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PubMed2005

Density functional theory study of the adsorption of alkanethiols on Cu(111), Ag(111), and Au(111) in the low and high coverage regimes.

The structure, the surface bonding, and the energetics of alkanethiols adsorbed on Cu(111), Ag(111), and Au(111) surfaces were studied under low and high coverages. The potential energy surfaces (PES) for the thiol/metal interaction were investigated in the absence and presence of externally applied electric fields in order to simulate the effect of the electrode potential on the surface bonding. The electric field affects the corrugation of the PES which decreases for negative fields and increases for positive fields. In the structural investigation, we considered the relaxation of the adsorbate and the surface. The highest relaxation in a direction perpendicular to the surface was observed for gold atoms, whereas silver atoms presented the highest relaxation in a plane parallel to the surface. The surface relaxation is more important in the low coverage limit. The surface bonding was investigated by means of the total and projected density of states analysis. The highest ionic character was observed on the copper surface whereas the highest covalent character occurs on gold. This leads to a strong dependence of the PES with the tilt angle of the adsorbate on Au(111) whereas this dependence is less pronounced on the other metals. Thus, the adsorbate-relaxation and the metal-relaxation contributions to the binding energy are more important on gold. The adsorption of thiols on gold was investigated on the 111 surface as well as on a surface with gold adatoms in order to elucidate the effect of thiols on the surface diffusion of gold. The CH(3)CH(2)S radical adsorbs ontop of the gold adatom. The diffusional barrier of the CH(3)CH(2)SAu species is lower than that for a bare gold adatom and is also lower than that for the bare thiol radical. The adsorption of the molecular species CH(3)SH and CH(3)CH(2)SH was also investigated on Au(111). They adsorb via the sulfur atom ontop of a gold atom. On the other hand, the adsorption of the alkanethiol radicals on the perfect 111 surfaces occurs on the face centered cubic (fcc)-bridge site in the low coverage limit for all metals and shifts toward the fcc site at high coverage on copper and silver.

Adsorption↗
PubMed2006

Magnetic iron oxide nanoparticles for biorecognition: evaluation of surface coverage and activity.

Modifying the surfaces of magnetic nanoparticles (MNPs) by the covalent attachment of biomolecules will enable their implementation as contrast agents for magnetic resonance imaging or as media for magnetically assisted bioseparations. In this paper we report both the surface coverage and the activity of IgG antibodies on MNPs. The antibodies were immobilized on gamma-Fe2O3 nanoparticles by conventional methods using aminopropyltriethoxy silane and subsequent activation by glutaraldehyde. Novel fluorescence methods were used to provide a quantitative evaluation of this well-known approach. Our results show that surface coverage can be stoichiometrically adjusted with saturated surface coverage occurring at approximately 36% of the theoretical limit. The saturated surface coverage corresponds to 34 antibody molecules bound to an average-sized MNP (32 nm diameter). We also show that the immobilized antibodies retain approximately 50% of their binding capacity at surface-saturated levels.

Antibodies↗
PubMed2006

Adsorption of fumaramide [2]rotaxane and its components on a solid substrate: a coverage-dependent study.

The coverage-dependent adsorption on Au(111) of a fumaramide [2]rotaxane and its components, a benzylic amide macrocycle and a fumaramide thread, is studied using high-resolution electron energy loss spectroscopy (HREELS). Up to monolayer coverage, the relative intensity of out-of-plane to in-plane phenyl ring vibrational modes indicates that the macrocycle adopts an orientation with the phenyl rings largely parallel to the surface. The formation of a chemisorption bond is evidenced by the presence of a Au-O stretching vibration. In contrast, the thread shows no evidence of chemisorption or a preferential orientation. The introduction of the thread into the macrocycle partly disrupts the film order so that the resulting chemisorbed rotaxane shows intermediate behavior with a preferential orientation up to 0.5 ML coverage. A decrease in film order and the absence of a preferred molecular orientation is observed for all three molecules at multilayer coverages. The spectral differences are addressed by molecular dynamics simulations in terms of the mobility of the phenyls of the three molecules on Au(111).

