Combinatorial synthesis and high-throughput photopotential and photocurrent screening of mixed-metal oxides for photoelectrochemical water splitting

A high-throughput method has been developed using a commercial piezoelectric inkjet printer for synthesis and characterization of mixed-metal oxide photoelectrode materials for water splitting. The printer was used to deposit metal nitrate solutions onto a conductive glass substrate. The deposited metal nitrate solutions were then pyrolyzed to yield mixed-metal oxides that contained up to eight distinct metals. The stoichiometry of the metal oxides was controlled quantitatively, allowing for the creation of vast libraries of novel materials. Automated methods were developed to measure the open-circuit potentials (Eoc), short-circuit photocurrent densities (Jsc), and current density vs. applied potential (J–E) behavior under visible light irradiation. The high-throughput measurement of Eoc is particularly significant because open-circuit potential measurements allow the interfacial energetics to be probed regardless of whether the band edges of the materials of concern are above, close to, or below the values needed to sustain water electrolysis under standard conditions. The Eoc measurements allow high-throughput compilation of a suite of data that can be associated with the composition of the various materials in the library, to thereby aid in the development of additional screens and to form a basis for development of theoretical guidance in the prediction of additional potentially promising photoelectrode compositions

Uncollapsing the wavefunction by undoing quantum measurements

We review and expand on recent advances in theory and experiments concerning the problem of wavefunction uncollapse: Given an unknown state that has been disturbed by a generalized measurement, restore the state to its initial configuration. We describe how this is probabilistically possible with a subsequent measurement that involves erasing the information extracted about the state in the first measurement. The general theory of abstract measurements is discussed, focusing on quantum information aspects of the problem, in addition to investigating a variety of specific physical situations and explicit measurement strategies. Several systems are considered in detail: the quantum double dot charge qubit measured by a quantum point contact (with and without Hamiltonian dynamics), the superconducting phase qubit monitored by a SQUID detector, and an arbitrary number of entangled charge qubits. Furthermore, uncollapse strategies for the quantum dot electron spin qubit, and the optical polarization qubit are also reviewed. For each of these systems the physics of the continuous measurement process, the strategy required to ideally uncollapse the wavefunction, as well as the statistical features associated with the measurement is discussed. We also summarize the recent experimental realization of two of these systems, the phase qubit and the polarization qubit.Comment: 19 pages, 4 figure

Detection and diversity of a putative novel heterogeneous polymorphic proline-glycine repeat (Pgr) protein in the footrot pathogen Dichelobacter nodosus

Dichelobacter nodosus, a Gram-negative anaerobic bacterium, is the essential causative agent of footrot in sheep. Currently, depending on the clinical presentation in the field, footrot is described as benign or virulent; D. nodosus strains have also been classified as benign or virulent, but this designation is not always consistent with clinical disease. The aim of this study was to determine the diversity of the pgr gene, which encodes a putative proline-glycine repeat protein (Pgr). The pgr gene was present in all 100 isolates of D. nodosus that were examined and, based on sequence analysis had two variants, pgrA and pgrB. In pgrA, there were two coding tandem repeat regions, R1 and R2: different strains had variable numbers of repeats within these regions. The R1 and R2 were absent from pgrB. Both variants were present in strains from Australia, Sweden and the UK, however, only pgrB was detected in isolates from Western Australia. The pgrA gene was detected in D. nodosus from tissue samples from two flocks in the UK with virulent footrot and only pgrB from a flock with no virulent or benign footrot for >10 years. Bioinformatic analysis of the putative PgrA protein indicated that it contained a collagen-like cell surface anchor motif. These results suggest that the pgr gene may be a useful molecular marker for epidemiological studies

The Asymptotic Number of Attractors in the Random Map Model

The random map model is a deterministic dynamical system in a finite phase space with n points. The map that establishes the dynamics of the system is constructed by randomly choosing, for every point, another one as being its image. We derive here explicit formulas for the statistical distribution of the number of attractors in the system. As in related results, the number of operations involved by our formulas increases exponentially with n; therefore, they are not directly applicable to study the behavior of systems where n is large. However, our formulas lend themselves to derive useful asymptotic expressions, as we show.Comment: 16 pages, 1 figure. Minor changes. To be published in Journal of Physics A: Mathematical and Genera

