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Low Coverage (low + coverage)
Selected AbstractsAdsorption of water in mordenite,An ab initio studyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2001Th. Demuth Abstract The adsorption of water in mordenite has been investigated using density functional theory using gradient corrections to the exchange,correlation functional. In the neutral complex water is strongly physisorbed through two different hydrogen bonds, the stronger between the acid site and the water oxygen atom, the weaker between a hydrogen atom of the adsorbed molecule and a framework oxygen atom. Strong polarizations and structural distortions of both the acid site and the molecule have been observed. To elucidate the question if a chemisorbed complex (creation of a hydroxonium ion) is possible, ab initio molecular dynamics have been performed, indicating that a protonation of water occurs even for the low coverage of one water molecule per unit cell. However, this ionic configuration cannot be stabilized by the electrostatic field of the zeolite framework and is therefore not a minimum of the potential energy surface. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 110,116, 2001 [source] The impact of the global financial crisis on social protection in developing countriesINTERNATIONAL SOCIAL SECURITY REVIEW, Issue 2 2010Anna McCord Abstract The global financial crisis has had a devastating effect on poverty levels in developing countries, and the social protection response to date, in the form of social assistance, has been limited, constrained by the weak systems and low coverage of pre-existing provision. Developing countries have struggled to honour pre-crisis social protection policy commitments due to declining revenues, and in this context the potential for expanding coverage to assist those further impoverished and the "new poor" are remote. Despite the expansionary fiscal stance adopted by many developing countries, the focus of policy responses to the crisis has been on protecting and stimulating growth. The focus has not been on social protection provision to assist the poor directly. Where social protection interventions have been made they have, in many cases, been limited to ad hoc and often regressive interventions such as generalized food or fuel subsidies, rather than more systemic and pro-poor interventions. However, there may be some scope for optimism, as the crisis has stimulated a number of initiatives to promote donor coordination and programming coherence, which may result in improvements in the efficiency and impact of future social protection programming. [source] Disability benefits and workers with HIV/AIDS: Coverage issues and challenges in the United Republic of TanzaniaINTERNATIONAL SOCIAL SECURITY REVIEW, Issue 4 2008Tulia Ackson Abstract This paper explores the effective non-availability of disability/invalidity benefits to formal sector employees with HIV/AIDS in the United Republic of Tanzania. The legal difficulty of establishing a direct connection between HIV/AIDS and employment injury and occupational diseases present a challenge to social security institutions and schemes which are simultaneously trying to come to grips with the mounting problems of the shrinkage of the formal sector and low coverage. Remedial policy responses are proposed. These identify the statutory and legal adjustments needed both to ensure convergence of eligibility criteria for invalidity benefit claims among the concerned institutions, and to ensure that qualifying conditions are both consistent and in line with contemporary approaches to disbility. The suggested adjustments would simplify and clarify eligibility criteria in cases of invalidity involving existing scheme members, potentially also allowing for a future expansion of benefit coverage better to reflect labour market realities. [source] Modification of Supramolecular Binding Motifs Induced By Substrate Registry: Formation of Self-Assembled Macrocycles and Chain-Like PatternsCHEMISTRY - A EUROPEAN JOURNAL, Issue 42 2009Leslie-Anne Fendt Abstract The self-assembly properties of two ZnII porphyrin isomers on Cu(111) are studied at different coverage by means of scanning tunneling microscopy (STM). Both isomers are substituted in their meso -positions by two voluminous 3,5-di(tert -butyl)phenyl and two rod-like 4,-cyanobiphenyl groups, respectively. In the trans -isomer, the two 4,-cyanobiphenyl groups are opposite to each other, whereas they are located at right angle in