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Topic: Hygroscopic


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In the News (Fri 24 May 19)

  
  Hygroscopic Seeding
The collision and coalescence process among liquid drops is also an important contributor to rain formation in many mixed-phase clouds, and the presence of supercooled drizzle-drops and raindrops enhances the rate of formation of precipitation in supercooled portions of clouds as well.
One method of seeding clouds to enhance precipitation is to introduce hygroscopic particles (salts) which readily take on water by vapor deposition in a supersaturated cloudy environment.
He argued that hygroscopic seeding initiated precipitation lower in the clouds, which, in turn, was not dispersed horizontally as much as the unseeded clouds by vertical wind shears.
rams.atmos.colostate.edu /gkss_node4.html   (1034 words)

  
  Hygroscopic - Wikipedia, the free encyclopedia
A hygroscopic substance is a substance that absorbs water readily from its surroundings.
Hygroscopic components of bullets generally compensate by being readily ignitable by heat or a spark.
Hygroscopic materials play an important role in buildings; wood is a highly hygroscopic material.
en.wikipedia.org /wiki/Hygroscopic   (443 words)

  
 Container Handbook - Section 13.2.1 Classification of goods according to moisture behavior
Hygroscopic goods, which, as living organisms separated from the parent plant, may have a tendency towards self-heating as a result of respiration processes in addition to mold, rot or fermentation (cereals, seed, oil-bearing seeds/fruits).
Hygroscopic goods which, as a result of processing methods, have a tendency, due to their residual oil content and/or critical water contents, towards self-heating and frequently towards spontaneous combustion (expeller, fish meal, cereal products).
Hygroscopic goods which, during storage and transport, may be subject to postfermentation as a result of previous processing methods (fermentation), as well as to usual biochemical and physical changes (tea, green coffee beans, raw cocoa, leaf tobacco).
www.containerhandbuch.de /chb_e/scha/scha_13_02_01.html   (795 words)

  
 Suction receptacle with hygroscopic filter - Patent 4228798
A hygroscopic filter is mounted between the fluid receiving port and the vacuum source for absorbing and collecting fluid entrained in the medical suction system while continuously permitting the passage of air from the interior of the fluid collection receptacle through the suction port to the vacuum source.
Hygroscopic filter 10 is effective for preventing the passage of solid particles, bacteria, nutrients, bacteria and aerosol particles from passing into the vacuum source of the suction receptacle assembly.
Hygroscopic filter 10 is formed in a generally conical shape and is inserted within connector 120, such that the central axis of hygroscopic filter 10 is disposed substantially parallel to the direction of air flow out of fluid collection receptacle 12.
www.freepatentsonline.com /4228798.html   (7942 words)

  
 Hygroscopic properties   (Site not responding. Last check: 2007-10-30)
The hygroscopic properties of the aerosol particles control their water content and thereby the actual size of the individual aerosol particles at a given ambient relative humidity.
Clearly, the hygroscopic properties of the aerosol particles are of vital importance for both the direct and indirect forcing of global climate by aerosols.
Reversing the argument, the observed hygroscopic properties of aerosol particles can be used as a sensitive indicator for the ability of aerosol dynamics models to account for the aerosol evolution.
www.fysik.lu.se /eriksw/hygrosc.htm   (291 words)

  
 Jahrbuch-CD der MPG 2003 - Hygroscopic properties and wate
The hygroscopic behavior of Aitken particles were determined in situ in four size classes (50, 100, 150, 250 nm) with a Hygroscopic Tandem Differential Mobility Analyzer for relative humidities (RH) of 60% and 90%.
The measured average growth factors of the "more" hygroscopic fraction were found to be at 1.43, 1.49, 1.56, and 1.63 for particles with a size of 50, 100, 150, and 250 nm, respectively.
The water-soluble volume fraction of the particles was estimated using a hygroscopic model, assuming that the particles consist of ammonium sulfate with an insoluble core.
www.mpg.de /forschungsergebnisse/wissVeroeffentlichungen/archivListenJahrbuch/2002/75/publZIM391.html   (499 words)

