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The aim of the present work is to synthesize, characterize, and test self-assembled anisotropic or Janus particles designed to load anticancer drugs for lung cancer treatment by inhalation. The particles were synthesized using binary... more
The aim of the present work is to synthesize, characterize, and test self-assembled anisotropic or Janus particles designed to load anticancer drugs for lung cancer treatment by inhalation. The particles were synthesized using binary mixtures of biodegradable and biocompatible materials. The particles did not demonstrate cyto- and genotoxic effects. Janus particles were internalized by cancer cells and accumulated both in the cytoplasm and nuclei. After inhalation delivery, nanoparticles accumulated preferentially in the lungs of mice and retained there for at least 24 h. Two drugs or other biologically active components with substantially different aqueous solubility can be simultaneously loaded in two-phases (polymer-lipid) of these nanoparticles. In the present proof-of-concept investigation, the particles were loaded with two anticancer drugs: doxorubicin and curcumin as model anticancer drugs with relatively high and low aqueous solubility, respectively. However, there are no o...
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<> RESULTS The results demonstrated the presence of a minimum experimental total adhesion density which occurs for samples with MD fibers at spacing less than the bacterial diameter (Fig. 2). Comparing to the bare surface this... more
<> RESULTS The results demonstrated the presence of a minimum experimental total adhesion density which occurs for samples with MD fibers at spacing less than the bacterial diameter (Fig. 2). Comparing to the bare surface this geometrical combination reduces bacterial adhesion by 40%. Additionally, our experimental results show that bacteria developed microcolonies (onset of biofilm formation) on the bare samples while the engineered surface inhibited colony formation.
Abstract A numerical solution to the defect chemical equations was used to model the defect population in europium-doped strontium cerate (ESC) at vapor partial pressure and oxygen partial pressure range in hydrogen atmosphere. The... more
Abstract A numerical solution to the defect chemical equations was used to model the defect population in europium-doped strontium cerate (ESC) at vapor partial pressure and oxygen partial pressure range in hydrogen atmosphere. The results of the simulation compared well with the work previously reported in the literature. The numerically simulated defect concentrations were then used to predict the conductivity and hydrogen permeability of ESC membranes as a function of temperature. Uniquely, the model was then validated by comparing the predictions with experimental data for ESC membranes. The results of that exercise showed that the model is in good agreement with the experiment at temperatures high enough that the effects of defect interaction can be ignored; and where the assumption of a dilute solution of defects is valid. The agreement with the experiment further enabled the model to be used to obtain credible predictions for the ambipolar conductivity of ESC and hydrogen flux through ESC as a function of feed side hydrogen partial pressure.
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Dynamic (flow — induced) expansion (dilation) of fine powders inside a rotating drum is investigated. Most previous work on powder dilation is based on two‐phase effects, where the presence of air either drives the flow (fluidized bed),... more
Dynamic (flow — induced) expansion (dilation) of fine powders inside a rotating drum is investigated. Most previous work on powder dilation is based on two‐phase effects, where the presence of air either drives the flow (fluidized bed), or air needs to be displaced for the powder to flow (hoppers). Experimental results show that for many common powders the bed dilates visibly up to 25%, depending on powder composition, particle size, and the rotation speed of the drum. Discrete element simulations were performed in parallel for various values of powder cohesion, rotation rates, and drum size. Results show qualitative agreement between experiments and simulations. In experiments, after the initial transient behavior, the density reached at equilibrium for all materials tested is lower than the static “bulk density” reported in the literature. In both experiments and simulations, increase in powder cohesion enhances dilation. DEM simulations are used to analyze local density fluctuati...
