Entrapment Process Research Articles

Potential carriers for biofertilizers: microstructural and entrapment properties

Abstract The suitability of carrier materials for the entrapment of bacteria is an important factor in developing biofertilizers as it determines their functional properties during use and storage. This study examines the microscopic structure and entrapment properties of several potential carriers for biofertilizers. The carriers studied included rice straw, sago dregs, cassava dregs, gum, carrageenan, pea fiber, and carboxymethyl cellulose (CMC), all in powder form. The entrapment process was carried out by mixing the bacterial solution (10%) of Rhizobium, Azotobacter, Bacillus, and Methylobacterium with the carrier material by spraying and shaking followed by air drying. CMC and carrageenan exhibited a swollen structure when mixed with a bacterial solution, forming lumps. Gum, pea fiber, sago dregs, and cassava dregs swelled slightly, while rice straw demonstrated a non-swollen fibrous structure. The incorporated bacteria appeared entrapped inside the lumps and/or adhered to the surface of the lumps or fibrous particles. The largest number of bacteria was found in gum (log10 6 – log10 7) and pea fiber (log10 4 to – log10 7), followed by cassava dregs (log10 2 – log10 7), CMC (log10 2 – log10 6), sago dregs (log10 5) and rice straw (log10 3 – log10 4), while no bacteria was observed in carrageenan. Most bacteria survived in the carrier with swelling properties and loose structures. In conclusion, the microstructure of carrier materials provides information that can describe bacterial entrapment properties. This study gives important insight useful in formulating carrier materials for developing biofertilizers.

Computational analysis of radon progeny deposition patterns in the human respiratory system

In the last year, the use of computational fluid dynamics (CFD) techniques has gained prominence as a powerful tool for modeling biological phenomena and influencing the design of biomedical devices. In this study, we utilized a computational fluid dynamics (CFD) model to simulate airflow and the deposition of aerosol particles within the human respiratory tract. To achieve this, we meticulously constructed a 3D model of the human tracheobronchial airways using SolidWorks software. Our computational analyses encompassed a range of breathing conditions, ranging from 15 to 60 (L/min). Through the application of discrete phase modeling (DPM), we investigate the behavior of two-phase flow dynamics. Our focus lies in the examination of aerosol particles, with diameters ranging from 1 to 10 (μm), in order to evaluate the influence of aerosol particle size on deposition rates. Our findings encompass velocity contour maps, deposition rates of aerosol particles, and insights into the process of aerosol particle entrapment at various locations within the respiratory tract. Our study reveals a direct correlation between higher inhalation rates and larger aerosol particle sizes, resulting in increased deposition rates. Additionally, we observe a heightened deposition of aerosol-particles at bronchi region. These computational results hold significant value in estimating the distribution of doses resulting from radon progeny exposure in distinct anatomical regions of the respiratory tract.

The compression-only behavior of coated microbubbles in a wall restricted flow.

The impact that the onset of the compression-only behavior of lipid shelled contrast agents bears on their dynamic interaction with a rigid wall under acoustic disturbances is investigated numerically in the context of axisymmetry. Wall presence is seen to not significantly affect the onset of compression-only since it only reduces the time frame required to trigger the effect. The standoff distance from the wall bears no significant effect on the amplitude threshold except that as it is reduced, it favors asymmetry by altering the compressed buckled shape around which the bubble oscillates. Above the amplitude threshold for parametric shape mode excitation, the onset of compression-only in the vicinity of a rigid wall typically interrupts the process of entrapment by reversing the direction of motion via the positive pressure drug that is generated as a result of the emerging concave upwards buckled shapes. Below this amplitude threshold, symmetric shapes or asymmetric shapes that are concave downwards continue to translate towards the wall where they perform saturated trapped pulsations around nearly spherical flattened or concave downwards buckled shapes. The latter shapes perform compression-only type pulsations and arise on the longer time scale required for the destabilization of the nearly spherical initially trapped shapes. Phase diagrams are constructed identifying regions of trapped pulsations, compression-only response, and microbubble collapse, in the parameter space defined by sound amplitude and shell viscoelastic properties.

