Splitting CO2 with a ceria-based redox cycle in a solar-driven thermogravimetric analyzer

Thermochemical splitting of CO₂ via a ceria-based redox cycle was performed in a solar-driven thermogravimetric analyzer. Overall reaction rates, including heat and mass transport, were determined under concentrated irradiation mimicking realistic operation of solar reactors. Reticulated porous ceramic (RPC) structures and fibers made of undoped and Zr⁴⁺-doped CeO₂, were endothermally reduced under radiative fluxes of 1280 suns in the temperature range 1200-1950 K and subsequently re-oxidized with CO₂ at 950-1400 K. Rapid and uniform heating was observed for 8 ppi ceria RPC with mm-sized porosity due to its low optical thickness and volumetric radiative absorption, while ceria fibers with μm-sized porosity performed poorly due to its opacity to incident irradiation. The 10 ppi RPC exhibited higher fuel yield because of its higher sample density. Zr⁴⁺-doped ceria showed increasing reduction extents with dopant concentration but decreasing specific CO yield due to unfavorable oxidation thermodynamics and slower kinetics.

Tunable thermodynamic activity of La x Sr1-x Mn y Al1-y O3-δ (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) perovskites for solar thermochemical fuel synthesis

Nonstoichiometric metal oxides with variable valence are attractive redox materials for thermochemical and electrochemical fuel processing. To guide the design of advanced redox materials for solar-driven splitting of CO₂ and/or H₂O to produce CO and/or H₂ (syngas), we investigate the equilibrium thermodynamics of the La _x Sr_1-x Mn _y Al_1-y O_3-δ perovskite family (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and La_0.6Ca_0.4Mn_0.8Al_0.2O_3-δ , and compare them to those of CeO₂ as the baseline. Oxygen nonstoichiometry measurements from 1573 to 1773 K and from 0.206 to 180 mbar O₂ show a tunable reduction extent, increasing with increasing Sr content. Maximal nonstoichiometry of 0.32 is established with La_0.2Sr_0.8Mn_0.8Al_0.2O_3-δ at 1773 K and 2.37 mbar O₂. As a trend, we find that oxygen capacities are most sensitive to the A-cation composition. Partial molar enthalpy, entropy and Gibbs free energy changes for oxide reduction are extracted from the experimental data using defect models for Mn⁴⁺/Mn³⁺ and Mn³⁺/Mn²⁺ redox couples. We find that perovskites exhibit typically decreasing enthalpy changes with increasing nonstoichiometries. This desirable characteristic is most pronounced by La_0.6Sr_0.4Mn_0.4Al_0.6O_3-δ , rendering it attractive for CO₂ and H₂O splitting. Generally, perovskites show lower enthalpy and entropy changes than ceria, resulting in more favorable reduction but less favorable oxidation equilibria. The energy penalties due to larger temperature swings and excess oxidants are discussed in particular. Using electronic structure theory, we conclude with a practical methodology estimating thermodynamic activity to rationally design perovskites with variable stoichiometry and valence.

Oxygen nonstoichiometry and thermodynamic characterization of Zr doped ceria in the 1573-1773 K temperature range

The thermodynamics and defect chemistry of Zr⁴⁺-doped ceria is investigated and discussed in regards to the efficiency of solar thermochemical redox cycles.

