle effects, leading to superior cyclability of the sulfur cathode with a low capacity decay of 0.038% per cycle for 500 cycles at a current rate of 1 C. More encouragingly, a highly dense S/TiS₂/TiO₂@MXene cathode exhibits a high volumetric energy density of 2476 Wh L⁻¹ (based on the volume of the composite) at a high sulfur mass loading of 7.5 mg cm⁻² and lean electrolyte of 5 µL mg⁻¹. The electrochemical performance is comparable to or even superior to the lithium-ion and lithium–sulfur batteries reported in the literature. This study provides an effective strategy to design stable and high-volumetric-energy-density lithium–sulfur batteries for practical energy storage applications.     

An analysis of spatial mobility of urban activities in downtown Denver

A much neglected area of inquiry in geography is the analysis of spatial processes. It seems necessary, therefore, to initiate more effort in this area by examining and modifying existing means of investigation, or suggesting new ones. Using downtown Denver as the study area, an investigation of the spatial pattern of five urban activities from 1947 to 1971, by applying a modification of an existing means of research, shows a general temporal trend that suggests the working of the spatial process of urban equifinality. It is necessary, however, to extend the investigation of the area to several more future time periods, or to conduct a comparison between this area with several other urban areas before a firmer conclusion can be derived.The author would like to thank Professor Roger Barry of the University of Colorado and Professor Arther Getis of Rutgers University for their comments and suggestions. Any errors, however, are the sole responsibility of the author.