Nutrients removal by high-rate activated sludge and its effects on the mainstream wastewater treatment

Conventional wastewater treatment technologies often involve energy-intensive processes, creating a need for more sustainable and efficient solutions. The high-rate activated sludge (HRAS) process, characterized by short sludge and hydraulic retention times, demonstrates proficient chemical oxygen demand (COD) removal with minimal oxidation and energy expenditure, positioning it as a promising approach for achieving energy-efficient wastewater treatment.This study addresses the nutrient removal efficiency of a demonstration-scale pilot plant (35 m3·d-1) operating for 497 days. It investigates the correlation between nutrient removal efficiencies, COD fractions, and suspended solids removal in real wastewater, without primary clarification.The process consistently achieves average removal efficiencies: 23% for total Kjeldahl Nitrogen (TKN), 7.3% for N-NH4+, 56% for total phosphorus (TP), and 11% for P-PO43-. The superior TP removal is attributed to the high particulate influent fractions (81%), underscoring the pivotal role of settling efficiency. The HRAS process effectively controls TP peak values, although its influence on TKN peaks is somewhat limited. This underscores HRAS's proficiency in mitigating phosphorus spikes in influent wastewater. In contrast, the lower TKN removal is associated with diminished particulate inlet fractions (46%).Nutrient removal mechanisms in HRAS mirror those of COD, primarily revolving around adsorption and entrapment processes, as opposed to conventional biological pathways. It also highlights the independence of oxidized COD, nitrogen, and phosphorus removal. Furthermore, a comprehensive analysis of the COD/TKN within HRAS effluent unveils the presence of a short-cut nitrification/denitrification process, supplemented by Anammox in the sidestream, as the most suitable pathway for downstream nitrogen removal. This revelation signifies a substantial advancement and positions HRAS as a potential initial stage of a partial nitritation/Anammox (PN/A) process within mainstream wastewater treatment.

Gas entrapment and pore formation in metal droplet-based 3D printing

Gas entrapment behavior during metal droplet deposition tends to form pore defects and discourages interfacial bonding between droplets, resulting in lower densities and poorer performance of printed components. Moreover, the gas entrapment process is influenced by the interaction of gas-liquid two-phase flow and non-isothermal solidification, which makes the interfacial behavior of droplets challenging to identify. Therefore, gaining insight into the gas entrapment behavior and pore formation mechanism at the bottom of molten droplets is essential. This paper established a model of two-dimensional axisymmetric numerical by combining the fluid volume tracking method and heat transfer solidification model. Single metal molten droplet deposition experiments verified the accuracy of the model. The evolution of solid phase fraction, velocity field, pressure field, and contact surface heat flux during the deposition of the molten droplet at low Weber numbers (0.1-10) was investigated comprehensively. The mechanisms of gas entrapment and pore formation were revealed. The effects of molten droplet impact velocity, contact angle, and surface tension on the gas film evolution process and pore morphology were further investigated. The results show that decreasing the droplet impact velocity causes capillary waves to contact the substrate surface and form local solidification, allowing the gas disk to evolve into central and two peripheral pores. Moreover, the pore breaks away from the substrate and remains inside the droplet when decreasing the droplet contact angle to 50°. Furthermore, the rate of gas disk retraction decreases as surface tension reduces, which may accentuate the resistance effect of the contact surface solidification layer on the gas disk retraction, thus changing the final morphology of the pores. These findings elucidate the mechanism of pore formation at the bottom of molten metal droplets and further understand the interfacial behavior of droplets in 3D-printed metal structures.

Heterogeneous Electrocatalytic Oxygen Evolution Reaction by a Sol-Gel Electrode with Entrapped Na3 [Ru2 (μ-CO3 )4 ]: The Effect of NaHCO3.

The Na3 [Ru2 (μ-CO3 )4 ] complex is acting as a water oxidation catalyst in a homogeneous system. Due to the significance of heterogeneous systems and the effect of bicarbonate on the kinetic, we studied the bicarbonate effect on the heterogeneous electrocatalyst by entrapping the Na3 [Ru2 (μ-CO3 )4 ] complex in a sol-gel matrix. We have developed two types of sol-gel electrodes, which differ by the precursor, and are demonstrating their stability over a minimum of 200 electrochemical cycles. The pH increases affected the currents and kcat for both types of electrodes, and their hydrophobicity, which was obtained from the precursor type, influenced the electrocatalytic process rate. The results indicate that NaHCO3 has an important role in the catalytic activity of the presented heterogeneous systems; without NaHCO3 , the diffusing species is probably OH- , which undergoes diffusion via the Grotthuss mechanism. To the best of our knowledge, this is the first study to present a simple and fast one-step entrapment process for the Na3 [Ru2 (μ-CO3 )4 ] complex by the sol-gel method under standard laboratory conditions. The results contribute to optimizing the WSP, ultimately helping expand the usage of hydrogen as a green and more readily available energy source.

