Diffusion with rearranging traps

A model for diffusion on a cubic lattice with a random distribution of traps is developed. The traps are redistributed at certain time intervals. Such models are useful for describing systems showing dynamic disorder, such as ion-conducting polymers. In the present model the traps are infinite, unlike an earlier version with finite traps, this model has a percolation threshold. For the infinite trap version a simple analytical calculation is possible and the results agree qualitatively with simulation.Comment: Latex, five figure

Quantum dots with two electrons: Singlet-triplet transitions

The magnetic character of the ground-state of two electrons on a double quantum dot, connected in series to left and right single-channel leads, is considered. By solving exactly for the spectrum of the two interacting electrons, it is found that the coupling to the continuum of propagating states on the leads, in conjunction with the electron-electron interactions, may result in a delocalization of the bound state of the two electrons. This, in turn, reduces significantly the range of the Coulomb interaction parameters over which singlet-triplet transitions can be realized. It is also found that the coupling to the leads favors the singlet ground-state.Comment: 8 pages, submitted to Phys. Rev.

USING RECENT ADVANCES IN 2D SEISMIC TECHNOLOGY AND SURFACE GEOCHEMISTRY TO ECONOMICALLY REDEVELOP A SHALLOW SHELF CARBONATE RESERVOIR: VERNON FIELD, ISABELLA COUNTY, MI.

Two major accomplishments resulted from Phase I. One is the success of the surface geochemistry program, which collected over 800 samples from the site of the 1st demonstration well in Vernon Field and has pretty well provided us with the tools to delineate favorable ground from unfavorable. The second is the recent detailed mapping of the Central Michigan Basin that for the first time revealed the presence of at least two major faults that control the location of many of the reservoirs in the Michigan Basin. These faults were located from structure maps obtained by contouring the surface of the Dundee Formation using top picks from 9861 wells in 14 counties. Faults were inferred where the contour lines were most dense (''stacked'')

USING RECENT ADVANCES IN 2D SEISMIC TECHNOLOGY AND SURFACE GEOCHEMISTRY TO ECONOMICALLY REDEVELOP A SHALLOW SHELF CARBONATE RESERVOIR: VERNON FIELD, ISABELLA COUNTY, MI.

In this reporting period, we extended the fault study to include more faults and developed new techniques to visualize the faults. We now have used data from the Dundee Formation to document 11 major faults in the Michigan Basin and are in the process of reviewing data from other horizons. These faults appear to control the locations of many of the large anticlinal structures in the Michigan Basin and likely controlled fluid movements as well. The surface geochemistry program is also moving along well with emphasis on measuring samples collected last sampling season. The new laboratory is now functional and has been fully staffed as of December. The annual project review has been set for March 7-9 in Tampa, Florida. Contracts are being prepared for drilling the Bower's prospects in Isabella County, Michigan, this spring or summer

Perceptions of COVID-19 vaccines among healthcare assistants: A national survey

Background: Limited COVID-19 vaccination acceptance among healthcare assistants (HCAs) may adversely impact older adults, who are at increased risk for severe COVID-19 infections. Our study objective was to evaluate the perceptions of COVID-19 vaccine safety and efficacy in a sample of frontline HCAs, overall and by race and ethnicity. Methods: An online survey was conducted from December 2020 to January 2021 through national e-mail listserv and private Facebook page for the National Association of Health Care Assistants. Responses from 155 HCAs, including certified nursing assistants, home health aides, certified medical assistants, and certified medication technicians, were included. A 27-item survey asked questions about experiences and perceptions of COVID-19 vaccines, including how confident they were that COVID-19 vaccines are safe, effective, and adequately tested in people of color. Multivariable regression was used to identify associations with confidence in COVID-19 vaccines. Results: We analyzed data from 155 completed responses. Among respondents, 23.9% were black and 8.4% Latino/a. Most respondents worked in the nursing home setting (53.5%), followed by hospitals (12.9%), assisted living (11.6%), and home care (10.3%). Respondents expressed low levels of confidence in COVID-19 vaccines, with fewer than 40% expressing at least moderate confidence in safety (38.1%), effectiveness (31.0%), or adequate testing in people of color (27.1%). Non-white respondents reported lower levels of confidence in adequate testing of vaccines compared to white respondents. In bivariate and adjusted models, respondents who gave more favorable scores of organizational leadership at their workplace expressed greater confidence in COVID-19 vaccines. Conclusion: Frontline HCAs reported low confidence in COVID-19 vaccines. Stronger organizational leadership in the workplace appears to be an important factor in influencing HCA's willingness to be vaccinated. Action is needed to enhance COVID-19 vaccine uptake in this important population with employers playing an important role to build vaccine confidence and trust among employees. © 2021 The American Geriatrics Society

Structural and biological identification of residues on the surface of NS3 helicase required for optimal replication of the hepatitis C virus

