Conway–Maxwell–Poisson distribution: Difference between revisions
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A '''Pickering emulsion''' is an [[emulsion]] that is stabilized by solid particles (for example [[colloidal]] [[silica]]) which adsorb onto the [[interface (chemistry)|interface]] between the two [[phase (matter)|phase]]s. This type of [[emulsion]] was named after [[Percival Spencer Umfreville Pickering|S.U. Pickering]], who described the phenomenon in 1907, although the effect was first recognized by Walter Ramsden in 1903.<ref>{{cite journal | doi= 10.1039/CT9079102001| title=Emulsions}} S.U. Pickering, J. Chem. Soc. 91 (1907) 2001</ref><ref>{{cite journal | doi= 10.1098/rspl.1903.0034 | title=Separation of Solids in the Surface-layers of Solutions and 'Suspensions'}} W. Ramsden, Proc. R. Soc. London 72 (1903) 156</ref> | |||
If | If oil and water are mixed and small oil droplets are formed and dispersed throughout the water, eventually the droplets will coalesce to decrease the amount of energy in the system. However, if solid particles are added to the mixture, they will bind to the surface of the interface and prevent the droplets from coalescing, thus causing the emulsion to be more stable. | ||
Properties such as [[hydrophobicity]], shape, and size of the particle can have an effect on the stability of the emulsion. The particle’s [[contact angle]] to the surface of the droplet is a characteristic of the hydrophobicity. If the contact angle of the particle to the interface is low, the particle will be mostly [[wetted]] by the droplet and therefore will not be likely to prevent coalescence of the droplets. Particles that are partially hydrophobic (i.e. contact angle of approximately 90°) are better stabilizers because they are partially wettable by both liquids and therefore bind better to the surface of the droplets. The stabilization energy is given by | |||
:<math>\Delta E\ = \pi r^2\gamma_{OW}(1-|cos{\theta_{OW}}|)^2</math> | |||
where r is the particle radius, <math>\gamma_{OW}</math> is the interfacial tension, and <math>\theta_{OW}</math> is the contact angle. When the contact angle is approximately 90°, the energy required to stabilize the system is at its minimum.<ref>Velikov,K.P., Velev, O.D. "Stabilization of thin films, foams, emulsions and bifluid gels with surface-active solid particles" In ''Colloid Stability and '', T. F. Tadros, Ed., Wiley-VCH Publ. Weinheim, 2007, pp. 277-306</ref> | |||
Generally, the phase that preferentially wets the particle will be the continuous phase in the emulsion system. | |||
Additionally, it has been demonstrated that the stability of the Pickering emulsions can be improved by the use of amphiphilic "[[Janus particles]]", due to the higher adsorption energy of the particles at the liquid-liquid interface.<ref>Binks B. P. and Fletcher P. D. I., Particles Adsorbed at the Oil-Water Interface: A Theoretical Comparison between Spheres of Uniform Wettability and “Janus” Particles, Langmuir, 17, 4708-4710, 2001.</ref> This is evident when observing [[Emulsion Stabilization Using Polyelectrolytes|emulsion stabilization using polyelectrolytes]]. | |||
Homogenised milk is an example of a Pickering-stabilized emulsion. Casein (protein) units are adsorbed at the surface of milk fat globules and act as a surfactant. The casein replaces the milkfat globule membrane, which is damaged during homogenisation. | |||
Recently, using latex particles for Pickering stabilization and then fusing these particles to form a permeable shell, a new form of capsule, called a colloidosome, has been developed. According to the definition of Dinsmore, a colloidosome is a selectively permeable capsule that is composed of colloidal particles.<ref>Dinsmore AD, Hsu MF, Nikolaides MG, Marquez M, Bausch AR, Weitz DA, Colloidosomes: Selectively permeable capsules composed of colloidal particles SCIENCE '''298''':1006-1009, 2002</ref> Moreover, Pickering emulsion droplets are suitable templates for [[micro-encapsulation]] and the formation of closed/non-permeable capsules as well.<ref> http://library.tue.nl/catalog/FullBB.csp?WebAction=ShowFullBB&RequestId=15676365_2&Profile=Default&OpacLanguage=dut&NumberToRetrieve=50&StartValue=1&WebPageNr=1&SearchTerm1=2011.6.712621&SearchT1=&Index1=Index1&SearchMethod=Find_1&ItemNr=1 </ref> <ref> http://www.slideshare.net/jorissalari/joris-salari-phd </ref> | |||
Recently, it was shown that also dispersions consisting of phase-separated aqueous polymer solutions can be stabilised using Pickering stabilisation.<ref>Poortinga AT, Microcapsules from Self-Assembled Colloidal Particles Using | |||
Aqueous Phase-Separated Polymer Solutions LANGMUIR '''24''':1644-1647, 2008,</ref> | |||
==See also== | |||
*[[Janus particles]] | |||
*[[Emulsion]] | |||
*[[Micro-encapsulation]] | |||
==References== | |||
{{reflist}} | |||
[[Category:Chemical mixtures]] | |||
[[Category:Condensed matter physics]] | |||
[[Category:Soft matter]] | |||
[[Category:Drug delivery devices]] | |||
[[Category:Dosage forms]] |
Revision as of 20:23, 18 January 2014
A Pickering emulsion is an emulsion that is stabilized by solid particles (for example colloidal silica) which adsorb onto the interface between the two phases. This type of emulsion was named after S.U. Pickering, who described the phenomenon in 1907, although the effect was first recognized by Walter Ramsden in 1903.[1][2]
If oil and water are mixed and small oil droplets are formed and dispersed throughout the water, eventually the droplets will coalesce to decrease the amount of energy in the system. However, if solid particles are added to the mixture, they will bind to the surface of the interface and prevent the droplets from coalescing, thus causing the emulsion to be more stable.