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ABSTRACT This article examines the effects and interactions of shear rate, shear strain on electrical and flow properties of pharmaceutical blends. An unexpectedly strong relation between the flow and passive electrical properties of... more
ABSTRACT This article examines the effects and interactions of shear rate, shear strain on electrical and flow properties of pharmaceutical blends. An unexpectedly strong relation between the flow and passive electrical properties of powders is observed to depend on the shear history of the powder bed. Charge density, impedance, dielectrophoresis, flow index, and dilation were measured for several pharmaceutical blends after they were subjected to a controlled shear environment. It was found that the increase in the shear strain intensified the electrical properties for blends that did not contain MgSt. The opposite effect was found in blends lubricated with MgSt. Different shear conditions resulted in different correlations between flow index and dilation. Flow properties of powders were found to improve with continuous exposure to shear strain. It was also found that flow properties correlated to charge acquisition and impedance for different shear treatments. © 2009 American Institute of Chemical Engineers AIChE J, 2010
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A technique for the production of poorly soluble drug nanoparticles utilizing an emulsion-template is demonstrated. This process is a scalable, three-stage operation for nanosuspension production for use in drug delivery where emulsion... more
A technique for the production of poorly soluble drug nanoparticles utilizing an emulsion-template is demonstrated. This process is a scalable, three-stage operation for nanosuspension production for use in drug delivery where emulsion droplets act as the site for the nucleation and particle growth. The active drug (griseofulvin, ascorbyl palmitate, sulfadiazine, or ibuprofen ) was dissolved in a partially-miscible dispersed oil-phase (using environmentally-safe oils: triacetin, ethyl acetate or n-butyl lactate), homogenized, and subsequently placed into a well mixed system of anti-solvent which extracts the partially miscible oil-phase causing a controlled precipitation inside each droplet. The product was a monodisperse suspension of 70-150 nm particles for each drug; which remain stable for several days to weeks. In an effort to further optimize the process, different types of emulsifier, including lecithin, sucrose esters, sorbitan esters (Tween), and polyglycol esters (Poloxame...
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We report Monte Carlo simulations of the solvation pressure between two planar surfaces, which represent the interface of spherical silica nanoparticles in supercritical carbon dioxide. Carbon dioxide (CO2) was modeled as an atomistic... more
We report Monte Carlo simulations of the solvation pressure between two planar surfaces, which represent the interface of spherical silica nanoparticles in supercritical carbon dioxide. Carbon dioxide (CO2) was modeled as an atomistic dumbbell or a spherical Lennard-Jones particle. The interaction between CO2 molecules and silica surfaces was characterized by the standard Steele potential with energetic heterogeneities representing the hydrogen bonds. The parameters for the solid-fluid interaction potentials were obtained by fitting our simulations to the experimental isotherms of CO2 sorption on mesoporous siliceous materials. We studied the dependence of the solvation force on the distance between planar silica surfaces at T = 318 K, at equilibrium bulk pressures p(bulk) ranging from 69 to 200 atm. At 69 atm, we observed a long-range attraction between the two surfaces, and it vanished when the pressure was increased to 102 and then 200 atm. The results obtained with different fluid models were consistent with each other. According to our observations, energetic heterogeneities of the surface have negligible influence on the solvation pressure. Using the Derjaguin approximation, we calculated the solvation forces between spherical silica nanoparticles in supercritical CO2 from the solvation pressures between the planar surfaces.
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Particles are important additives for altering and enhancing the properties of polymers. When the particle size approaching the fundamental length scale of the material, new mechanical, optical, and electrical properties arise, which are... more
Particles are important additives for altering and enhancing the properties of polymers. When the particle size approaching the fundamental length scale of the material, new mechanical, optical, and electrical properties arise, which are not present in the conventional macroscopic counterpart. For example, the dielectric constant of a polymer fluid can be increased by addition of ceramic nanoparticles with high permittivity. Some new polymeric and ceramic materials have been identified as promising candidates for the fabrication of high dielectric strength capacitors. Systems, such as titania, strontium titanate, and barium titanate dispersed in perfluoropoly(ether), poly(dimethyl siloxane), and poly(butadiene), have been investigated in several experimental works. In addition, silica (SiO2) nanoparticles embedded in a polyethylene (PE) melt has been identified to offer desired dielectric constants. For this system, experimental study by Riman et al. [1] indicates that at nanopartic...