This work encompasses the thermodynamic characterization and critical evaluation of Zr⁴⁺ doped ceria, a promising redox material for the two-step solar thermochemical splitting of H₂O and CO₂ to H₂ and CO. As a case study, we experimentally examine 5 mol% Zr⁴⁺ doped ceria and present oxygen nonstoichiometry measurements at elevated temperatures ranging from 1573 K to 1773 K and oxygen partial pressures ranging from 4.50 × 10^–3 atm to 2.3 × 10^–4 atm, yielding higher reduction extents compared to those of pure ceria under all conditions investigated, especially at the lower temperature range and at higher p_O2. In contrast to pure ceria, a simple ideal solution model accounting for the formation of isolated oxygen vacancies and localized electrons accurately describes the defect chemistry. Thermodynamic properties are determined, namely: partial molar enthalpy, entropy, and Gibbs free energy. In general, partial molar enthalpy and entropy values of Zr⁴⁺ doped ceria are lower. The equilibrium hydrogen yields are subsequently extracted as a function of the redox conditions for dopant concentrations as high as 20%. Although reduction extents increase greatly with dopant concentration, the oxidation of Zr⁴⁺ doped ceria is thermodynamically less favorable compared to pure ceria. This leads to substantially larger temperature swings between reduction and oxidation steps, ultimately resulting in lower theoretical solar energy conversion efficiencies compared to ceria under most conditions. In effect, these results point to the importance of considering oxidation thermodynamics in addition to reduction when screening potential redox materials.

Nanocrystalline silver dressings as an efficient anti-MRSA barrier: a new solution to an increasing problem

The emergence of multi-drug-resistant strains of bacteria represents a particular challenge in the field of wound management. The aim of the current study was to investigate whether nanocrystalline silver dressings possess the physical properties to act as a barrier to the transmission of methicillin-resistant Staphylococcus aureus (MRSA) in the laboratory setting and in a clinical setting. Initially, MRSA suspension and colony culture experiments were performed showing that nanocrystalline silver dressings act as potent and sustained antimicrobial agents, efficiently inhibiting MRSA penetration. Subsequently, a double-centre clinical trial was initiated using nanocrystalline silver dressings as a cover for 10 MRSA colonized wounds in a total of seven patients. By delineating the MRSA load on the upper side of the dressing and the wound bed each time the dressing was changed (i.e. after 1, 24, 48 and 72 h), nanocrystalline silver dressings were found to provide a complete, or almost complete, barrier to the penetration/spread of MRSA in 95% of readings. In addition, 67% of all wound observations showed a decrease in the MRSA load with an eradication rate of 11%. We believe that nanocrystalline silver dressings may become an important part of local MRSA management, with cost benefits to both patients and the healthcare system.

Protein-DNA interaction and CpG methylation at rep*/vIL-10p of latent Epstein-Barr virus genomes in lymphoid cell lines

The viral interleukin-10 promoter (vIL-10p), overlapping the rep* element in the Epstein-Barr virus (EBV) genome, is a promoter element active mostly in the late phase of the lytic cycle and immediately upon infection of B cells. rep* was, through transfection experiments with small plasmids, characterised as a cis element supporting oriP replicative function. In this study, in vivo protein binding and CpG methylation at rep*/vIL-10p were analysed in five cell lines that harbour strictly latent EBV genomes. Contrary to the invariably unmethylated dyad symmetry element (DS) of oriP, rep*/vIL-10p was highly methylated and showed only traces of protein binding in all examined cell lines. This result is in agreement with vIL-10p being an inactive promoter of EBV genomes, and makes it less likely that rep* functions as a replicative element of latent EBV genomes.

Epigenetics of latent Epstein-Barr virus genomes: high resolution methylation analysis of the bidirectional promoter region of latent membrane protein 1 and 2B genes

We analysed the methylation patterns of CpG dinucleotides in a bidirectional promoter region (LRS, LMP 1 regulatory sequences) of latent Epstein-Barr virus (EBV) genomes using automated fluorescent genomic sequencing after bisulfite-induced modification of DNA. Transcripts for two latent membrane proteins, LMP 1 (a transforming protein) and LMP 2B, are initiated in this region in opposite directions. We found that B cell lines and a clone expressing LMP 1 carried EBV genomes with unmethylated or hypomethylated LRS, while highly methylated CpG dinucleotides were present at each position or at discrete sites and within hypermethylated regions in LMP 1 negative cells. Comparison of high resolution methylation maps suggests that CpG methylation-mediated direct interference with binding of nuclear factors LBF 2, 3, 7, AML1/LBF1, LBF5 and LBF6 or methylation of CpGs within an E-box sequence (where activators as well as repressors can bind) is not the major mechanism in silencing of the LMP 1 promoter. Although a role for CpG methylation within binding sites of Sp1 and 3, ATF/CRE and a sis-inducible factor (SIF) cannot be excluded, hypermethylation of LRS or regions within LRS in LMP 1 negative cells suggests a role for an indirect mechanism, via methylcytosine binding proteins, in silencing of the LMP 1 promoter.