Properties such as hydrophobicity, shape, and size of the particle can have an effect on the stability of the emulsion. The particle’s contact angle to the surface of the droplet is a characteristic of the hydrophobicity. If the contact angle of the particle to the interface is low, the particle will be mostly wetted by the droplet and therefore will not be likely to prevent coalescence of the droplets. Particles that are partially hydrophobic (i.e. contact angle of approximately 90°) are better stabilizers because they are partially wettable by both liquids and therefore bind better to the surface of the droplets. The stabilization energy is given by
where r is the particle radius, is the interfacial tension, and is the contact angle. When the contact angle is approximately 90°, the energy required to stabilize the system is at its minimum.[3]
Generally, the phase that preferentially wets the particle will be the continuous phase in the emulsion system.
Additionally, it has been demonstrated that the stability of the Pickering emulsions can be improved by the use of amphiphilic "Janus particles", due to the higher adsorption energy of the particles at the liquid-liquid interface.[4] This is evident when observing emulsion stabilization using polyelectrolytes.
Homogenised milk is an example of a Pickering-stabilized emulsion. Casein (protein) units are adsorbed at the surface of milk fat globules and act as a surfactant. The casein replaces the milkfat globule membrane, which is damaged during homogenisation.
Recently, using latex particles for Pickering stabilization and then fusing these particles to form a permeable shell, a new form of capsule, called a colloidosome, has been developed. According to the definition of Dinsmore, a colloidosome is a selectively permeable capsule that is composed of colloidal particles.[5] Moreover, Pickering emulsion droplets are suitable templates for micro-encapsulation and the formation of closed/non-permeable capsules as well.[6] [7]
Recently, it was shown that also dispersions consisting of phase-separated aqueous polymer solutions can be stabilised using Pickering stabilisation.[8]
See also
References
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- ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang S.U. Pickering, J. Chem. Soc. 91 (1907) 2001 - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang W. Ramsden, Proc. R. Soc. London 72 (1903) 156 - ↑ Velikov,K.P., Velev, O.D. "Stabilization of thin films, foams, emulsions and bifluid gels with surface-active solid particles" In Colloid Stability and , T. F. Tadros, Ed., Wiley-VCH Publ. Weinheim, 2007, pp. 277-306
- ↑ Binks B. P. and Fletcher P. D. I., Particles Adsorbed at the Oil-Water Interface: A Theoretical Comparison between Spheres of Uniform Wettability and “Janus” Particles, Langmuir, 17, 4708-4710, 2001.
- ↑ Dinsmore AD, Hsu MF, Nikolaides MG, Marquez M, Bausch AR, Weitz DA, Colloidosomes: Selectively permeable capsules composed of colloidal particles SCIENCE 298:1006-1009, 2002
- ↑ http://library.tue.nl/catalog/FullBB.csp?WebAction=ShowFullBB&RequestId=15676365_2&Profile=Default&OpacLanguage=dut&NumberToRetrieve=50&StartValue=1&WebPageNr=1&SearchTerm1=2011.6.712621&SearchT1=&Index1=Index1&SearchMethod=Find_1&ItemNr=1
- ↑ http://www.slideshare.net/jorissalari/joris-salari-phd
- ↑ Poortinga AT, Microcapsules from Self-Assembled Colloidal Particles Using Aqueous Phase-Separated Polymer Solutions LANGMUIR 24:1644-1647, 2008,