We perform molecular dynamics simulations of friction for atomically thin Xe films sliding on Ag(111). We determine the inverse of the coefficient of friction (i.e. slip time) by direct calculation of the decay of the center of mass... more
We perform molecular dynamics simulations of friction for atomically thin Xe films sliding on Ag(111). We determine the inverse of the coefficient of friction (i.e. slip time) by direct calculation of the decay of the center of mass velocity after applying an external force, as well as from the velocity autocorrelation function. We find that the slip time exhibits a drop followed by a sharp increase in a range of coverage near one monolayer. The slip time then levels off with further coverage increases in agreement with previously reported experiments. Our simulations suggest that the friction found in this system is dominated by phonon excitations.
Research Interests: Paraguay, Public Health, Latin America, Pregnancy, Humans, and 15 moreFemale, Animals, Blood sampling, Polymerase Chain Reaction, Incidence, Chagas disease, Prenatal screening, Newborn Infant, Early Detection, Pregnant Women, Pan American Health Organization, Enzyme Linked Immunosorbent Assay, The American, immunoglobulin M, and Medical and Health Sciences
This paper describes a new method to quantitatively measure the flow characteristics of unconfined cohesive powders in a rotating drum. Cohesion plays an important role, affecting flow properties/characteristics, mixing rates, and... more
This paper describes a new method to quantitatively measure the flow characteristics of unconfined cohesive powders in a rotating drum. Cohesion plays an important role, affecting flow properties/characteristics, mixing rates, and segregation tendencies. The method ...
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... this article, we present a discrete element method model to simulate flow, mixing, and heat ... Granular flow and heat transport properties are taken simultaneously into account in order to ...Simulation results for the heat transfer... more
... this article, we present a discrete element method model to simulate flow, mixing, and heat ... Granular flow and heat transport properties are taken simultaneously into account in order to ...Simulation results for the heat transfer of granular material in calciners and impregnators are ...
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ABSTRACT Janus particles are defined as isotropic amphiphilic particles having different chemical or physical properties in two surface regions. Biocompatible or biodegradable polymeric Janus particles have many potential applications in... more
ABSTRACT Janus particles are defined as isotropic amphiphilic particles having different chemical or physical properties in two surface regions. Biocompatible or biodegradable polymeric Janus particles have many potential applications in drug delivery, such as acting as a stabilizer for nanocrystal drug suspensions or site-specific drug delivery vehicles. The so-called internal phase separation method is widely used to produce polymeric Janus particles because it is applicable to most polymers and amenable to scale up. In this method, when the volatile organic solvent is completely evaporated, Janus particles are formed in the aqueous system. The morphology and stability of such particles depend on various interfacial tensions. It is inconvenient and costly to screen good combinations of biocompatible/biodegradable polymers capable of producing Janus particles by measuring surface/interfacial tensions in polymeric Janus particle aqueous system. Little atomistic simulation work has been done to explore the interfacial interactions governing Janus particle formation. Interfacial tensions and binding energies of various systems were approximated using atomistic simulations to determine whether Janus particle formation is favorable under the given conditions. The simulated systems consisted of poly(lactic-co-glycolic acid) (PLGA 50:50) and poly-e-caprolactone (PCL) as the matrix polymers and SDS as surfactant. Wang et al. developed a geometry map for predicting the final morphology of polystyrene (PS)/poly(methylmetacrylate) (PMMA) composite particles prepared via internal phase separation in which the particle morphology is dependent upon the interfacial tensions of the system. Specifically, the ratio of the interfacial tension between the aqueous phase and polymer phase to the interfacial tension between the oil phase and aqueous phase normalized by the interfacial tension between the oil and polymer phases corresponds to a region on the geometry map. Inside the region for Janus particle formation, there is a range of possible architectures ranging from acorn-like to crescent moon. When applied to our PLGA/PCL system, this map accurately predicted the resulting morphology of PLGA/PCL Janus particles formed by internal phase separation in an oil-in-water emulsion template based on interfacial tensions calculated for PLGA-PCL, PLGA-water, and PCL-water with and without surfactant in the aqueous phase. Additionally, the presence of drug was explored via simulations. In some cases, the inclusion of drug affects the thermodynamics of Janus particle formation. For example, the introduction of 5% w/w griseofulvin was found to significantly alter the interfacial tensions of the system, whereas the same mass fraction of curcumin does not. Simulation results were experimentally validated. The multitude of surfactant choices and drug compounds currently available makes it impossible to experimentally test each one to find the optimal formulation. Determining the effects of different drugs and surfactants on interfacial tensions and corresponding particle morphology via atomistic modeling prior to experimentation enables rational design of Janus particles.