Protein-DNA binding and CpG methylation at nucleotide resolution of latency-associated promoters Qp, Cp, and LMP1p of Epstein-Barr virus

Epstein-Barr viral (EBV) latency-associated promoters Qp, Cp, and LMP1p are crucial for the regulated expression of the EBNA and LMP transcripts in dependence of the latency type. By transient transfection and in vitro binding analyses, many promoter elements and transcription factors have previously been shown to be involved in the activities of these promoters. However, the latency promoters have only partially been examined at the nucleotide level in vivo. Therefore, we undertook a comprehensive analysis of in vivo protein binding and CpG methylation patterns at these promoters in five representative cell lines and correlated the results with the known in vitro binding data and activities of these promoters from previous transfection experiments. Promoter activity inversely correlated with the methylation state of promoters, although Qp was a remarkable exception. Novel protein binding data were obtained for all promoters. For Cp, binding correlated well with promoter activity; for LMP1p and Qp, binding patterns looked similar regardless of promoter activity.

De novo DNA methylation at nonrandom founder sites 5' from an unmethylated minimal origin of DNA replication in latent Epstein-Barr virus genomes

Latent episomal genomes of Epstein-Barr virus, a human gammaherpesvirus, represent a suitable model system for studying replication and methylation of chromosomal DNA in mammals. We analyzed the methylation patterns of CpG dinucleotides in the latent origin of DNA replication of Epstein-Barr virus using automated fluorescent genomic sequencing of bisulfite-modified DNA samples. We observed that the minimal origin of DNA replication was unmethylated in 8 well-characterized human cell lines or clones carrying latent Epstein-Barr virus genomes as well as in a prototype virus producer marmoset cell line. This observation suggests that unmethylated DNA domains can function as initiation sites or zones of DNA replication in human cells. Furthermore, 5' from this unmethylated region we observed focal points of de novo DNA methylation in nonrandom positions in the majority of Burkitt's lymphoma cell lines and clones studied while the corresponding CpG dinucleotides in viral genomes carried by lymphoblastoid cell lines and marmoset cells were completely unmethylated. Clustering of highly methylated CpG dinucleotides suggests that de novo methylation of unmethylated double-stranded episomal viral genomes starts at discrete founder sites in vivo. This is the first comparative high-resolution methylation analysis of a latent viral origin of DNA replication in human cells.

Analysis of methylation patterns in the regulatory region of the latent Epstein-Barr virus promoter BCR2 by automated fluorescent genomic sequencing

We analyzed the methylation patterns of CpG dinucleotides in the regulatory region of the latent Epstein-Barrvirus (EBV) promoter BCR2 (also called C promoter, Cp) using automated fluorescent genomic sequencing after bisulfite-induced modification of DNA. BCR2 is one of the alternative promoters for transcripts encoding the growth-transformation-associated nuclear antigens EBNA 1-6 which are expressed in a host cell phenotype dependent manner. Well characterized clones isolated from the Burkitt's lymphoma (BL) line Mutu differing from each other as to their phenotype and EBV latent gene expression were used in the present study. We found that in Mutu BL III clone 99 which is actively using the BCR2 promoter the regulatory sequences are unmethylated with two exceptions (position 10702 and 10799). In contrast, there are 15 methylated cytosines in the same region in Mutu BL I clone 216 where the BCR2 promoter is silent. Cytosines which are potential targets of DNA methyltransferase in the immediate vicinity or within the attachment sites of cellular C promoter binding factors CBF1 and CBF2 remained hypomethylated in Mutu BL I clone 216. This suggests a role for a hypermethylated region (nucleotides 10666 -10865, -639 to -440 bases upstream from the beginning of the TATA box at position 11305) in silencing of the BCR2 promoter in these cells.