Journal Article↗
PubMed2006

Bond character of thiophene on Ge(100): Effects of coverage and temperature.

We have studied the adsorption and decomposition of thiophene (C4H4S) on Ge(100) using scanning tunneling microscopy (STM), high-resolution core-level photoemission spectroscopy (HRPES), and density functional theory (DFT) calculation. Analysis of S 2p core-level spectra reveals three adsorption geometries, which we assign to a Ge-S dative bonding state, a [4 + 2] cycloaddition bonding state, and a decomposed bonding state (desulfurization reaction product). Furthermore, we found that the number ratio of the three adsorption geometries depended on the molecular coverage and the annealing temperature. At low coverages, the kinetically favorable dative bonding state is initially formed at room temperature. As the molecular coverage increases, thermodynamically stable [4 + 2] cycloaddition reaction products are additionally produced. In addition, we found that as the surface temperature increased, the [4 + 2] cycloaddition reaction product either possibly desorbed as molecular thiophene or decomposed to form a metallocycle-like species (C4H4Ge2) and a sulfide (Ge2S). We systematically elucidate the changes in the bonding states of adsorbed thiophene on Ge(100) according to the thiophene coverage and annealing temperature.

Journal Article↗
PubMed2002

The use of allogeneic cultivated keratinocytes for the early coverage of deep dermal burns - indications, results and problems.

Since 1995, keratinocytes are grown into cultures and used as allografts for the coverage of deep dermal defects in our burn unit. Donor skin samples are mostly acquired from other burn patients. In addition, special methods of skin preservation allow us the use of skin, which has been taken in redundancy for split thickness skin grafting from nonburned patients.Thirty five patients with deep partial thickness burns in the face were treated since 1996 according to the following concept: Dermabrasion or tangential excision was performed before the 5(th) day following trauma. If viable dermis was present, the wounds were covered with sheets of allogeneic cultivated keratinocytes. In cases of deeper defects, autologous skin grafts were applied. In 23 cases, epithelialisation was achieved within 10 days, in 8 patients, a prolonged duration until complete healing was observed. In 5 faces, coverage of residual defects with skin grafts was necessary. The mentioned problems of wound healing occurred from infection, incomplete excision of burn eschar and a depth of the wound which was retrospectively seen too deep for the treatment with keratinocytes. At follow up, patients were examined clinically and functionally with Frey's faciometer(R), which is an instrument for quantification of mimic movements. In cases of uncomplicated healing, a nearly complete restitution was found.Other indications include deep dermal burns in children and the coverage of early excised wounds in adults, with a reasonable amount of viable dermis remaining, both resulting in a significant reduction of donor-site morbidity. In severely burned adults with limited donor sites, it offers the possibility of immediate definite coverage of large areas.

Journal Article↗
PubMed2003

Negative symptoms, anger, and social support: response of an inpatient sample to news coverage of the September 11 terrorist attacks.

We examined the reactions of 17 male inpatients on a secure psychiatric unit to television news coverage of the September 11 attacks. All had psychotic diagnoses. We hypothesized that self-exposure and affective response to the news coverage and use of social support would be influenced by predominance of negative symptoms. Additionally, we examined for the emergence of common stress symptoms and exacerbations of psychosis. Results showed a dose-response relationship between amount of viewing and magnitude of response to the coverage. Anger was the emotion most clearly tied to coverage exposure and the other response variables. A wide range of stress symptoms was reported. Hypotheses concerning the influence of negative symptoms were partially supported. A significant minority of the patients disclosed exacerbation of psychotic symptoms in response to the attacks. Patients who reported a negative emotional reaction were more likely to talk to others about the attacks, but social contact did not predictably lead to affective relief.

Adult↗
PubMed2004

Improving physician coverage of pneumococcal vaccine: a randomized trial of a telephone intervention.