ABSTRACT Catalyst impregnation is one of the most crucial steps for preparing industrial catalysts. In this process, metal salts or complexes are typically dissolved in an aqueous solution and contacted with a porous oxide catalyst... more
ABSTRACT Catalyst impregnation is one of the most crucial steps for preparing industrial catalysts. In this process, metal salts or complexes are typically dissolved in an aqueous solution and contacted with a porous oxide catalyst support such as alumina (Al2O3) or silica (SiO2). During a contact time of typically 30-60 minutes the metal is adsorbed from the solution onto the high surface area support. The catalyst is dried and further pretreated to transform the metal from its precursor state into its active form. Generally, the process of impregnation is performed in rotating vessels with one or more nozzles that distribute the solution with the metal precursor into the catalyst support. This study aims to optimize the impregnation process by studying the fundamental process of water absorption to and transfer within particles using a combination of designed experiments and discrete element method (DEM) based mechanistic modeling. A Patterson-Kelly double cone blender with a retrofitted impregnator featuring a central spray nozzle was used for experimental study. The catalyst support in the form of spherical beads of &amp;gamma-Alumina was impregnated using 1M Copper (II) Nitrate Trihydrate solution. Experiments were ten minutes in duration; each minute seven samples were removed from the catalyst bed using a disposable powder thief for a total weight of approximately two grams bed; samples were 3.5 cm apart. Samples were dried and weighed for water content. Subsequently, samples were soaked in 10 mL of 0.1 M HCl for 12 hours to remove the metal, the resulting solutions were then tested for copper concentration using an Ocean Optics (USA) UV-Spectrophotometer. Three flow rates (1.5, 2.5 and 5L/Hr) were used for impregnation. It was found that the water and metal distribution was more uniform at low spray rates. Density segregation was also observed with heavier particles (due to water impregnation) preferring the center region of the bed. The computational study using discrete element method was performed using EDEM (DEMSolutions Inc.). The contact model was modified so that there were two groups of particles, the Alumina particles and the smaller water droplets which form a spray. The water droplets add their weight to the Alumina particles as soon as they hit them. Once supersaturated, the Alumina particles can transfer water to any unsaturated particle. The DEM simulations agree with the experimental findings and suggest that lower flow rates produce a more uniform moisture distribution in the bed.
In the manufacturing of heterogeneous catalysts, the impregnation of active metals onto a porous catalyst support is a crucial preparation step that may significantly affect the activity and selectivity of the resulting catalysts... more
In the manufacturing of heterogeneous catalysts, the impregnation of active metals onto a porous catalyst support is a crucial preparation step that may significantly affect the activity and selectivity of the resulting catalysts particles. In a typical dry impregnation (pore filling or incipient wetness impregnation) process, metal solutions are sprayed over a particulate bed in a mixing vessel until the pore volume is reached. Current scale-up practices lead to poor fluid distribution and a wider particle size distribution. There are two issues to consider when scaling up the process: the balance between inertial and gravitational forces and the size and magnitude of the spray flow pattern as a function of system scale. In this work, we use a Discrete Element Method (DEM) and work with two dimensionless numbers, Froude number (Fr) and Spray Flux number ( Ψ ), to characterize the scale up of the system. Froude number measures the ratio of inertial force to gravitational force. A go...