Estimation of the volume of trapped gas and the use of sidetracking as a method of its additional recovery using hydrodynamic modeling in the tNavigator software product

The problem of extracting trapped gas from flooded gas deposits has become increasingly important over the past decades. At the end of the development of gas fields, the problem arises of low-pressure gas remaining in the reservoir, which, due to a number of geophysical and geological factors, can be trapped. Removing trapped gas becomes a difficult and costly process. The article considers the process of gas entrapment in the reservoir as a result of the introduction of bottom water into the deposit of one of the real fields in Western Siberia. An algorithm for calculating the volumes of trapped gas is described. The trapped gas volume was estimated using a hydrodynamic model in the tNavigator software product. The dependence of the trapped gas volumes on the cell sizes in the model is estimated.

Electroosmosis-driven heat transfer in Jeffrey fluid flow through tapered porous channel

The present research offers a physical explanation for the intricate movement in porous media. It details the electroosmotic factors that drive momentum transmission and regulate the mixing process, as well as the flow and thermal properties such as velocity, flow rate, streamlines, pressure, and temperature. This model is founded on an investigation of non-Newtonian fluid flow by electroosmosis in a tapering duct influenced by porosity. Modeling the momentum, continuity, and heat equations involves combining Gauss’s law, the Poisson equation, Darcy’s resistance, and the Jeffrey model equation. To recommend a physical interpretation, exact solutions are calculated for partial differential equations. Examining the controlling parameters enables the identification of the appropriate fluctuations in the temperature field, velocity field, and pressure gradient. The governing equations are solved using approximations for low Reynold number, long wavelength, and Debye–Huckel linearization. For the purpose of demonstrating thermal analysis, contours are utilized to discuss the entrapment process and temperature profile fluctuations caused by various factors. In addition, a comparison is made between electroosmotic flow in uniform and nonuniform channels for intrauterine fluid flow and other industrial applications, such as the transmission of industrial fluids under complex regimes for a variety of thermal systems.

Transient simulation of slag entrapment in a tundish

A transient multiphase flow model is established by solving the heterogeneous dynamic equation to simulate the process of the slag entrapment in the tundish, which can provide data for the trial production to reduce the tundish residue on the premise of ensuring no slag entrapment. A numerical simulation of critical slag entrapment height of 60 t tundish under different steel throughputs is analyzed, and the following conclusions are obtained: when the steel throughput is 3.5 t/min, 4.5 t/min, 5.5 t/min, and 6.4 t/min, the critical time of the risk of slag entrapment are 1042 s, 691 s, 561 s, and 476 s after casting end, respectively. The heights of slag entrapment are 186.9 mm, 202.9 mm, 220.5 mm, and 222.5 mm, and the heights without slag entrapment are 202.4 mm, 214.6 mm, 236.1 mm, and 238.0 mm with the throughput of 3.5 t/min, 4.5 t/min, 5.5 t/min, and 6.4 t/min.

Numerical Investigation of Air Entrapment Dynamics for High-Speed Thermal Spraying

For thermal spraying, bubble entrapments are highly undesired, as this would lead to pores in the final coating and lower its adhesion quality. This understanding warrants an investigation of the process behind their formation. Nevertheless, the air entrapment process is difficult to study via experimental methods since molten droplets are always opaque and hard to visualize. Most numerical models are focused on air entrapment at the moment of impact, which could only explain the pores observed around the center of the splat. Here, in this paper, the air entrapment of a micron-sized molten nickel droplet impacting on a stainless-steel substrate is numerically studied. The results show that, besides the air entrapped during the high-speed impacting (impacting air bubbles/IM bubbles), bubbles may also be entrapped due to the fallback of the pointed-out finger on the edge during the spreading process (spreading air bubbles/SP bubbles). The number and size of the entrapped SP bubbles are related to the solidification rate and spreading rate. Therefore, both low (50 m/s) and high (200 m/s) impacting speeds could achieve an entrapped bubble ratio that is about 10% lower than that of a medium one (100 m/s). However, the formed coating is thick for low impacting speeds, and the low entrapped bubble ratio is obtained due to the cut-off of the peripherical fingers, which is actually unwanted.