the cis -isomer. For coverage up to one monolayer, the cis- substituted porphyrins self-assemble to form oligomeric macrocycles held together by antiparallel CN,,,CN dipolar interactions and CN,,,H-C(sp2) hydrogen bonding. Cyclic trimers and tetramers occur most frequently but everything from cyclic dimers to hexamers can be observed. Upon annealing of the samples at temperatures >150,°C, dimeric macrocyclic structures are observed, in which the two porphyrins are bridged by Cu atoms, originating from the surface, under formation of two CN,,,Cu,,,NC coordination bonds. The trans -isomer builds up linear chains on Cu(111) at low coverage, whereas for higher coverage the molecules assemble in a periodic, densely packed structure. Both cis - and trans -bis(4,-cyanobiphenyl)-substituted ZnII porphyrins behave very differently on Cu(111) compared to similar porphyrins in literature on less reactive surfaces such as Au(111) and Ag(111). On the latter surfaces, there is no signal visible between molecular orientation and the crystal directions of the substrate, whereas on Cu(111), very strong adsorbate,substrate interactions have a dominating influence on all observed structures. This strong porphyrin,substrate interaction enables a much broader variety of structures, including also less favorable intermolecular bonding motifs and geometries. [source] Equilibrium Coverage Fluctuations: A New Approach to Quantify Reversible Adsorption of ProteinsCHEMPHYSCHEM, Issue 3 2005Eike Lüthgens Binding kinetics of proteins on sensor devices: A new approach to simultaneously determine the rate constants of adsorption and desorption of proteins on surfaces at low coverage from the power spectrum of equilibrium coverage fluctuations is proposed and verified by dynamic Monte Carlo simulations (see picture). [source] Theoretical study on adsorption and diffusion of N atoms on Cu low-index surfaceCHINESE JOURNAL OF CHEMISTRY, Issue 11 2004Zhao-Yu Diao Abstract The adsorption and diffusion of N atoms on the three low-index Cu planes were studied using 5-parameter Morse potential (5-MP) method, and the best theory-experiment agreement was obtained. N atom of Cu(100) surface sit on the fourfold hollow site with the vertical height of 0.018 nm closely coplanar with the topmost copper layer, and the four CuN bond lengths are 0.182 nm and the fifth CuN distance is 0.199 nm. For Cu(111) system, the existence of aberrant Cu(100) reconstructed structure is approved at higher coverage, and at low coverage the structure is almost an ideal Cu(111) surface structure. With respect to Cu(110) system, the N atoms are adsorbed at LB and H3 sites, not at SB site. The diffusion passage and diffusion barrier of adsorbed N atoms were also studied. [source] Magnetisation dynamics of Fe nanoclusters exchange-coupled to magnetic substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2004C. Binns Abstract Synchrotron radiation was used to study exposed Fe nanoclusters with controlled sizes in the size range 140,270 atoms (1.5,1.8 nm) deposited in situ from a gas aggregation source on to magnetic vitrovac amorphous ribbons. Magnetic linear dichroism in the angular distribution (MLDAD) of the Fe 3p core level photoemission was used to show that the clusters are exchange-coupled to the substrate with an interface molecular field of about 20 T. The switching dynamics was studied on the nanosecond timescale by time-resolved spin-polarised photoemission. At low coverages, below the percolation threshold, when the film consists of separated islands the switching dynamics of the cluster islands is identical to the clean substrate. At around the percolation threshold, however, the data indicates that the magnetic reversal propagates faster in the cluster film than in the substrate. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] CO Adsorption on a LaNi5 Hydrogen Storage Alloy Surface: A Theoretical InvestigationCHEMPHYSCHEM, Issue 11 2008Song Han Dr. Abstract Density functional theory calculations are carried out to study CO adsorption on the (001) surface of a LaNi5 hydrogen storage alloy. At low coverages, CO favors adsorption on NiNi bridge sites. With an increase in CO coverage, the decrease in the adsorption energy is much larger for NiNiCO bridge adsorption than that for NiCO on-top adsorption. Thus, the latter sites in the relatively stable adsorption structure are preferentially utilized at high CO coverages. The nature of the bonding between CO and the LaNi5 (001) surface is analyzed in detail. [source] | ||||||||||