Intentional drug overdose: predictors of clinical course in the intensive care unit

OBJECTIVE

To examine the characteristics of patients admitted to the Medical Intensive Care Unit (MICU) after intentional drug overdose.

DESIGN

Retrospective chart review, descriptive.

SETTING

Midwestern teaching hospital.

SUBJECTS

Convenience sample of 43 patients admitted to the MICU after intentional drug overdose.

OUTCOME MEASURES

Survival and disposition of those patients who survived and were discharged from the MICU.

RESULTS

Ninety-five percent of the patients survived and were discharged from the MICU; Acute Physiology and Chronic Health Evaluation II scores ranged from 1 to 29 (mean, 8); Glascow Coma Scale scores ranged from 3 to 15 (mean 12.5); five patients were intubated and two patients had serious electrocardiograph changes requiring pharmacologic intervention for dysrhythmia.

CONCLUSIONS

Neurologic findings were the best indicators of serious complications after drug overdose. THerefore, patients with a Glascow Coma Scale score of more than six, and who are not intubated, may not need admission to an intensive care unit.

Protocol therapy for acute asthma: therapeutic benefits and cost savings

BACKGROUND

To evaluate the therapeutic and financial benefits of protocol therapy for acute asthma using standard medications.

MATERIALS AND METHODS

This study employed a sequential design in which the influence of an asthma care path on hospital admissions, length of stay (LOS) in the emergency department, and return visits were evaluated for 1 year. This information was contrasted with similar data obtained from the 8 months immediately before the protocol was implemented (preprotocol) and a 12-month period after strict adherence to it had declined (admixture).

RESULTS

In all, 526 acute exacerbations of asthma were treated with the care path, and 429 and 558 episodes were evaluated during the preprotocol and admixture periods, respectively. There were no significant differences between the presenting clinical or physiologic features of any group. With the protocol, 77% of the patients resolved their symptoms within 1:47 +/- 0.02 hours:minutes of arrival in the emergency department with a 2% return rate within 24 hours. The algorithms used quickly identified those needing hospitalization. Patients not meeting the criteria for discharge after receiving the treatments employed typically did not resolve their symptoms for days (average hospital stay 4.1 +/- 0.2 days). Compared with the preprotocol period, the care path significantly reduced the LOS by 50 minutes, the number of urgent and intensive care unit admissions by 27% and 41%, respectively, and the frequency of return visits within 24 hours by 66%. Charges to patients and third-party payors decreased $395,000. When adherence to the protocol diminished, LOS, admissions, and returns rose significantly toward preprotocol values and the financial benefits were lost.

CONCLUSIONS

Asthma protocol therapy, based primarily upon aggressive use of sympathomimetics in association with serial monitoring of key indices of improvement, provides prompt and efficient relief for acute exacerbations of asthma. Such an approach yields significant financial benefit while quickly identifying individuals who require hospitalization, and it also detects physician practice patterns that can have potentially detrimental impacts on patient care.

A hospital-based, hazardous materials decontamination and treatment unit: utilization patterns over a nine-month period

Federal [U.S.] law and the Joint Commission on the Accreditation of Healthcare Organizations mandate plans and mechanisms for response by hospitals to hazardous material incidents/accidents be developed and implemented. This paper describes the response of the University Hospitals of Cleveland to these regulations and to the anticipated needs of the community and local industry. The physical plant constructed and its relationship to the emergency department personnel for staffing this unit are described. Utilization patterns since implementation of this program are presented.