Preparation of entrapment-based microcolumns for analysis of drug-humic acid interactions by high-performance affinity chromatography

Reversible interactions between drugs and humic acid in water can be an important factor in determining the bioavailability and effects of these pharmaceuticals as micropollutants in the environment. In this study, microcolumns containing entrapped humic acid were used in high-performance affinity chromatography (HPAC) to examine the binding of this agent with the drugs tetracycline, carbamazepine, ciprofloxacin, and norfloxacin. Parameters that were varied to optimize the entrapment of humic acid within HPLC-grade porous silica included the starting concentration of humic acid, the mass ratio of humic acid vs silica, and the method of mixing the reagents with the support for the entrapment process. The highest retention for the tested drugs was obtained when using supports that were prepared using an initial humic acid concentration of 80 mg mL−1 and a humic acid vs silica mass ratio of 600 mg per g silica, along with preincubation of the humic acid with hydrazide-activated silica before the addition of a capping agent (i.e., oxidized glycogen). Characterization of the humic acid support was also carried out by means of TGA, FTIR, SEM, and energy-dispersive X-ray spectroscopy. The binding constants measured by HPAC for the given drugs with entrapped Aldrich humic acid gave good agreement with values reported in the literature under similar pH and temperature conditions for this and other forms of humic acid. Besides providing valuable data on the binding strength of various drugs with humic acid, this work illustrates how HPAC may be used as an analytical tool for screening and characterizing the interactions of drugs and man-made contaminants with humic acid or related binding agents in water and the environment.

A numerical study of air entrapment during the droplet impact on a solid substrate

AbstractA numerical investigation is conducted to study the air entrapment phenomenon when two different liquids such as water and diesel droplet are impacted on the solid surface. The beginning of the air entrapment process was observed during droplet impact on a solid substrate forming a dimple underneath the droplet. The air film thus trapped underneath the droplet started evolving into the air bubble. This journey of evolution mainly comprises phases like an inertial retraction of air film, contraction, and pinch‐off of the secondary droplet inside the air bubble for a water droplet impact case. The volume of fluid approach has been utilized to track the progress of air film evolution. The influence of surface wettability has been observed on the evolution of air film into the air bubble by taking four different values of contact angle pertaining to the hydrophilic surface (θ = 10° and 35°) and hydrophobic surface (θ = 90° and θ = 120°). The air bubble was found to get detached from the substrate for the hydrophilic surface (θ = 35°) and observed to remain attached to the substrate for the hydrophobic surface. The variation of pressure underneath the droplet was also investigated as the droplet reaches the substrate. The effect of surface tension has been studied on the evolution of air film by impacting the diesel droplet on the same substrate keeping the same wettability condition (θ = 35°). The lower surface tension of the diesel droplet as compared to the water droplet delayed the process of air film evolution and consequently decreases the retraction speed of air film. Also, the air bubble remains attached to the surface. Furthermore, the air bubble detaches from the surface for an even higher wettability condition (θ = 10°). Thus surface wettability and surface tension become two important factors governing the development of entrapped air film and bubble elimination in many practical applications.

An approach for quantification of the heterogeneity of DNAPL source zone geometries

Many studies have investigated the migration and entrapment processes of source zones from dense non-aqueous phase liquid (DNAPL) contamination under different conditions. However, the characterization of occupying area by source zone (or source shape) in water-saturated aquifers is still rudimentarily considered. In this study, we demonstrated this issue (1) by providing a brief review of existing approaches for source shape consideration, (2) by proposing an approach with simple shape parameters based on the non-uniformity of source widths, and (3) by providing exemplary applications of our proposed approach on shapes already published in previous research works. Our literature review suggested that the source zone in mathematical approaches is generally characterized as simple geometrical shapes (arbitrary lines or rectangles) or system-defined parameters that contrast to complex and discontinuous shapes observed in the real world. But the characterization of such complex shapes is still not possible with acceptable efforts. Therefore, we proposed an approach to parameterize the source shape by considering the variation of width and midpoints over the depth of the entire source zone and formulate four parameters based on population statistics (mean, standard deviation). To illustrate the suitability of our approach, we applied it to the results of lab experiments, and by analyzing these complex shapes, we highlighted the potential for improving the characterization techniques of non-uniformity of the source zones.