  
 United States Patent Application: 0040167219
The method as claimed in claim 1, characterized in that the hygroscopic substance is carnitine, preferably L-carnitine, or a carnitine derivative or salt thereof, in that the organic acid is citric acid, (-)-hydroxycitric acid, vitamin C or another physiologically acceptable organic acid, and in that the metal hydroxide is magnesium hydroxide or calcium hydroxide.
This is the cause of a lack of storability of the solid substance and of simple powder mixtures prepared therefrom, and causes problems such as inadequate flowability during the further processing of pure solid carnitine or powdered mixtures containing carnitine in the human food, animal feed or drugs industry.
A hygroscopic substance means for the purposes of the present invention a substance which on storage under standard conditions is prone to conglutination or deliquescence through uptake of water.
appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=50&s1="20040167219".PGNR.&OS=DN/20040167219&RS=DN/20040167219   (4537 words)

  
 1996 Building Publications - Hygroscopic Stress and Failure of Coating/Metal Systems.   (Site not responding. Last check: 2007-10-30)
The values of hygroscopic stress obtained are correlated with the results of other tests such as electrochemical impedance spectroscopy, water uptake, adhesion, thermal analysis.
The role of the hygroscopic stress in organic coating degradation is discussed.
It is suggested that this stress participates in formation and/or enlargement of pathways in the coating, which enables the transport of the electrolyte to the metallic substrate provoking its corrosion.
fire.nist.gov /bfrlpubs/build96/art038.html   (120 words)

  
 Beach, Hygroscopic Breathers and Disposable Hygroscopic Breathers
The hygroscopic agent is partially reactivated by the dry air passing back through, thereby permitting longer periods between recharging or replacing.
Every Beach hygroscopic breather is manufactured in a durable, shock-absorbing clear plastic casing with resilient qualities to withstand the customary abuse associated with heavy manufacturing equipment.
Manufactured with a hygroscopic agent, Beach breathers have the capability to extract water vapor from the air as it is drawn through the unit.
www.jbii.com /AirFiltration/beach5.html   (848 words)

  
 [No title]   (Site not responding. Last check: 2007-10-30)
The decrease in hygroscopic water from pith to fibrovascular bundles to rind to root is thought to be due to increasing cell wall thickness, i.e.
If the upper limit to hygroscopic water at 10?Bx is taken to be 20.6%, assuming a small unstated stress level (Mangion and Player 1991); then, between the upper and lower limits, hygroscopic water must be defined in terms of temperature, solution concentration, (vapour or) pore pressure and effective stress in the fibre skeleton.
The reduction in hygroscopic water with increasing effective stress in the solid phase is perceived to be an effect caused by the displacement of loosely bound water as fibre particles approach.
www.ae.su.oz.au /~mcbain/papers/hygro.html   (3536 words)

  
 [No title]   (Site not responding. Last check: 2007-10-30)
a hygroscopic material dispersed in polyvinyl alcohol, or (2) a deliquescent material dispersed in an organic polymer, may further include a solid support, wherein a mixture of such materials is distributed across a surface of the solid support.
In another embodiment, a composition in accordance with the present invention may be formed by admixing the components comprising a hygroscopic material and a molten organic polymer to form a fluid admixture, and cooling the fluid admixture to a non-fluid or solid state.
More specifically, one or more of the hygroscopic materials of the present invention may be mixed with a suitable solvent to yield a solution, and the solution may then be used to impregnate the solid support by, for example.
www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/08784.010208&ELEMENT_SET=DECL   (5358 words)

  
 Hygroscopic composite material - Patent 4818602
This hygroscopic composite material retains its hygroscopicity for a long period of time by enhancing its humidity absorbing function by generating free water in the porous body and by discharging the free water.
In the case where the hygroscopic composite material absorbs humidity continuously under the condition of high temperatures, free water is generated in a large quantity in the porous body and the porous body cannot retain all the free water generated and thus water trickles outside the porous body.
The hygroscopic composite material was obtained by laminating filter paper (average diameter of micropores=20.mu.), instead of the porous body of Embodiment 1, to the humidity absorbing body of Embodiment 1.
www.freepatentsonline.com /4818602.html   (2528 words)