Improved pneumococcal vaccine (PPV) immunization for seniors is a national goal of the Medicare program. This study examined whether adding a simple telephone follow-up to an existing mailed physician performance feedback under the Medicare program would increase the impact on billed pneumococcal immunizations. Medicare fee-for-service claims data were used to select New York primary care physicians with high volume (n = 732) or African-American serving (n = 329) practices. All practices received mailed feedback on their 1999 Medicare practice specific PPV coverage rates, along with educational materials and offers of assistance. Practices were also randomized to receive telephone calls directing attention to the mailing and further promoting improvements in PPV coverage or no active follow-up. Physicians randomized to telephone follow-up showed significantly higher rates of practice specific PPV coverage in 2000 than those receiving the routine mailing only, and 27% vs. 17% (p = 0.01) of high volume physicians and 34% vs. 22% (p = .052) of African American serving physicians achieved at least a 5% increase in their cumulative PPV claims coverage. This study concludes that telephone follow-up is an effective and straightforward method to enhance the impact of practice specific feedback to promote improvements in Medicare PPV immunization. However, improved methods may be needed to induce a large percentage of physicians to change.

Aged↗
PubMed2000

Scanning electron microscopic analysis of endothelial cell coverage and quality in large vessels from multi-organ donors: effects of preservation on endothelial cell integrity.

Endothelial cell integrity (coverage and quality) of large donor vessels is important because these vessels are used for vascular reconstructions in solid-organ transplantation. Disruption of the endothelial cell monolayer will initiate blood coagulation and may lead to thrombosis of large vessels, often resulting in the loss of the transplanted organ. Iliac arteries and veins, removed from 10 heart-beating multi-organ donors at the end of the donor procedure, were analyzed using scanning electron microscopy at three different time points of preservation. Endothelial cell coverage and quality were determined immediately after removal from the donor, after 10 h (time of transplantation) and 7 d storage in 'University of Wisconsin' cold preservation solution (UW). Endothelial cell coverage decreased during the preservation of arteries, but was maintained in veins. Storage of the veins for 7 d in plastic bags showed a decreased endothelial cell coverage compared to storage in glass vials. Early removal of the blood vessels and proper storage, free floating and in clean UW, may improve maintenance of the endothelial cell integrity. These findings may be important in order to reduce the risk of thrombosis and, consequently, organ failure after transplantation. Furthermore, vessels with maintained endothelial cell integrity after 7 d may be used for in vitro research.

Adenosine↗
PubMed2002

The palatal advanced flap: a pedicle flap for primary coverage of immediately placed implants.

The placement of implants immediately after tooth extraction has become a relatively common event. This approach has gained popularity because it reduces the time between tooth extraction and placement of the final prosthetic restoration. One problem that remains unresolved with this procedure, however, is that there is usually space left in the area surrounding the coronal portion of the implant. As none of the techniques published to date is completely satisfactory, we developed an approach that is a modification of the palatal pedicle flaps used for closure of oro-antral fistulas. This technique allows for precise rotational advancement of the palatal tissue in a coronal direction, thus facilitating complete coverage of the extraction site. The procedure was used on 38 patients treated for primary coverage of postextraction placed implants. Thirty-two of the patients required single tooth replacement, three patients received two implants each, and three patients received three implants each. In 27 of the cases, the procedure was performed in conjunction with barrier membranes; of the 38 cases, 25 patients required the use of DFDBA to fill the defect created by the extraction procedure. The average defect width was 4.70 +/- 0.2 mm. Complete primary coverage was obtained in all cases without any changes in the size or anatomy of the buccal vestibule; complete coverage was maintained over the entire healing period of 6-8 months (mean +/- SEM, 6.49 +/- 0.10 months). Even with guided tissue regeneration cases, there was no exposure of the barrier membrane or cover screw of the implant during healing. After a period of 1-5 years (mean +/- SEM, 39.35 +/- 2.69 months), none of the implants was lost. We conclude that the palatal advanced flap procedure is useful, fast, and easy to perform in cases of immediate implant placement after tooth extraction.