Effect of the Presence of Iodide on the Electron Injection Dynamics of Dye-Sensitized TiO_2-Based Solar Cells

The electron injection dynamics of dye-sensitized TiO_2-based solar cells have been investigated to determine the effects of replacing the I_3^−/I^− redox system by non-redox-active supporting electrolytes. TiO-2 films were sensitized with Ru(dcbpy)_2(NCS)_2, where dcbpy = 4,4′-dicarboxylic acid-2,2′-bipyridine (the “N3” dye), and placed in contact with either M(ClO_4) or M(I_3−/I−) solutions (M = Li^+ or (n-C_4H_9)_4N^+); cells that contained I_3−/I− were fully functional solar cells whose steady-state photocurrents were directly measured. In (n-C_4H_9)_4N^+-containing solutions, significant differences were observed between the measured kinetics when ClO_4^− was replaced by the redox-active I3^−/I^− system. In particular, a ps time scale loss of the metal-to-ligand charge-transfer excited-state of the N3 dye, associated with electron injection, that was observed in cells containing either LiClO_4 or [(n-C_4H_9)4N]ClO_4 was absent in fully functional solar cells that contained [(n-C_4H_9)_4N]I/I_2. These results underscore the importance of performing kinetics measurements on this class of solar cells under operational conditions if one is to obtain reliable correlations between the dynamics data and the steady-state performance metrics of the solar cell devices

Disease-modifying drugs for knee osteoarthritis: can they be cost-effective?

OBJECTIVE: Disease-modifying osteoarthritis drugs (DMOADs) are under development. Our goal was to determine efficacy, toxicity, and cost thresholds under which DMOADs would be a cost-effective knee OA treatment. DESIGN: We used the Osteoarthritis Policy Model, a validated computer simulation of knee OA, to compare guideline-concordant care to strategies that insert DMOADs into the care sequence. The guideline-concordant care sequence included conservative pain management, corticosteroid injections, total knee replacement (TKR), and revision TKR. Base case DMOAD characteristics included: 50% chance of suspending progression in the first year (resumption rate of 10% thereafter) and 30% pain relief among those with suspended progression; 0.5%/year risk of major toxicity; and costs of $1,000/year. In sensitivity analyses, we varied suspended progression (20-100$1,000-$7,000). Outcomes included costs, quality-adjusted life expectancy, incremental cost-effectiveness ratios (ICERs), and TKR utilization. RESULTS: Base case DMOADs added 4.00 quality-adjusted life years (QALYs) and$230,000 per 100 persons, with an ICER of $57,500/QALY. DMOADs reduced need for TKR by 15$3,000/year achieved ICERs below $100,000/QALY if the likelihoods of suspended progression and pain relief were 20$5,000, these ICERs were attained if the likelihoods of suspended progression and pain relief were both 60%. CONCLUSIONS: Cost, suspended progression, and pain relief are key drivers of value for DMOADs. Plausible combinations of these factors could reduce need for TKR and satisfy commonly cited cost-effectiveness criteri

Lifetime risk and age of diagnosis of symptomatic knee osteoarthritis in the US

OBJECTIVE: To estimate the incidence and lifetime risk of diagnosed symptomatic knee osteoarthritis (OA) and the age at diagnosis of knee OA based on self-reports in the US population. METHODS: We estimated the incidence of diagnosed symptomatic knee OA in the US by combining data on age-, sex-, and obesity-specific prevalence from the 2007-2008 National Health Interview Survey, with disease duration estimates derived from the Osteoarthritis Policy (OAPol) Model, a validated computer simulation model of knee OA. We used the OAPol Model to estimate the mean and median ages at diagnosis and lifetime risk. RESULTS: The estimated incidence of diagnosed symptomatic knee OA was highest among adults ages 55-64 years, ranging from 0.37% per year for nonobese men to 1.02% per year for obese women. The estimated median age at knee OA diagnosis was 55 years. The estimated lifetime risk was 13.83%, ranging from 9.60% for nonobese men to 23.87% in obese women. Approximately 9.29% of the US population is diagnosed with symptomatic knee OA by age 60 years. CONCLUSION: The diagnosis of symptomatic knee OA occurs relatively early in life, suggesting that prevention programs should be offered relatively early in the life course. Further research is needed to understand the future burden of health care utilization resulting from earlier diagnosis of knee OA. Copyright 2013 by the American College of Rheumatology