  
 Hygroscopic properties and water-soluble volume fraction of atmospheric particles in the diameter range from 50 nm to ...
Hygroscopic properties and water-soluble volume fraction of atmospheric particles in the diameter range from 50 nm to 3.8 μm during LACE 98
Hygroscopic properties of atmospheric aerosol particles in the Aitken, large, and giant particle range were studied during the Lindenberg Aerosol Characterization Experiment (LACE 98) in a rural area 80 km southeast of Berlin.
The corresponding estimated water-soluble volume fractions for the “more” hygroscopic particles were about 0.47, 0.52, 0.59, and 0.68, whereas the estimated water-soluble volume fractions of the “less” hygroscopic particles were in the order of 0.1.
www.agu.org /pubs/crossref/2002/2000JD000228.shtml   (610 words)

  
 Laboratory of Atmospheric Chemistry
Special emphasis is put on the investigation of the influence of organic species on the hygroscopic behaviour of inorganic salts, because atmospheric aerosols consist of mixtures of both substances.
The hygroscopic growth of pure citric acid particles was measured with the EDB at ETH (Figure 6) and with the H-TDMA at PSI (Figure 7).
First hygroscopicity measurements have already been performed at this facility where a gaseous precursor (1,3,5-trimethylbenzene) was exposed to photo-oxidation in an air/NOx mixture.
lac.web.psi.ch /LAC_Projects/organics/organics_home.html   (2032 words)

  
 [No title]   (Site not responding. Last check: 2007-10-30)
Hygroscopic and/or deliquescent drugs, by definition, are prone to experiencing these adverse effects when exposed to environments with even moderate humidity.
One such means consists of mixing levothyroxine sodium with a complexing agent such as polyvinylpyrrolidone, dissolving the resulting mixture in a polar organic solvent, adding a cellulose carrier such as microcrystalline cellulose, and drying the resulting mixture to yield a complex of levothyroxine sodium adsorbed on the cellulose carrier.
In a composition prepared by simple blending of a hygroscopic and/or deliquescent filler with a solid dispersion, such moisture absorption can lead to an increase in mass of the composition when the composition is exposed to high humidity.
www.wipo.int /cgi-pct/guest/getbykey5?KEY=04/60353.041007&ELEMENT_SET=DECL   (6033 words)

  
 HarvestBuild | Natural Building Science   (Site not responding. Last check: 2007-10-30)
Hygroscopicity is the ability of a material to absorb, store, and release water vapor.
Hygroscopicity is important because hygroscopic materials are able to moderate humidity levels throughout the seasons, maintaining a relatively constant indoor relative humidity level by absorbing water vapor during periods of high humidity and releasing water vapor during periods of low humidity.
Earth plaster is significantly more hygroscopic than concrete stucco—during the same time period, earth plaster can either absorb or release nearly five times the quantity of water vapor as concrete stucco; earth plaster is also ten times faster at absorbing or releasing the same quantity of water vapor as concrete stucco.
www.harvestbuild.com /hygroscopicity.html   (325 words)

  
 Characterization of Hygroscopic Swelling Behavior of Mold Compounds and Plastic Packages   (Site not responding. Last check: 2007-10-30)
Hygroscopic swelling behavior of mold compounds is analyzed by a novel experimental procedure using a whole-field displacement technique.
Large variation in moisture content at the virtual equilibrium state is observed, while the coefficient of hygroscopic swelling is shown to not vary significantly.
The hygroscopic strains must be considered for reliability assessment when a package is subjected to environments where the relative humidity fluctuates.
www.calce.umd.edu /articles/abstracts/2004/characterization.htm   (206 words)

  
 Hygroscopic aerosols
The swelling of hygroscopic particles with an increase in relative humidity generates haze particles that are significantly larger than their dry particle sizes.
Hänel (1976) proposed simple models for the growth of hygroscopic aerosols as a function of relative humidity based on theoretical considerations and observational evidence.
Generally, as the water uptake by the particles gets more and more important, the real and imaginary parts of their refractive index tend to decrease (Figure 3), as the real part of the refractive index of pure water is lower than the one associated to dry particles and its imaginary part is zero.
www.rap.ucar.edu /staff/tardif/CUprojects/ATOC5235/hygroscopic_aerosols.htm   (602 words)