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Research Interests: Mechanical Engineering, Chemical Engineering, Cryogenics, Mass Transfer, Manufacturing, and 15 moreHeat Transfer, Granular Flow, Discrete Element Method, Heat Transport, Catalyst, Drying, Fabrication, DEM, Heat transfer coefficient, High performance, Granular Materials, Granular Material, Granular Media, Experimental Validation, and Material Properties
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When a binary mixture of granular materials, differing in shape or size, is poured into a quasi-two-dimensional silo, segregation of the mixture is observed. Depending on the size ratio d2/d1 of the species, the mixture segregates... more
When a binary mixture of granular materials, differing in shape or size, is poured into a quasi-two-dimensional silo, segregation of the mixture is observed. Depending on the size ratio d2/d1 of the species, the mixture segregates completely or partially into the pure species. To study the partial-segregation effect we propose a theoretical model based on the work of Boutreux and de Gennes [J. Phys. I 6, 1295 (1996)] but we introduce more realistic collision functions. To compare the partial- and complete-segregation effects, we also discuss calculations for the complete-segregation model proposed by Makse [Phys. Rev. E 56, 7008 (1997)]. Our experiments confirm the analytical solutions for both types of segregation. We find that the transition from complete segregation to partial segregation appears as the size ratio of the species is decreased below a critical value, which is found to be d2/d1 approximately 1.4 for our system. Our experimental and analytical studies predict the regime for applicability of both partial- and complete-segregation models in terms of the size ratio of the species and the respective model parameters.
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We report molecular simulation studies on the interaction forces between silica nanoparticles in supercritical carbon dioxide at 318 K. Our goal is to find a better understanding of the interparticle solvation forces during rapid... more
We report molecular simulation studies on the interaction forces between silica nanoparticles in supercritical carbon dioxide at 318 K. Our goal is to find a better understanding of the interparticle solvation forces during rapid expansion of supercritical solutions. The parameters for interatomic potentials of fluid-fluid and solid-fluid interactions are obtained by fitting our simulations to (i) experimental bulk CO(2) phase diagram at a given temperature and pressure and (ii) CO(2) sorption isotherms on silica at normal boiling and critical temperatures. Our simulations show that the interaction forces between particles and supercritical CO(2) at near-critical pressure of p=69 atm (i.e., slightly below critical condition) reaches a minimum at distances of 0.5-0.8 nm between the outer surfaces of the particles and practically vanishes at distances of approximately 3 nm. The attraction is most prominent for densely hydroxylated particle surfaces that interact strongly with CO(2) via hydrogen bonds. The effective attraction between silica and CO(2) is significantly weaker for dehydroxylated particles. We also compared fluid sorption and interparticle forces between supercritical CO(2) and subcritical nitrogen vapor, and our results showed qualitative similarities, suggesting that the CO(2) configuration between the particles resembles a liquidlike junction.
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It is currently of great interest to the pharmaceutical industry to control the size and agglomeration of nano- and micro-particles for the enhancement of drug delivery. Typically, surfactants and polymers are used as additives to... more
It is currently of great interest to the pharmaceutical industry to control the size and agglomeration of nano- and micro-particles for the enhancement of drug delivery. Typically, surfactants and polymers are used as additives to interact with and stabilize the growing crystal surface, thus controlling size and agglomeration; however, selection is traditionally done empirically or using heuristics. The objective of this study was to use molecular dynamic simulations to investigate and predict additive interactions, and thus, evaluate the stabilization potential of individual and multiple additives on the surface of the model drug fenofibrate. Non-ionic surfactant Tween 80, anionic surfactant sodium dodecyl sulfate (SDS), and polymers hydroxypropyl methylcellulose (HPMC) and Pullulan were evaluated individually on three distinct crystal surfaces [(001), (010), (100)], as well as in surfactant-polymer combinations. HPMC was determined to have the strongest interaction with the surfaces of the fenofibrate crystal, and therefore, was predicted to be the most effective individual additive. A mixture of HPMC with SDS was determined to be the most effective mixture of additives, and more effective than HPMC alone, indicating a synergistic effect. The predictions of mixed additives indicated a relative order of effectiveness as follows: HPMC-SDS&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;HPMC-Tween 80&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;Pullulan-Tween 80&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;Pullulan-SDS. The simulations were subsequently validated by an anti-solvent crystallization of fenofibrate where it was found that HPMC individually, and a mixture of HPMC-SDS, produced the smallest and most stable crystals, as measured by laser diffraction; this, in combination with measurements of the crystal growth rate in the presence and absence of additives confirmed the results of the simulations.