Large-scale paleo water-table rise in a deep desert aquifer recorded by dissolved noble gases

• Very high amounts of dissolved noble gases were identified in a deep desert aquifer. • Large water table fluctuations during past pluvial periods are reconstructed. • Hydrogeological settings highly affect the air entrapment and dissolution process. • Similar excess air dissolution patterns are identified in distinct desert aquifers. Illuminating past hydrological and climatological conditions in arid regions may provide insights into future trends in groundwater availability. The main objective of this study is to explore paleorecharge processes in the deep regional Nubian Sandstone Aquifer (NSA), which stretches below the hyperarid deserts of the Sinai Peninsula (Egypt) and the Negev (Israel), using dissolved noble gas data. Extremely high amounts of dissolved excess air (Ne concentrations up to 4 × solubility equilibrium) were observed in the ancient ( 81 Kr-depleted) groundwater that was recharged during past pluvial epochs in the basin. The observed unique excess air signal and the clear spatiotemporal structure of the noble gas compositions in the aquifer are hypothesized to reflect two major characteristics of the groundwater system: (a) large-scale, long-term rises in the water table that facilitate the entrapment and dissolution of air bubbles under increased hydrostatic pressure, and (b) the geological settings in the southern recharge area in Sinai, including an almost horizontal position of the layers and intercalation of low-permeability rock formations within the aquifer, which inefficiently reject air bubbles from groundwater, thereby allowing for substantial entrapment of bubbles that dissolve as the water table rises. Enhanced dissolution of entrapped air was also observed in other paleo-groundwater-containing regional sandstone aquifers across North Africa, which, together with the recent findings from the NSA, suggest that large-scale water table fluctuations have likely extensively occurred during past pluvial periods over these (and possibly other) arid regions. A preliminary assessment of noble gas recharge temperatures (NGTs) indicates an apparent decoupling of surface and water table temperatures in the case of deep aquifers with a thick (hundreds of m) unsaturated zone. This observed decoupling calls for a re-evaluation of previously obtained NGT records and a need for future work to consider the modification of NGTs due to soil air fractionation and geothermal heating of the underlying deep unsaturated zones.

Thermosensitive poly(N-isopropylacrylamide)-grafted magnetic-cored dendrimers for benzene uptake

A series of thermosensitive and magneto-responsive dendrimers was synthesized based on magnetic-cored dendrimers (MCD) and carboxylic end-capped poly(N-isopropylacrylamide) (PNIPAM) to obtain PNIPAM-g-MCD. Thermo-response profiles of the PNIPAM-g-MCD from dynamic light scattering within the temperature range of 25–45 °C indicated that the lower critical solution temperature (LCST) of the PNIPAM-g-MCD was 32 °C. The physical size of the PNIPAM-g-MCD decreased as the temperature increased above the LCST. The initial hydrodynamic size of the PNIPAM-g-MCDs at 25 °C was 298.6 nm and reached 226.4 nm at 45 °C upon heating. Adsorption of benzene onto the PNIPAM-g-MCD at 25 °C was assessed, and the results showed that hydrophobic benzene was included within the internal cavities of lipophilic PNIPAM-g-MCD to maintain a thermodynamically stable state. Entrapment effects of the PNIPAM-g-MCD were confirmed at 45 °C, and the removal efficiency of benzene increased considerably to 50% when benzene was adsorbed, and the entrapment process was added. The shrunken PNIPAM terminal groups aggregated and trapped benzenes within the cavities of PNIPAM-g-MCD to prevent escape into the aqueous solution. Un-trapped benzene was removed through coalescence with PNIPAM-g-MCD because hydrophobic interactions prevailed with increasing temperature. PNIPAM-g-MCD were also able to form emulsions below the LCST and disrupted emulsions above the LCST in oil-water emulsions.