  
 Honolulu Star-Bulletin Features /2004/12/15/
But brown sugar is very hygroscopic, so it holds on to moisture.
Actually, all sugar is hygroscopic, but brown sugar is more so than regular white, granulated sugar.
The final recipe used white sugar in combination with light brown sugar, which is less hygroscopic than the usual dark brown.
starbulletin.com /2004/12/15/features/story1.html   (1026 words)

  
 Hygroscopicity/Sorption behavior
A measure of the hygroscopicity of a product is consequently the magnitude of the increase or decrease in its water content as a function of relative humidity at a certain temperature.
Weakly hygroscopic products exhibit no or only a slight change in their water content as a consequence of variations in relative humidity.
Over a wide range, the product exhibits low hygroscopicity (anhydrous form); once the flow moisture point has been reached, the product rapidly absorbs large amounts of water vapor, causing it to deliquesce (hydrous form), as in the case of many crystalline products (salt, sugar, potash, tartaric acid).
www.tis-gdv.de /tis_e/misc/hygro.htm   (1229 words)

  
 Hygroscopic Material   (Site not responding. Last check: 2007-10-30)
For a hygroscopic substance, call it MX, there is a chemical equilibrium reaction of the general form: MX(H2O)n[solid or liquid]
MX[solid or liquid] + n H2O[vapor] At equilibrium the pressure of the water vapor has some value -- for efficient hygroscopic substances it is desirable that this be as small as possible.
Thus CaCl2 forms a hydrate, silica gel absorbs water, and liquid nitrogen (a very efficient hygroscopic agent) just condenses the water to a temperature of 77 K. At this temperature the vapor pressure of water is essentially zero.
www.newton.dep.anl.gov /askasci/chem00/chem00541.htm   (414 words)

  
 Hygroscopic properties of levoglucosan and related organic compounds characteristic to biomass burning aerosol particles
In this study, hygroscopic properties of five organic compounds (levoglucosan, D-glucose, and vanillic, syringic, and 4-hydroxybenozoic acids), which are major pyrolysis products of wood, were measured using a tandem differential mobility analyzer.
Levoglucosan, which is typically the most abundant species in wood burning aerosols, showed a significant hygroscopic growth for particles with a diameter of 100 nm.
Significant hygroscopic growth was also observed for D-glucose, whose growth factor is quite similar to that of levoglucosan.
www.agu.org /pubs/crossref/2004/2004JD004962.shtml   (377 words)

  
 RAP Projects - UAE Rainfall Enhancement Project - Hygroscopic Seeding
In contrast to silver-iodide seeding performed at -10 C to enhance ice nucleation, this technique is based on an enhancement of the coalescence process in the clouds as a means to increase rainfall.
In the past ten years, a new approach to hygroscopic seeding has been explored in summertime convective clouds in South Africa as part of the National Precipitation Research Programme (Mather et al., 1997).
If the CCN that are introduced into the cloud from the seeding flare are larger in size than the natural CCN, the introduced CCN will activate preferentially over the natural CCN and change the character of the droplet size distribution to favor coalescence and the formation of rain.
www.rap.ucar.edu /projects/UAE/hygroscopic_seeding.html   (445 words)

  
 Midwifery Today Forums - Hygroscopic Dilators
A prospective randomized evaluation of a hygroscopic cervical dilator, Dilapan, in the preinduction ripening of patients undergoing induction of labor.
CONCLUSIONS: Preinduction cervical ripening with hygroscopic dilators does not shorten the length of labor or lower the cesarean section rate in patients undergoing induction of labor.
Hygroscopic dilators absorb endocervical and local tissue fluids, causing the device to expand within the endocervix and providing controlled mechanical pressure.
www.midwiferytoday.com /forums/topic.asp?TOPIC_ID=5526   (410 words)

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