Adult↗
PubMed2000

Visual cortex maps are optimized for uniform coverage.

Cat visual cortex contains a topographic map of visual space, plus superimposed, spatially periodic maps of ocular dominance, spatial frequency and orientation. It is hypothesized that the layout of these maps is determined by two constraints: continuity or smooth mapping of stimulus properties across the cortical surface, and coverage uniformity or uniform representation of combinations of map features over visual space. Here we use a quantitative measure of coverage uniformity (c') to test the hypothesis that cortical maps are optimized for coverage. When we perturbed the spatial relationships between ocular dominance, spatial frequency and orientation maps obtained in single regions of cortex, we found that cortical maps are at a local minimum for c'. This suggests that coverage optimization is an important organizing principle governing cortical map development.

Animals↗
PubMed2003

Construction and usage of a onefold-coverage shotgun DNA microarray to characterize the metabolism of the archaeon Haloferax volcanii.

Haloferax volcanii is a moderately halophilic archaeon that can grow aerobically and anaerobically with a variety of substrates. We undertook a novel approach for the characterization of metabolic adaptations, i.e. transcriptome analysis with a onefold-coverage shotgun DNA microarray. A genomic library was constructed and converted into a polymerase chain reaction (PCR) product library, which was used to print two DNA microarrays, a 960-spot test array used for optimization of microarray analysis and a 2880-spot onefold-coverage array. H. volcanii cultures were shifted from casamino acid-based metabolism to glucose-based metabolism, and the transcriptome changes were analysed with the onefold-coverage array at five time points covering the transition phase and the onset of exponential growth with the new carbon source. About 10% of all genes were found to be more than 2.5-fold regulated at at least one time point. The genes fall into five clusters of kinetically co-regulated genes. For members of all five clusters, the results were verified by Northern blot analyses. The identity of the regulated genes was determined by sequencing. Many co-regulated genes encode proteins of common functions. Expected as well as a variety of unexpected findings allowed predictions about the central metabolism, the transport capacity and the cellular composition of H. volcanii growing on casamino acids and on glucose. The microarray analyses are in accordance with the growth rates and ribosome contents of H. volcanii growing on the two carbon sources. Analysis of the results revealed that onefold-coverage shotgun DNA microarrays are well suited to characterize the regulation of metabolic pathways as well as protein complexes in response to changes in environmental conditions.

Gene Expression Profiling↗
PubMed2001

Medicare health maintenance organizations and traditional coverage: perceptions of health care among beneficiaries with disabilities.

OBJECTIVE: To determine whether perceptions of access to, affordability of, and quality of health care services differ for Medicare beneficiaries with disabilities in health maintenance organizations (HMOs) and traditional Medicare coverage. DESIGN: Bivariate and multivariate analyses were conducted to determine the relationship between Medicare coverage type and perceptions of health care access, affordability, and quality. SETTING: Noninstitutionalized Medicare beneficiaries across the United States. PARTICIPANTS: A random sample of 6116 beneficiaries who qualify for Medicare as working-age disabled (n = 2250), or who qualify as elderly and have at least 1 instrumental activities of daily living limitation (n = 3866). This subsample of the nationally representative Medicare Current Beneficiary Survey (MCBS) represents 11,627,107 beneficiaries with disabilities. INTERVENTION: Questions about perception of access to primary care, affordability of care, and quality of care. Data derived from the 1994 MCBS Access to Care File. MAIN OUTCOME MEASURES DEPENDENT VARIABLES: perceptions of access to primary care, affordability, and satisfaction with quality of care. INDEPENDENT VARIABLES: indicators of managed care status and health status level, severity of disability, Medicare qualification, age, and gender. RESULTS: Beneficiaries with disabilities in HMOs perceive better access to primary care services, and greater affordability of health services than those with traditional Medicare coverage. Beneficiaries in poor health or with the most severe disabilities were most likely to perceive access and cost difficulties, regardless of coverage type. CONCLUSION: Medicare managed care appears generally to be meeting 2 of its goals-better access to primary care and more affordable care-though these advantages are not being shared by those with poor health status and/or severe disabilities.