The hepatitis C virus (HCV) nonstructural protein 3 (NS3) is a multifunctional enzyme with serine protease and DEXH/D-box helicase domains. A crystal structure of the NS3 helicase domain (NS3h) was generated in the presence of a single-stranded oligonucleotide long enough to accommodate binding of two molecules of enzyme. Several amino acid residues at the interface of the two NS3h molecules were identified that appear to mediate a proteinprotein interaction between domains 2 and 3 of adjacent molecules. Mutations were introduced into domain 3 to disrupt the putative interface and subsequently examined using an HCV subgenomic replicon, resulting in significant reduction in replication capacity. The mutations in domain 3 were then examined using recombinant NS3h in biochemical assays. The mutant enzyme showed RNA binding and RNA-stimulated ATPase activity that mirrored wild type NS3h. In DNA unwinding assays under single turnover conditions, the mutant NS3h exhibited a similar unwinding rate and only ∼2-fold lower processivity than wild type NS3h. Overall biochemical activities of the mutant NS3h were similar to the wild type enzyme, which was not reflective of the large reduction in HCV replicative capacity observed in the biological experiment. Hence, the biological results suggest that the known biochemical properties associated with the helicase activity of NS3h do not reveal all of the likely biological roles of NS3 during HCV replication. Domain 3 of NS3 is implicated in protein-protein interactions that are necessary for HCV replication. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc

Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

Large-scale periodicity in the distribution of QSO absorption-line systems

The spatial-temporal distribution of absorption-line systems (ALSs) observed in QSO spectra within the cosmological redshift interval z = 0.0--4.3 is investigated on the base of our updated catalog of absorption systems. We consider so called metallic systems including basically lines of heavy elements. The sample of the data displays regular variations (with amplitudes ~ 15 -- 20%) in the z-distribution of ALSs as well as in the eta-distribution, where eta is a dimensionless line-of-sight comoving distance, relatively to smoother dependences. The eta-distribution reveals the periodicity with period Delta eta = 0.036 +/- 0.002, which corresponds to a spatial characteristic scale (108 +/- 6) h(-1) Mpc or (alternatively) a temporal interval (350 +/- 20) h(-1) Myr for the LambdaCDM cosmological model. We discuss a possibility of a spatial interpretation of the results treating the pattern obtained as a trace of an order imprinted on the galaxy clustering in the early Universe.Comment: AASTeX, 13 pages, with 9 figures, Accepted for publication in Astrophysics & Space Scienc

Coronal Diagnostics from Narrowband Images around 30.4 nm

Images taken in the band centered at 30.4 nm are routinely used to map the radiance of the He II Ly alpha line on the solar disk. That line is one of the strongest, if not the strongest, line in the EUV observed in the solar spectrum, and one of the few lines in that wavelength range providing information on the upper chromosphere or lower transition region. However, when observing the off-limb corona the contribution from the nearby Si XI 30.3 nm line can become significant. In this work we aim at estimating the relative contribution of those two lines in the solar corona around the minimum of solar activity. We combine measurements from CDS taken in August 2008 with temperature and density profiles from semiempirical models of the corona to compute the radiances of the two lines, and of other representative coronal lines (e.g., Mg X 62.5 nm, Si XII 52.1 nm). Considering both diagnosed quantities from line ratios (temperatures and densities) and line radiances in absolute units, we obtain a good overall match between observations and models. We find that the Si XI line dominates the He II line from just above the limb up to ~2 R_Sun in streamers, while its contribution to narrowband imaging in the 30.4 nm band is expected to become smaller, even negligible in the corona beyond ~2 - 3 R_Sun, the precise value being strongly dependent on the coronal temperature profile.Comment: 26 pages, 11 figures; to be published in: Solar Physic

Structure, Photophysics and the Order-Disorder Transition to the Beta Phase in Poly(9,9-(di -n,n-octyl)fluorene)

X-ray diffraction, UV-vis absorption and photoluminescence (PL) spectroscopy have been used to study the well-known order-disorder transition (ODT) to the beta phase in poly(9,9-(di n,n-octyl)fluorene)) (PF8) thin film samples through combination of time-dependent and temperature-dependent measurements. The ODT is well described by a simple Avrami picture of one-dimensional nucleation and growth but crystallization, on cooling, proceeds only after molecular-level conformational relaxation to the so called beta phase. Rapid thermal quenching is employed for PF8 studies of pure alpha phase samples while extended low-temperature annealing is used for improved beta phase formation. Low temperature PL studies reveal sharp Franck-Condon type emission bands and, in the beta phase, two distinguishable vibronic sub-bands with energies of approximately 199 and 158 meV at 25 K. This improved molecular level structural order leads to a more complete analysis of the higher-order vibronic bands. A net Huang-Rhys coupling parameter of just under 0.7 is typically observed but the relative contributions by the two distinguishable vibronic sub-bands exhibit an anomalous temperature dependence. The PL studies also identify strongly correlated behavior between the relative beta phase 0-0 PL peak position and peak width. This relationship is modeled under the assumption that emission represents excitons in thermodynamic equilibrium from states at the bottom of a quasi-one-dimensional exciton band. The crystalline phase, as observed in annealed thin-film samples, has scattering peaks which are incompatible with a simple hexagonal packing of the PF8 chains.Comment: Submitted to PRB, 12 files; 1 tex, 1 bbl, 10 eps figure