Research Interests: Crystal Growth, Interaction, Atomistic Simulation, Drug delivery, Crystallization, and 15 morePolymers, Pharmaceutical industry, Glucans, Hydroxypropyl Methylcellulose, Agglomeration, Anionic Surfactant, Excipients, Drug Stability, Molecular Dynamic Simulation, Fenofibrate, Molecular Structure, Methylcellulose, Sodium Dodecyl Sulfate, Laser diffraction, and Pharmacology and pharmaceutical sciences
This communication correlates two empirical methods; flow in a rotating drum with flow in bench scale hoppers. The flow characteristics of 13 cohesive granular materials were studied in the gravitational displacement Rheometer (GDR) and... more
This communication correlates two empirical methods; flow in a rotating drum with flow in bench scale hoppers. The flow characteristics of 13 cohesive granular materials were studied in the gravitational displacement Rheometer (GDR) and compared to flow in hoppers of varying angle and discharge diameter at fixed temperature and moisture conditions. The GDR proved to be an effective and convenient
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Research Interests: Engineering, Environmental Engineering, Chemical Engineering, Civil Engineering, Lattice Theory, and 15 moreLinear Elasticity, Drug delivery, Applied Economics, Interfacial Tension, Droplets, CHEMICAL SCIENCES, Dissipative particle dynamics, Biological systems, Finite Volume Method, Chemical Engineering Science, Cell Wall, Droplet Size Distribution, Coarse Grained Soil, Blood Vessel, and Dynamic equilibrium
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Atherosclerosis is a condition resulting from the accumulation of oxidized low-density lipoproteins (oxLDLs) in arterial walls. Previously developed macromolecules consisting of alkyl chains and polyethylene glycol (PEG) on a mucic acid... more
Atherosclerosis is a condition resulting from the accumulation of oxidized low-density lipoproteins (oxLDLs) in arterial walls. Previously developed macromolecules consisting of alkyl chains and polyethylene glycol (PEG) on a mucic acid backbone, termed nanolipoblockers (NLBs) are hypothesized to mitigate the uptake of oxLDL by macrophage scavenger receptors. In this work, we developed a coarse grained model to characterize the interactions between NLBs with a segment of human scavenger receptor A (SR-A), a key receptor domain that regulates cholesterol uptake and foam cell conversion of macrophages, and studied NLB ability to block oxLDL uptake in PBMC macrophages. We focused on four different NLB configurations with variable molecular charge, charge location, and degree of NLB micellization. Kinetic studies showed that three of the four NLBs form micelles within 300 ns and of sizes comparable to literature results. In the presence of SR-A, micelle-forming NLBs interacted with the receptor primarily in an aggregated state rather than as single unimers. The model showed that incorporation of an anionic charge near the NLB mucic acid head resulted in enhanced interaction with the proposed binding pocket of SR-A compared to uncharged NLBs. By contrast, NLBs with an anionic charge located at the PEG tail showed no interaction increase as NLB aggregates were predominately observed to interact away from the oxLDL binding site. Additionally, using two different methods to assess the number of contacts that each NLB type formed with SR-A, we found that the rank order of contacts coincided with our experimental flow cytometry results evaluating the ability of the different NLBs to block the uptake of oxLDL.
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Adsorbed noble-gas atoms donate (on the average) a fraction of an electronic charge to the substrate metal. The effect has been experimentally observed as an adsorptive change in the electronic work function. The connection between the... more
Adsorbed noble-gas atoms donate (on the average) a fraction of an electronic charge to the substrate metal. The effect has been experimentally observed as an adsorptive change in the electronic work function. The connection between the effective net atomic charge and the binding energy of the atom to the metal is theoretically explored.