Activities of Daily Living↗
PubMed2002

[Efforts concerning the health target of age-specific coverage levels in over 90% of the population of Saxony-Anhalt].

At the first health conference in Saxony-Anhalt held at Magdeburg in March 1998 six health objectives were defined, among them the objective to increase to 90% the vaccination coverage level of the population. To achieve this goal the participants decided to establish a working group composed of representatives of 20 institutions and organisations interested in vaccination strategies. Subgroups were constituted for the following components of the objective: improvement of the data basis, completion of the special knowledge of physicians and other medical personnel, public information campaigns, and improvement of the structural framework. More than 50 actions per year were initiated or co-ordinated taking into account the special profiles of the institutions and organisations involved. In this way a better identification of the participants with the project was achieved and waste of strength and time was avoided. The data basis was assessed using generally available or newly created parameters such as the incidence of notified vaccine-preventable diseases, measles seroprevalence, and vaccination coverage levels among children aged 5-6 years. Approaches to target group related activities of the working group were derived from these parameters. The most remarkable results of these activities include the definition of age specific vaccination coverage levels, the establishment of a certificate for physicians who have completed a vaccination training course, a monthly press release on vaccination subjects, the design of a poster presentation, the composition of foil-based age group specific lectures, and the establishment of frame conditions for a recall system for practising physicians. The first hurdles on the way to a high age specific vaccination coverage levels have been taken. Further work must be done to improve the use of offered vaccinations and to complete the available data. Therefore, additional target group-related projects and actions are planned for the years to come.

Age Factors↗
PubMed2004

Absolute surface coverage measurement using a vibrational overtone.

Determination of absolute surface coverage with sub-monolayer sensitivity is demonstrated using evanescent-wave cavity ring-down spectroscopy (EW-CRDS) and conventional CRDS by employing conservation of the absolute integrated absorption intensity between gas and adsorbed phases. The first C-H stretching overtones of trichloroethylene (TCE), cis-dichloroethylene, and trans-dichloroethylene are probed using the idler of a seeded optical parametric amplifier having a 0.075 cm(-1) line width. Polarized absolute adsorbate spectra are obtained by EW-CRDS using a fused-silica monolithic folded resonator having a finesse of 28 500 at 6050 cm(-1), while absolute absorption cross sections for the gas-phase species are determined by conventional CRDS. A measure of the average transition moment orientation on the surface, which is utilized for the coverage determination, is derived from the polarization anisotropy of the surface spectra. Coverage measurement by EW-CRDS is compared to a mass-spectrometer-based surface-uptake technique, which we also employ for coverage measurements of TCE on thermally grown SiO(2) surfaces. To assess the potential for environmental sensing, we also compare EW-CRDS to optical waveguide techniques developed previously for TCE detection.

Journal Article↗
PubMed2005

Coverage dependent desorption dynamics of deuterium on Si(100) surfaces: interpretation with a diffusion-promoted desorption model.

We studied coverage dependence of time-of-flight (TOF) spectra of D2 molecules thermally desorbed from the D/Si(100) surface. The mean translational energies Et of desorbed D2 molecules were found to increase from 0.20+/-0.05 eV to 0.40+/-0.04 eV as the desorption coverage window was decreased from 1.0 ML> or =thetaD> or =0.9 ML to 0.2 ML> or =thetaD> or =0 ML, being consistent with the kinetics switch predicted in the interdimer mechanism. The measured TOF spectra were deconvoluted into 2H, 3H, and 4H components by a curve fitting method along the principle of detailed balance. As a result, it turned out that the desorption kinetics changes from the 4H to the 3H situation at high coverage above thetaD=0.9 ML, while the 2H desorption is dominant for a quite wide coverage region up to thetaD=0.8 ML. A dynamic desorption mechanism by which the desorption is promoted by D-atom diffusion to dangling bonds was proposed.