Air entrapment of a neutral drop impacting onto a flat solid surface in electric fields

When a charge neutral drop impacts on a flat solid substrate, a small air bubble is always trapped underneath due to the lubrication pressure coming from the viscous stress in the squeezed air film. Herein we find experimentally and numerically that the process of the air entrapment and the initial contact state of the drop with the substrate can be profoundly altered via an external electric field. In an electric field, the induced electric stresses at the bottom of the drop increase drastically right before the drop contacts the substrate, which acts against the lubrication pressure, resulting in reduced initial contact radius and air bubble size. When the external electric field reaches a critical value, the electrical stress accelerates the flow near the bottom of the drop and generates a conical tip quickly instead of a dimple, resulting in a centre contact and eliminating the air bubble entrapment. Based on the dipole mirror charge model, we find the dimensionless strength of critical electric field scales with the square root of capillary number based on the air viscosity. This scaling law of the critical electric field for eliminating the air bubble entrapment is verified experimentally and numerically. This work may offer a new way to mitigate defects caused by air bubble entrapment for inkjet printing and droplet-based additive manufacturing.

Entrapment processes in the emigration regime: The presence of migration bans and the absence of bilateral labor agreements in domestic work in Nepal

Abstract This Article offers an integrated analysis of the combined effect of the presence of migration bans and the absence of BLAs in domestic work in the emigration regime of Nepal. It identifies, acknowledges, critiques, and contributes to the critical literature highlighting entrapment processes in labor relations and immigration regimes by demonstrating the presence of such in the emigration regime. Drawing on the empirical findings of a participatory action research (PAR) project conducted in Nepal, the Article demonstrates how restrictive emigration policies and practices entail entrapment processes constitutive of the existing historical, cultural, gendered, racialized, and classed constraints impacting the lives of Nepalese citizens. The Article contributes to the critical literature that seeks to advance migrants’ rights, arguing that experiencing, encountering and escaping entrapment processes in the emigration regime impacts their agency when navigating immigration regimes and labor relations. This contribution advances the existing efforts to establish oft-ignored emigration regimes as important epistemological sites of research, theorization, and intervention.

The Importance of the Geometry of the Down Sprue in the Gravity Casting Process.

This article presents the results of experiments on the optimization of down sprue geometry in the process of pouring sand molds. Theoretical assumptions and computer simulation tests are presented. The starting point was the theory and experience of gas entrapment caused mainly by a poorly designed gating system and the down sprue. Simulations were performed using Magmasoft software. First, initial studies were carried out to determine how the geometry (mainly the channel cross-section) of the sprue affects the problem, and then a detailed experiment was carried out on the so-called ‘short sprue’ version. The air entrapment process was analyzed, as were the parameters of the liquid alloy flow that passes through the analyzed channels. Nine geometric versions of the sprue were proposed and analyzed, and the results allowed us to conclude which sprue geometry is the best from the point of view of minimization of the gas entrapment problem.

Numerical simulation of slag entrapment process during the end of casting in tundish

ABSTRACT The slag entrapment process under two different initial conditions during the end of casting in tundish is studied. A 3D multiphase mathematical model was developed to simulate the slag entrapment behaviour. The critical slag entrapment time (t s) and the corresponding critical slag entrapment height (h cs) were predicted. The results show the h cs increases, the t s decreases as the casting speed increases, but their relationships are not linear. The influence of casting speed on the h cs in the range of 1.25–1.5 m min−1 is higher than other ranges. The h cs simulated from the steady flow field is higher than that from the static state. When the casting speed is 1.50 m min−1, the difference between the h cs calculated from two different initial conditions is the largest, reaching 9.83 mm (8.42%). The numerical simulation results are verified by a 1:2 scaled water model.

Periodic corner holes on the Si(111)-7×7 surface can trap silver atoms

Advancement in nanotechnology to a large extent depends on the ability to manipulate materials at the atomistic level, including positioning single atoms on the active sites of the surfaces of interest, promoting strong chemical bonding. Here, we report a long-time confinement of a single Ag atom inside a corner hole (CH) of the technologically relevant Si(111)-7×7 surface, which has comparable size as a fullerene C60 molecule with a single dangling bond at the bottom center. Experiments reveal that a set of 17 Ag atoms stays entrapped in the CH for the entire duration of experiment, 4 days and 7 h. Warming up the surface to about 150 °C degrees forces the Ag atoms out of the CH within a few minutes. The processes of entrapment and diffusion are temperature dependent. Theoretical calculations based on density functional theory support the experimental results confirming the highest adsorption energy at the CH for the Ag atom, and suggest that other elements such as Li, Na, Cu, Au, F and I may display similar behavior. The capability of atomic manipulation at room temperature makes this effect particularly attractive for building single atom devices and possibly developing new engineering and nano-manufacturing methods.