Journal Article↗
PubMed2005

Coverage dependence of oxygen decomposition and surface diffusion on rhodium 111: a DFT study.

A systematic study of oxygen adsorption, decomposition and diffusion on Rh111 and its dependence on coadsorbed oxygen molecules has been performed using density functional theory calculations. First, the bonding strength between metal surface and adsorbed oxygen molecules has been studied as a function of initial oxygen coverage. The bonding strength decreases with increasing oxygen coverage, which points towards a self-inhibition of the adsorption process. The potential energy hypersurface (PES) for the dissociation of oxygen molecules adsorbed on a threefold fcc position perpendicular to the surface was calculated using a combined linear/quadratic synchronous transit method with conjugate gradient refinements. The results indicate that a minor amount of oxygen on the surface enhances the decomposition of further oxygen molecules, while this process is inhibited at higher coverage. Moreover, PES calculations of a single site jump of atomic oxygen on rhodium 111 indicate that the activation energy increases as well with increasing oxygen coverage. All results are discussed with respect to a rhodium based catalytic NOx reduction/decomposition system proposed by Nakatsuji, which decomposes nitrogen oxides in oxygen excess.

Journal Article↗
PubMed1998

A method to determine the coverage of ivermectin distribution in onchocerciasis-control programmes.

Onchocerciasis is a human filarial infection responsible for an estimated 750,000 blind and severely visually disabled people. In some African countries, this disease represents the main cause of blindness, with considerable socio-economic impact on the affected communities. Since the introduction of ivermectin as a microfilaricidal agent, there is hope that visual loss from onchocerciasis can be eliminated through community-based ivermectin-distribution programmes. The African Programme for Onchocerciasis Control (APOC) has now been initiated, by the World Health Organization and World Bank, to distribute ivermectin in 19 African countries where onchocerciasis is endemic. Estimates of ivermectin coverage in distribution programmes for onchocerciasis control have so far been based on the number of treatments given, in any one year, to a target population. There is a need for a standardized method to evaluate, measure and monitor coverage over time. In April 1996, a cluster random-sampling method was used to calculate coverage with ivermectin in an urban population of 30,000 people in the Central African Republic. The method was adapted from that used to determine coverage by the WHO Expanded Programme on Immunization. It proved to be inexpensive and easy to perform, requiring only local equipment and personnel. The method used and results obtained in Bossangoa and the potential use of the technique in other distribution programmes are discussed.

Adult↗
PubMed2002

Vaccination coverage estimates by EPI cluster sampling survey of children (18-24 months) in Flanders, Belgium.

UNLABELLED: A random cluster sample according to the EPI cluster sampling technique was conducted in 1999 in Flanders (North Belgium) to ascertain the vaccination coverage of 18 to 24-mo-old children. Polio is the only mandatory vaccine. Diphtheria-tetanus-pertussis (DTP), Haemophilus influenzae type b (Hib), hepatitis B (HB) and measles-mumps-rubella (MMR) are included in the recommended schedule of vaccinations. For Hib and HB, a minimal cost was charged. Professional interviewers conducted interviews with the parents of 1110 children randomly selected in 89 municipalities. Analysis was conducted on the results of 1005 children. The coverage level (95% confidence interval) for the full schedule was 96% (95-97) for polio, 89% (87-91) for DTP, 78% (74-82) for Hib, 68% (64-72) for HB and 83% (81-87) for MMR. The vaccinations were administered by the regional children's health organization (70%), paediatricians (17%) and GPs (11%). No sociodemographic factors could be associated with vaccination coverage. One province showed significantly (p < 0.01) lower vaccination coverage levels compared with those of the other four provinces for DTP (91% vs 82%), Hib (78% vs 53%), HB (73% vs 46%) and MMR (87% vs 66%). CONCLUSION: There is a need for more and better information about vaccination for parents as well as for the healthcare providers.

Belgium↗